Marine Science News

Animals sleep, but little is known about how sharks do it

Sharks can sleep with their eyes open. (Shutterstock)
Michael Liam Kelly, Simon Fraser University

Sharks used to figure prominently in my nightmares: coming after me in the ocean, rivers, swimming pools. But after spending some time with these elusive creatures in 2015, a more compelling question started to keep me up at night — do the very creatures that invade my dreams engage in sleep themselves?

As the world’s leading — and only — authority in sleep in elasmobranchs (sharks and rays), my research team and I have begun to unravel this enigma, and our latest findings of physiological evidence of sleep in sharks are the most conclusive on the topic yet.

Circadian rhythms

Quiescence, or inactivity, is often the most basic behavioural characteristic that we associate with sleep. It was indeed this behaviour that my team set out to identify when we began our investigations into the presence of sleep in sharks. Specifically, we studied the presence of circadian-organized activity patterns, as sleep is controlled by the circadian clock (an internal, biochemical oscillator) in many animals.

Sharks are a unique group of vertebrates, however, as many species swim continuously to passively push oxygen-rich seawater over their gills — these are known as ram ventilators. Other species manually pump seawater over their gills while remaining motionless (buccal pumpers).

A study we conducted in 2020 found the presence of daily activity patterns in all the species investigated, buccal pumpers and ram ventilators alike. Importantly, these patterns were found to be internally regulated (circadian in nature) in buccal pumping species. This was a major discovery and a great step in the right direction, but were periods of inactivity indicative of sleep?

a group of sharks swimming
Some sharks need to constantly swim to passively push oxygen-rich seawater over their gills. (Tomas Gonzalez de Rosenzweig/Unsplash)

Sleep or quiet restfulness?

An animal’s responsiveness and awareness of external stimulation is reduced when asleep due to a sensory shutdown, or attenuation. As sleep researchers, we can exploit this ubiquitous sleep characteristic to behaviourally distinguish sleep from quiet restfulness.

Our 2021 study found that buccal pumping sharks were less responsive to mild electrical pulses following five minutes of inactivity. This became the criteria for our working definition of sleep in these animals.

Sleep is also internally regulated, so that animals can recover lost sleep by sleeping more. This characteristic was absent in the sharks in our study — they did not make up sleep following periods of sleep deprivation. This phenomenon is also >absent during sleep in other marine fishes.

These somewhat conflicting results highlight an important point: behaviour can be deceptive and misleading. Animals can appear to be asleep while being awake and >vice versa. Sadly, behaviour alone is often not enough to reliably identify sleep in animals.

The physiology of shark sleep

To conclusively verify our working definition of sleep in buccal pumping sharks (more than five minutes of inactivity is sleep), my team set out to find physiological evidence of sleep that aligned with what we had seen behaviourally.

To do this, we recorded changes in metabolic rates in New Zealand’s draughtsboard shark via recordings of oxygen consumption over a 24-hour period. A drop in metabolic rate during sleep has been reported in many animals and is considered a reliable physiological indicator of sleep.

Research shows that some shark species who actively pump water through their gills show behaviours associated with sleep.

We also recorded subtle behaviours associated with sleep in other animals, such as eye state (open/closed) and body posture (upright/flat). We found there to be no significant difference in metabolic rates between swimming sharks and sharks engaging in periods of inactivity that lasted less than five minutes.

When sharks were inactive for five minutes or longer, however, metabolic rates dropped dramatically. This physiological change was also accompanied by a conspicuous shift in posture, with sharks transitioning from an upright position (sitting up on their pectoral fins) to a completely recumbent position. Eye state, however, was found to be unrelated to the sharks’ state of consciousness, as the animals were often observed sleeping with eyes open.

Taken together, these data are the most conclusive evidence for sleep in sharks and verify our previous behavioural findings.

Moving forward

Sleep has been found in all animals studied to date, stretching as far back on the evolutionary scale as and jellyfish. As the earliest living, jawed vertebrates, sharks play an important role in helping us understanding the evolutionary history of sleep in vertebrates.

Our research has come a long way in uncovering the previously unanswered question of sleep in sharks, but we have only touched the tip of the iceberg. Now that we know that (at least some) sharks do indeed sleep, the next question to answer is how they sleep.

Nothing is known about sleep in ram ventilating sharks. Their need for constant swimming to facilitate gas exchange suggests they have likely evolved interesting adaptations to permit sleep under this unusual lifestyle. Our group is now conducting electrophysiological studies of brain activity that will provide comprehensive insight into the form that sleep takes in these animals. The Conversation

Michael Liam Kelly, Postdoctoral research fellow, Neuroscience, Simon Fraser University

April 7 2022

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Sculptures headed for Great Barrier Reef display

Artworks that will be the newest additions to a north Queensland underwater museum can be viewed on land. The Museum of Underwater Art (MOUA) has launched its next series of sculptures at a special exhibit at Townsville’s Museum of Tropical Queensland.

The Ocean Sentinels above the surface exhibit allows locals and visitors to enjoy the five artworks before they begin to transform into their own micro reefs when placed on the Great Barrier Reef.

MOUA Board Director Paul Victory said the exhibit was about connecting with as many people as possible and to spark meaningful conversation around the Great Barrier Reef and its future.

“The chance to see the world-class sculptures in the flesh and learn about their stories, promoting reef conservation and the link between art and science to a wider audience, is incredible,” Mr Victory said.

“This unique exhibit allows the public to enjoy and experience the next stage of the Museum of Underwater Art and learn about the important work we've been doing with coral planting, reef health surveys, providing education and work opportunities for Indigenous guides, and more.”

Sculptures celebrate scientists

World-renowned artist Jason deCaires Taylor designed and created the sculptures that celebrate the work of eight marine scientists and community members, who have been influential in our understanding of reef protection.

“I hope that in years to come a variety of endemic species such as corals, sponges and hydroids will change the sculptures' appearance in vibrant and unpredictable ways,” Mr deCaires Taylor said.

“Like the Great Barrier Reef itself, they will become a living and evolving part of the ecosystem, emphasising both its fragility and its endurance.”It is envisaged the new sculptures will be installed by June 2022 with the final location to be decided by the Great Barrier Reef Marine Park Authority.

The pieces will be installed in shallow depths, providing the perfect experience for snorkellers to get up close to the sculptures, broadening MOUA's offering to a larger group of people, who are more inclined to snorkel.

From the UK to Townsville

The pandemic meant Mr deCaires Taylor had to create them in his United Kingdom studio.The artworks were carefully shipped to Townsville where a selection were installed in the Museum of Tropical Queensland for display until 15 May.

Queensland Museum Network CEO Dr Jim Thompson said it was a wonderful collaboration between the Museum of Tropical Queensland and the Museum of Underwater Art to produce this unique display.

“These sculptures are destined for the ocean, so for people to see them in the museum and learn about them before they are installed underwater is something really special,” Dr Thompson said.

The Museum of Underwater Art exhibits include Ocean Siren, off Townsville’s The Strand, and Coral Greenhouse at John Brewer Reef, which can be visited by booking a trip with one of the approved commercial tourism operators.

18 March 2022

Original article:

https://www.racq.com.au/articles/out-and-about/2022/3/sculptures-headed-for-great-barrier-reef-display

What causes a tsunami? An ocean scientist explains the physics of these destructive waves

On Jan. 15, 2022, coastal areas across California were placed under a tsunami warning. Gado via Getty Images
Sally Warner, Brandeis University

On Jan. 15, 2022, the Hunga Tonga-Hunga Ha’apai volcano in Tonga erupted, sending a tsunami racing across the Pacific Ocean in all directions.

As word of the eruption spread, government agencies on surrounding islands and in places as far away as New Zealand, Japan and even the U.S. West Coast issued tsunami warnings. Only about 12 hours after the initial eruption, tsunami waves a few feet tall hit California shorelines – more than 5,000 miles away from the eruption.

I’m a physical oceanographer who studies waves and turbulent mixing in the ocean. Tsunamis are one of my favorite topics to teach my students because the physics of how they move through oceans is so simple and elegant.

Waves that are a few feet tall hitting a beach in California might not sound like the destructive waves the term calls to mind, nor what you see in footage of tragic tsunamis from the past. But tsunamis are not normal waves, no matter the size. So how are tsunamis different from other ocean waves? What generates them? How do they travel so fast? And why are they so destructive?

A satellite view a large ash cloud and shockwave.
When the Hunga Tonga-Hunga Ha'apai volcano erupted, it launched ash into the atmosphere, created a powerful shock wave and displaced a huge amount of water, generating a tsunami that raced across the ocean. Japan Meteorological Agency via WikimediaCommons, CC BY

Deep displacement

Most waves are generated by wind as it blows over the ocean’s surface, transferring energy to and displacing the water. This process creates the waves you see at the beach every day.

Tsunamis are created by an entirely different mechanism. When an underwater earthquake, volcanic eruption or landslide displaces a large amount of water, that energy has to go somewhere – so it generates a series of waves. Unlike wind-driven waves where the energy is confined to the upper layer of the ocean, the energy in a series of tsunami waves extends throughout the entire depth of the ocean. Additionally, a lot more water is displaced than in a wind-driven wave.

Imagine the difference in the waves that are created if you were to blow on the surface of a swimming pool compared to the waves that are created when someone jumps in with a big cannonball dive. The cannonball dive displaces a lot more water than blowing on the surface, so it creates a much bigger set of waves.

Earthquakes can easily move huge amounts of water and cause dangerous tsunamis. Same with large undersea landslides. In the case of the Tonga tsunami, the massive explosion of the volcano displaced the water. Some scientists are speculating that the eruption also caused an undersea landslide that contributed to the large amount of displaced water. Future research will help confirm whether this is true or not.

This simulation from the National Oceanic and Atmospheric Administration shows how tsunami waves propagated away from an earthquake that occurred about 600 miles from Tonga in 2021.

Tsunami waves travel fast

No matter the cause of a tsunami, after the water is displaced, waves propagate outward in all directions – similarly to when a stone is thrown into a serene pond.

Because the energy in tsunami waves reaches all the way to the bottom of the ocean, the depth of the sea floor is the primary factor that determines how fast they move. Calculating the speed of a tsunami is actually quite simple. You just multiply the depth of the ocean – 13,000 feet (4,000 meters) on average – by gravity and take the square root. Doing this, you get an average speed of about 440 miles per hour (700 kilometers per hour). This is much faster than the speed of typical waves, which can range from about 10 to 30 mph (15 to 50 kph).

This equation is what oceanographers use to estimate when a tsunami will reach faraway shores. The tsunami on Jan. 15 hit Santa Cruz, California, 12 hours and 12 minutes after the initial eruption in Tonga. Santa Cruz is 5,280 miles (8,528 kilometers) from Tonga, which means that the tsunami traveled at 433 mph (697 kph) – nearly identical to the speed estimate calculated using the ocean’s average depth.

A flooded airport runway covered in debris.
Many tsunamis, including the 2011 Tsunami in Japan, move inland and can flood areas far from the coast. U.S. Air Force photo/Staff Sgt. Samuel Morse via WikimediaCommons

Destruction on land

Tsunamis are rare compared to ubiquitous wind-driven waves, but they are often much more destructive. The 2004 Indian Ocean tsunami killed 225,000 people. More than 20,000 lost their lives in the 2011 Japan tsunami.

What makes tsunamis so much more destructive than normal waves?

An animation showing waves approaching a shoreline.
As waves approach shore, they get pushed upward by the rising seafloor. Régis Lachaume via Wikimedia Commons, CC BY-SA

In the open ocean, tsunami waves can be small and may even be undetectable by a boat at the surface. But as the tsunami approaches land, the ocean gets progressively shallower and all the wave energy that extended thousands of feet to the bottom of the deep ocean gets compressed. The displaced water needs to go somewhere. The only place to go is up, so the waves get taller and taller as they approach shore.

When tsunamis get to shore, they often do not crest and break like a typical ocean wave. Instead, they are more like a large wall of water that can inundate land near the coast. It is as if sea level were to suddenly rise by a few feet or more. This can cause flooding and very strong currents that can easily sweep people, cars and buildings away.

Luckily, tsunamis are rare and not nearly as much of a surprise as they once were. There is now an extensive array of bottom pressure sensors, called DART buoys, that can sense a tsunami wave and allow government agencies to send warnings prior to the arrival of the tsunami.

If you live near a coast – especially on the Pacific Ocean where the vast majority of tsunamis occur – be sure to know your tsunami escape route for getting to higher ground, and listen to tsunami warnings if you receive one.

The eruption of the Hunga Tonga-Hunga Ha’apai volcano severed the main communication cable that connects the people of Tonga to the rest of the world. While the science of tsunamis can be fascinating, these are serious natural disasters. Only a few deaths have been reported so far from Tonga, but many people are missing and the true extent of the damage from the tsunami is still unknown.The Conversation

Sally Warner, Assistant Professor of Climate Science, Brandeis University

January 19 2022

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Sponges can survive low oxygen and warming waters. They could be the main reef organisms in the future

Valerio Micaroni
James Bell, Te Herenga Waka — Victoria University of Wellington; Rob McAllen, University College Cork, and Valerio Micaroni, Te Herenga Waka — Victoria University of Wellington

Sponges are ancient marine animals, very common throughout the world’s oceans and seem less affected by ocean warming and acidification.

Our latest research shows they can also survive low levels of oxygen.

This is a surprising finding because most sponges are rarely exposed naturally to low oxygen in modern seas.

We propose their tolerance is the result of their long evolutionary history and exposure to variable oxygen concentrations through geological time.

As our oceans continue to warm due to climate change, they are expected to hold less oxygen.

The ability of sponges to survive low-oxygen conditions means they are likely to tolerate these possible future environments better than other organisms living on the seafloor.

This graph shows different marine organisms that live permanently attached to the seafloor and their different thresholds for low-oxygen conditions.
Different marine organisms that live permanently attached to the seafloor have different thresholds for low-oxygen conditions. Author provided

There are an estimated 8000-plus sponge species in the oceans. They are multicellular organisms with a body architecture built around a system of water canals, pores and channels allowing water to be pumped and circulated through them.

Their specialised pumping and feeding cells, called choanocytes, are highly efficient. Sponges can pump the equivalent of their own body volume in a matter of seconds.

Images of four different sponge species, with different shapes and colours.
There are thousands of different sponge species in the world’s oceans. Author provided

In modern oceans, sponges are often the most abundant organisms in rocky reef environments. They fulfil important ecological functions as part of bottom-dwelling (benthic) communities worldwide.

Sponges have many roles in marine ecosystems, but their water-processing ability and efficiency at capturing small particles is the most important because it links the water column with the seafloor. Sponges also support diverse seafloor communities by transforming carbon.

Some sponge species have been shown to be very tolerant to climate change stressors, particularly changing temperature and acidity (measured as pH). This means sponges could be future winners in changing oceans.

Sponges in past oceans

We know that sponges are ancient organisms, but recently described 890-million-year-old fossils have turned our understanding of evolution on its head.

Most major animal groups, including arthropods and worms, first appear in the fossil record during a period known as the Cambrian explosion, 540 million years ago. But if the newly-described fossils are indeed sponges, they would have existed nearly 300 million years earlier, significantly pushing back the date of Earth’s earliest known animals.

If the ancestors of modern sponges are about 900 million years old, they would have evolved and survived during the Marinoan glaciation, 657-645 million years ago, when the oceans were extremely low in oxygen.

They would have also likely experienced wide fluctuations in other environmental conditions such as pH, temperature and salinity through evolutionary time.

Sponge tolerance to low oxygen

Our recent environmental tolerance experiments support this scenario, showing they are surprisingly tolerant to low levels of oxygen.

We assessed the response of sponges to moderate and severe low-oxygen events in a series of laboratory experiments on four species from the northeast Atlantic and southwest Pacific. Sponges were exposed to a total of five low-oxygen treatments, with increasing severity (40%, 20%, 6%, 5% and 1.5% air saturation) over seven to 12 days.

We found the sponges generally very tolerant of hypoxia. All but one of the species survived in the extreme experimental conditions, and that species only began to die off at the lowest oxygen concentration. In most experiments, hypoxic conditions did not significantly affect the sponges’ respiration rates, which suggests they can take up oxygen at very low concentrations in the surrounding environment.

As a response to the low oxygen, sponges displayed a number of shape and structural changes, likely maximising their ability to take up oxygen at these low levels.

Images of sponges show they changed their shape and structure in response to low-oxygen oxygen conditions.
Sponges changed their shape and structure in response to low-oxygen conditions. Author provided

Sponges in future oceans

Warmer ocean water holds less oxygen, and ocean deoxygenation is one of the major consequences of climate change.

Warmer water also becomes more buoyant than cooler water, which reduces the mixing of surface oxygenated water with deeper layers that naturally contain less oxygen. At the same time, warmer temperatures increase the demand of organisms for oxygen as metabolic rates increase and stress responses are initiated.

While oxygen levels in the ocean are only expected to fall on average by 4% across all oceans, these effects are likely to be much more extreme locally and regionally. In coastal waters, climate-driven ocean deoxygenation can be exacerbated by a process called eutrophication, essentially an increase in nutrients. This fuels plankton blooms, and when bacteria breakdown the dead phytoplankton, they use up all the oxygen.

Since the land is generally the source of these excess nutrients, shallow coastal areas are most at risk. These are areas where rocky reefs are typically dominated by sponges, particularly just below the depth of light penetration (typically 20-30m).

Our finding lends further support to the idea that sponges will be the survivors if our oceans continue to warm. The Conversation

James Bell, Professor of Marine Biology, Te Herenga Waka — Victoria University of Wellington; Rob McAllen, Professor of Marine Conservation, University College Cork, and Valerio Micaroni, PhD Candidate in Coastal and Marine Biology and Ecology, Te Herenga Waka — Victoria University of Wellington

January 17 2022

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Tsunami reported broadly across the Southwest Pacific and on the East coast of Australia.

Tsunami recorded at the Gold Coast sand pumping jetty. From www.qld.gov.au.
Tsunami recorded at the Gold Coast sand pumping jetty. From www.qld.gov.au.

A wide spread Tsunami wave has been recorded by tide gauges From Cooktown in far north Queensland to Spring Bay in Southern Tasmania. The Tsunami was generated by an undersea volcanic eruption in Tonga in the southern Pacific ocean. 

 

The Tsunami height recorded at the Gold Coast in Queensland reached 0.82 m at 22:54 (AEST). in the plot to the right the red line is the residual when tide levels are removed. the highest wave height was not the first wave but recorded hours later.

Site   Time (AEST) Tsunami height

 Nuku'Alofa, Tonga

21.10S  175.20W 15:46 1.19 m

Suva, Fiji

18.10S  178.42E 17:03 0.36 m

Pago Pago, Samoa

14.30S  170.69W 16:40 0.55 m

Apia, Samoa

13.67S  171.83W 18:06 0.27 m

Rarotonga, Cook Islands

21.20S  159.78W 19:56 0.74 m

Funafuti, Tuvalu

8.50S  179.20E 18:24 0.11 m

East Cape, NZ

37.50S  178.17E 19:15 0.38 m

Lifou Island, New Caledonia

20.90S  167.28E 17:33 0.29 m
Ouinne, New Caledonia 22.00S  166.83E 19:21 0.67 m
Norfolk Island, Australia 29.10S  167.95E 21:00 1.27 m
Port Villa, Vanuatu 17.80S  168.31E 19:50 1.18 m
Luganville, Vanuatu 15.50S  167.33E 19:06 0.29 m
DART 55023, Coral Sea 2, 14.72S  153.54E 21:44 Detected
Gold Coast, Australia 27.90S  153.43E 22:54 0.82 m
Charleston, NZ 41.83S  171.33E 23:35 0.65 m
Port Kembla, Australia 34.50S  151.00E 02:50 0.65 m
Twofold Bay, Australia 37.00S  150.00E 23:30 0.77 m
Spring Bay, Australia 42.50S  147.93E 21:00 0.27 m
Rosslyn Bay, Australia 23.20S  150.79E 03:05 0.25 m
Jackson Bay, NZ 43.97S  168.62E 23:50 1.14 m
Coffs Harbour, Australia 0.30S  153.15E 10:30 0.43 m
Lord Howe Island, Australia 31.52S  159.06E 08:00 0.50 m
Eden, Australia 37.07S  149.91E 10:15 0.40 m

What is the value of a wave? How changes to our coastline could wipe out surfing’s benefits

Shutterstock

Before COVID-19, global surf tourism spending was estimated at up to A$91 billion per year. And since the start of the pandemic, demand for surfing has boomed as people increasingly turn to outdoor activities. But surfing’s benefits to human well-being aren’t often studied in economics terms. This is a major knowledge gap we are now trying to fill. Such research is important. Changes to the coastline such as from sea walls and groynes can dramatically reduce the quality of surfing waves. But the consequences of coastal developments on surfing are often poorly understood and rarely quantified before projects start. It’s crucial we understand the real value of surfing, before we lose the myriad of benefits they bring – not only to Australia’s 1.2 million active surfers, but to hundreds of coastal towns where surfing underpins the local economy and lifestyle.

Surfing economics

There are many studies on the economic value of Australian beach pastimes such as fishing, swimming and diving. But not for surfing. Internationally, we know surfing is a major direct contributor to the economy of wave-rich places. However, until recently, the value of surfing to human well-being has been largely unaccounted for.

Surfing is a major direct contributor to many local economies all over the world. Shutterstock

This is despite recent evidence pointing to surfing’s positive social and health outcomes, including among war veterans and children with chronic illnesses.

Surfing Economics is an emerging field of research that documents and quantifies the total economic value of surfing. This can include, for example, increased house prices near good quality breaks, or social welfare benefits people derive from visiting surf beaches.

Building on the few previous surfing economics studies in Australia, our research aims to calculate the total economic value of surfing.

Our forthcoming study on the Noosa World Surf reserve, so far, demonstrates that the local economic contribution of surfing is in the order of hundreds of millions of dollars. This in terms of surfers’ welfare, as well as direct spending on surf gear and travel.

Waves forming around rocks in Noosa. Shutterstock

Overseas, the economic contribution is a little clearer. A 2017 study used satellite imagery to demonstrate that economic activity grows faster near good-quality surf breaks, particularly in developing countries such as Indonesia and Brazil.

In the UK alone, the overall annual impact of surfing on the national economy is calculated at up to £5 billion (over A$9 billion).

How coastal projects make or break waves

Swell waves are typically formed by winds blowing many kilometres offshore. It’s perhaps easy to think that this natural,distant origin means there’s nothing we can do about the formation of waves.

But the truth is surfing waves are the product of complex interactions between waves, tides, currents, wind and the shape of the seabed. Shallow coral reefs, headlands and sand banks are responsible for making highly sought-after waves.

By directly or indirectly impacting any of these factors, wave quality has been changed for better – or for worse.

Mundaka in Spain had world-renowned waves, until dredging in a nearby river affected the swells. Shutterstock

The world-renowned Mundaka wave, in northern Spain, temporally disappeared because dredging of the nearby rivermouth changed ocean dynamics. This resulted in a decline in economic activity and the cancellation of the Billabong Pro World Championship in 2005 and 2006.

In the Portuguese island of Madeira, the construction of a rock-wall severely disrupted the formation of the Jardim do Mar wave in 2005, and a fall in local economic growth rates followed. In Peru, the extension of a fishing pier negatively impacted Cabo Blanco, one of Peru’s best barrelling waves, by shortening its length.

Closer to home, the Ocean Reef Marina, currently under construction in Perth’s north, will significantly impact three local surf breaks. About 1.5 kilometres of mostly unmodified beaches are being redeveloped into a brand new marina.

Studies have shown that well planned coastal management interventions can dramatically increase benefits to surfers and non-surfers alike.

One of the most iconic examples is the “Superbank” at Snapper Rocks in the Gold Coast. There, a world class wave forms thanks to river sediment being relocated through the Tweed Sand Bypassing Project.

World-class waves at Snapper Rock in the Gold Coast. Shutterstock

The project is costly to operate and has impacted nearby beaches. But its expenses are outweighed by improvements to surf quality and beach amenity, which underpin the local economy and the nature-based, active lifestyle the Gold Coast is famous for.

Giving waves legal protection

Building on efforts nearly 40 years ago to protect Victoria’s iconic Bells Beach wave, Peru and New Zealand have granted statutory protection to their surf breaks under environmental protection laws.

In practice, this means threats to surf breaks by coastal activities, such as sewage discharges or building offshore structures, must be avoided or mitigated.

Similar recognition and valuation of surfing resources is necessary and would be highly beneficial for Australia.

A rigorous, science-based evaluation of surfing’s total economic value could serve to inform cost-benefit analysis of coastal management programs. These may include fighting erosion to protect the coastline, or building artificial surf reefs.

In these uncertain times of COVID-19, many of us cannot yet travel far away. But with 85% of Australians living by the coast, many of us can still catch a wave at our doorstep – and that is priceless.The Conversation

Ana Manero, Research Fellow, Australian National University; Alaya Spencer-Cotton, Research assistant, The University of Western Australia; Javier Leon, Senior lecturer, University of the Sunshine Coast, and Neil Lazarow, Senior Research Consultant, CSIRO

January 10 2022

This article is republished from The Conversation under a Creative Commons license. Read the original article.

From enormous tides to millions of shells, here are 6 unique beaches for your summer road trip

A sandy beach with rocky headland. Hannah Power.
Hannah Power, University of Newcastle

As lockdowns ease and we head into summer, many Australians have started thinking about their beach holiday. For most people, a beach involves sun, sand, salt, and waves. A beach is a beach – right?

For coastal scientists and engineers, it’s a little different. We wonder how these beaches are made and why they are so different.

Australia has over 35,000 kilometres of coastline to explore, and our beaches can differ radically. In Australia’s south, where tides are smaller and waves bigger, we get high energy beaches with lots of surf and sand. The north’s larger tides and smaller waves mean the beaches look quite different – they’re flatter, with big intertidal zones. Some even have mud instead of sand.

To pique your interest, here are six beaches from around the country with special characteristics, all well worth exploring on your summer road trip or beach holiday.

A map of Australia showing how wave height and tidal range vary around the country.
How wave heights and tides vary around Australia. The tidal range at each beach is shown by one point. Author provided figure; mean significant wave height data from CAWCR wave hindcast, tide model data courtesy Robbi Bishop-Taylor.

1. Sandy Cape – end of the line for the sand islands

K’gari (Fraser Island), Queensland.

Waves and storms along the east coast, from the New South Wales/Victoria border to K'Gari in Queensland, usually come from the south and southeast. This drives longshore sediment transport, a process where sand is moved up the coast by waves and wave-driven currents.

As the sand moves along the NSW coast and into Queensland, it beach-hops its way north, encountering natural barriers like headlands as well as human barriers such as breakwaters. Sand will often skirt these barriers in pulses, as tends to happen at Byron Bay.

As the coast turns to the west in southeast Queensland, the sand keeps getting pushed north. That’s how Australia got the largest sand islands in the world: Minjerribah (South and North Stradbroke), Mulgumpin (Moreton), Yarun (Bribie), and finally K’gari.

The northernmost point of K’gari, Sandy Point, marks where the sand heads underwater, moving along the continental shelf before dropping off the edge and sliding down the slope into the deep abyssal plains.

If you make it to this beach, you can see sand being swirled away into deeper water – the very end of the above-water part of the cycle.

Sand flowing north from Sandy Cape on K'gari. Data: Geoscience Australia Landsat 5 and 8 Geomedian. Compilation: Will Farebrother.

2. The Funnel – the biggest tides in Australia

Collier Bay, Western Australia

The Kimberley region of Australia is home to the biggest tides in the country. Unfortunately, there aren’t many tide gauges in this area, with over 1,000km between instruments in places. So, to find the beach with the biggest tides, we either have to collect more data or use a computer model.

When we model the tides for every Australian beach, The Funnel in Collier Bay comes out as the beach with the biggest tides. Its range is a whopping 13.5 metres!

Getting to this beach might be tricky as you’ll need to arrive by boat. But it would be worth the trip, as the beach at high tide is composed of cobbles and likely sand and mud at low tide. Watching the tide roar in would be something to see – just watch out for crocs!

Slider shows satellite images of The Funnel at low and high tide. Author supplied. Image Source: Planet.

3. Goolwa Beach – the high energy beach

South Australia

When rivers as big as the Murray – whose basin covers one-seventh of mainland Australia – meet the ocean, they normally form huge deltas like the Mississippi or the Nile.

But because of Australia’s age, low rainfall and water extraction for agriculture, the Murray-Darling Basin only delivers a relatively small amount of water and sediment to the coast. So instead of a classic river delta at the end of the Murray, unusually, we have a beach system.

Goolwa Beach is part of this system, its fine sands representing the last barrier to the mighty Murray River on its journey to the ocean. The beach is also exposed to the huge waves rolling in from the Southern Ocean. That makes it one of our highest energy beaches – so much so it’s the archetype of the high energy beach type called “dissipative” in our Australian beach classification system.

Panorama of a beach with lots of waves.
Panorama of Goolwa Beach. Hannah Power.

4. Amity Beach – the beach with sinkholes

Minjerribah, Queensland

The islands of Minjerribah (North Stradbroke) and Mulgumpin (Moreton) form the barrier separating Moreton Bay near Brisbane from the Coral Sea. Between them lies Rainbow Channel through which the tide flows in and out of Moreton Bay.

These fast tidal currents cause large amounts of sand to form shifting sand shoals on both the ocean and bay sides of the channel.

Amity Beach sits on the edge of this channel and the constantly changing dynamics of this system cause “sinkholes” to occur regularly on this beach. Rainbow Beach near K'Gari is better known due to its habit of swallowing cars, but Amity Beach is unique. Why? Because the sinkholes always occur in the same place.

That makes it the only place in the world where scientists and engineers can reliably observe this amazing phenomenon to work out why sinkholes occur and how they work.

Satellite images of Amity Beach when the sinkhole is present or absent. Author provided. Image source: Google Earth.

5. Shell Beach – walk on millions of shells

Shark Bay, Western Australia

Most of us tend to think of beaches as being made up by sand, but they don’t have to be. Beaches can be made of mud or cobbles or even just shells.

Shell Beach in Shark Bay is a rarity as it’s almost entirely made up of trillions of shells, with the piles up to 10m deep.

These shells all come from one mollusc, the Fragum cockle. The reason there are so many of these shells is because the waters of Shark Bay are saltier than the ocean.

This hypersaline environment makes it hard for most species to survive. That means the Fragum cockle has very few competitors or predators and can proliferate. Just remember to bring some footwear!

beach made of shells
Shell Beach at Shark Bay. Shutterstock

6. Bengello Beach – a time capsule made of sand

New South Wales

Coastal scientists and engineers love data about beaches, and especially long-term records of how much sand is on a beach.

Bengello Beach in southern NSW represents the longest record of beach surveys in Australia with measurements every 2-6 weeks since January 1972.

These measurements have captured beach erosion during storms and its subsequent recovery. Data like this underpins models forecasting how our beaches will respond to climate change.

Bengello is also a living snapshot of beach evolution, capturing the way many of Australia’s beaches have changed since sea level stabilised at about today’s level after the last ice age.

If you walk from the road to the beach, you pass over ridges of ancient sand dunes. These formed as the beach slowly built out towards the sea over the last 6,000 years, as waves and currents piled up more and more sand on the beach.

Three photos showing a beach before and after an erosion event and after the recovery.
The storm erosion and recovery cycle at Bengello Beach. Images show the beach before the June 2016 storm, after the storm, and after recovery in 2019. The graphs show a cross-section of the beach at the time of each photo. Author provided figure; data and photos Roger McLean.

When road-tripping to Australia’s beaches, remember to check local weather and marine forecasts to make sure it’s safe to swim and leave only your footprints behind. And if you make it to any of these beaches, why not share your knowledge about their significance with your travel buddies?The Conversation

Hannah Power, Associate Professor in Coastal and Marine Science, University of Newcastle

This article is republished from The Conversation under a Creative Commons license. Read the original article.

23 December 2021

La Niña just raised sea levels in the western Pacific by up to 20cm. This height will be normal by 2050

Shutterstock
Shayne McGregor, Monash University

Severe coastal flooding inundated islands and atolls across the western equatorial Pacific last week, with widespread damage to buildings and food crops in the Federated States of Micronesia, Marshall Islands, Papua New Guinea and Solomon Islands.

On one level, very high tides are normal at this time of year in the western Pacific, and are known as “spring tides”. But why is the damage so bad this time? The primary reason is these nations are enduring a flooding trifecta: a combination of spring tides, climate change and La Niña. La Niña is a natural climate phenomenon over the Pacific Ocean known for bringing wet weather, including in eastern Australia. A less-known impact is that La Niña also raises sea levels in the western tropical Pacific. In a terrifying glimpse of things to come, this current La Niña is raising sea levels by 15-20 centimetres in some western Pacific regions – the same sea level rise projected to occur globally by 2050, regardless of how much we cut global emissions between now and then. So let’s look at this phenomena in more detail, and why we can expect more flooding over the summer.

These spring tides aren’t unusual

Low-lying islands in the Pacific are considered the frontline of climate change, where sea level rise poses an existential threat that could force millions of people to find new homes in the coming decades.

Last week’s tidal floods show what will be the new normal by 2050. In the Marshall Islands, for example, waves were washing over boulder barriers, causing flooding on roads half a metre deep.

This flooding has coincided with the recent spring tides. But while there is year to year variability in the magnitude of these tides that vary from location to location, this year’s spring tides aren’t actually unusually higher than those seen in previous years.

For instance, tidal analysis shows annual maximum sea levels at stations in Lombrom (Manus, Papua New Guinea) and Dekehtik (Pohnpei, Federated States of Micronesia) are roughly 1-3cm higher than last year. Meanwhile, those at Betio (Tarawa, Kiribati) and Uliga (Majuro, Marshall Islands) are roughly 3-6cm lower.

This means the combined impacts of sea level rise from climate change and the ongoing La Niña event are largely responsible for this year’s increased flooding.

A double whammy

The latest assessment report from the Intergovernmental Panel on Climate Change finds global average sea levels rose by about 20cm between 1901 and 2018.

This sea level rise would, of course, lead to more coastal inundation in low-lying regions during spring tides, like those in the western tropical Pacific. However, sea level rise increases at a relatively small rate – around 3 millimetres per year. So while this can create large differences over decades and longer, year to year differences are small.

This means while global mean sea level rise has likely contributed to last week’s floods, there is relatively small differences between this year and the previous few years.

This is where La Niña makes a crucial difference. We know La Nina events impact the climate of nations across the Pacific, bringing an increased chance of high rainfall and tropical cyclone landfall in some locations.

But the easterly trade winds, which blow across the Pacific Ocean from east to west, are stronger in La Niña years. This leads to a larger build up of warm water in the western Pacific.

Warm water is generally thicker than cool water (due to thermal expansion), meaning the high heat in the western equatorial Pacific and Indonesian Seas during La Niña events is often accompanied by higher sea levels.

This year is certainly no different, as can be seen in sea surface height anomaly maps here and here.

From these maps, along with past studies, it’s clear Pacific islands west of the date line (180⁰E) and between Fiji and the Marshall Islands (15⁰N-15⁰S) are those most at risk of high sea levels during La Niña events.

What could the future hold?

We can expect to see more coastal flooding for these western Pacific islands and atolls over the coming summer months. This is because the La Niña-induced sea level rise is normally maintained throughout this period, along with more periods with high spring tides.

Interestingly, the high sea levels related to La Niña events in the northern hemisphere tend to peak in November-December, while they do not peak in the southern hemisphere until the following February-March.

This means many western Pacific locations on both sides of the equator will experience further coastal inundation in the short term. But the severity of these impacts is likely to increase in the southern hemisphere (such as the Solomon islands, Tuvalu and Samoa) and decrease in the northern hemisphere (such as the Marshall Islands and the Federated States of Micronesia).

Looking forward towards 2050, a further 15-25cm of global average sea level rise is expected. La Niña events typically cause sea levels in these regions to rise 10-15cm above average, though some regions can bring sea levels up to 20cm.

Given the projected sea level rise in 2050 is similar to the La Niña-induced rise in the western Pacific, this current event provides an important insight into what will become “normal” inundation during spring tides.

Unfortunately, climate projections show this level of sea level rise by 2050 is all but locked in, largely due to the greenhouse gas emissions we’ve already released.

Beyond 2050, we know sea levels will continue to rise for the next several centuries, and this will largely depend on our future emissions. To give low-lying island nations a fighting chance at surviving the coming floods, all nations (including Australia) must drastically and urgently cut emissions. The Conversation

Shayne McGregor, Associate Professor, and Associate Investigator for the ARC Centre of Excellence for Climate Extremes, Monash University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Dec 16 2021

Movement of plankton between tropical marine ecosystems drives 'sweet spots' for fishing

A new analysis suggests that the movement of plankton and plankton-eating fish play a central role in driving local spikes of extreme biological productivity in tropical coral reefs, creating "sweet spots" of abundant fish. Renato Morais of James Cook University in Townsville, Australia, and colleagues present these findings in a study publishing November 2nd in the open-access journal PLOS Biology.

Although some ecosystems are limited by their intrinsic productivity (from photosynthesis, for example), previous research has shown that mobile resources like plankton can serve as vectors that transfer energy and nutrients from offshore ecosystems to coral reef ecosystems. Such transfers of resources between ecosystems are known as spatial subsidies, and they enable ecosystems to surpass the limits of their intrinsic capabilities for biological productivity, resulting in more abundant life. However, the extent to which the movement of plankton and plankton-eating fish boost abundance in tropical marine ecosystems has been unclear.

To help clarify and quantify this role, Morais and colleagues integrated and analyzed extensive data from visual fish counts. One dataset covered the tropical waters of the Indian Ocean and much of the Pacific, while the other fish count data came from three specific tropical locations that were representative of the diversity of coral reef ecosystems found in the larger dataset. The analysis revealed that plankton-eating fish do indeed play a major, widespread role as vectors of spatial subsidies to tropical coral reefs. By feeding on offshore plankton, they deliver extra resources to reef ecosystems and thereby drive local periods of extreme biological productivity—including for their own predators. In these "sweet spots," plankton-eating fish are responsible for more than 50 percent of the total fish production, and people might find conditions there optimal for bountiful fishing.

The researchers note that their findings hold particular significance for the future of tropical reef fisheries. Coral reefs continue to degrade, and offshore productivity is expected to decline, so sweet spots that concentrate these dwindling resources may increase in importance for fishers. Morais adds, "How do tropical oceans sustain high production and intense coastal fisheries despite occurring in nutrient-poor oceans? Spatial subsidies vectored by planktivorous fishes dramatically increase local reef fish biomass production, creating 'sweet spots' of fish concentration. By harvesting oceanic productivity, planktivorous fishes bypass spatial constraints imposed by local primary productivity, creating 'oases' of tropical marine biomass production."

 

Original article: Morais RA, Siqueira AC, Smallhorn-West PF, Bellwood DR (2021) Spatial subsidies drive sweet spots of tropical marine biomass production. PLoS Biol 19(11): e3001435. doi.org/10.1371/journal.pbio.3001435

 

Nov 10 2021

White sharks can easily mistake swimmers or surfers for seals. Our research aims to reduce the risk

Elias Levy/Wikimedia Commons, CC BY
Laura Ryan, Macquarie University and Charlie Huveneers, Flinders University

The presumed death of 57-year-old Paul Millachip in an apparently fatal shark bite incident near Perth on November 6 is a traumatising reminder that while shark bites are rare, they can have tragic consequences.

Despite the understandably huge media attention these incidents generate, there has been little scientific insight into how and why they happen.

Sharks in general, and white sharks in particular, have long been described as “mindless killers” and “man-eaters”.

But our recent research confirms that some bites on humans may be the result of mistaken identity, whereby the sharks mistake humans for their natural prey based on visual similarities.

Sharks have an impressive array of senses, but vision is thought to be particularly important for prey detection in white sharks. For example, they can attack seal-shaped decoys at the surface of the water even though these decoys lack other sensory cues such as scent.

The visual world of a white shark varies substantially from that of our own. White sharks are likely colourblind and rely on brightness, essentially experiencing their world in shades of grey. Their eyesight is also much less acute than ours – in fact, it’s probably more akin to the blurry images a human would see underwater without a mask or goggles.

The mistaken identity theory

Bites on surfers have often been explained by the fact that, seen from underneath, a paddling surfer looks a lot like a seal. But this presumed similarity has only previously been assessed based on human vision, using underwater photographs to compare their silhouettes.

Recent developments in our understanding of sharks’ vision have now made it possible to examine the mistaken identity theory from the shark’s perspective, using a virtual system that generates “shark’s-eye” images.

In our study, published last month, we and our colleagues in Australia, South Africa and the United Kingdom compared video footage of seals and of humans swimming and paddling surfboards, to predict what a young white shark sees when looking up from below.

Shark's-eye images of surfer and seal
‘Shark’s-eye view’ of a paddling surfer and seal, suggesting white sharks may struggle to differentiate the two. Author provided

We specifically studied juvenile white sharks – between of 2m and 2.5m in length – because data from New South Wales suggests they are more common in the surf zone and are disproportionately involved in bites on humans. This might be because juvenile sharks are more likely to make mistakes as they switch to hunting larger prey such as seals.

Our results showed it was impossible for the virtual visual system to distinguish swimming or paddling humans from seals. This suggests both activities pose a risk, and that the greater occurrence of bites on surfers might be linked to the times and locations of when and where people surf.

Our analysis suggests the “mistaken identity” theory is indeed plausible, from a visual perspective at least. But sharks can also detect prey using other sensory systems, such as smell, sound, touch and detection of electrical fields.

While it seems unlikely every bite on a human by a white shark is a case of mistaken identity, it is certainly a possibility in cases where the human is on the surface and the shark approaches from below.

However, the mistaken identity theory cannot explain all shark bites and other factors, such as curiosity, hunger or aggression are likely to also explains some shark bites.

Can this knowledge help protect us?

As summer arrives and COVID restrictions lift, more Australians will head to the beach over the coming months, increasing the chances they might come into close proximity with a shark. Often, people may not even realise a shark is close by. But the past weekend gave us a reminder that shark encounters can also tragically result in serious injury or death.

Understanding why shark bites happen is a good first step towards helping reduce the risk. Our research has inspired the design of non-invasive, vision-based shark mitigation devices that are currently being tested, and which change the shape of the silhouette.

We still have a lot to learn about how sharks experience their world, and therefore what measures will most effectively reduce the risks of a shark bite. There is a plethora of devices being developed or commercially available, but only a few of them have been scientifically tested, and even fewer – such as the devices made by Ocean Guardian that create an electrical field to ward off sharks – have been found to genuinely reduce the risk of being bitten. The Conversation

Laura Ryan, Postdoctoral Researcher, Department of Biological Sciences, Macquarie University and Charlie Huveneers, Associate professor, Flinders University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Nov 10 2021

Meet the penis worm: don’t look away, these widespread yet understudied sea creatures deserve your love

Wikimedia, CC BY-SA
Daryl McPhee, Bond University

Am I not pretty enough? This article is part of The Conversation’s series introducing you to unloved Australian animals that need our help.


Australia’s oceans are home to a startling array of biodiversity — whales, dolphins, dugongs and more. But not all components of Aussie marine life are the charismatic sort of animal that can feature in a tourism promotion, documentary, or conservation campaign.

The echiuran, or spoon worm, is one such animal. It is also called the penis worm.

There is no “Save the Echiuran Foundation” and no influencers selling merchandise to help save them. But these phallic invertebrates are certainly worth your time as integral and fascinating members — of Australia’s marine ecosystems.

What makes them so interesting?

Taxonomists have classified echiurans in various different ways over the years, including as their own group of unique animals. Today, they’re considered a group of annelid worms that lost their segmentation. There is uncertainty about the exact number of species, but an estimate is 236.

The largest echiuran species reach over two metres in length! They have a sausage-shaped muscular trunk and an extensible proboscis (or tongue) at their front end. The trunk moves by wave like contractions.

Most echiurans live in marine sand and mud in long, U-shaped burrows, but some species also live between rocks. And they’re widespread, living up to 6,000 metres deep in the ocean all the way to the seashore, worldwide.

Some species live between rocks. Shutterstock

For example, one species, Ochetostoma australiense, is a common sight along sandy or muddy shorelines of Queensland and New South Wales, where it sweeps out of its burrow to collect and consume organic matter.

In fact, their feeding activities are something to behold, as they form a star-like pattern on the surface that extends from their burrow opening.

In another species, Bonella viridis, there is a striking difference> between the males and females — the females are large (about 15 centimetres long) and the males are tiny (1-3 millimetres). Most larvae are sexually undifferentiated, and the sex they end up as depends on who’s around. The larvae metamorphose into dwarf males when they’re exposed to females, and into females when there are no other females present.

Males function as little more than a gonad and are reliant on females for all their needs.

Another common name for the penis worm is the fat innkeeper worm. Alison Young/iNaturalist

Why they’re so important

Echiurans perform a range of important ecological functions in the marine environment. They’re known as “ecosystem engineers” - organisms that directly or indirectly control the availability of resources, such as food and shelter, to other species. They do this mainly by changing the physical characteristics of habitats, for example, by creating and maintaining burrows, which can benefit other species.

Echiurans also have a variety of symbiotic animals, including crustaceans and bivalve molluscs, residing in their burrows. This means both animals have a mutually beneficial relationship. In fact, animals from at least eight different animal groups associate with echiuran burrows or rock-inhabiting echiurans — and this is probably an underestimate.

Two phallic worms on the sand
There are an estimated 236 species of penis worm. Rogerl Josh/iNaturalist, CC BY-NC

They’re beneficial for humans, too. Their burrowing and feeding habits aerate and rework sediments. Off the Californian coastline, for example, scientists noted how these activities reduced the impacts of wastewater on the seabed.

And they’re an important part of the such as the houndsharks, and species of commercial significance such as Alaskan plaice. Some mammals feast on them, too, such as the in the Bering Sea, and the southern sea otter. In Queensland they also contribute to the diet of the critically endangered eastern curlew.

And many people eat them in East and Southeast Asia, where they’re chopped up and eaten raw, or used as a fermented product called gaebul-jeot. They (allegedly) taste slightly salty with sweet undertones.

A southern sea otter snacking on a penis worm. Shutterstock

The unloved billions

In Australia there is very little known about the biology and ecological roles of our echiuran fauna. This can also be said of many of Australia’s soft sediment marine invertebrates — the unloved billions.

We simply do not understand the population dynamics of even the large and relatively common echiuran species, and the human processes that threaten them. Given their role as ecosystem engineers, impacts to echiuran populations can flow on to other components of the seabed fauna, imperilling entire ecosystems.

A blue penis worm
Not all species are a fleshy pink colour. Wayne Martin/iNaturalist, CC BY-NC

We can, in general terms, predict that populations have suffered from the cumulative effects of urbanisation and coastal development. This includes loss and modification of habitats, and changes to water quality.

Populations may also be harmed by undersea seismic activities used in oil and gas exploration, but this is still poorly understood. Until recently, scientists knew only of the threats seismic activity posed to the hearing of whales and dolphins. It’s becoming clearer they can also affect the planet’s vital invertebrate species.

You may have spotted penis worms along the seashore. Shutterstock

It is a dilemma for marine conservation when so little is known about a species that impacts cannot be reliably predicted, and where there is little or no impetus to improve this knowledge base.

We cannot simply presume an animal does not play an important role in an ecosystem because it lacks charisma.

In George Orwell’s novel Animal Farm, it was said “All animals are equal but some animals are more equal than others”. This remains abundantly true in terms of how humans view animals. But we must move away from this philosophy if we are to conserve and restore the planet’s fragile ecosystems.

Daryl McPhee, Associate Professor of Environmental Science, Bond University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

August 18 2021

Snorkelers discover rare, giant 400-year-old coral – one of the oldest on the Great Barrier Reef

Richard Woodgett
Adam Smith, James Cook University; Nathan Cook, James Cook University, and Vicki Saylor, Indigenous Knowledge

Snorkellers on the Great Barrier Reef have discovered a huge coral more than 400 years old which is thought to have survived 80 major cyclones, numerous coral bleaching events and centuries of exposure to other threats. We describe the discovery in research published today.

Our team surveyed the hemispherical structure, which comprises small marine animals and calcium carbonate, and found it’s the Great Barrier Reef’s widest coral, and one of the oldest.

It was discovered off the coast of Goolboodi (Orpheus Island), part of Queensland’s Palm Island Group. Traditional custodians of the region, the Manbarra people, have called the structure Muga dhambi, meaning “big coral”.

For now, Muga dhambi is in relatively good health. But climate change, declining water quality and other threats are taking a toll on the Great Barrier Reef. Scientists, Traditional Owners and others must keep a close eye on this remarkable, resilient structure to ensure it is preserved for future generations.

coral and snorkellers
Muga dhambi is the widest coral structure recorded on the Great Barrier Reef. Richard Woodgett

Far older than European settlement

Muga dhambi is located in a relatively remote, rarely visited and highly protected marine area. It was found during citizen science research in March this year, on a reef slope not far from shore.

We conducted a literature review and consulted other scientists to compare the size, age and health of the structure with others in the Great Barrier Reef and internationally.

We measured the structure at 5.3 metres tall and 10.4 metres wide. This makes it 2.4 metres wider than the widest Great Barrier Reef coral previously measured by scientists.

Muga dhambi is of the coral genus Porites and is one of a large group of corals known as “massive Porites”. It’s brown to cream in colour and made of small, stony polyps.

These polyps secrete layers of calcium carbonate beneath their bodies as they grow, forming the foundations upon which reefs are built.

Muga dhambi’s height suggests it is aged between 421 and 438 years old – far pre-dating European exploration and settlement of Australia. We made this calculation based on rock coral growth rates and annual sea surface temperatures.

The Australian Institute of Marine Science has investigated more than 328 colonies of massive Porites corals along the Great Barrier Reef and has aged the oldest at 436 years. The institute has not investigated the age of Muga dhambi, however the structure is probably one of the oldest on the Great Barrier Reef.

Other comparatively large massive Porites have previously been found throughout the Pacific. One exceptionally large colony in American Samoa measured 17m × 12m. Large Porites have also been found near Taiwan and Japan.

Mountainous island and blue sea
Muga dhambi was discovered in waters off Goolboodi (Orpheus Island). Shutterstock

Resilient, but under threat

We reviewed environmental events over the past 450 years and found Muga dhambi is unusually resilient. It has survived up to 80 major cyclones, numerous coral bleaching events and centuries of exposure to invasive species, low tides and human activity.

About 70% of Muga dhambi consisted of live coral, but the remaining 30% was dead. This section, at the top of the structure, was covered with green boring sponge, turf algae and green algae.

Coral tissue can die from exposure to sun at low tides or warm water. Dead coral can be quickly colonised by opportunistic, fast growing organisms, as is the case with Muga dhambi.

Green boring sponge invades and excavates corals. The sponge’s advances will likely continue to compromise the structure’s size and health.

We found marine debris at the base of Muga dhambi, comprising rope and three concrete blocks. Such debris is a threat to the marine environment and species such as corals.

We found no evidence of disease or coral bleaching.


to come
The structure may be compromised by the advance of a sponge species across Muga dhambi (sponge is the darker half in this image). Richard Woodgett

‘Old man’ of the sea

A Traditional Owner from outside the region took part in our citizen science training which included surveys of corals, invertebrates and fish. We also consulted the Manbarra Traditional Owners about and an appropriate cultural name for the structure.

Before recommending Muga dhambi, the names the Traditional Owners considered included:

  • Muga (big)
  • Wanga (home)
  • Muugar (coral reef)
  • Dhambi (coral)
  • Anki/Gurgu (old)
  • Gulula (old man)
  • Gurgurbu (old person).

Indigenous languages are an integral part of Indigenous culture, spirituality, and connection to country. Traditional Owners suggested calling the structure Muga dhambi would communicate traditional knowledge, language and culture to other Indigenous people, tourists, scientists and students.


coral rock under water with sky
It’s hoped the name Muga dhambi will encourage recognition of the connection Indigenous people have to the coral structure. Richard Woodgett

A wonder for all generations

No database exists for significant corals in Australia or globally. Cataloguing the location of massive and long-lived corals can be benefits.

For example from a scientific perspective, it can allow analyses which can help understand century-scale changes in ocean events and can be used to verify climate models. Social and economic benefits can include diving tourism and citizen science, as well as engaging with Indigenous culture and stewardship.

However, cataloguing the location of massive corals could lead to them being damaged by anchoring, research and pollution from visiting boats.

Looking to the future, there is real concern for all corals in the Great Barrier Reef due to threats such as climate change, declining water quality, overfishing and coastal development. We recommend monitoring of Muga dhambi in case restoration is needed in future.

We hope our research will mean current and future generations care for this wonder of nature, and respect the connections of Manbarra Traditional Owners to their Sea Country.


The Conversation

Adam Smith, Adjunct Associate Professor, James Cook University; Nathan Cook, Marine Scientist , James Cook University, and Vicki Saylor, Manbarra Traditional Owner, Indigenous Knowledge

August 20 2021

This article is republished from The Conversation under a Creative Commons license.

Juvenile sea turtles ingest hundreds of plastic pieces in Australian waters

Juvenile green sea turtle. Credit: M. Turner
Juvenile green sea turtle. Credit: M. Turner

“Post-hatchling turtles have adapted to enter the oceanic zone (for green, loggerhead, hawksbill, and olive ridley turtles) or shallow coastal waters (flatback turtles) where they feed opportunistically on a range of organisms. “Normally, these habitats are ideal for their development, but the rapid introduction of plastic debris among their natural food items has made the environments risky.”

Plastic ingestion can cause sea turtles to die from laceration or obstruction of the gastrointestinal tract, as well as malnutrition and chemical contamination.

The study also found plastic in the turtles of Eastern Australia waters was mostly hard fragments likely from a range of consumable products, while Indian Ocean plastics were mostly fibres – possibly from fishing ropes or nets.

Aug 6 2021

Adapted from: https://www.tropicnow.com.au/2021/august/2/jcu-finds-baby-sea-turtles-ingesting-hundreds-of-plastic-pieces-in-australian-waters

Read the original study here: https://www.frontiersin.org/articles/10.3389/fmars.2021.699521/full

Australia’s marine industry value jumps by 28% over two years

Australia’s marine industry contributes more than $80 billion annually to the national economy according to a report released today. The AIMS Index of Marine Industry is a biannual update of the value the marine sector provides to Australia’s wealth by Deloitte Access Economics, commissioned by AIMS. Assistant Minister for Forestry and Fisheries and for Industry Development Senator Jonathon Duniam, who released the report, said Australia’s marine industry was one of the most important, vital and fastest-growing parts of the Australian economy. “The value of Australia’s marine industry increased by more than a quarter between 2015-16 and 2017-18 and has seen a four-fold increase over the past two decades,” he said.

“To put it in perspective, our $81.2 billion blue economy produced more than the agricultural sector ($58.9 billion), coal mining ($69.7 billion) and heavy and civil engineering construction ($68.5 billion) in 2017-18.

“This isn’t surprising if you consider that more than 85% of our population is concentrated near the coast and more than 70% of Australia’s territory lies beneath the ocean.”

Gas, shipbuilding and tourism driving growth

 

 The report found that the total income of the marine industry increased substantially in the two years (by almost 28%), driven by growth in offshore natural gas production (up 79%), shipbuilding and repair (up 57%), and marine tourism (up 11%). Other marine-based activities include, transport, aquaculture and fishing, with the whole marine sector employing nearly 340,000 full time workers.

Chief Executive Officer Dr Paul Hardisty said AIMS’ scientific research contributed to the sustainable productivity of many of marine industries while protecting our oceans. “Marine-based industries build economic value, create employment, and improve people’s livelihoods,” he said.  “AIMS is here to help ensure that this occurs in a way that also preserves and protects our unique marine ecosystems now and in the future.” The report, now in its eighth edition, includes breakdowns of key marine industry sub-sectors by state or territory for the first time. The report acknowledges the COVID-19 pandemic brought unprecedented disruption to the Australian economy which will be measured by the next index due to be published in 2022.

The AIMS Index of Marine Industry is a biannual economic update of Australia’s marine sector. The 2020 edition uses the latest data from 2017–18.

From www.aims.gov.au, 

July 2 2021

 

Turning the tables – how table corals are regenerating reefs decades faster than any other coral types

New research out today shows the Great Barrier Reef’s iconic table corals can regenerate coral reef habitats 14 times higher – that’s more than two decades faster – than any other coral type.

Table corals have been dubbed as “extraordinary ecosystem engineers” – with new research showing these unique corals can regenerate coral reef habitats on the Great Barrier Reef faster than any other coral type. The new study highlights the importance of tabular Acropora, and is led by the Australian Institute of Marine Science (AIMS) in collaboration with the Great Barrier Reef Marine Park Authority, the University of Queensland and The Nature Conservancy. AIMS scientist and lead author Dr Juan Carlos Ortiz said the research showed overall reef recovery would slow considerably if table corals declined or disappeared on the Great Barrier Reef. “Table corals are incredibly fast growing. Habitats in exposed reef slopes recover from disturbances at a rate 14 times higher – that’s more than two decades faster – when table corals are abundant,” he said.  “Their large, flat plate-like shape provides vital protection for large fish in shallow reef areas and serves as a shelter for small fishes, with some species almost entirely dependent on table corals. “Even after death these corals provide value, as their skeletons are the preferred place for young corals of all types to settle.” Table corals, also known as plate corals, are mostly found in upper reef slopes exposed to wave action, at most mid-shelf and offshore reefs in the Great Barrier Reef. The study found table corals to have unique combination of characteristics: they provided valuable ecological functions, are among the most sensitive coral types and, most importantly, their role was threatened by a low diversity of species which have this growth form. The authors suggest protecting table corals could be an additional management focus. Targeting management to a particular coral type based on its ecosystem function — rather than their risk of extinction alone — would be ground-breaking in terms of ecosystem-based management. 

Great Barrier Reef Marine Park Authority’s Assistant Director and study co-author Dr Rachel Pears said table corals were fast growing and sensitive species. “Table corals are still frequently seen on outer reefs, but their presence shouldn’t be taken for granted as they are vulnerable to combined impacts,” she said. “These corals do not handle intensifying thermal stress well, are easily killed by anchor damage, highly susceptible to diseases, and are the preferred meal for crown-of-thorns starfish. “The good news is there are tangible actions we can take to protect these corals such as targeted crown-of-thorns starfish control and anchoring restrictions.”  University of Queensland’s scientist and study co-author Professor Peter Mumby said while table corals promoted high rates of recovery, they did not necessarily bring high biodiversity.  “We know table corals do a big service for these reefs, but it’s not a silver bullet for recovery,” he said.  “Protecting table corals could be part of a suite of actions that look at reef recovery, with other management focused more specifically on protecting biodiversity.”  

Professor Mumby said it was also important to remember the biggest threat to the reef was climate change, and effective global action to reduce emissions significantly was paramount to protecting coral reefs. The research drew on decades of data from AIMS long term monitoring program, revealing coral reef habitats took up to 32 years to recover, from 5% coral cover to 30% coral cover, where table corals had not recolonised after disturbances. These low recovery rates were in stark contrast to reefs where table corals returned and recolonised, with these habitats recovering to 30% coral cover in just seven and a half years.  

Given their extraordinary ecosystem function, the research indicated table corals should also be considered in restoration initiatives, like coral enhancement or assisted colonisation. “Anyone who has been on the mid-shelf or offshore areas of the Great Barrier Reef would have seen table corals,” Dr Ortiz said. “We can think of table corals as the iconic charismatic ‘mega coral’ of the Great Barrier Reef, just like whales, turtles and dolphins are the Reef’s iconic charismatic megafauna.”  The study, titled Important ecosystem function, low redundancy and high vulnerability: the trifecta argument for protecting the Great Barrier Reef’s tabular Acropora, was published in Conservation Letters.  

2 June 2021

From www.aims.gov.au, 

https://www.aims.gov.au/news-and-media/turning-tables-how-table-corals-are-regenerating-reefs-decades-faster-any-other-coral-type

Can we use bio-fouling organisms to help extract energy from waves?

People living near the coast are familiar with the power of ocean waves. What we see when a typical wave breaks on a beach is the endpoint of a global energy conversion story. It starts with the sun’s heat driving winds whose energy generates ocean waves which grow and often travel thousands of kilometres. In this way, the ocean collects an enormous amount of energy. There’s enough energy in waves coming ashore that every metre of coastline could power around five average homes, and much more during storms. Capturing this energy is not a new idea, but one that faces many challenges. Our research illustrates the potential of enlisting biology in a reversal of the typical marine engineering view that “bio-fouling is bad”. Instead, it looks possible to use the added drag generated by allowing marine organisms to grow on a “naked” wave energy extractor.

Decarbonising energy generation

The continuing interest in innovations in wave power is because most economies now have targets to reduce greenhouse gas emissions over the coming decades. New Zealand has promised to reduce net emissions of all greenhouse gases (except methane from livestock) to zero by 2050. Clearly better energy efficiency is paramount. There is no point investing in clean energy supply and then wasting it, because no form of energy generation is without impact. Solar and wind power are the fastest growing forms of renewable supply globally, but this puts increasing pressure on valuable land. And during times of high demand, the variability of optimal wind and solar conditions is a challenge.

With two thirds of our planet covered in seawater, capturing the energy embodied within ocean waves and tides makes a lot of sense. While some tidal energy technology is now commercially viable, wave energy is following a more convoluted trajectory, with many options for how the conversion actually happens.

New Zealand excels in marine innovation in extreme yachting and aquaculture, but there is almost no maritime engineering focused on marine energy generation, despite having an exclusive economic zone 15 times larger in area than the country’s landmass.

Untapped wave energy

Regardless of the design, wave energy converters are vulnerable to damage in inevitable storms. Despite this challenge, current technologies like the Wello Penguin are getting close to being able to produce energy at a cost comparable with other renewable energy generation methods. What has really pushed the marine renewable energy field forward in the last decade has been the growth of offshore fixed-foundation wind farms. This has been a game changer as it socialised the marine setting and, through scale, increased the economic viability of the supply chain. It is common to look to nature to help in environmental design. Energy converter designs are often inspired by nature, with ideas ranging from nodding ducks to sea snakes. Some designs get more serious in how they use biomimicry. Our research explores a hybrid solution, combining physics and biology, as a pathway for future marine energy. The Bio-Oscillator looks at how species like large macroalgae and mussels could be integrated into the submerged structure of a wave-power generator. This is possible because parts of the structure are required only to add drag and inertia and experience only relatively little motion during operation.

Using local species of algae or mussels has several benefits. They grow and regenerate naturally and, importantly, will have only limited impact if they are damaged during storms. It is also common to look at ways to connect renewable energy sources to existing ocean infrastructure such as navigation buoys or aquaculture farms. Approaches like the Bio-Oscillator could generate both a harvestable crop of shellfish or macroalgae – as well as producing renewable energy. The United Nations decade of ocean science for sustainable development is a perfect setting for exploring the many opportunities that now exist to reduce energy emissions and, in doing so, head off the forecast threats caused by our present way of living.

June 7 2021

First published https://www.miragenews.com/can-we-use-bio-fouling-organisms-to-help-572463/

Southern reefs survive the hot summer of 2020

Under the right conditions, corals can recover from bleaching events. This is the case for multiple reefs in the southern Great Barrier Reef, which avoided wide-spread mortality from the 2020 mass coral bleaching event. These reefs escaped prolonged heat stress and did not have ongoing impacts from crown-of-thorns starfish – giving the corals a chance to bounce back from bleaching. Australian Institute of Marine Science’s (AIMS) monitoring program team leader Dr Mike Emslie said the six reefs, spanning offshore between Shoalwater Bay and Agnes Waters, were observed closely by scientists because of their specific disturbance history. “These reefs were the perfect candidates for our team to observe their recovery, the corals were not severely bleached and did not have extra stress from the coral eating starfish,” he said. “What is often misunderstood is corals do not immediately die from bleaching – bleaching is a stress response, and they can recover if given the opportunity. 

AIMS diver doing a bleaching survey. Copyright AIMS,, CCBY.
AIMS diver doing a bleaching survey. Copyright AIMS, CCBY.

“Our preliminary results show these reefs appear to have had little impact from the 2020 mass coral bleaching, with  an increase of hard coral cover at most reefs. “This increase is what we predict in the absence of disturbance. The reefs were given the opportunity to recover because 75% of southern reefs were not exposed to sustained temperatures expected to cause mortality and were also free the from the additional stressors of crown-of-thorns starfish.” Research Program Director Dr Britta Schaffelke said disturbances, such as crown-of-thorns starfish, can be significant in hindering the recovery process of reefs following bleaching events. “AIMS scientists lead world-class research in this effort to understand cumulative impacts on coral reefs,” she said. While the 2019-2020 mass coral bleaching event was the third event in five years, it was the first time such  widespread bleaching has occurred in the southern region. “These results are encouraging for the southern region –  but we are still in the water conducting surveys all along   the Great Barrier Reef to understand the full impact of the 2020 mass bleaching event, and indeed other disturbances, for both coral mortality and recovery,” said Dr Emslie.

 

AIMS’ Long-Term Monitoring Program has measured the condition of reefs more than 30 years, spreading over 490 reefs within the Great Barrier Reef Marine Park. AIMS’ Annual Summary Report on coral reef condition for 2019/20 is drawn from surveys undertaken between September 2019 and June 2020.

From www.aims.gov.au, 

2 March 2021

AI to ‘go fish’

Artificial intelligence may soon be counting and classifying Australia’s tropical fish populations if at least one of the four Australian technology businesses to receive Australian Government seed funding is successful. The four small to medium-sized businesses are sharing funding of almost $400,000 from the latest round of the Department of Industry, Science, Energy and Resources’ Business Research and Innovation Initiative. The businesses will use the funding to address a challenge set by the Australian Institute of Marine Science (AIMS). 

 

They will each run a project to scope the feasibility of creating an innovative solution to analyse fish video survey data, harnessing advanced technologies such as machine learning and artificial intelligence.

Currently, AIMS uses Baited Remote Underwater Video Stations (BRUVS) to capture footage of fish populations to better understand reef health. The method can give estimates of the fish species present, their numbers, sizes and biomass which provide critical indicators of the health of the fish community, but it has a drawback. This BRUVS footage, which can capture up to 70 different species per video, is manually analysed by an experienced researcher – a labour-intensive and time-consuming task which limits the ability to scale-up data collection.

 

The challenge is to develop technology that can learn to identify different species, count them, and measure fish length, quickly and efficiently delivering critical information about fish communities, removing the potential for observer bias. The solution needs to be easy enough for a non-technical user to operate – such as citizen scientists and Indigenous and local communities – which would lead to a significant scaling up of the data collected in Australia and beyond. It could also provide opportunities to expand the monitoring other marine life including sharks, rays and sea snakes. AIMS Technology Development Engineering Team Leader Melanie Olsen said it was AIMS’ first BRII Challenge and they were delighted with the strong interest it attracted and the large number of high-quality applications. The four companies (Tekno (GAIA Resources), Mapizy, Silverpond and Harrier Project Management) will be competing to produce the most compelling feasibility study. The top two solutions will then each be eligible for a grant of up to $1 million to work with AIMS to develop a prototype.

 

“We look forward to working closely with these technology innovators to develop a solution that could potentially revolutionise the way diverse fish populations are monitored, not only in Australia, but across the world,” Ms Olsen said. “This is another example of the way we work with industry to apply new technologies, such as AI, to the problems our ecologists are facing and to expand our capabilities and the services we can deliver to the Australian public.” 

From AIMS first published: https://www.aims.gov.au/news-and-media/ai-go-fish, 

8 February 2021

West coast reefs warming up

Scientists are keeping a close eye on reefs along the west coast of Australia, with sea surface temperatures reaching levels where some coral bleaching is occurring. The thermal stress has been accumulating over the high-risk summer period and is expected to continue until April, according to forecasts from the Bureau of Meteorology (BoM). 

Australian Institute of Marine Science’s (AIMS) coral ecologist Dr James Gilmour said the areas of concern include reefs in the Pilbara, Ningaloo, Shark Bay and the Abrolhos. “Low level bleaching has already been observed in parts of Exmouth Gulf and in the Dampier Archipelago, which were reported by officers from the Department of Biodiversity Conservation and Attractions (DBCA),” he said.

 

 “While cloud cover and rainfall from a recent tropical low has reduced some heat stress, the risk of bleaching will continue in the coming weeks in central to southern Western Australian reefs.” The recurring threat of bleaching to WA coral reefs has galvanised collaborative efforts across government and research institutions, drawing on the most current observations and forecasts based on data provided by BoM, National Oceanic and Atmospheric Administration (NOAA), CSIRO, the Integrated Marine Observing System (IMOS) and the University of Western Australia (UWA).

“In the coming weeks, we’ll have many eyes on the reef to report coral bleaching and in-water surveys will be conducted by several research agencies, including AIMS, DBCA and CSIRO,” Dr Gilmour said. “This week we are conducting in-water surveys around Ningaloo – this monitoring will extend to other reefs at risk in the coming weeks.

 

“We are encouraging people who are visiting these reefs to download our app ArcGIS Collector and report any sightings of coral bleaching.” Currently, on the other side of Australia, temperatures are below bleaching thresholds for the most part of the Great Barrier Reef. The 2020-2021 summer has been characterised by a La Niña event, which is forecasted by BoM to last until Autumn. This climate driver has meant above average rainfall has been likely for eastern and some northern parts of Australia, meaning a lower risk of bleaching in the Kimberley and the Great Barrier Reef.

From www.aims.gov.au

First published: https://www.aims.gov.au/news-and-media/west-coast-reefs-warming, 

16 February 2021 

Octogenarian snapper found in WA becomes oldest tropical reef fish by two decades

An 81-year-old midnight snapper caught off the coast of Western Australia has taken the title of the oldest tropical reef fish recorded anywhere in the world. The octogenarian fish was found at the Rowley Shoals—about 300km west of Broome—and was part of a study that has revised what we know about the longevity of tropical fish.

The research identified 11 individual fish that were more than 60 years old, including a 79-year-old red bass also caught at the Rowley Shoals. Australian Institute of Marine Science (AIMS) Fish Biologist Dr Brett Taylor, who led the study, said the midnight snapper beat the previous record holder by two decades. “Until now, the oldest fish that we’ve found in shallow, tropical waters have been around 60 years old,” he said. “We've identified two different species here that are becoming octogenarians, and probably older.”

 

Dr Taylor said the research will help us understand how fish length and age will be affected by climate change.

“We’re observing fish at different latitudes—with varying water temperatures—to better understand how they might react when temperatures warm everywhere,” he said. The study involved four locations along the WA coast, as well as the protected Chagos Archipelago in the central Indian Ocean. It looked at three species that are not targeted by fishing in WA; the red bass (Lutjanus bohar), midnight snapper (Macolor macularis), and black and white snapper (Macolor niger). Co-author Dr Stephen Newman, from the WA Department of Primary Industries and Regional Development, said long-lived fish were generally considered more vulnerable to fishing pressure.

 

“Snappers make up a large component of commercial fisheries in tropical Australia and they’re also a key target for recreational fishers,” he said. “So, it’s important that we manage them well, and WA’s fisheries are among the best managed fisheries in the world.” Marine scientists are able to accurately determine the age of a fish by studying their ear bones, or ‘otoliths’. Fish otoliths contain annual growth bands that can be counted in much the same way as tree rings. Dr Taylor said the oldest red bass was born during World War I.

“It survived the Great Depression and World War II,” he said. “It saw the Beatles take over the world, and it was collected in a fisheries survey after Nirvana came and went.” “It’s just incredible for a fish to live on a coral reef for 80 years.”

 

The research is published in the journal Coral Reefs.

 

Funding was provided by the Bertarelli Foundation and contributed to the Bertarelli Programme in Marine Science.

1 December 2020

Squid-inspired robot swims with nature’s most efficient marine animals

Scientists at the University of Southampton and University of Edinburgh have developed a flexible underwater robot that can propel itself through water in the same style as nature’s most efficient swimmer – the Aurelia aurita jellyfish.

The findings, published in Science Robotics, demonstrate that the new underwater robot can swim as quickly and efficiently as the squid and jellyfish which inspired its design, potentially unlocking new possibilities for underwater exploration with its lightweight design and soft exterior.

Co-author Dr Francesco Giorgio-Serchi, Lecturer and Chancellor’s Fellow, at the School of Engineering, University of Edinburgh, said: “The fascination for organisms such as squid, jellyfish and octopuses has been growing enormously because they are quite unique in that their lack of supportive skeletal structure does not prevent them from outstanding feats of swimming.” The “cost of transport” (the ration of power to speed and weight) is used to compare efficiencies of species across biology, and by this measure the jellyfish is the most efficient animal in nature, easily beating running and flying animals and bony fish. The new robot was developed at the University of Southampton and is the first submersible to demonstrate the benefits of using resonance for underwater propulsion. Resonance refers to large vibrations that occur when applying a force at the ideal frequency, like pushing a child on a swing. This allows the robot to use very little power but generate large water jets to push itself forward. The simple but effective mechanism used consists of a rubber membrane enclosing eight 3D-printed flexible ribs, which together form a ‘propulsive bell’. A small piston in the top half of the robot taps this bell repeatedly so that it expands and then springs back. This mimics a jellyfish’s swimming technique and produced the jets of fluid to propel the robot through the water. When the piston operates at with the correct frequency – the natural resonance for the components – the robot can move at one body length per second and match the efficiency of the Aurella aurita jellyfish.

The latest tests show the new robot is ten to fifty times more efficient than typical small underwater vehicles powered by propellers. This increased efficiency, combined with the additional benefits of the robot’s soft, flexible exterior would make it ideal for operating near sensitive environments such as a coral reef, archaeological sites, or even in waters crowded with swimmers. Co-author Thierry Bujard, a Masters student in Naval Architecture at the University of Southampton, designed and built the robot in a matter of months. Thierry said, “Previous attempts to propel underwater robots with jetting systems have involved pushing water through a rigid tube but we wanted to take it further so we brought in elasticity and resonance to mimic biology. I was really surprised by the results, I was confident that the design would work but the efficiency of the robot was much greater than I expected.” Dr Gabriel Weymouth, Associate Professor in the University’s School of Engineering, who supervised the project added, “The great thing about using resonance is that we can achieve large vibrations of the propulsive bell with a very small amount of power; we just need to poke it out of shape and let the elasticity and inertia do the rest. This has allowed us to unlock the efficiency of propulsion used by sea creatures that use jets to swim.

“The last decade has seen a surge in research into flexible and biologically-inspired robots, such as Boston Dynamic’s “Big Dog”, because they can be much more versatile than standard industry robots. This research demonstrates that these concepts can also be applied to underwater robotics.

“There are still many challenges and exciting possibilities to explore with soft underwater robotic technologies. We are now looking to extend the concept behind this robot to a fully manoeuvrable and autonomous underwater vehicle capable of sensing and navigating its environment.”

 

January 21 2021

 

Original article: https://www.miragenews.com/squid-inspired-robot-swims-with-nature-s-most-efficient-marine-animals/

 

Abundant corals and fishes emerge from the ancient contours of Arafura Marine Park

Scientists have collected the first fine-scale maps and imagery of reefs and submarine canyons in the rarely visited Arafura Marine Park, revealing seafloor environments with surprisingly diverse coral and fish communities. The survey team from the Australian Institute of Marine Science (AIMS) and Geoscience Australia returned to Darwin on the weekend after a two-week voyage on RV Solander. The voyage was supported by the Australian Government’s National Environmental Science Program Marine Biodiversity Hub.

AIMS Research Program Leader, Dr Karen Miller, said there were vast knowledge gaps in the northern marine bio-region and this new knowledge would enable Australia to better understand and protect the universal value of the environment. “Information from this research voyage will provide critical baseline data to guide the management and protection of the Arafura Marine Park and sea country,” Dr Miller said. “This in turn will contribute to sustainable economic opportunities, and provide for the enjoyment and benefit of this special environment for current and future generations.”

Survey locations in the Arafura Marine Park. Credit: Geoscience Australia
Survey locations in the Arafura Marine Park. Credit: Geoscience Australia

The survey focused on deep and shallow pockets of reef amid the park’s sediment plains. These reefs are where invertebrates such as sponges and corals can attach and form habitat for other marine life. In the north of the park, at the outer edge of Australia’s continental shelf, the scientists visited Pillar Bank, part of an ancient river system that began its transformation to ocean some 14,000 years ago. In the shallow, southern area of the park, they visited Money Shoal, some 200 km north-east of Darwin. Both areas were mapped in detail using multibeam sonar, covering a total area of 350 square kilometres. Guided by the new maps, scientists stationed baited cameras on the seafloor, towed a video camera behind the ship, and sampled the sediments to build inventories of marine life.

A 3D bathymetry map of Money Shoal in Arafura Marine Park. Credit: Geoscience Australia
A 3D bathymetry map of Money Shoal in Arafura Marine Park. Credit: Geoscience Australia

The survey focused on deep and shallow pockets of reef amid the park’s sediment plains. These reefs are where invertebrates such as sponges and corals can attach and form habitat for other marine life.

In the north of the park, at the outer edge of Australia’s continental shelf, the scientists visited Pillar Bank, part of an ancient river system that began its transformation to ocean some 14,000 years ago. In the shallow, southern area of the park, they visited Money Shoal, some 200 km north-east of Darwin.

Both areas were mapped in detail using multibeam sonar, covering a total area of 350 square kilometres. Guided by the new maps, scientists stationed baited cameras on the seafloor, towed a video camera behind the ship, and sampled the sediments to build inventories of marine life.

First published at: https://www.aims.gov.au/news-and-media/abundant-corals-and-fishes-emerge-ancient-contours-arafura-marine-park © 1996-2019 Australian Institute of Marine Science

17 November 2020

Biggest fish in the sea are girls

Female whale sharks grow more slowly than males but end up being larger, research suggests.

A decade-long study of the iconic fish has found male whale sharks grow quickly, before plateauing at an average adult length of about eight or nine metres. Female whale sharks grow more slowly but eventually overtake the males, reaching an average adult length of about 14 metres.

 

Australian Institute of Marine Science fish biologist Dr Mark Meekan, who led the research, said whale sharks have been reported up to 18 metres long. “That’s absolutely huge—about the size of a bendy bus on a city street,” he said. “But even though they’re big, they’re growing very, very slowly. It’s only about 20cm or 30cm a year.” In conducting the research, scientists visited Western Australia’s Ningaloo Reef for 11 seasons between 2009 and 2019. They tracked 54 whale sharks as they grew—a feat made possible by a unique ‘fingerprint’ of spots on each whale shark that can be used to identify individual fish. AIMS marine scientist Dr Brett Taylor said the team recorded more than 1000 whale shark measurements using stereo-video cameras.

“It’s basically two cameras set up on a frame that you push along when you’re underwater,” he said.

“It works the same way our eyes do—so you can calibrate the two video recordings and get a very accurate measurement of the shark.”

AIMS' Dr Mark Meekan measures the length of a whale shark using a stereovideo camera. Photo: Andre Rerekura

 

The study also included data from whale sharks in aquaria. Dr Meekan said it is the first evidence that males and female whale sharks grow differently. For the females, there are huge advantages to being big, he said.

“Only one pregnant whale shark had ever been found, and she had 300 young inside her,” Dr Meekan said.

“That’s a remarkable number, most sharks would only have somewhere between two and a dozen. “So these giant females are probably getting big because of the need to carry a whole lot of pups.” Whale sharks are Western Australia’s marine emblem, and swimming with the iconic fish at Ningaloo Reef boosts the local economy to the tune of $24 million a year. But they were listed as endangered in 2016. Dr Meekan said the discovery has huge implications for conservation, with whale sharks threatened by targeted fishing and ships strikes.

 

“If you’re a very slow-growing animal and it takes you 30 years or more to get to maturity, the chances of disaster striking before you get a chance to breed is probably quite high,” he said. “And that’s a real worry for whale sharks.” Dr Meekan said the finding also explains why gatherings of whale sharks in tropical regions are made up almost entirely of young males. “They gather to exploit an abundance of food so they can maintain their fast growth rates,” he said. Dr Taylor said learning that whale sharks plateau in their growth goes against everything scientists previously thought. “This paper has really re-written what we know about whale shark growth,” he said. Dr Meekan and Dr Taylor are based in Perth, Western Australia. The research was published today in the journal Frontiers in Marine Science.

Feature image: Andre Rerekura

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16 September 2020

Mystery pufferfish circles discovered in Australia's north-west

Mystery circles providing evidence of a potential new species of pufferfish have been discovered in Australia’s north-west by researchers at The University of Western Australia and Australian Institute of Marine Science.

The research, published in the Journal of Fish Biology, placed the discovery at more than 5500km away from the only other similarly described structures off Amami-Oshima Island in southern Japan. The discovery was made on the North West Shelf of Western Australia when 22 mystery circles were spotted on video footage collected by Fugro during an inspection of the Echo Yodel subsea infrastructure – operated by Woodside on behalf of the North West Shelf Project participants – and while surveying fish along the ancient coastline.  

The circles, which are the first to be found in Australia, were recognised by the researchers as the complex underwater structures created by the white-spotted pufferfish previously thought to be found only in southern Japan.

 

Most notably the size, number of ridges and presence of an intricate central circle with two outer rings makes them comparable to those found in Japanese waters. Originally found at depths of less than 30m in Japan, the finding in the north-west extends their depth occurrence to 137m. Sightings of pufferfish were captured in the immediate vicinity of the circles, near the subsea infrastructure, from Woodside footage using a remotely operated vehicle and an autonomous underwater vehicle, although further investigation was needed to classify the species. 

 

Lead author Todd Bond from UWA’s Oceans Institute and School of Biological Sciences said the discovery of the unique circle structures were most likely produced by a male pufferfish species to use as a nest.

“The pufferfish species responsible cannot be identified from the images collected but it is possibly a new species,” Mr Bond said. “Not only does this discovery spark intrigue and wonder among scientists and the general public, it also provides an insight into the reproductive behaviour and evolution of pufferfish globally.”

Matthew Birt from AIMS said the discovery showed the importance of working alongside industry to uncover the wealth of information so far undiscovered.  “Industry routinely conduct video surveys of their assets which are often located in deep and remote waters,” Mr Birt said. “So it’s great that operators of oil and gas infrastructure share their video imagery to build on our existing scientific knowledge. “We can now focus on mapping the distribution of these elaborate pufferfish structures and plan scientific expeditions to collect biological samples so that we can identify and classify the fish.”

First published at https://www.aims.gov.au/news-and-media/mystery-pufferfish-circles-discovered-australias-north-west

 17 September 2020

 

Aerial surveys can keep swimmers and sharks safe

A new study has found that drones have the potential to contribute to effective shark bite management strategies that do not require culling sharks or killing other animals as by-catch. This new study from Southern Cross University looks at “developing the use of drones for non-destructive shark management and beach safety.” The study’s author Dr Andrew Colefax has used drones fitted with artificial intelligence technology to track more than 100 great white sharks along the coast of New South Wales.

 

In his report, he says there is an increasing need to address human-wildlife conflict in ways that support conservation. However, with current approaches, this balance is seldom achieved. “Shark bites are a well-known human-wildlife conflict, which has presented many management challenges. White (Carcharodon carcarius), bull (Carcharhinus leucas) and tiger (Galeocerdo cuvier) sharks are responsible for the majority of shark bite incidents, both in Australia and globally. Traditionally, addressing perceptions of shark bite risk from these species involved lethal approaches (e.g. mesh nets and drumlines). However, social attitudes are changing towards having greater conservation sentiment, and the cost to wildlife of lethal strategies is increasingly criticised. Therefore, there is widely acknowledged need for a reliable alternative to mitigating shark bites that does not impact marine wildlife. Drones (unmanned aerial vehicles) may contribute to a solution that reduces shark bite risk to a socially acceptable level." 

 

According to the study, overall, drones have potential to contribute to effective shark bite management strategies that do not require culling sharks or impacting bycatch species commonly affected by lethal strategies, and due to the rapidly advancing development of drone-related technologies, the utility of drones for reducing the risk of shark bites can be further improved upon. Read the full study.

 

It’s vital that we ensure the safety of beachgoers as well as protect sharks and their key role in ocean health.

 

First published: https://www.seashepherd.org.au/latest-news/drones-sharks-study/

 

15 September 2020

First ever global survey of reef sharks reveals widespread decline

A landmark new study published today in Nature by Global FinPrint reveals sharks are virtually absent on many of the world’s coral reefs. Sharks were not observed on nearly 20 percent of the 371 reefs surveyed in 58 countries, indicating a widespread decline that has largely gone undocumented until this global survey.

Fortunately, Australia is a country where shark populations on coral reefs are still largely intact. The most common shark species observed were grey reef, whitetip reef and blacktip reef sharks.

Dr Mark Meekan, from the Australian Institute of Marine Science in Perth and Principal Investigator for the Global FinPrint project in the Indian Ocean region said good management plays a key role in determining the status of reef sharks. “Our survey not only reveals the plight of sharks on coral reefs, which is in many cases very worrying, it also reveals how control of shark fishing can make effective conservation gains,” Dr Meekan said. Australia was one of several nations where the study revealed that shark conservation on coral reefs is working. Other nations include the Bahamas, the Federated States of Micronesia, French Polynesia, the Maldives, and the United States. Dr Meekan said reef sharks play an important role maintaining a healthy ecosystem. “Sharks are important for the ecology of coral reefs, particularly at a time when they are facing so many other threats from climate change. But few people realise that reef sharks are also an important part of the economies of many small island nations around the world because they are a key attraction for reef tourism. “Rebuilding shark numbers isn’t just good sense ecologically – it also makes good sense economically,” Dr Meekan said. 

AIMS scientist Dr Michelle Heupel, and Global FinPrint Principal Investigator in the Western Pacific, said this world first study relied on cooperation and collaboration of colleagues in many nations and territories across the globe. “Hundreds of scientists, researchers, and conservationists captured and analysed more than 15,000 hours of video from surveys of 371 reefs in 58 countries, states and territories around the world over four years. “We hope these findings will help countries continue to maintain shark populations or make management changes to improve their status,” she said. Funded by the Paul G. Allen Family Foundation, the Global FinPrint’s survey data were generated from baited remote underwater video systems (BRUVS) consisting of an underwater video camera attached to a bait bag containing a small amount of fish. Coral reef ecosystems were surveyed with BRUVS in four key geographic regions: The Indo-Pacific, Pacific, the Western Atlantic and the Western Indian Ocean. As well as AIMS, other coordinating organisations working on the project came from Florida International University, Curtin University, Dalhousie University, and James Cook University. 

For more information and a new global interactive data-visualized map of the Global FinPrint survey results, visit https://globalfinprint.org.

First published at: https://www.aims.gov.au/news-and-media/first-ever-global-survey-reef-sharks-reveals-widespread-decline

23 July 2020

Coral bleaching detected off Kimberley coast

Scientists have discovered a significant coral bleaching event at one of Western Australia’s healthiest coral reefs.

More than 250 kilometres west of Broome, the Rowley Shoals is one of only two reef systems in the State to have recorded high and stable coral cover throughout the past decade.

In April and May 2020, the Australian Institute of Marine Science (AIMS) and the Department of Biodiversity, Conservation and Attractions (DBCA) conducted surveys of the reef system, supported by Parks Australia and Australian Border Force, to confirm reports of significant coral bleaching.

Data obtained revealed that bleaching was variable across the Rowley Shoals, with estimates ranging between one and 30 percent of the corals bleached. One site on Clerke Reef experienced up to 60 percent of the corals bleached. Further aerial surveys of the North Kimberley and Lalang-garram marine parks found coral bleaching to be patchy and less severe than at Rowley Shoals.

Following temperature alerts issued by the Bureau of Meteorology (BOM), aerial flights by Australian Border Force provided the first evidence of coral bleaching at Western Australia’s remote coral reef atolls Image: Australian Border Force DBCA’s Marine Monitoring Coordinator Dr Thomas Holmes attributed the bleaching to an unusually warm and prolonged ocean temperature off the coast of the Kimberley. “By global standards, Western Australia still has relatively healthy reefs, but seawater temperature is increasing around the world as a result of climate change. This is causing corals to bleach and die from heat stress more frequently and at scales not previously observed,” Dr Holmes said.

The extent and severity of bleaching varied across the Rowley Shoals, ranging from 10% to over 60% bleaching at some sites. Image: Chris Tucker

 

AIMS’ coral ecologist Dr James Gilmour said that bleaching had badly affected other offshore atolls and the inshore Kimberley region in 2016/17. “Coral bleaching can devastate entire reef systems and dramatically alter associated communities of marine plants and animals,” Dr Gilmour said. “Some corals will regain their symbiotic algae and recover, while those corals that have been severely bleached are likely to die.”

 

At the worst affected sites, even the robust massive corals at 20m depth had bleached. Image: Chris Tucker

Follow up surveys as a part of DBCA and AIMS long-term monitoring programs are currently planned for later this year to determine the full effect of the event on the coral communities. The bleaching survey of Rowley Shoals was conducted as part of AIMS’ North West Shoals to Shore Research Program funded by Santos Ltd.

 

First published https://www.aims.gov.au/news-and-media/coral-bleaching-detected-kimberley-coast

14 July 2020

Coastal pollution reduces genetic diversity of corals, reef resilience

A new study published in the journal PeerJ by researchers at the University of Hawaii found that human-induced environmental stressors have a large effect on the genetic composition of coral reef populations in Hawaii.

The National Science Foundation-funded scientists confirmed that there is an ongoing loss of sensitive genotypes in nearshore coral populations due to stressors from poor land-use practices and coastal pollution. This reduced genetic diversity compromises reef resilience.

This research provides valuable information to coral reef managers in Hawaii and around the world who are developing approaches and implementation plans to enhance coral reef resilience and recovery through reef restoration and stressor reduction.

The study identified that genetic relationships between nearshore corals in Maunalua Bay, Oahu, and those from sites on West Mau were closer than relationships to corals from the same islands, but farther offshore.

This pattern can be described as isolation by environment in contrast to isolation by distance. This is an adaptive response by the corals to watershed discharges that contain sediment and pollutants from land.

“While the results were not surprising, they demonstrate the need to control local sources of stress while addressing the root causes of global climate change,” said Robert Richmond, director of the Kewalo Marine Laboratory and co-author of the study. “The findings show the need to track biodiversity at multiple levels.”

While the loss of coral colonies and species is easy to see with the naked eye, molecular tools are needed to uncover the effects of stressors on the genetic diversity within coral reef populations. “This study shows the value of applying molecular tools to ecological studies supporting coral reef management,” stated Kaho Tisthammer, lead researcher on the paper.

The work was a collaborative effort among researchers at the university’s Kewalo Marine Laboratory, Pacific Biosciences Research Center, and the Hawaii Institute of Marine Biology. “This work highlights the importance of limiting pollution, sediment, and agricultural runoff to nearshore coral reefs,” says Dan Thornhill, a program director in NSF’s Division of Ocean Sciences. “Protecting biodiversity is essential, as that diversity is needed in helping corals and other marine life adapt to changing oceans. Selecting for resilience to pollution may eliminate coral genotypes that resist disease, tolerate higher temperatures, and continue to grow in more acidic and oxygen-depleted waters.”

9 April 2020

First published: https://www.miragenews.com/coastal-pollution-reduces-genetic-diversity-of-corals-reef-resilience/

Coronavirus is killing Australia's lobster export market

Shutterstock
Eva Plaganyi, CSIRO; Nicole Murphy, CSIRO; Roy Aijun Deng, CSIRO; Sean Pascoe, CSIRO, and Trevor Hutton, CSIRO

Currents are strong around the Torres Strait Islands, lying between Australia’s northern-most tip and Papua New Guinea. When the tidal conditions are right and the waters relatively still, though, up to 230 islanders – a sizeable percentage of the islands’ roughly 4,000 indigenous inhabitants – will board small boats and head out to the surrounding reefs. There they will dive down and search the underwater outcrops for lobsters, grabbing the crustaceans by hand. It’s laborious work compared with lobster fishing in other parts of Australia, where fishers bait “pots”, then simply pull up the pots with lobsters inside. The tropical rock lobsters of the Torres Strait, however, are sensitive creatures and generally won’t crawl into a trap. By hand is the only sure way to catch them. But, until a few weeks ago, it has been worth it. A fisher can sell a live lobster from these waters for $65-95 a kilogram. That makes it worth holding them in water-filled crates and then flying them to wholesalers in Cairns. There they are processed and transported to domestic and international markets.

Tropical lobsters caught in Torres Strait. Eva Plaganyi-Lloyd, Author provided

The most lucrative market is China. Its appetite for live rock lobster makes up about half the value of Australia’s seafood exports (A$660 million of A$1.4 billion). Now, though, lobster fishers are staying home. There hasn’t been a regular lobster shipment to China since January 26. With the Wuhan coronavirus suspected to have originated from wild animals in the city’s Huanan Seafood Wholesale Market, Chinese authorities have temporarily banned all wild animal trade. Lobster and other wild-caught aquatic products are exempt from the ban, but demand has plummeted due to people staying home and avoiding both markets and restaurants.This collapse has come at a time that would normally be one of peak demand, and peak prices, due to Chinese New Year festivities. Our industry sources report prices for live lobsters are down 50% to 80%.

An advertisement for rock lobsters in the Queensland Asian Business Weekly on January 31 2020, shows drastically reduced prices, from A$258 a kilogram to A$148 a kilogram, for large lobsters. Author supplied, Author provided

It’s a huge blow to the economy of Torres Strait, along with the rest of Australia’s live seafood export industry.

Loss of livelihoods

Lobster fishing is among the highest-value economic activities in the strait. Indigenous islanders have limited alternatives to make money, given their geographical isolation. As scientists fortunate to work closely with traditional owners in the Torres Strait over the past decade, we’re saddened to see this devastating impact on livelihoods.

Author Eva Plaganyi-Lloyd with a tropical rock lobster. Eva Plaganyi-Lloyd, Author provided

CSIRO researchers have worked in the strait for more than three decades to help local people sustain their traditional way of life and conserve the marine environment for future generations. This is no easy feat, considering the resources are also shared with an Australian non-Islander sector and traditional owners from Papua New Guinea. The region’s wild marine fisheries have been thriving thanks to good management and a strong sense of custodianship by the Islanders.

CSIRO scientists doing a survey of tropical lobster numbers. These annual surveys are used with fishery data to calculate the season quotas for the fishery. CSIRO, Author provided

New harvest strategies for fishing lobster and bêche-de-mer (sea cucumbers) were implemented in December 2019. These took years of research and consultation. This included augmenting scientific surveys with information from fishers to work out sustainable catches. The new strategies followed a disastrous lobster-fishing year in 2018, when our scientific surveys suggested the lobster population was in trouble due to conditions created by extreme El Niño events. The fishery had to be closed two months early, with substantial economic impact. It was nonetheless an example of Torres Strait Islanders putting sustainability before short-term gain.

No offsets

Now they have the coronavirus to contend with. The loss of income from those in the fishing business affects other small businesses and ripples throughout the local community. Selling to the frozen seafood market is an option, but prices are much lower, and there’s a point at which the time, effort and cost of catching a tropical rock lobster make it uneconomical. Boat fuel, for one thing, is expensive. Sales of frozen seafood to China have also taken a dive. For some Australian fisheries it’s possible taking fewer fish this season will mean a larger fish population next year. So next year’s catch quotas could be adjusted up without jeopardising the marine population. This could partially offset losses this year. But that’s not an option for the Torres Strait lobster fishery. That’s because by the time a lobster is big enough to catch, usually in its third year of life, it is also ready to migrate, walking several hundred kilometres to the east of the fishery area. So catching fewer lobsters this year won’t mean they are around to catch next year. It is a unique fishery in this regard.

Planning sustainable exports

This impact of the coronavirus on Torres Strait Islanders shows how connected global trade now is. What it also demonstrates is the importance of deliberate and distributed growth in export markets for them to be sustainable. Heavy dependence on a single market carries a big risk. As things stand, we can expect demand for seafood in China will remain low for some time to come. This is an opportune time to rethink sustainable export growth strategies.The Conversation

This article is republished from The Conversation under a Creative Commons license. Read the original article.

19 February 2020

Shark nets are destructive and don’t keep you safe – let’s invest in lifeguards

New research says there is no reliable evidence that shark nets protect swimmers. Ben Rushton/AAP
Leah Gibbs, University of Wollongong; Lachlan Fetterplace, Swedish University of Agricultural Sciences, and Quentin Hanich, University of Wollongong

As Australians look forward to the summer beach season, the prospect of shark encounters may cross their minds. Shark control has been the subject of furious public debate in recent years and while some governments favour lethal methods, it is the wrong route.

Our study, published today in People and Nature, presents further evidence that lethal shark hazard management damages marine life and does not keep people safe.

We examined the world’s longest-running lethal shark management program, the New South Wales Shark Meshing (Bather Protection) Program, introduced in 1937. We argue it is time to move on from shark nets and invest further in lifeguard patrol and emergency response.

A scalloped hammerhead caught in a shark net off Palm Beach in Sydney, in March 2019. HSI-AMCS-N McLachlan

Managing shark bite

In NSW, 51 beaches between Newcastle and Wollongong are netted. The nets don’t provide an enclosure for swimmers. They are 150 metres long and suspended 500 metres offshore. In the process of catching targeted sharks they also catch other animals including turtles, rays, dolphins, and harmless sharks and fish.

Catching and killing sharks might seem a commonsense solution to the potential risk of shark bite to humans. But the story is not so simple.

A young tiger shark cruising near Coffs Harbour, NSW. EPA

Multiple factors influence shark bite incidence, including climate change, prey species distribution and abundance, water quality, human population, beach-use patterns, and lifeguard patrols.

Most research and public debate focuses on human safety or marine conservation. Our research sought to bring the two into conversation. We considered a range of factors that contribute to safety and conservation outcomes. This included catch of target and non-target species in nets, damage to marine ecosystems, global pressures on oceans, changing beach culture, human population growth and changes in lifeguarding and emergency response. Here’s what we found.

Fewer sharks, fewer bites

As the graph below shows, shark catch in the NSW netting program has fallen since the 1950s. This includes total shark numbers and numbers of three key target species: white shark (also known as great white or white pointer), tiger shark and bull shark.

Total shark catch per 100 net days 1950-2019. Authors

This suggests there are fewer sharks in the water, which is cause for alarm. The three target species are recognised by Australian and international institutions as threatened or near-threatened.

Our analysis shows shark bite incidence is also declining over the long term. The trend isn’t smooth; trends rarely are. The last two decades have seen more shark bites than the previous two. This is not surprising given Australia’s beach use has again grown rapidly in recent decades.

But if we take a longer term view, we see that shark bite incidence relative to population is substantially lower from the mid-20th century than during the decades before.

The decline in shark bite incidence is great news. But key points are frequently overlooked when society tries to make sense of the figures.

Shark bite incidents in NSW per million people per decade, including fatalities and injuries. Authors

Lifeguard patrol and emergency response are key

In NSW, lifeguard beach patrol grew over the same time period as the shark meshing program. More people swam and surfed in the ocean from the early 20th century as public bathing became legal. The surf lifesaving and professional lifeguard movements grew rapidly in response.

Today, 50 of the 51 beaches netted through the shark meshing program are also patrolled by lifeguards or lifesavers. Yet improved safety is generally attributed to the mesh program. The role of beach patrol is largely overlooked.

So, claims that shark bite has declined at netted beaches might instead be interpreted as decline at patrolled beaches. In other words, reduced shark interactions may be the result of beach patrol.

More good news is that since the mid-20th century the proportion of shark bites leading to fatality has plummeted. This is most likely the result of enormous improvements in beach patrol, emergency and medical response.

A surfer treated by paramedics after a shark bite near Ballina in NSW.

It’s time to move on from shark nets

Debate over shark management is often polarised, pitting human safety against marine conservation. We have brought together expertise from the social sciences, biological sciences and fisheries, to move beyond a “people vs sharks” debate.

There is no reliable evidence that lethal shark management strategies are effective. Many people oppose them, institutions are moving away from them, and threatened species are put at risk.

The NSW Department of Primary Industries, manager of the shark meshing program, is investing strongly in new non-lethal strategies, including shark tagging, drone and helicopter patrol, personal deterrents, social and biophysical research and community engagement. Our study provides further evidence to support this move.

Investing in lifeguard patrol and emergency response makes good sense. The measures have none of the negative impacts of lethal strategies, and are likely responsible for the improved safety we enjoy today at the beach.The Conversation

More lifeguards would help prevent shark bite. AAP

Leah Gibbs, Senior Lecturer in Geography, University of Wollongong; Lachlan Fetterplace, Environmental Assessment Specialist, Swedish University of Agricultural Sciences, and Quentin Hanich, Associate Professor, University of Wollongong

This article is republished from The Conversation under a Creative Commons license. Read the original article.

4 December 2019

250 Million Pieces of Trash at Remote Top End Australian Beach

 

A Sea Shepherd beach clean-up campaign in Northeast Arnhem Land has further exposed the catastrophic impact of marine plastic pollution on mainland Australia.

 

The Shocking Reality

Over seven tonnes of marine plastic pollution was removed by ten volunteers from Sea Shepherd Australia and Indigenous Rangers from the Dhimurru Aboriginal Corporation in a two-week-long collaboration at Djulpan Beach on the shores of the Gulf of Carpentaria, Northern Territory.

 

During the campaign, Sea Shepherd conducted scientific surveys across the 14-kilometre stretch of beach in collaboration with marine plastic pollution expert Dr Jennifer Lavers.

 

Findings from the surveys concluded that there were an estimated 250 million pieces of marine debris present.

 

 

Untrashing Djulpan: the Campaign

So remote and untouched by human contact is Djulpan Beach, Rangers cut a 4WD track from the nearest road to allow access for vehicles and equipment. The volume and density of plastic pollution removed from Djulpan was at a scale that the Sea Shepherd volunteers had not seen before on a mainland Australian beach, despite having facilitating over 600 clean-ups in the past three years.

Around 4.5 tonnes of the debris removed were consumer items including:

●  plastic lids, tops and pump sprays (14494 pieces) 

●  plastic drink bottles (6054 pieces)

●  cigarette lighters (3344 pieces

●  personal care and pharmaceutical packaging (4881 pieces)

●  thongs (3769 pieces)

●  toothbrushes, hair brushes and hair ties (775 pieces) and

●  toys such as chess pieces (64 pieces)

 

In many cases, the plastic items were so degraded that when volunteers went to pick them up, they crumbled into plastic dust.

 

The remaining 2.5 tonnes was made up of 72 different types of discarded fishing nets or ghost nets, some of which contained turtle bones.

 

Hundreds of plastic items were found with multiple animal bites, including those from fish and turtles. The stretch of coast that Djulpan is located on is home to six of the seven species of marine turtles which are all listed as ‘Vulnerable’ or ‘Endangered’ under the Environmental Protection and Biodiversity Conservation (EPBC) Act 

 

Much of the trash found along Cape Arnhem originates from ocean currents and trade winds above Australia that pushes the debris into the Gulf of Carpentaria in a clockwise direction before washing ashore.

“The marine debris littering our beaches saddens us. Not only is it killing our turtles and other marine life, it also pollutes some of our sacred areas. The rangers work hard to try and keep the beaches clean, but we need to stop the rubbish going into the ocean in the first place.” -- Managing Director of the Dhimurru Aboriginal Corporation Mandaka Marika.

 

“What we found when we arrived at the beach on day one looked like something out of Armageddon, with plastic pieces visible across the entire beach as far as the eye could see.  This campaign clearly shows that even in a remote place like Arnhem Land, that nowhere is safe from human-induced plastic pollution” -- Sea Shepherd Australia’s National Marine Debris Coordinator Liza Dicks.

What can you do?

Australia simply cannot turn a blind eye to the impacts that plastic pollution is having – whether it be on Australian shores or at the regional or global level. We need to come together and act now as a collective to ensure there is a solution to this increasing global environmental issue.

 

First published by SeaShephard: https://www.seashepherd.org.au/latest-news/untrashing-djulpan/

22 Sep 2019

Climate change may change the way ocean waves impact 50% of the world’s coastlines

Mark Hemer, CSIRO; Ian Young, University of Melbourne; Joao Morim Nascimento, Griffith University, and Nobuhito Mori, Kyoto University

The rise in sea levels is not the only way climate change will affect the coasts. Our research, published today in Nature Climate Change, found a warming planet will also alter ocean waves along more than 50% of the world’s coastlines.

If the climate warms by more than 2℃ beyond pre-industrial levels, southern Australia is likely to see longer, more southerly waves that could alter the stability of the coastline.

Scientists look at the way waves have shaped our coasts – forming beaches, spits, lagoons and sea caves – to work out how the coast looked in the past. This is our guide to understanding past sea levels.

But often this research assumes that while sea levels might change, wave conditions have stayed the same. This same assumption is used when considering how climate change will influence future coastlines – future sea-level rise is considered, but the effect of future change on waves, which shape the coastline, is overlooked.

Changing waves

Waves are generated by surface winds. Our changing climate will drive changes in wind patterns around the globe (and in turn alter rain patterns, for example by changing El Niño and La Niña patterns). Similarly, these changes in winds will alter global ocean wave conditions.

Further to these “weather-driven” changes in waves, sea level rise can change how waves travel from deep to shallow water, as can other changes in coastal depths, such as affected reef systems.

Recent research analysed 33 years of wind and wave records from satellite measurements, and found average wind speeds have risen by 1.5 metres per second, and wave heights are up by 30cm – an 8% and 5% increase, respectively, over this relatively short historical record.

These changes were most pronounced in the Southern Ocean, which is important as waves generated in the Southern Ocean travel into all ocean basins as long swells, as far north as the latitude of San Francisco.

Sea level rise is only half the story

Given these historical changes in ocean wave conditions, we were interested in how projected future changes in atmospheric circulation, in a warmer climate, would alter wave conditions around the world.

As part of the Coordinated Ocean Wave Climate Project, ten research organisations combined to look at a range of different global wave models in a variety of future climate scenarios, to determine how waves might change in the future.

While we identified some differences between different studies, we found if the 2℃ Paris agreement target is kept, changes in wave patterns are likely to stay inside natural climate variability.

However in a business-as-usual climate, where warming continues in line with current trends, the models agreed we’re likely to see significant changes in wave conditions along 50% of the world’s coasts. These changes varied by region.

Less than 5% of the global coastline is at risk of seeing increasing wave heights. These include the southern coasts of Australia, and segments of the Pacific coast of South and Central America.

On the other hand decreases in wave heights, forecast for about 15% of the world’s coasts, can also alter coastal systems.

But describing waves by height only is the equivalent of describing an orchestra simply by the volume at which it plays.

Some areas will see the height of waves remain the same, but their length or frequency change. This can result in more force exerted on the coast (or coastal infrastructure), perhaps seeing waves run further up a beach and increasing wave-driven flooding.

Similarly, waves travelling from a slightly altered direction (suggested to occur over 20% of global coasts) can change how much sand they shunt along the coast – important considerations for how the coast might respond. Infrastructure built on the coast, or offshore, is sensitive to these many characteristics of waves.

While each of these wave characteristics is important on its own, our research identified that about 40% of the world’s coastlines are likely to see changes in wave height, period and direction happening simultaneously.

While some readers may see intense waves offering some benefit to their next surf holiday, there are much greater implications for our coastal and offshore environments. Flooding from rising sea levels could cost US$14 trillion worldwide annually by 2100 if we miss the target of 2℃ warming.

How coastlines respond to future climate change will be a response to a complex interplay of many processes, many of which respond to variable and changing climate. To focus on sea level rise alone, and overlooking the role waves play in shaping our coasts, is a simplification which has great potential to be costly.



The authors would like to acknowledge the contribution of Xiaolan Wang, Senior Research Scientist at Environment and Climate Change, Canada, to this article. The Conversation

Mark Hemer, Principal Research Scientist, Oceans and Atmosphere, CSIRO; Ian Young, Kernot Professor of Engineering, University of Melbourne; Joao Morim Nascimento, PhD Candidate, Griffith University, and Nobuhito Mori, Professor, Kyoto University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

20 Aug 2019

No-take marine areas help fishers (and fish) far more than we thought

A juvenile Plectropomus leopardus from the Whitsundays. David Williamson/James Cook University
Dustin Marshall, Monash University and Liz Morris, Monash University

One hectare of ocean in which fishing is not allowed (a marine protected area) produces at least five times the amount of fish as an equivalent unprotected hectare, according to new research published today.

This outsized effect means marine protected areas, or MPAs, are more valuable than we previously thought for conservation and increasing fishing catches in nearby areas.

Previous research has found the number of offspring from a fish increases exponentially as they grow larger, a disparity that had not been taken into account in earlier modelling of fish populations. By revising this basic assumption, the true value of MPAs is clearer.

Marine Protected Areas

Marine protected areas are ocean areas where human activity is restricted and at their best are “no take” zones, where removing animals and plants is banned. Fish populations within these areas can grow with limited human interference and potentially “spill-over” to replenish fished populations outside.

Obviously MPAs are designed to protect ecological communities, but scientists have long hoped they can play another role: contributing to the replenishment and maintenance of species that are targeted by fisheries.

Wild fisheries globally are under intense pressure and the size fish catches have levelled off or declined despite an ever-increasing fishing effort.

Yet fishers remain sceptical that any spillover will offset the loss of fishing grounds, and the role of MPAs in fisheries remains contentious. A key issue is the number of offspring that fish inside MPAs produce. If their fecundity is similar to that of fish outside the MPA, then obviously there will be no benefit and only costs to fishers.

Big fish have far more babies

Traditional models assume that fish reproductive output is proportional to mass, that is, doubling the mass of a fish doubles its reproductive output. Thus, the size of fish within a population is assumed to be less important than the total biomass when calculating population growth.

But a paper recently published in Science demonstrated this assumption is incorrect for 95% of fish species: larger fish actually have disproportionately higher reproductive outputs. That means doubling a fish’s mass more than doubles its reproductive output.

When we feed this newly revised assumption into models of fish reproduction, predictions about the value of MPAs change dramatically.

Author provided

Fish are, on average, 25% longer inside protected areas than outside. This doesn’t sound like much, but it translates into a big difference in reproductive output – an MPA fish produces almost 3 times more offspring on average. This, coupled with higher fish populations because of the no-take rule means MPAs produce between 5 and 200 times (depending on the species) more offspring per unit area than unprotected areas.

Put another way, one hectare of MPA is worth at least 5 hectares of unprotected area in terms of the number of offspring produced.

We have to remember though, just because MPAs produce disproportionately more offspring it doesn’t necessarily mean they enhance fisheries yields.

For protected areas to increase catch sizes, offspring need to move to fished areas. To calculate fisheries yields, we need to model – among other things – larval dispersal between protected and unprotected areas. This information is only available for a few species.

We explored the consequences of disproportionate reproduction for fisheries yields with and without MPAs for one iconic fish, the coral trout on the Great Barrier Reef. This is one of the few species for which we had data for most of the key parameters, including decent estimates of larval dispersal and how connected different populations are.

No-take protected areas increased the amount of common coral trout caught in nearby areas by 12%. Paul Asman and Jill Lenoble/Flickr, CC BY

We found MPAs do in fact enhance yields to fisheries when disproportionate reproduction is included in relatively realistic models of fish populations. For the coral trout, we saw a roughly 12% increase in tonnes of caught fish.

There are two lessons here. First, a fivefold increase in the production of eggs inside MPAs results in only modest increases in yield. This is because limited dispersal and higher death rates in the protected areas dampen the benefits.

However the exciting second lesson is these results suggest MPAs are not in conflict with the interests of fishers, as is often argued.

While MPAs restrict access to an entire population of fish, fishers still benefit from from their disproportionate affect on fish numbers. MPAs are a rare win-win strategy.

It’s unclear whether our results will hold for all species. What’s more, these effects rely on strict no-take rules being well-enforced, otherwise the essential differences in the sizes of fish will never be established.

We think that the value of MPAs as a fisheries management tool has been systematically underestimated. Including disproportionate reproduction in our assessments of MPAs should correct this view and partly resolve the debate about their value. Well-designed networks of MPAs could increase much-needed yields from wild-caught fish. The Conversation

Dustin Marshall, Professor, Marine Evolutionary Ecology, Monash University and Liz Morris, Administration Manager, Monash University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

July 4 2019

Next generation corals undergo first field tests on the Great Barrier Reef

AIMS divers assessing the feasibility of a reef restoration technique called Assisted Gene Flow on the central Great Barrier Reef. Image from www.aims.gov.au
AIMS divers assessing the feasibility of a reef restoration technique called Assisted Gene Flow on the central Great Barrier Reef. Image from www.aims.gov.au

Hundreds of juvenile corals bred at the Australian Institute of Marine Science (AIMS) have survived being transplanted on the Great Barrier Reef, in a promising early test to help corals increase their resilience to marine heatwaves. The trial aims to show young coral offspring produced from mixing corals from warm northern reefs, with cooler central corals, can survive in cooler environments. This is the first test to assess the feasibility of the technique called Assisted Gene Flow at this larger scale on the Great Barrier Reef. The seven-month-old corals have one parent from the warmer northern reaches of the Reef and the other from the cooler central Reef.

AIMS marine scientist Dr Kate Quigley says research has shown the offspring inherit heat tolerance from their northern parents, and in time, they may pass on these heat tolerant genes and make reefs more resistant to future marine heat waves. “Last year we collected corals from the far north of the Great Barrier Reef that survived previous heat waves, and we flew them nearly 1000km to AIMS in Townsville,” Dr Quigley said.

“We have cross-fertilised them with corals from the middle of the Reef to see if the heat tolerance is passed on.”

Dr Line Bay, who leads AIMS’ research into reef recovery, adaptation and restoration, said Assisted Gene Flow, was helping nature to do what it does naturally, and is one of several techniques being developed at AIMS to help coral survive higher future ocean temperatures in coming decades. “When corals get too hot they are damaged and bleach, and this can lead to extensive mortality as we have recently seen on the Great Barrier Reef,” Dr Bay said. “If corals are to persist into the future, they have to cope with these increasing temperatures, and because of the rate of warming, they will have to become more tolerant fast. “We are focussed on developing new solutions for managing our coral reefs in a warming future.”

Hundreds of tiny juvenile corals are now living on these terracotta tiles on the central Great Barrier Reef. Image from www.aims.gov.au
Hundreds of tiny juvenile corals are now living on these terracotta tiles on the central Great Barrier Reef. Image from www.aims.gov.au

AIMS researchers took the same species of corals from three sites in the northern region, and two sites on the central Great Barrier Reef and cross-fertilised them in climate-controlled tanks at the National Sea Simulator in Townsville, to produce dozens of distinct genetic crosses. The National Sea Simulator is the world’s most advanced research aquarium. These crosses were then settled onto terracotta tiles and moved to a site on the Great Barrier Reef, in March.

This first expedition to check on these coral juveniles has just returned, and researchers are analysing the results. “We found many of the warm-adapted corals have survived the now quite cool waters of the central Reef,” Dr Quigley said. “This early result supports further testing of Assisted Gene Flow as a management action tool for corals in a warming future.” The field tests will add to results from experiments in the National Sea Simulator which showed these juvenile corals with at least one parent from the far northern Great Barrier Reef, are significantly more likely to survive high temperatures. AIMS researchers plan to return to the test site in October to check in again on how the corals are growing and surviving.

 

This research is partly funded by the partnership between the Australian Government’s Reef Trust and the Great Barrier Reef Foundation.

First published by AIMS July 2 2019

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