Welcome to tropical Sydney, where colourful surgeonfishes and parrotfishes are plentiful, corals have replaced kelp forests, and underwater life seems brighter, more colourful and all-round better. Or is it?
While this vision of a future Sydney is just an embellished cartoon of what climate change would do off the city’s coastline, our recent research does point to a widespread “tropicalisation” of temperate coastlines such as Sydney within the next few decades. This may sound pleasant, but it can lead to unwanted consequences.
Climate models suggest that ocean temperatures off Sydney are just decades away from becoming “tropical”. A “business as usual” scenario of increasing CO2 emissions suggests winter sea surface temperatures will consistently exceed 18 degrees C between 2020 and 2030. And summer sea surface temperatures will consistently exceed 25 degrees C between 2040 and 2060.
Eastern Australia waters represent a climate change hotspot, with warming rates occurring twice as fast as the global average. A key reason for this is a strengthening of the East Australian Current, which pushes warm tropical water southwards.
Other oceanic hotspots around the world include southern Japan, south east USA, south east Africa and eastern South America. All these regions have in common the influence of strong ocean currents running close to the shore bringing warm tropical water.
So what will warmer ocean temperatures do to Sydney? Examining what’s happening within these other hotspots can help us to make some predictions.
In our study, recently published in Proceedings of the Royal Society B, we show how tropical fishes are becoming increasingly abundant in many warming hotspots. Indeed, tropical fishes are already a common feature in Sydney during the late summer months, and some have even started to survive over winter.
And fish are not the only organisms moving. Tropical corals have also started to make their way down the NSW coastline, and researchers are now on the look out for them in the waters off Sydney.
Nobody would complain if the only consequence of climate change was more species of marine life — greater biodiversity. However with these gains also come substantial losses. And the biggest losers are underwater algal forests.
Canopy algae, or seaweeds, are the linchpin of temperate coastlines. They provide food and shelter to hundreds of species, and fulfil a role similar to trees in terrestrial forests. However algal forests need relatively cool water to survive, and this is becoming increasingly elusive in these regions.
A dramatic example of warmer water on algal forests occurred during the extreme ocean heat wave off Western Australia associated with the massive La Niña in early 2011. Extreme ocean warming lasted only a few weeks, caused an unprecedented decline of algal forests and the temperate marine life communities they support.
So why is warm water damaging to algal forests? There are a few reasons. High temperatures can directly stress algae by damaging the machinery that supports their survival. Warmer tropical water also carries fewer nutrients, which the algae need to grow.
And now our research is uncovering a new mechanism leading to the loss of algal forests: increased grazing by the very same tropical fishes that we were initially so happy to see along our coastlines.
The harmful effect of warm-water fish on temperate reefs is most evident in southern Japan and the eastern Mediterranean, where algal forests have dramatically declined.
In a paper published last week in the Journal of Ecology, we show how the invasion of tropical rabbitfish in the eastern Mediterranean has created eerie barren areas extending over hundreds of kilometres. These new habitats support less than half the species found in the nearest algal forests.
Similarly, off southern Japan over 40% of algal forests have disappeared since the 1990s; a phenomenon known as isoyake. Increased annual grazing rates by tropical rabbitfish and parrotfish appear to be the primary culprit. Now corals dominate at many sites.
Japanese people are famous for their love of algae — they have dedicated shrines and eat them with nearly every meal. Consequently there is considerable concern over their loss. It has also resulted in the complete collapse of abalone fisheries, and the cultivation of other commercially important species such as the Japanese amberjack is becoming increasingly difficult.
So what can we do to stop temperate algal forests turning tropical? To prevent further dramatic changes we ultimately need to reduce our CO2 emissions. In the meantime, we could also encourage new fisheries in temperate reefs that target tropical fishes. Rabbitfish, for example, are considered a delicacy in many Indo-pacific countries and already make up a sizeable component of fisheries catches in the eastern Mediterranean.
Adriana Vergés, Lecturer in marine ecology, UNSW Australia and Alex Sen Gupta, Senior Lecturer, School of Biological, Earth and Environmental Sciences, UNSW Australia
This article was originally published on The Conversation. Read the original article.
September 16, 2014
Researchers studying fish populations have uncovered the impact fishing has had on the world's coral reefs and charted a roadmap for the recovery of reef ecosystems currently under threat from overfishing.
Coral reefs are home to thousands of species of fish and provide millions of people with food and income, yet reef ecosystems have been severely depleted by fishing.
"By studying remote and marine protected areas, we were able to estimate how much fish there would be on coral reefs without fishing, and how long it should take newly protected areas to recover,” says study lead author, Dr Aaron MacNeil from the Australian Institute of Marine Science.
“This allows us to gauge the impact of reef fisheries, and make informed management decisions that include timeframes for recovery," Dr MacNeil says.
As part of a global study into the recovery potential of coral reefs published in the journal Nature, the researchers examined more than 800 reefs around the world.
They found that the vast majority of fished reefs are missing more than half of their expected fish populations.
"Although fishing has more than halved fish numbers on many reefs, we were encouraged to find that substantial biomass remained where some form of management was in place. By keeping this extra biomass on the reef, people who chose to manage their fisheries dramatically increased their sustainability,” adds Dr MacNeil.
The study found that most fished reefs would take about 35 years of protection to recover, while the most depleted areas would take almost 60 years.
While marine reserves are the most effective way of recovering fish populations, the researchers agree that a one size fits all approach of locking away reef resources is not feasible for many communities dependent on fishing.
“Changes in fishing practices can result in a significant return of key fish species over time,” says co-author, Dr Nick Graham from the ARC Centre of Excellence for Coral Reef Studies at James Cook University.
“Fish play important roles in the overall functioning of coral reef ecosystems, for example in controlling seaweed and invertebrates. By linking fisheries to ecology, we can now uncover important ecosystem functions for a given level of fish biomass,” says Dr Graham.
"Restrictions on types of gears, species caught, or local customs, all ensured substantial recovery in fish feeding groups. However, only completely closed marine protected areas successfully returned large predatory fish to the ecosystem," Dr Graham says.
Dr MacNeil says fisheries managers have the potential to arrest a key threat to coral reefs.
"Where previously we have been managing reef fisheries not really knowing how depleted fish stocks were, we now have a roadmap for recovery that tells us not only where we are with fish biomass, but where we might want to go, and how long it will take to get there” he says
“Importantly, this new map charts a course for coral reef fisheries that includes everyone, not just those who can afford to wall off large areas."
Co-author, Dr Tim McClananhan, from the Wildlife Conservation Society in New York, says “the findings will help fishers determine how much catch to take and how much to leave behind.”
"These results give clear consequences for taking too much fish, and uncover the ecological benefits of different forms of fisheries management. The methods used in this study are simple enough that fishers and managers can take the weight and pulse of their reef and keep it in a healthy range that had not previously been defined."
He adds that by choosing to conserve resources and the ecosystem functions they provide, fishers and managers have the ability to plan for recovery and help reefs remain productive in the face of increasing stress from climate disturbances.
Examples of reefs that are heavily degraded and near collapse include those in Papua New Guinea, Guam, St Lucia and Antigua. Meanwhile, reefs that are doing relatively well under fishing restrictions include Australia’s Great Barrier Reef, Belize Barrier Reef, Pitcairn and Easter Islands.
After developing a mathematical model that determines the recovery potential of a reef, the team found that on average it takes about 35 years of protection before fish stocks return to pristine levels, while the most depleted reefs require 59 years of protection
The paper, Recovery potential of the world’s coral reef fishes by M. Aaron MacNeil, Nicholas A.J. Graham, Joshua E. Cinner, Shaun K. Wilson, Ivor D. Williams, Joseph Maina, Steve Newman, Alan M. Friedlander, Stacy Jupiter. Nicholas V.C. Polunin, and Tim McClanahan is published in the journal Nature.
The University of Queensland were also key research partners in this study.
Source Australian Institute of Marine Science
Laurence McCook, James Cook University and Britta Schaffelke, Australian Institute of Marine Science
To protect and manage environmental treasures like the Great Barrier Reef requires a strong foundation of science, but what should agencies and political leaders do when the science is as widely debated as it has been for dredging and disposal in the Great Barrier Reef?
Over the past 15 months, we have led a process with a panel of experts to provide an independent overview of the current knowledge of the effects of dredging and sediment disposal in the Great Barrier Reef World Heritage Area. Our panel included a very diverse range of expertise and experience, from years in the dredging industry, to physical oceanographers and coral ecologists.
The report, published yesterday, covers the effects of dredging on the physical and chemical environment, flow-on effects on the habitats and biodiversity, cumulative impacts, effects of land-based disposal, and next steps for management.
The report shows, for example, that although direct effects are localised, dredging and disposal may have been making significant contributions to suspended sediments in inshore waters of the Great Barrier Reef.
Given the complexity of the issue, the report can’t provide conclusive answers to all of the questions reef managers face, but it does provide a comprehensive and balanced interpretation of the available evidence. By clearly distinguishing what is known (and agreed by the experts), what is definitively not known, and what is uncertain (that is, still debated by the experts), the report not only provides a clearer way forward for managers, but clearly identifies the knowledge gaps we still need to address.
So what does the report tell us? It says that dredging and sediment disposal can change the physical and chemical environment, and thus affect the biological values of the Great Barrier Reef World Heritage Area. But these effects will differ between locations, and also be influenced by the different types and extents of dredging and sediment disposal.
Direct removal by excavation, and burial during disposal, only affect relatively small areas, although within those areas the effects are obviously severe. Dredging and disposal don’t occur on coral reefs within the Great Barrier Reef area.
Both dredging and marine disposal create significant plumes of suspended sediment, causing increased cloudiness in the water and reducing the light available to marine organisms.
Importantly, the report concludes that both disposed sediments and dispersed sediments from dredge plumes have the potential to be re-suspended and transported by waves and ocean currents, and to contribute to the long-term, chronic increase in fine suspended sediment concentrations in the inshore Great Barrier Reef.
The extent to which this occurs and affects marine life was not agreed by the expert panel. In particular, the panellists had differing views on whether sediment from dredging was significant compared with background levels of resuspension and inputs of fine sediments in river run-off from catchments. However, calculations suggest that previous large dredging operations had potentially very significant effects.
Most experts do agree that increased levels of fine sediments, and associated nutrients, are, along with climate change, seriously affecting the long-term health of the Great Barrier Reef. Understanding dredging in the context of inshore sediment dynamics is a serious gap in our knowledge.
In general, dredged material from near the Great Barrier Reef has few chemical contaminants, and there are robust management procedures to avoid disposal of such material at sea.
The report breaks down and summarises the risks to coral reefs, seagrass meadows, mangroves and estuaries, pelagic (open water) and seafloor habitats, along with the risks to fish and other wildlife of conservation concern, such as dugongs, marine turtles and seabirds. These effects will vary greatly with the location, timing and extent of dredging and disposal. But if dredging and disposal have been significantly increasing fine sediments supply, it is possible that long-term impacts on inshore ecosystems have been under-estimated. We know that chronic increases in suspended sediments have been affecting inshore coral reefs and seagrass beds.
What is clear is that the extent of future impacts in the marine environment will be very significantly improved with the impending bans on disposal of capital dredging in the marine environment, recently announced by the federal and Queensland governments. The proposed ban on disposal of capital material in the Marine Park is open for public comment until this Friday 27 March.
Following a ban on disposal of capital material within the marine environment, there remains the challenge of managing the remaining impacts of dredging, including disposal of maintenance dredged sediments in marine environments, and disposal of capital dredging material on land.
The Expert Panel identified a number of potentially serious impacts and challenges involved in disposing of dredge material on land or in reclamation, including loss of coastal habitats, runoff of seawater and fine sediments from dredged material, and potential acid sulphate soils.
Our panel prioritised identifying what we do know about dredging, but also found significant areas of insufficient knowledge. Most of the panel also agreed on the need to follow up our report with a similar analysis of the social, economic, cultural and heritage aspects of dredging and sediment disposal, including the impacts on Indigenous culture and heritage.
Given the complexity of the Great Barrier Reef ecosystem, and the range of expert views, the intention of this process was never to provide a single, conclusive answer. Rather, our report provides a strong foundation for progressing both knowledge and management directions, and it appears it is already doing that.
This article was originally published on The Conversation. Read the original article.
By John Gunn, Australian Institute of Marine Science
AUSTRALIA 2025: How will science address the challenges of the future? In collaboration with Australia’s chief scientist Ian Chubb, we’re asking how each science discipline will contribute to Australia now and in the future. Written by luminaries and accompanied by two expert commentaries to ensure a broader perspective, these articles run fortnightly and focus on each of the major scientific areas. In this instalment we dive into marine science.
Why are our oceans important to us? How is our health, the health of the environment, the strength of our economy and indeed, our future, dependent on the seas? How can marine science help us, collectively, to sustainably develop our marine-based industries and at the same time protect our unique marine ecosystems so that they can be appreciated and enjoyed by future generations?
In many ways, Australia is defined by the oceans that surround us. We have the third largest ocean territory in the world. The majority of our trade travels by sea, vast offshore oil and gas resources earn vital export income and offer a long term, cleaner energy source than coal and our fisheries and aquaculture industries provide healthy food.
We are custodians of two magnificent marine World Heritage Areas – the Great Barrier Reef and Ningaloo Reef – and we are a nation that loves to sit by, swim, surf, dive, fish and sail in the (mostly) clean waters and healthy marine ecosystems that surround our continent.
Australia’s affinity with our ocean estate is perhaps best exemplified by the fact that 85% of our population lives within 50km of the coast.
Marine industries contributed approximately A$42 billion to our economy in 2010. This is projected to grow to approximately A$100 billion by 2025 with the expansion of current industries and development of new opportunities in areas such as renewable energy. As a nation we will increasingly be dependent on our “blue economy” for our future prosperity.
In addition to their economic and aesthetic value, our oceans also provide a suite of essential “ecosystem services” – most importantly in their role within the global climate system. Since the end of the 18th century, about 30% percent of human-induced carbon dioxide emissions have been taken up by the oceans while over the past 50 years, they have absorbed about 90% of the extra heat generated through the impacts of the greenhouse effect.
The moderating influence of the oceans as our planet warms, and their very strong influences on our island continent’s weather, impact on every Australian, every day.
If Australia, and indeed the world at large, is to continue to enjoy and grow the benefits accrued from our oceans, we need to face up to and meet a number of significant (and in some cases urgent) challenges.
Australia’s marine science community recently collaborated with governments, not-for-profit organisations and the private sector to produce the report Marine Nation 2025: Marine Science to Support Australia’s Blue Economy.
Marine Nation 2025 outlined six, interconnected “grand challenges” facing Australia, each of which has a significant marine dimension with gaps in understanding or requirement for tools that can be addressed by marine science:
The multidisciplinary nature of marine science, the geographic scale and connectedness of marine systems, and the complexity of the challenges above mean that in the majority of cases no one institution (or in the case of industry, one company) can build the evidence base or tools required to adequately address these challenges, even at local scales.
Thus, a dedicated and coordinated effort across our national marine science community, governments and industry is required.
Coordination can (and should) ensure that resources are used efficiently and strategically, and allow the full breadth of the marine science community – from the fundamental work conducted across the university sector, to the translational and applied science conducted by national science agencies such as CSIRO, Geoscience Australia and the Australian Institute of Marine Science (AIMS) – to have the maximum impact.
A couple of recent cases illustrate of how strategic, collaborative efforts across organisations and sustained investment in national-scale infrastructure provide vital support for decision makers across government and private sectors.
CSIRO oceanographer David Griffin has been involved in the search for Malaysian Airlines flight MH370 this year.
He used advanced models of ocean currents around Australia developed through a collaboration between CSIRO, the Bureau of Meteorology and the Australian Navy over the past decade, to determine likely movement of wreckage and allow search and rescue operations to pinpoint their activities.
The same models can also be used to track and predict oil spills, missing boats, valuable fish stocks and guide Navy operations.
The critical data required by the models comes from Australia’s Integrated Marine Observing System (IMOS), a national, collaborative infrastructure facility set up eight years ago. IMOS has become an international leader in ocean observing and is now the critical observational foundation for much of Australia’s marine science.
Two strategic and sustained marine science investments – in ocean observations and modelling – provide the fantastic capability for David’s work, and many other applications to come.
Similarly, following the UNESCO World Heritage Committee’s questions about our management of the Great Barrier Reef World Heritage Area, Australia’s response has relied heavily on the body of evidence provided by strategic investment in marine science conducted over the past 30 years.
Science doesn’t always tell a good news story – the AIMS long term monitoring has shown that half of the Great Barrier Reef’s coral cover has been lost over the past 27 years due to the cumulative impacts of cyclones, Crown of Thorns starfish and bleaching (caused by heat stress).
Importantly though , the research conducted by AIMS, the ARC Centre of Excellence for Coral Reef Studies (lead by James Cook University) and others also provides the evidence base for understanding ecosystem health and development of policy and regulation to stop the decline and rebuild the reef.
Australia has world class, and in many areas world leading, marine science capability. Appropriately, over the past few years the marine science community has recognised the need to work together and is increasingly collaborating in providing big-scale science focused on national and global needs.
But if we are to rise to the challenges of our growing “blue economy”, we will need to do much more. We will need to take a long-term outlook and focus effort on both the development of science capability (human and physical) and securing the best possible returns to Australia through its effective coordination and utilisation.
The first steps along this pathway are clear:
Marine sciences deliver data and modelling on oceanographic patterns benefiting weather forecast and maritime safety, provide information underlying sustainable seafood harvesting and production and knowledge on marine life underpinning biodiscoveries.
Yet it is a challenge to carry out marine research throughout the huge realm of Australia’s maritime jurisdiction. Australia has only a small fleet of research vessels for coastal and offshore waters and needs a better alliance of shore-based marine field stations. Ocean exploration relies on technological innovations.
As much of the oceans are still unexplored, curiosity driven research can provide useful discoveries such as alternative products to benefit human health. The Census of Marine Life illustrated the highly diverse marine life in Australia’s seas, but taxonomy is a threatened skill unless the tide turns for museum research funding.
Rigorous experimental hypothesis testing, using shore- and sea-based facilities equipped with operating funds, technical and research staffing, can support mitigation of cumulative impacts and global warming. Marine research strengthens monitoring into the health of Australia’s seas facing growing economic use, the effectiveness of marine protected areas and biosecurity of marine invasive species.
Understanding marine ecosystems requires multidisciplinary approaches and a well-connected network of scientists. At times of highly competitive research circumstances, appreciation for collaborative skills has to increase.
Higher education in marine sciences, including maritime engineering, provides an informed and versatile work force to address challenging scientific questions and generate knowledge for decision making on the wise use of the seas around us. Continued participation in international programs on ocean exploration will strengthen Australia’s position as a leading nation for marine sciences.
How inappropriate to call this planet Earth when it is quite clearly Ocean.
- Arthur C Clarke
The global ocean is humankind’s common heritage and responsibility. Ocean under Australian jurisdiction is significantly larger than the nation’s landmass. Our 0.3% of the world’s population is custodian for 3.8% of the world’s ocean, by far the greatest responsibility per capita among the G20 nations.
Effectively managing our vast public marine domain requires understanding it, yet our ignorance of the dynamic ocean is profound:
Australia’s vital and growing blue economy critically depends on understanding and managing the sea, through both national efforts (such as the Integrated Marine Observing System) and international partnerships (such as the International Ocean Discovery Program).
But much of the nation’s capability in the three pillars of marine research — observation, experimentation and modelling — across the major marine scientific disciplines — biology, chemistry, geoscience and physics — is precarious due to short-term and therefore vulnerable support.
In the context of a to-be-developed national strategy for marine science, increased and sustainable investment in exploratory, basic, applied and translational marine research — in both human capability and infrastructure — as well as improved underpinning primary, secondary and tertiary education in science and mathematics are needed to ensure a healthy, productive and resilient ocean for present and future generations.
This article is part of the Australia 2025: smart science series, co-published with the Office of the Chief Scientist
This article was originally published on The Conversation. Read the original article.
Scientists from The Australian Institute of Marine Science (AIMS) and the University of Western Australia (UWA) are leading research into using smart technology to learn more about the migrations of the world’s largest marine animals.
While tracking animals began in the 1950s, in contrast, studies of human mobility have only been a very recent development. These studies are made possible by the fact that we carry our own personal GPS system – a smart phone – which over time generates huge datasets about human behaviour.
These large datasets, and the novel analyses used, highlight an opportunity that can be applied to understanding the movements of marine megafauna, one of the key groups for which a large amount of tracking data exists.
“For example, early satellite tracking data from albatrosses was an inspiration for the study on how humans move in the environment. Even though our discipline of studying animal movement has been around longer, it has been overtaken in terms of advancements given the access to large data brought about by the internet and smart phones. Data sharing would allow us to reach the same level of understanding,” said AIMS Research Scientist and UWA Adjunct Assistant Professor, Dr Michele Thums.
A group of renowned national and international multidisciplinary researchers, including physicists, animal biologists and ecologists, will attend the ‘Marine Megafauna Synthesis Group’ workshop in Perth next week to share their data and work together to compare the movements and behaviors of these animals on a global scale, using novel approaches from the study of human mobility.
Thums explained that collaborative research group presented a unique approach to advancing knowledge about the movements of megafauna worldwide, by data sharing and applying the approaches developed by scientists studying human mobility.
The tracking data from marine mammals, birds, reptiles and large fishes will be collated and synthesised, with the intention of providing new insights into their movement and behavior as well as preparing a road-map for developing a publically available data storage facility for animal tracking data.
The many small-scale projects have resulted in hundreds of thousands of individual animals being tracked over time and combining all these data in such a facility would allow for significant advances to be made.
UWA Research Associate Dr Ana Sequeira said that involving a multi-disciplinary group to analyse such data and pose questions from their multiple perspectives would assist in promoting advances not only in ecology but also in other disciplines.
Dr Thums and Dr Sequeira are also involved in UWA’s first crowd-sourcing campaign in two separate projects involving the tracking of turtle hatchlings and on a larger scale, the whale sharks at Ningaloo. Both projects have huge community appeal and provide opportunities for the community to become involved in marine research involving monitoring of marine megafauna.
Professor Daniel Costa from the University of California, a key participant in the working group, has been a pioneer in tracking marine megafauna movements and behaviour using telemetry for many years. He co-founded the Tagging of Pacific Predators Program, a multidisciplinary effort to study the movement patterns of 23 species of marine vertebrate predators in the North Pacific Ocean.
“Some of the most exciting advances in our field have come from the interaction across disciplines,” said Professor Costa.
“This meeting will bring together individuals who know how to tag marine animals with individuals who are adept at analysing large data sets. Together we should gain new insights into our data that we could never have achieved on our own.”
From: Australian Institute of Marine Science, http://www.aims.gov.au/. CCBY
By Iain McCalman, University of Sydney and Stephen Palumbi, Stanford University
Reef historian Iain McCalman, in Sydney, and reef scientist Stephen Palumbi, in California, are monitoring reef degradation from opposite sides of the planet. They compared notes.
Iain McCalman: A recent report found that the Great Barrier Reef had lost 50% of its living coral. This was mainly from cyclones and the damages of Crown of Thorns starfish. Then there are the new threats of coral bleaching and acidification.
Are the problems you are finding in the US old ones that have mounted up and intensified? Or are they new challenges coming from human-stimulated climate change?
Steve Palumbi: All coral reefs in the world suffer from the same problems – they’re smothered by sediment, choked by weedy algae, blasted, dug up and stripped of most of their fish. Then there’s climate change making the oceans hot, sour and stormy.
Worst off are the reefs of the Caribbean, suffering from more than 500 years of incremental impact from western civilization, mostly in the form of poor stewardship. But even the far-flung reefs of the Pacific that the US manages have some combination of local stresses.
It seems to me that what the Great Barrier Reef has – that US reefs do not – is a central place in the hearts and minds of the public. Sure, most people in the US like corals and fish, but our reefs have not reached celebrity status. What kind of extra oomph does celebrity give the Great Barrier Reef? Has it been important in keeping it healthy?
Iain McCalman: The Great Barrier Reef’s popularity has helped control some things such as tourist pollution and the overfishing of parrot fish that graze on algae and keep corals clean.
Yet we haven’t been able to deter our governments from building massive new Reef ports and there are more and bigger coal ports on the way.
What worries me, too, is that waters warmed by greenhouse gases will cause big outbreaks of coral bleaching this coming summer, with stressed corals turning white as they expel the symbiotic algae that normally live within them. Another one degree or so will hurt corals that have been hit before: this time they may not recover.
Steve Palumbi: I’m also worried about coral bleaching. This week along the US Pacific coast we have had record temperatures on land and in Monterey Bay – well, it is still very cold by Great Barrier Reef standards, about 60F (16C), but it is warm for us! And a look at the latest map of ocean temperatures shows a lot of red – these are places where the ocean is 1-2 degrees warmer than the usual annual maximum.
Iain McCalman: We are predicting something similar, especially because we seem to be entering an El Niño weather phase when the Pacific is generally warmer anyway, though Charlie Veron, one of our great coral scientists, says that every year is becoming an El Niño year in Australia as far as corals are concerned.
Steve Palumbi: Every year is a hot one … that seems to be what the world is seeing across the continents and the seas. Way back when people first stumbled on the fact that corals bleached when the temperature rose too much, they found something else: corals in warmer climates near the equator bleached at a higher temperature than corals living in cooler waters.
We have seen this on a small scale in American Samoa where we work, and have shown that individual coral colonies living in warm water acclimate to the heat by changing their physiology. And whole populations of corals adapt to heat by having the right genetic makeup across about 100 genes.
Can we use this discovery? Turns out we can in two ways. We can locate and protect these heat-resistant corals. And we can try transplanting them to see if they in fact retain their heat resistance. We expect them to lose a little ground. How much is the question.
I’d love to think this will give us a leg up in replanting future reefs. I am not sure yet, because reef restoration has been so difficult. Does the Great Barrier Reef have any successful restored, replanted reefs?
Iain McCalman: Not that I know of. Moreover, with a government skeptical about climate change, a good deal of the work of this kind on adaptation is being shelved. Five of the Directors of the Great Barrier Reef Marine Park Authority recently resigned in protest against the cutting of programs concerned with responding to climate change.
Five directors of the Great Barrier Reef Marine Park Authority recently took redundancy packages, among them its former climate change director Paul Marshall, who said budget cuts have left the agency without a dedicated climate program.
But I also wanted to ask you about acidification. As the amount of CO2 in the atmosphere rises, oceans absorb more and it turns into carbonic acid in seawater. How do you rate the mounting acidification of the oceans from absorption of CO2 as a threat to corals?
It seems to be the elephant in the room: its consequences go beyond endangering corals to threaten other marine species as well. Some scientists seem to think it will deliver the death blow to coral reefs, if other things don’t get them first. What’s your feeling?
Steve Palumbi: Acidification is not the elephant in the room yet, it’s the elephant on the bus … due to get here any time now. The best data suggest that acidification has huge effects, from slowing down coral growth to changing the behavior of coral reef fish so that they get eaten more easily. Those effects are not strong yet, but they are coming quickly as CO2 builds up in the atmosphere.
CO2 and acidification takes 50 years to reverse. Think of stopping distance – a speeding car takes a long time to stop. So too with acidification.
And that is what I worry about. Because by the time the effect of that CO2 is killing corals, it will be too late to do anything about it. It’s like cancer treatment. If you’re lucky, they find a tumor when it is small and maybe isn’t even bothering you. But that tiny tumor is a huge threat, and we jump on it to fix it.
But I want to circle back to something you brought up at the beginning. Australia is selling coal to China, I hear. What is going on?
Iain McCalman: This issue of coal lies at the heart of current threats to the Great Barrier Reef, and symbolizes an economic mindset that reef lovers everywhere are up against. Our government has decided that Australia’s economic future lies in selling cheap coal to China and India. To do this the Federal and Queensland state governments need to expand existing coal ports on the Reef because these provide the cheapest and quickest shipping routes to Asia.
Quite apart from discouraging investment in renewable energy by backing fossil fuels, this decision has fraught implications for the health of the Reef and its waters.
Because the reef is too shallow for massive container ships, the new coal ports all entail extensive dredging of the seafloor. Thankfully public agitation has temporarily deflected the government’s original plan to dump three million cubic meters of dredged silt from Abbot Point into the reef channel, where it would choke corals and swamp sea grasses. Even so, dredging will stir up immense amounts of sediment as well as coral-threatening bacteria.
The vastly increased tonnage of container ships churning up and down the tricky reef channel represents a further threat from reef accidents and oil spillages, both of which have occurred a number of times in the recent past. There are plans, too, for several new mega-sized coal mines to be opened nearby, requiring similar access to the Great Barrier coastline and lagoon.
To call this policy short-sighted is an understatement. It sacrifices one of the wonders of the world and a substantial economic asset for Australian tourism; and this at a time when even China is trying to wean itself from using polluting coal.
The Great Barrier Reef might be an icon for us in Australia, as you said, Steve, but we seem to have governments that are proud to be icon bashers.
Steve Palumbi: I am thinking about a wonderful passage in your book, about Captain Cook navigating the Great Barrier Reef’s intricate tributaries, straining his considerable navigational skills to delicately thread his small ship up coral-filled canals. Now blast a modern coal ship through there, and what would you expect to happen? Cook’s ship was threatened by the Great Barrier Reef. Now the tables have turned.
I can’t help also to think about one of the last major threats to the whole Great Barrier Reef - the crown of thorns starfish. It wasn’t too long ago that this voracious predator was wasting reefs all along Australia. The way you describe the dangers of mining and ports makes me want to call this new threat the Coal of Thorns.
The Coal of Thorns may prove to be an even bigger threat - because it is something the reef has never seen and it is on an industrial scale that could threaten even this biggest biological structure on Earth. And all to help China pollute their own air! What happens after you build all these ports, you export the coal and China turns to their vast supplies of natural gas? Dead reef and a dead exporting business.
When the coral-eating Crown of Thorns began devastating the Reef in the 1960s, people tried everything to stop it. Folks picked them up by the thousands and burned them. They poisoned them. They fought them up and down the length of Australia. They would have loved to have the problem solved by simply passing a law.
This threat from coal is a problem created specifically by people. And it could be solved by people in a way that was never available for the starfish scourge – a simple sign of a pen could do away with this major threat.
This article was amended on October 28, 2014, to clarify the circumstances of the departure of the five former directors of the Great Barrier Reef Marine Park Authority.
Iain McCalman receives funding from Australian Research Council.
Stephen Palumbi receives funding from the U.S. National Science Foundation, the Gordon and Betty Moore Foundation and the David and Lucile Packard Foundation.
This article was originally published on The Conversation. Read the original article.
Shellfish reefs will be re-created on the bottom of Port Phillip Bay in a historic project that aims to improve marine habitats in Victoria’s largest bay.
Researchers say that if the reefs can be successfully established as expected, they would provide healthy habitats for shellfish like mussels and oysters. They would also provide habitat, shelter and food options for fish such as snapper, flathead, rockling and many other fish that live in the bay. They would also help improve water quality.
Shells from mussels, scallops and oysters that have been discarded by the seafood industry and restaurants could be sought as part of the project. They would eventually be placed in the bay at one of three locations, in order to form a base for the early stage of the shellfish reefs. Some artificial material could also be used.
But the project requires more than old shells. Millions of baby oysters and mussels, which will be bred at the Victorian Shellfish Hatchery at Queenscliff, will be used to colonise the reefs in the $270,000 pilot project. The baby oysters and mussels will attach themselves to shells at the hatchery, before they are placed in the water on top of the old shells.
The project, to commence this year, is expected to be formally announced on Saturday by Agriculture Minister Peter Walsh, the minister responsible for fisheries. It will be funded jointly, with $120,000 from the state’s Recreational Fishing Initiative, and $150,000 from The Nature Conservancy, an international organisation that undertakes conservation works around the world.
A patchwork of reefs will be restored at three locations, near Geelong, Chelsea and St Kilda, in about eight to 12 metres of water.
Paul Hamer, a senior research scientist at Fisheries Victoria, said it was a very exciting project. ‘‘Ultimately we’re going to try and recreate shellfish habitat and shellfish reefs, that were once highly abundant in Port Phillip Bay and provided habitat for a whole range of fish and other marine creatures, like crabs, octopus, squid, mostly invertebrate species. Crabs, other crustaceans, other shellfish that grow on the oysters and the mussels,’’ he said.
‘‘Years ago in the deeper, sub-tidal parts of the bay there were lots of shellfish, lots of shell beds that provided these substrates and these habitats for these animals to live in,’’ Dr Hamer said. But many of the bay’s shellfish reefs had been lost due to dredge fishing of oysters in the 19th century, and in the 20th century, dredge fishing for scallops and mussels from the 1960s to 1990s.
‘‘Shellfish reefs have often been called ecosystem engineers. The oysters themselves create habitat for other species, by providing substrates for other things to settle on. And a whole bunch of little hiding places in amongst their shells for other animals to live and avoid predators,’’ he said.
Mr Walsh said the work would occur under a landmark partnership. ‘‘Shellfish beds are recognised as important ecological features of Port Phillip Bay as they can provide key fish habitat valued by both commercial and recreational fishers,’’ he said.
Mr Walsh said the project was ‘‘expected to significantly improve fish habitat and recreational fishing opportunities. While this is the first Australian reef restoration effort, the project will test a range of reef restoration methods based on successful overseas experiences.’’
James Fitzsimons from The Nature Conservancy said the project would create ‘‘a more structured, robust habitat, which was originally there in the bay and originally there for much of south-east Australia. It’s really re-creating a 3D habitat that we’ve lost in the bay”.
Dr Fitzsimons said the group had been involved in about 100 shellfish reef restoration projects in America – experience which would help this project. ‘‘This is the first shellfish reef
restoration project in Australia, as far as we know,’’ he said.
September 29 2014
Drum lines will not be deployed off WA beaches this summer after the state's Environmental Protection Authority (EPA) advised against extending the Government's controversial catch and kill shark policy.
The regulator's chairman, Paul Vogel, said the available information and evidence did not provide the organisation with a high level of confidence.
Premier Colin Barnett said the recommendation meant drum lines would not be in place off the WA coast this summer.
Sea Shepherd’s WA Shark Campaigner Natalie Banks stated, “This is a tremendous victory for the people that understand the vital and important role sharks play in the health of our oceans. Finally their voices have been heard from all over the globe.”
Managing Director Jeff Hansen stated, “The EPA should be congratulated for listening to the people, listening to the science and giving sharks and future generations the respect they deserve. The worlds children need healthy oceans and healthy oceans need sharks.”
The WA Government should be acknowledged and encouraged to continue with their other alternatives, to pursue shark mitigation life saving techniques that don’t kill marine life.
The WA shark cull caught a total of 172 sharks over the 3-month trial, with the majority of these being tiger sharks. 50 tiger sharks of breeding size (mostly female) were shot and dumped out to sea. Tiger sharks only re-produce every few years and only a small number of their pups survive to maturity. The majority of the so called “alive-released” sharks were in such a poor state that their chances of survival were slim to none. The WA Government had applied for a three-year extension.
Hawaii tried culling sharks for 18 years and it made no difference to shark related incidents.
Sea Shepherd would like to congratulate and acknowledge supporters, the general community, the “No WA Shark Cull” movement, all the people that attended the rallies, EDOWA, the shark scientists, the Greens, Labor, select Liberal MPs and the numerous conservation groups that kept the pressure and the focus on ensuring that in the end logic, public opinion, science and sense would prevail for our oceans.
Sea Shepherd is now urging the Hon. Greg Hunt, Federal Environment Minister to listen to the public, to listen to the science and put forth shark mitigation strategies that assist with human safety without killing marine life.
“To know that we can look out to iconic, world renowned and beautiful places like Cottesloe Beach and not see drum lines this summer is a wonderful feeling. What we have off the Western Australian coast is nature on a grand scale and in todays world, this is rare and unique and should be celebrated”, stated Jeff Hansen, Managing Director, Sea Shepherd Australia.
Sea Shepherd would love to have a dialog with the West Australian state government to collaborate on alternatives that actually assist with beach goers safety, without killing our marine life or making our beaches less safe like the drum lines did.
Sea Shepherds Operation APEX Harmony is committed to seeing an end to drum lines and nets around Australia’s coast that merely provide a false sense of security by killing thousands of marine life, including whales and dolphins. Its 2014 and these archaic, indiscriminate killers should be taken out and replaced, where there is a demand, with non-lethal alternatives.
“We had no choice but to take this challenge on for the sharks, especially when drum lines were placed basically right in front of our office. No matter how hard this fight got, no matter how tired we became, we could never give up, because the alternative was to do nothing. To do nothing would mean the continued destruction of our worlds oceans and to quote Captain Paul Watson, the one thing worth fighting for on this planet, is life!” said Jeff Hansen, Managing Director, Sea Shepherd Australia.
September 11 2014
Researchers from the Australian Institute of Marine Science (AIMS) and the CSIRO have conducted a global literature review examining how better land management in upstream catchments helps to protect coastal coral reefs from agricultural pollution. The research is published in the UK peer reviewed journal, Marine Pollution Bulletin today.
“Our research has shown that coral reefs will benefit from improved river and catchment management. By looking at examples where better managing agricultural pollution has improved coastal water quality worldwide, we now understand how better to protect coastal rivers and coral reefs,” said AIMS Marine Ecologist, Dr Frederieke Kroon.
While climate change is considered the most serious risk to coral reefs around the world, agricultural pollution threatens approximately 25% of the total global reef area. With agricultural land use currently being the main source of sediment and nutrients delivered to the Great Barrier Reef Marine Park, the scientists hope that their findings will inform improved management of land-based pollution.
Based on their findings, the scientists suggest that targeted regulatory approaches and upscaling of catchment management will assist the protection of reefs. They also suggest that long-term maintenance of scientifically robust monitoring programs is critical to ensure that better management results in desired improvements of downstream coral reef ecosystems.
“Our research has shown that coastal water quality and ecosystems will benefit from improved agricultural management in upstream catchments. By looking at examples where agricultural management has improved coastal water quality and ecosystems around the world, we can now better inform catchment management for future protection of coastal coral reefs,” Kroon said.
Examples from the research of worldwide projects demonstrate that transformative change in river and catchment management for better outcomes for coastal ecosystems is achievable. In China, for example, implementation at large spatial scales of land terracing, tree and grass planting, and construction of sediment trapping dams has decreased sediment fluxes in the Yellow and Yangtze basins.
“Similar transformative change in tropical river and catchment management will improve coastal water quality and increase the resilience of downstream coral reefs in the face of climate change,”.Kroon concluded.
Original publication: Marine Pollution Bulletin
From: Australian Institute of Marine Science, (2010). Global Study Shows that Healthy Rivers Help Create Healthy Reefs. AIMS Web Publications <http://www.aims.gov.au/docs/media/latest-releases>
July 20 2014
In a world-first study published today, researchers say dredging activity near coral reefs can increase the frequency of diseases affecting corals.
“At dredging sites, we found more than twice as much coral disease than at our control sites,” says the lead author of the study, Joe Pollock, a PhD candidate from the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University (JCU) and the Australian Institute of Marine Science (AIMS).
“Corals require both light and food to survive,” Pollock explains. “And unfortunately, dredging impacts corals on two fronts: increased turbidity means less light for photosynthesis, while increased levels of sediment falling onto the coral can interfere with their ability to feed.”
Already low on energy, the corals then must spend further energy cleaning the extra sediment from their surface. Such an energy imbalance can lead to chronic coral stress.
“Just like in any other organism, it seems that chronic stress can lead to increased levels of disease in corals,” Pollock says.
In the past 20 years, the frequency of coral disease has risen across the world, and has become a significant factor in global coral reef decline. In the Caribbean, disease has diminished coral cover by as much as 95 percent in some locations.
This is the first study to examine the link between dredging and coral disease in nature. It was conducted near Barrow Island, off the West Australian coast. The site is close to where an 18-month, 7-million cubic metre dredging project took place, developing a channel to accommodate ships transporting liquefied gas to a nearby processing plant. The site was in otherwise very good condition.
The most common diseases affecting corals after dredging events are the ‘white syndromes’, where the coral tissues fall off, leaving behind exposed, white coral skeletons. These coral diseases are chronic, and there are fears that they may linger well after the completion of dredging operations.
Dr Britta Schaffelke from AIMS, a co-author on the study, says numerous environmental stressors have been suggested as potential drivers of coral disease.
“Turbidity and sedimentation are critical pressures on the health of coral reefs and are affected by many human activities, especially in the coastal zone,” Schaffelke says.
“What this study does is highlight a direct link of coral disease to sedimentation and turbidity.”
Coastal industries provide economic stability, food security and reliable energy to billions of people around the world. As the pace of coastal development and demand for larger harbours escalates, the impact of elevated sediment and turbidity on the health of marine species is now a worldwide concern.
“Dredging is a pressing issue on many coral reefs throughout the world, including the Great Barrier Reef,” says Pollock.
“A solid understanding of the impacts of dredging, sediment and turbidity on coral health will be indispensable in the development of well-informed management and monitoring strategies for vulnerable coral reef ecosystems,” he concludes.
For further information or an interview, please contact:
The published paper - Sediment and turbidity associated with offshore dredging increase coral disease prevalence on nearby reefs by Frederic Joseph Pollock, Joleah B Lamb, Stuart N Field, Scott F Heron, Britta Schaffelke, George Shedrawi, David G Bourne and Bette L Willis - can be accessed at http://dx.plos.org/10.1371/journal.pone.0102498
From: Australian Institute of Marine Science, (2010). Study links
dredging to deseased corals. AIMS Web Publications <http://www.aims.gov.au/docs/media/latest-releases>
April 1 2014
AIMS scientists together with a team from The University of Western Australia, CSIRO and the University of San Diego have analysed coral cores from the eastern Indian Ocean to understand how the unique coral reefs of Western Australia are affected by changing ocean currents and water temperatures. The research was published today in the international journal Nature Communications. The findings give new insights into how La Niña, a climate swing in the tropical Pacific, affects the Leeuwin current and how our oceans are changing.
"Due to the lack of long-term observations of marine climate we used long coral cores, with annual growth bands similar to tree rings, to provide a record of the past. We obtained records of past sea temperatures by measuring the chemical composition of the coral skeleton from year to year. This showed how changing winds and ocean currents in the eastern Indian Ocean are driven by climate variability in the western tropical Pacific Ocean," said Dr Jens Zinke (Assistant Professor at the UWA Oceans Institute and AIMS-UWA scientist). The long coral records allowed the scientists to look at these patterns of climate variability back to 1795 AD.
La Niña events in the tropical Pacific result in a strengthened Leeuwin Current and unusually warm water temperatures and higher sea levels off southwest Western Australia.
"A prominent example is the 2011 heat wave along WA's reefs which led to coral bleaching and fish kills," said Dr Ming Feng CSIRO Principal Research Scientist.
The international team found that in addition to warming sea surface temperatures, sea-level variability and Leeuwin Current strength have increased since 1980. The coral cores also reveal that the strong winds and extreme weather of 2011 off Western Australia are highly unusual in the context of the past 215 years. The authors conclude that this is clear evidence that global warming and sea-level rise is increasing the severity of these extreme events which impact the highly diverse coral reefs of Western Australia, including the Ningaloo Reef World Heritage site.
"Given ongoing global climate change, It is likely that future La Niña events will result in more extreme warming and high sea-level events with potentially significant consequences for the maintenance of Western Australia's unique marine ecosystems," said Dr Janice Lough, AIMS Senior Principal Research Scientist.
The researchers used core samples of massive Porites colonies from the Houtman-Abrolhos Islands, the most southerly reefs in the Indian Ocean which are directly in the path of the Leeuwin Current. Using the chemical composition of the annual coral growth bands they were able to reconstruct sea surface temperature and Leeuwin Current for 215 years, from 1795 to 2010.
©Australian Institute of Marine Science 2011
A previously unknown Purple Jellyfish with metre-long arms and a purple bell has washed up on Coolum Beach on the Sunshine Coast in South East Queensland. Speculation mounts over whether it is a sign of a new species or that we just havent seen it washed up before. May 27 2014
May 26 2014
Mark Spalding is a senior marine scientist at The Nature Conservancy.
My colleagues and I have worked out how much carbon there is in the world's mangrove forests, give or take a bit. And we mapped it. And here's why these findings are tremendously important.
They quantify what some of us in marine conservation have been saying for a decade or more: that mangrove forests are among the most carbon rich habitats on the planet; and that, although they occupy just a fraction of the world's surface, they pack a punch.
Anyone concerned about preserving nature's value - carbon sequestration and all the other benefits mangroves provide us - needs to think hard about this.
Double the biomass of tropical forests overall
Because on average, mangroves have double the living biomass of tropical forests overall. This means that if you want to slow carbon emissions, one of the first places you could look would be in the mangroves.
In a stunning victory for the whales, the International Court of Justice (ICJ) in The Hague announced their binding decision today in the landmark case of Australia v. Japan, ruling that Japan’s JARPA II whaling program in the Antarctic is not for scientific purposes and ordering that all permits given under JARPA II be revoked. The news was applauded and celebrated by Sea Shepherd Conservation Society USA and Sea Shepherd Australia, both of which have directly intervened against Japanese whalers in the Southern Ocean.
Representing Sea Shepherd in the courtroom to hear the historic verdict were Captain Alex Cornelissen, Executive Director of Sea Shepherd Global and Geert Vons, Director of Sea Shepherd Netherlands. They were accompanied by Sea Shepherd Global’s Dutch legal counsel.
The case against Japan was heard by the ICJ in July of last year to decide whether Japan is in breach of its international obligations in implementing the JARPA II “research” program in the Southern Ocean, and to demand that Japan cease implementation of JARPA II and revoke any related permits until Japan can make assurances that their operations conform with international law.
In a vote of 12 to 4, the ICJ ruled that the scientific permits granted by Japan for its whaling program were not scientific research as defined under International Whaling Commission regulations. It ordered that Japan revoke the scientific permits given under JARPA II and refrain from granting any further permits under that program.
Prior to the verdict, there had been some speculation that the ICJ would not permit the hunting of endangered fin and humpback whales, but it would compromise and allow the hunting of minke whales. However, it has been Sea Shepherd’s contention all along that — no matter the species — no whales should be killed, especially in a sanctuary. Sanctuary means “a place of refuge or safety; a nature reserve” where animals are protected. To allow killing in an internationally designated sanctuary is to make a mockery of international agreements made by those countries who established the sanctuary in 1994. At that time, 23 countries supported the agreement and Japan was the only IWC member to oppose it.
Even the Ambassador from Japan to the U.S., Kenichiro Sasae, during a public meeting in Los Angeles in December 2013 attended by representatives of Sea Shepherd USA, had this to say about whales and whaling: ”As an individual, I like whales and if you go out and see the whales, there is no reason for us to kill this lovely animal. But it’s history and it’s politics, I would say. There are a small number of Japanese people still trying to get this won. But mainstream Japanese are not eating whale anymore.” At the same meeting, Ambassador Sasae stated that Japan will abide by the ICJ ruling.
Sea Shepherd Conservation Society’s international volunteer crew stood on the frontlines in the hostile and remote waters of Antarctica for eight years and then Sea Shepherd Australia took up that gauntlet for the last two years and will keep confronting Japanese whalers in Antarctica until we can once and for all bring an end to the killing in this internationally designated “safety zone” for whales. Over the years, Sea Shepherd has been the only organization to directly intervene against Japan’s illegal commercial whaling conducted under the guise of research, with their claims of research globally questioned. Indeed, Sea Shepherd has been the only thing standing between majestic whales and the whalers’ harpoons, as these internationally protected species — many of them pregnant — migrate through Antarctic waters each year.
“With today’s ruling, the ICJ has taken a fair and just stance on the right side of history by protecting the whales of the Southern Ocean Whale Sanctuary and the vital marine ecosystem of Antarctica, a decision that impacts the international community and future generations,” said Captain Alex Cornelissen of Sea Shepherd Global.
“Though Japan’s unrelenting harpoons have continued to drive many species of whales toward extinction, Sea Shepherd is hopeful that in the wake of the ICJ’s ruling, it is whaling that will be driven into the pages of the history books,” he said.
“Despite the moratorium on commercial whaling, Japan has continued to claim the lives of thousands of the gentle giants of the sea in a place that should be their safe haven,” said Sea Shepherd Founder, Captain Paul Watson. “Sea Shepherd and I, along with millions of concerned people around the world, certainly hope that Japan will honor this ruling by the international court and leave the whales in peace.”
"The International Court of Justice findings that Japan's whaling is illegal vindicates a decade of courageous actions by Captain Paul Watson and his crews," Sea Shepherd Australia Chariman Bob Brown said.
"All across Australia people will be celebrating this win due to Sea Shepherd and their huge public support for protecting whales in this country that led to the Australian Government to take this legal action. Australian Prime Minister Tony Abbott should tell Japan, 'Never cross the equator again with a whale harpoon gun'," Dr. Brown continued.
"This result gives further credit to Sea Shepherd for not only upholding Australian Federal laws also International laws in defending the Southern Ocean Whale Sanctuary for the whales and for future generations." said Jeff Hansen, Sea Shepherd Australia Managing Director.
Sea Shepherd Global will have the ships prepared to return to the Southern Ocean in December 2014 should Japan choose to ignore this ruling. If the Japanese whaling fleet returns, Sea Shepherd crew will be there to uphold this ruling against the pirate whalers of Japan.
By Dominique Roche, Australian National University
Have you ever been snorkelling or scuba diving on a windy day when there are lots of waves? Did you notice how much that flow of water against your body affected your ability to swim and control your movements underwater? Well, fish feel the same way!
Water flow, in waves and currents, plays a huge role in determining whether fish can survive in freshwater or marine habitats. Some species, such as tuna or salmon, are designed for high speed swimming, and thrive in fast flowing water.
Others, such as pufferfish, are not so well equipped to handle the challenges of living in high flow environments, and prefer the peace and calm of sheltered lagoons.
But even good swimmers have their limits. For example, high rates of water discharge from hydroelectric dams can hinder the upstream movements of fish – think of North American salmon or Macquarie perch in Australia.
Not all individual fish are affected the same, of course. Bigger, stronger adults are generally more capable of fighting against strong currents, but smaller, younger fish will be less likely to make it. This has obvious consequences for the age structure and survival of fish populations in the long run.
On the Australian coastline, waves created by winds are a major physical force that fish have to contend with.
Some fish species are “rovers” without a fixed home range, and constantly swim over large areas in search of food or mates. Examples include species of surgeonfish and parrotfish. Since they do not need to defend a territory, these fish can take advantage of waves to help them move around, much like surfers do.
In contrast, many other species, such as damselfish, have small territories that they defend vigorously against unwelcome intruders to protect their food and other resources. To do this, they constantly have to swim against the water flow to avoid being swept away.
Colleagues and I have found that fish spend a lot more energy when they have to swim against big waves compared to a regular, steady current at the same average speed. This makes sense: humans also burn a lot more energy during interval training (when constantly changing between a sprint and a jog) compared to running at a constant speed.
Many fish species regularly face these challenges, especially on Australia’s Great Barrier Reef.
Coral reefs are shallow habitats because corals need light to photosynthesise and produce their food. Because of their proximity to the surface, coral reefs are often very wavy habitats. This poses a real challenge for the estimated 25% of marine species found on coral reefs, 4,000 of which are fish.
Researchers are increasingly concerned that accelerating changes in weather patterns are affecting fish and other aquatic organisms. Rivers, lakes and coastal habitats are ecologically, socially and economically important places, so it’s worth investing the time to research the impacts of climate change on these areas.
If waves are costly for some fish, then why don’t they move to calmer locations? Fish can swim, after all. And some won’t even have to swim very far to reach calmer waters. Water velocity can vary across very small scales on coral reefs.
A new underwater instrument was developed at James Cook University to measure wave forces on the sea floor.
A study from January this year using this device showed that water speeds decrease dramatically the deeper you go on coral reefs at Lizard Island. On a windy day, the water flow speed at 9m below the surface is about one quarter of the flow speed at 3m depth.
But there are many reasons why fish might not move to calmer reefs or go deeper to avoid waves:
Our understanding of how fish deal with waves, let alone adapt to changes in their flow environment, is very limited.
Answers to many important questions remain elusive – what aspects of their shape, physiology and behaviour allow certain species to thrive in their current habitats?
How do waves affect important phenomena like the outcome of predator-prey encounters, competition between individuals, or the survival of small, larval fish on the reef?
How does water flow interact with other stressors like temperature changes, ocean acidification and fishing pressure in shaping our changing marine communities?
Ultimately, more research into these questions will help us understand how fish might respond to expected changes in their flow environment. These answers will be critical to inform marine resource managers and help them identify and target species that are especially sensitive to increases in wave intensity.
Dominique Roche receives funding from the Australian Research Council Centre of Excellence for Coral Reef Studies.
This article was originally published on The Conversation. Read the original article.
By Jessica Meeuwig, University of Western Australia
One of the most common justifications for Western Australia’s shark cull is the longstanding use of baited hooks - or drum lines - in regions such as Queensland.
Two key questions need answering. First, is there clear evidence that drum lines reduce the number of human fatalities from sharks? And second, what is their cost in terms of killing marine wildlife?
To that end, I have analysed publicly available figures for human fatalities in Queensland with data on the program’s shark catch, to provide an assessment of its effectiveness.
Over more than half a century, the program has taken a large toll on wildlife, while any increase in human safety has been equivocal at best.
As of December 2013, there were 369 drum lines and 30 nets deployed off the Queensland coast, mostly near swimming beaches. The program has grown steadily since it began in April 1962 with the deployment of 24 drum lines on the Gold Coast; it now extends to Cairns across a total of ten regional areas.
Drum lines and shark catches graph Click here to open in new window.
Between 1853 and 2013 there were at least 71 human fatalities due to unprovoked shark attacks in Queensland, with the majority of these attributed to tiger sharks and only a single fatality to white sharks.
Queensland shark fatalities at beaches with drum lines graph Click here to open in new window.
During these 160 years, the average fatality rate varied. From 1850 to 1910 it was 0.32 fatalities per year, but then a spike in fatalities in the 1920s saw the average increase to 1.1 per year. After that, the rate of fatal attacks generally declined, falling to a low of 0.2 per year in the 1990s. Since 1962, when the drum line program began, the fatality rate has averaged 0.37 per year, a number not significantly different than that previous to the 1920s.
The graph shows that there has been a significant decline in Queensland’s rate of shark attack fatalities but that it started 40 years before drum lines were first deployed. There has been no further reduction in fatalities since the program began, despite half a century of increasing drum line deployments.
Note also that these statistics include fatalities in areas with and without drum lines. Of the 71 reported Queensland fatalities, 50 were in areas such as the outer Great Barrier Reef or Moreton Bay, where no drum lines (or nets) are present.
In areas without drum lines, the average fatality rate, calculated on a decadal basis, was 0.34 per year before 1970 (used as a cut off point given the 1960s saw only relatively few drum limes compared to the full program now implemented) and 0.24 afterwards. Even without drum lines, fatalities declined by 28% between these two periods.
In areas with drum lines, fatality rates fell from 0.05 to 0.02 fatalities per year pre- and post installation of the drum lines, a decline of 70%. This suggests that the fatality rate fell more rapidly in areas with drum lines than those without.
However, this result is deceptive. Of the seven locations with drum lines only (no nets), six had recorded only a single fatal attack prior to the installation of drum lines (ranging from 5 to 95 years before the lines were deployed). Only Kissing Point had a history of more than one fatality (in 1916, 1933 and 1955) before drum lines were installed in 1965. So for the most part, this apparently rapid decline represents the difference between one attack that could have occurred up to 95 years ago, and no attacks today at a limited number of sites.
This highlights the problems we face when trying to understand patterns in shark attacks and the effect of mitigation programs – fatalities are such rare events that differentiating between random coincidence and underlying patterns is fraught with difficulty.
In contrast to their contribution to human safety, one thing we can be certain of is drum lines' ecological cost. The most recent available data show that Queensland caught some 6250 sharks on drum lines between 2001 and 2013, or an average of 480 animals per year.
This catch included 35 different species, the most common being tiger sharks (41%), bull sharks (17%) and black tip reef whalers (12%). White sharks, although considered a key target species in WA, represent less than 1% of the Queensland catch with about five caught per year.
Only 3% of the sharks killed on Queensland drum lines are considered not to be at conservation risk. According to the International Union for Conservation of Nature, four species, representing 5.2% of the catch, are “endangered”; nine species (9.6% of the catch) are "vulnerable”; and 15 species (80.6%) are classed as “near threatened”. Only six species (1%) are considered to be of “least concern”, while one species (2%) is considered “data deficient”.
Sharks longer than 3 metres have been classified as dangerous to humans, at least in WA. Yet only 11% of the animals culled in Queensland were larger than this – the average size of sharks captured on the drum lines was 1.9 metres.
In terms of reproductive maturity, all of the white sharks and most of the tiger and bull sharks that were caught were juveniles. As a key strategy for shark recovery is the protection of large breeding individuals, this may appear a reasonable outcome. But equally, juvenile deaths will ultimately reduce the future population of breeding adults.
Based on this analysis, we can conclude that:
Shark-related fatalities in Queensland have declined in both areas with and without drum lines, with the steepest rates of decline before their installation.
The effectiveness of drum lines is difficult to evaluate, as the rates of attacks before and after their deployment are both very low. Moreover, 83% of drum lines are deployed at locations where a fatal attack has never occurred.
The ecological cost of drum lines is high, with 97% of sharks caught since 2001 considered to be at some level of conservation risk, and 89% caught in areas where no fatalities have occurred.
It could be argued that the drum line program in Queensland is justified simply because it may remove sharks from popular areas. However, it is a very blunt tool and ignores the important ecological roles that sharks play in our oceans.
Moreover, its success in reducing human fatalities is hard to validate. The decreases may simply reflect broader declines in shark populations, driving down encounter rates despite the increased human presence in the ocean. Or they may simply be random.
There are non-lethal techniques that can potentially achieve much better outcomes. Humans and sharks alike could benefit from an approach that embraces new ideas, rather than one that has produced little measurable effect in half a century, other than to kill threatened species.
Correction: data labelling in interactive maps was amended February 23.
Jessica Meeuwig does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.
This article was originally published on The Conversation. Read the original article.