The double burden of climate change
A new study on the effects of climate change in five tropical countries has found fisheries are in more trouble than agriculture, and poor people are in the most danger. Distinguished Profess
Understanding of the links between coral reef ecosystems, the goods and services they provide to people, and the wellbeing of human societies.
Examining the multi-scale dynamics of reefs, from population dynamics to macroevolution
Advancing the fundamental understanding of the key processes underpinning reef resilience.
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Researchers have discovered some good news for fish populations living on coral reefs hit by climate change.
Renato Morais is a PhD candidate from the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University (JCU). He led a study that looked at how fish on a bleached coral reef get their food.
“We already knew that coral reef fish rely on food drifting in from the sea, such as plankton,” Mr Morais said.
“But, we didn’t know exactly how important this was,” he said.
Mr Morais and Professor David Bellwood, also from Coral CoE at JCU, combined high-resolution surveys and individual biomass production estimates to generate the first map of where the energy comes from for all fish on a coral reef.
“We looked at everything from gobies to coral trout and large jacks, assessing more than 18,000 fish from over 300 species,” said Mr Morais.
“We found that various transport mechanisms, such as currents and tides, interact with the reef and bring in vast amounts of plankton.”
The pair found that for every kilogram of fish produced on the reef more than 400 grams of that kilogram relied on food derived from the open ocean, rather than the reef itself. This rises to almost 600 grams on the side of the reef facing the open ocean.
“This means, that for many reefs, food from outside can sustain fish populations, even when the coral is badly damaged,” Prof Bellwood said.
The scientists found that areas of the reef that were more exposed to the open ocean produced the largest quantities of fish – with reef slopes being the most fruitful.
“The discovery that reef fish get so much of their food from off-reef sources was encouraging, especially because many species that feed on oceanic material have a history of disappearing after coral loss,” said Mr Morais.
“This is the first time we have been able to put all species in perspective,” said Prof Bellwood. “Our study offers hope that reefs subject to coral loss can still be productive.”
“The reefs may be damaged but they are still incredibly valuable.”
The study is published today: Morais R and Bellwood D (2019). ‘Pelagic Subsidies Underpin Fish Productivity on a Degraded Coral Reef’. Current Biology: https://doi.org/10.1016/j.cub.2019.03.044
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An international team of researchers have described a remarkable new species of fish that lived in the sea in the time of the dinosaurs in the late Jurassic about 150 million years ago.
The new species of bony fish had teeth like a piranha, which the researchers from the ARC Centre of Excellence for Coral Reef Studies (Coral CoE, Australia) and Jura-Museum Eichstätt (Germany), suggest they used as piranhas do: to bite off chunks of flesh from other fish.
As further support for that notion, the team also found the victims – other fish that had apparently been nibbled on – in the same limestone deposits in South Germany (the quarry of Ettling in the Solnhofen region) where this piranha-like fish was found.
“This is an amazing parallel with modern piranhas which feed predominantly not on flesh but the fins of other fishes. It’s a remarkably smart move as fins regrow, a neat renewable resource. Feed on a fish and it is dead; nibble its fins and you have food for the future.”
The newly described fish is part of the world famous collections in the Jura-Museum in Eichstätt. It comes from the same limestone deposits that contained the first feathered proto-bird known as Archaeopteryx.
Careful study of the fossilized specimen’s well preserved jaws revealed long, pointed teeth on the exterior of the vomer, a bone forming the roof of the mouth, and at the front of both upper and lower jaws. Additionally, there are triangular teeth with serrated cutting edges on the pre-articular bones that lie along the side of the lower jaw.
The tooth pattern and shape, jaw morphology and mechanics suggest a mouth equipped to slice flesh or fins, the international team of researchers report. The evidence points to the possibility that the early piranha-like fish may have exploited aggressive mimicry in a striking parallel to the feeding patterns of modern piranha.
“We were stunned that this fish had piranha-like teeth,” Dr Martina Kölbl-Ebert of Jura-Museum Eichstätt (JME-SNSB) said.
“It comes from a group of fishes (the pycnodontids) that are famous for their crushing teeth. It is like finding a sheep with a snarl like a wolf. But what was even more remarkable is that it was from the Jurassic.”
“Fish as we know them, bony fishes, just did not bite flesh of other fishes at that time. Sharks have been able to bite out chunks of flesh, but throughout history bony fishes have either fed on invertebrates or largely swallowed their prey whole. Biting chunks of flesh or fins was something that came much later,” Kölbl-Ebert explained
Or, so it had seemed.
“The new finding represents the earliest record of a bony fish that bit bits off other fishes, and what’s more, it was doing it in the sea,” Bellwood said, noting that today’s piranhas all live in freshwater.
“So when dinosaurs were walking the earth and small dinosaurs were trying to fly with the pterosaurs, fish were swimming around their feet tearing the fins or flesh off each other.”
The researchers call the new find a “staggering example of evolutionary versatility and opportunism.” With one of the world’s best known and studied fossil deposits continuing to throw up such surprises, they intend to keep up the search for even more fascinating finds.
Citation: Kölbl-Ebert, M, Ebert, M, Bellwood, DR & Schulbert, C (2018) A Piranha-like Pycnodontiform Fish from the Late Jurassic. Current Biology 278(21): 3516 – 3521 DOI: 10.1016/j.cub.2018.09.013
Prof David Bellwood (AUSTRALIA) – on leave until Nov.
Dr Martina Kölbl-Ebert (GERMANY)
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New research reveals that global warming also affects fish who depend on corals.
The Great Barrier Reef (GBR) is revered for its kaleidoscope of colour. New international research led by PhD student Laura Richardson of the ARC Centre of Excellence for Coral Reef Studies at James Cook University reveals that coral bleaching events not only whitewash corals, but can also reduce the variety of fish occupying these highly-valued ecosystems.
The study was conducted by researchers at James Cook University and Lancaster University, U.K., who examined 16 reefs off Lizard Island, in the northern section of the GBR. The quantity and types of coral and fish species were surveyed before, during and after the 2016 mass bleaching event caused by a global heatwave.
“The widespread impacts of heat stress on corals have been the subject of much discussion both within and outside the research community. We are learning that some corals are more sensitive to heat-stress than others, but reef fishes also vary in their response to these disturbances,” said lead author Ms Richardson.
“Fish assemblages are significantly impacted by loss of coral cover as a result of bleaching events, and some fishes are more sensitive than others,” said co-author Prof Nick Graham of Lancaster University.
The loss of corals affected some types of fish more than others. Following the bleaching event, researchers recorded a sharp drop in the diversity of fish communities as the mix or species changed.
Fish that are highly dependent on branching corals, such as butterflyfish, declined the most.
“Prior to the 2016 mass bleaching event, we observed significant variation in the number of fish species, total fish abundance and functional diversity among different fish communities. Six months after the bleaching event, however, this variation was almost entirely lost,” said co-author Dr Andrew Hoey of ARC Centre of Excellence for Coral Reef Studies at James Cook University.
“Also known as ‘biotic homogenisation,’ this tendency towards individual and community similarity is increasingly considered one of the most pressing, but largely unrecognised, biodiversity crises faced globally.”
Citation: Richardson, LE, Graham, NAJ, Pratchett, MS, Eurich, JG, and Hoey, AS (2018). Mass coral bleaching causes biotic homogenization of reef fish assemblages. Global Change Biology, doi:10.1111/gcb.14119
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Lancaster University, Lancaster Environment Centre
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New research examining the possible impacts of ocean acidification provides fresh hope for the survival of reef fish.
Just as when a camera lens comes into focus, the latest research published today sharpens understanding of the implications of ocean acidification on reef fish behaviour, yielding promising results for their current and near-future survival.
Chemical changes in the ocean, as a result of climate change, are leading to a more acidic environment, referred to as ‘ocean acidification’ (OA). In a laboratory setting, these changes have been shown to lead to a range of risky behaviours in the affected fish, with some fish unable to flee from their finned foes effectively.
But, when researchers recalibrated experiments to adjust for natural daily changes in concentrations of dissolved carbon dioxide (CO2), the primary chemical driver of OA, they found that the fish were less affected than previously thought.
“Shallow water habitats where reef fish live can experience substantial natural fluctuations in water chemistry throughout the day,” explained senior author Professor Philip Munday, of the ARC Centre of Excellence for Coral Reef Studies (CoralCoE) at James Cook University.
“For example, carbon dioxide levels on coral reefs are often much lower during the day than they are at night.
“Our data suggests that these natural daily changes in water chemistry are enough to provide fish with a recovery period, reducing their sensitivity to higher carbon dioxide levels,” said Michael D. Jarrold, lead author of the study and PhD student at James Cook University.
The study published today in Scientific Reports, utilised state-of-the-art facilities at James Cook University and at the Australian Institute of Marine Science’s National Sea Simulator (SeaSim) to mimic the natural conditions of a coral reef environment.
“It’s the first time these dynamic natural conditions have been reproduced in a laboratory setting to test their potential influence on the behaviour of coral reef fish,” explained Mr. Jarrold.
“We are thrilled about what we’ve found,” he added. “Our results provide a greater level of optimism for reef fish populations in the future.”
Previous OA research has largely used stable, open ocean conditions to guide the experimental design.
“Broadly speaking, such studies reported reduced anti-predator responses, as compared with the control group,” said Prof Munday.
“Such abnormal behaviours were feared to pose significant ecological consequences for fish populations,” he explained.
The researchers’ ability to precisely control the complex combinations of environmental variables required to accurately simulate both naturally occurring and human-influenced water conditions was crucial to achieving this breakthrough.
“With the world’s most advanced experimental marine technology at our finger tips, and the considerable efforts of our specially skilled team, the SeaSim was able to recreate the natural daily CO2 cycles found on the reef,” said Craig Humphrey, co-author and SeaSim precinct manager at the Australian Institute of Marine Science.
“We’re excited to play a part in such fantastic and novel research.”
The paper titled: “Diel CO2 cycles reduce severity of behavioural abnormalities in coral reef fish under ocean acidification” is available online at:
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Mr Michael D. Jarrold
James Cook University
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In a world first study, researchers at the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University have unlocked the genetic mystery of why some species are able to adjust to warming oceans.
In a collaborative project with scientists from the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, the researchers examined how reef fish’s genes responded after several generations living at higher temperatures.
“Some fish have a remarkable capacity to adjust to higher water temperatures over a few generations of exposure,” says Dr Heather Veilleux from the Coral CoE.
“But until now, how they do this has been a mystery.”
Using cutting-edge molecular tools the research team identified 53 key genes that are involved in long-term, multi-generational acclimation to higher temperatures.
“By understanding the function of these genes we can understand how fish cope with higher temperatures,” explains Dr Veilleux.
“We found that shifts in energy production are key to maintaining performance at high temperatures,” says Dr Veilleux.
“Immune and stress responses also helped fish cope with warmer water.”
The project involved rearing coral reef fish at different temperatures for multiple generations in purpose-built facilities at James Cook University.
“We then used state-of-the-art genetic methods to examine gene function in the fish,” says Dr Tim Ravasi from KAUST.
“ By matching gene expression to metabolic performance of the fish we were able to identify which genes make acclimation to higher temperatures possible,” adds Professor Philip Munday from the Coral CoE.
The study is the first to reveal the molecular processes that may help coral reef fishes and other marine species adjust to warmer conditions in the future.
“Understanding which genes are involved in transgenerational acclimation, and how their expression is regulated, will improve our understanding of adaptive responses to rapid environmental change and help identify which species are most at risk from climate change and which species are more tolerant,” Dr Veilleux says.
Molecular processes of transgenerational acclimation to a warming ocean, by Heather D. Veilleux, Taewoo Ryu, Jennifer M. Donelson, Lynne van Herwerden, Loqmane Seridi, Yanal Ghosheh, Michael L. Berumen, William Leggat, Timothy Ravasi and Philip Munday is published in the journal Nature Climate Change.
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Scientists at the ARC Centre of Excellence for Coral Reef Studies at James Cook University say more needs to be done to protect vulnerable table corals on the Great Barrier Reef.
Researchers studying the role of table corals have found that they provide vital sun protection for large fish in shallow reef areas.
They found that the corals are so important that if lost, the fish that depend on them will leave the reef.
“The loss of table corals denies fishes important habitat, which they use to shelter from the sun, avoiding harmful UV-radiation, just as we might sit under an umbrella at the beach,” says study lead author James Kerry.
“Large fishes maintain balanced coral reef ecosystems, they’re the predators that help control fish populations,” says study co-author Professor David Bellwood.
“These fish are important for reefs and people; lose your table corals and you lose your coral trout,” Professor Bellwood explains.
The scientists say this is particularly concerning as table corals are especially vulnerable to the pressures currently facing the Great Barrier Reef.
The corals are highly susceptible to ocean acidification and bleaching, and are the preferred meal of the destructive crown of thorns starfish.
Given their shape, table corals are also easily toppled and are often destroyed in cyclones.
“Ultimately we need to conserve table corals because they are the primary structure on the Reef that provides shelter from the sun’s harmful rays. However, because they are so vulnerable to climate change and other growing threats, this is going to be a major challenge,” James Kerry says.
“The research suggests that we need to do everything we can to promote the health of the Great Barrier Reef, and in doing so, reduce the multiple threats facing these valuable corals.”
The functional role of tabular structures for large reef fishes: avoiding predators or solar irradiance? By J.T. Kerry and D.R. Bellwood is published in the journal Coral Reefs.
Do Tabular corals constitute keystone structures for fishes on coral reefs? By J.T Kerry and D.R. Bellwood is published in the journal Coral Reefs
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A simple test of the number of fish living on a coral reef can be used as a roadmap to restore degraded reefs and fishers’ livelihoods according to a global study published in the journal Nature.
An international team of marine scientists surveyed more than 800 coral reefs worldwide to develop a diagnostic test of reef health.
“By studying remote and marine protected areas, we were able to estimate how many fish would be on a coral reef 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.
Coral reefs are home to thousands of species of fish and provide food and income for millions of people, particularly those in the developing world. Yet the scientists found that the vast majority of fished reefs they examined have lost more than half of their fish.
Marine reserves are the most effective way to recover fish populations, however, there are no benchmarks to determine if the protection is effective, or whether a reserve has recovered enough to be fished again.
The authors say it is also not feasible to lock away reef resources indefinitely when so many people depend on them for their livelihoods.
To solve this problem, the team studied the fish biomass on coral reefs around the world and discovered that near-pristine reefs contain 1,000 kilos (a tonne) of fish per hectare. Using this figure as a benchmark, they found that 83 per cent of fished reefs have lost more than half of their fish biomass (volume of fish).
From their work the scientists were able to determine that once protected, previously fished reefs take about 35 years to recover, while heavily depleted reefs take almost 60 years.
Co-author, Dr Nick Graham from the ARC Centre of Excellence for Coral Reef Studies at James Cook University says it was encouraging to find that substantial biomass remained where some form of management was in place.
“Changes in fishing practices can result in a significant return of key fish species over time,” Dr Graham says.
“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.
“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.”
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
Co-author, Dr Tim McClanahan, 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.
“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,” Dr McClanahan says.
“By choosing to conserve resources, fishers and managers have the ability to plan for recovery and help reefs remain productive in the face of increasing stress from climate disturbances.”
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.
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Dr Nicholas Graham, Coral CoE, +61 (0)466 432 188, email@example.com
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Stress isn’t just a problem for the modern Australian mother: it’s also a big issue for female fish and their offspring on the Great Barrier Reef.
Groundbreaking research by Dr Mark McCormick, a Chief Investigator in the Australian Research Council Centre of Excellence for Coral Reef Studies based at James Cook University has found that stressed mother fish have smaller babies, with lower chances of survival.
And one thing that causes a female fish plenty of stress is aggro from lots of other female fish.
“Stressed fish may not seem like a big issue for people, but we’ve now found clear evidence that stress is an important factor in the health of fish populations and their ability to renew themselves,” Dr McCormick says.
“It’s about the resilience of the whole population and its ability to withstand other kinds of stresses, like poor water quality, reef damage or overfishing, which human activities place on them.”
“This has big implications for the sustainable management of both fish stocks, which supply our food, and sensitive marine ecosystems like the GBR which we rely on for tourism.”
Dr McCormick’s research into damselfish, Pomacentrus ambionensis, shows that the number of other females interacting with breeding females had a direct impact on the size of the young fry, which were mostly smaller and less able to survive.
“We set up some experiments where we introduced more females into a confined area where there was a breeding pair. We found that the more females present, the higher the levels of aggression between them – and the higher the levels of the stress-hormone, cortisol, in their ovaries.
“While the number of eggs produced remained the same, the baby fish were noticeably smaller and less able to survive or settle on the reef.”
Other research confirms that the size of fry is a big factor in ultimate survival rates, and hence, in the resilience of the population overall and its ability to recover from setbacks.
“The implication of these findings for the resilience of the population is that, when population densities are low and patchily distributed, such as at the limits of geographic ranges, maternal conditions will promote the production of large larvae that may have a higher probability of surviving.”
Dr McCormick’s research showed that pairs of damselfish breeding in isolation produced the biggest and most viable offspring – the so-called “silver spoon effect” in which privileged offspring have better chances.
He theorises that the ability to cope with stress – and produce large, healthy fry – may also be a factor in determining which females contribute to the future population and influence how resilient it will be.
“Round the world we’ve seen fish populations under great pressure from fishing and other human activities. This sort of research underpins our understanding of fish population dynamics – and the factors which can cause a population to collapse or to recover,” he adds.
McCormick, MI (2006). “Mothers Matter: Crowding leads to stressed mothers and smaller offspring in Marine Fish.” Ecology 87(5): 1104–1109.
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