Future too warm for baby sharks
New research has found as climate change causes the world’s oceans to warm, baby sharks are born smaller, exhausted, undernourished and into environments that are already difficult for them to survi
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Corals growing in high-latitude reefs in Western Australia can regulate their internal chemistry to promote growth under cooler temperatures, according to new research at the ARC Centre of Excellence for Coral Reef Studies at The University of Western Australia.
The study, published today in Proceedings of the Royal Society B, suggests that ocean warming may not necessarily promote faster rates of calcification of corals on sub-tropical reefs where temperatures are currently cool (lower than 18C).
Lead author Claire Ross said the study was carried out over two years in Western Australia’s Bremer Bay, 515km south-east of Perth in the Great Southern region. Bremer Bay is a renowned diving, snorkelling and tourism hot spot due to its stunning crystal clear waters, white sand and high marine biodiversity.
“For two years we used cutting-edge geochemical techniques to link the internal chemistry of the coral with how fast the corals were growing in a high-latitude reef,” Ms Ross said.
“These high-latitude reefs (above 28 degrees north and below 28 degrees south) have less light and lower temperatures compared to the tropics, and essentially they provide natural laboratories for investigating the limits for coral growth.”
Ms Ross said the researchers expected the corals to grow slower during winter because the water was colder and light levels lower but they were surprised to find the opposite pattern.
“We were able to link the remarkable capacity for cold-water corals to maintain high growth during winter to the regulation of their internal chemistry,” she said.
“We also found that there was more food in the water for corals during winter compared to summer, indicating that (in addition to internal chemical regulation) corals may feed more to sustain growth.”
Coral reefs are one of world’s most valuable natural resources, providing a habitat for many ocean species, shoreline protection from waves and storms, as well as being economically important for tourism and fisheries.
However, the capacity for corals to build their skeletons is under threat due to CO2-driven climate change. The effects of climate change on coral reefs are likely to vary geographically, but relatively little is known about the growth rates of reefs outside of the tropics.
“Our study is unique because it is among the first to fully decipher the corals’ internal chemistry,” Ms Ross said. “The findings of this study help better understand and predict the future of high-latitude coral reefs under CO2-driven climate change.”
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Citation:Ross, CL, Schoepf, V, DeCarlo, TM, McCulloch, MT (2018). Mechanisms and seasonal drivers of calcification in the temperate coral Turbinaria reniformis at its latitudinal limits. Proceedings of the Royal Society B. Volume 285 (1879). DOI: 10.1098/rspb.2018.0215
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Scientists from the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at The University of Western Australia (UWA) have found that some corals are able to combat the effects of ocean acidification by controlling their own chemistry.
Coral reefs play an important role in protecting coastlines from damage caused by waves and storms, but also provide habitat and shelter for many marine organisms. However, major environmental challenges such as climate change, threaten the survival of coral reefs worldwide.
The world-first study is a breakthrough for marine science because the scientists have identified marine species that are resilient to ocean changes, which will help better understand how to protect coral reefs in the future.
Lead author Dr Thomas DeCarlo said rising carbon dioxide (CO2) levels in the atmosphere were reflected in the ocean, which leads to ocean acidification.
“Acidification hampers the ability of the coral to form skeletons and shells which are the building blocks of reefs,” Dr DeCarlo said.
“In the past few decades, hundreds of experiments have shown that corals have a highly diverse response to ocean acidification depending on the species. However, the reasons why some are more tolerant than others are not clearly understood.
Dr DeCarlo and his team developed a new method to understand the internal chemistry of corals by using specialised equipment that measures the characteristics of the molecules in coral.
“The method showed corals with the most resistance are tolerant because of the way they are able to regulate their calcium levels,” Dr DeCarlo said. “This technique means scientists can identify species that are relatively resistant to ocean acidification.”
“However, we are also looking at the costs associated with resisting acidification, which may potentially make acidification-resistant corals more vulnerable to other stressors.”
Co-author Professor Malcolm McCulloch said previous studies found that even the more hardy coral species lose their ability to adapt to ocean acidification when they bleach under extreme heat events, as experienced in 2016.
“When a coral bleaches, it expels its ‘powerhouse’ – zooxanthellae symbionts, and loses the energy needed to keep its internal mechanisms running,” he said. ”The longer corals stay bleached, the less likely they are to recover.”
The paper, Coral resistance to ocean acidification linked to increased calcium at the site of calcification is published in Proceedings of the Royal Society B
Citation: DeCarlo, TM, Comeau, S, Cornwall, CE, and McCulloch, MT (2018). Coral resistance to ocean acidification linked to increased calcium at the site of calcification. Proc. R. Soc. B 20180564. DOI: http://dx.doi.org/10.1098/rspb.2018.0564
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Coral reefs can naturally protect coasts from tropical cyclones by reducing the impact of large waves before they reach the shore, according to scientists.
Tropical cyclones wreak havoc on coastal infrastructure, marine habitats and coastal populations across the world. However, Dr. Michael Cuttler, from the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at The University of Western Australia (UWA), says that for coastlines facing a direct cyclone impact, a fringing reef can protect the beach from extensive erosion.
“Reefs can effectively protect shorelines because of their ability to cause waves to break offshore, thus limiting the energy impacting the coastline,” he said.
Dr. Cuttler and several of his Coral CoE colleagues studied Ningaloo Reef – Australia’s largest fringing reef system, and a UN World Heritage site – during Tropical Cyclone Olwyn in 2015. Olwyn was a Category 3 severe tropical cyclone that caused extensive damage along the coast of Western Australia.
The team observed that the shoreline remained largely unscathed because of the protection provided by its offshore reef.
“The large waves generated by the cyclone were effectively dissipated by the reef situated offshore,” Dr. Cuttler explained.
“The little erosion that did occur was due to smaller waves that were generated by wind within the lagoon.”
The shape, or geomorphology, of the reef – with its steep forereef slope, shallow reef crest and reef flat, and relatively shallow lagoon – is representative of most fringing reefs worldwide.
“In this study, we also compared similar cyclone impacts on coastlines without reefs and found that these beaches were eroded up to ten times more than the beach at Ningaloo,” Dr. Cuttler said.
While the findings of Dr. Cuttler’s study indicated that coral reefs can effectively protect coastlines from tropical cyclones and other large wave impacts, it also suggested that for reef systems with lagoons, local wind effects cannot be ignored when attempting to model or predict the impact of cyclones.
He also warned that the ability of reefs to protect adjacent coastlines was threatened by both sea level rise and slowing rates of reef accretion.
“These changes may ultimately increase the amount of wave energy reaching the coastline and potentially enhance coastal erosion,” he said.
Few studies before have measured the hydrodynamic conditions and morphological responses of such a coastline in the presence of a tropical cyclone.
Dr. Cuttler and his Coral CoE colleagues found the results could be used to assess coastal hazards facing reef-fringed coastlines due to extreme tropical cyclone conditions, and would become increasingly relevant as climate change alters the status of coral reefs globally.
Paper: Cuttler, MV, Hansen, JE, Lowe, RJ and Drost, EJ (2018). Response of a fringing reef coastline to the direct impact of a tropical cyclone. Limnol. Oceanogr., 3: 31-38. doi:10.1002/lol2.10067
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A study has found that coral with high levels of fat or other energy reserves can withstand the impact of annual coral bleaching events, compared to coral with lower levels of fat reserves.
Coral bleaching events occur when sea temperatures rise as the result of climate change. This results in the breakdown of the symbiosis between the coral and their zooxanthellae (which gives coral most of its colour) and threatens the survival of the coral.
The study was carried out by scientists from The University of Western Australia’s Oceans Institute and the ARC Centre of Excellence for Coral Reef Studies, The Ohio State University’s School of Earth Sciences and the University of Delaware’s School of Marine Science and Policy.
Lead author, Dr Verena Schoepf from the ARC Centre of Excellence for Coral Reef Studies at UWA and a Research Associate from the Oceans Institute, says tropical coral is extremely sensitive to heat stress.
“Three global bleaching events have already occurred since the 1980s and will likely occur annually later this century. Therefore, it has become more urgent than ever to know how tropical coral can survive annual bleaching – one of the major threats to coral reefs today,” she said.
“Already bleaching events have resulted in significant amounts of coral dying causing impact to ocean ecosystems, but up until now it was largely unknown whether coral could recover between annual bleaching events.”
Dr Schoepf says the research which simulated annual coral bleaching found some species of coral such as the mustard hill coral (Porites astreoides) were severely affected by repetitive bleaching events, but other coral such as the finger coral (Porites divaricata) and the mountainous star coral (Orbicella faveolata) could recover quickly.
“When coral is bleached, it no longer gets enough food energy and so it starts slowing down in growth and loses its fat and other energy reserves – just like humans do during times of hardship,” she says.
“The coral then becomes increasingly weak and susceptible to disease, and when bleaching is prolonged, it can die.”
Dr Andrea Grottoli from The Ohio State University’s School of Earth Sciences says over the next decades, coral bleaching events were likely to occur more and more frequently and increasingly impact coral reefs around the world, contributing to their worldwide decline.
“Bleaching will significantly change the future of coral reefs with heat sensitive coral unable to recover,” Dr Grottoli says.
“Our research will help with predicting the persistence of coral reefs because knowledge of their capacity to recover from annual bleaching is critical information for these models.”
The research, which was funded by the USA National Science Foundation to Drs. Grottoli and Warner, will be published in the international journal Proceedings of the Royal Society B: Biological Sciences here on Wednesday 18 November.
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Jess Reid (UWA Media) (+61 8) 6488 6876
An international team of scientists, led by the ARC Centre of Excellence for Coral Reef Studies at the University of Western Australia, has analysed coral cores from three reefs in the eastern Indian Ocean to understand how marine heat waves unfold among the unique coral reefs of Western Australia.
The research, which also involved researchers from Australian Institute of Marine Science (AIMS), Curtin University, CSIRO and the University of Santa Barbara California, was published today in the international journal Nature Communications.
Research team leader, Professor Malcolm McCulloch from the ARC Centre of Excellence for Coral Reef Studies at UWA, said the findings provided new insights into how the change in air temperature between the Maritime Continent and the central Pacific affected the wind and ocean circulation leading up to heat waves in the far away south-eastern Indian Ocean.
The Maritime Continent is a term commonly used by scientists to describe the region between the Indian and Pacific Oceans including the archipelagos of Indonesia, Borneo, New Guinea, the Philippine Islands, the Malay Peninsula and the surrounding seas.
“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,” Professor McCulloch said.
“By measuring the chemical composition of the coral skeleton from year to year we could see how changing winds and ocean currents in the eastern Indian Ocean were impacted by climate variability in the western tropical Pacific Ocean.”
Dr Jens Zinke, a Senior Research Fellow at Curtin University and lead author of the research paper while at UWA, said the long coral records allowed the scientists to look at the occurrence of marine heat waves as far back as 1795.
When the Maritime Continent is warmer than the central Pacific, a pattern amplified during strong La Niña events in the tropical Pacific, it creates an ocean temperature gradient which reinforces warming in the far western Pacific and south-eastern Indian Ocean.
Dr Zinke said this happened through a series of ocean-atmosphere interactions that resulted in a strengthened Leeuwin Current and unusually warm water temperatures and higher sea levels off south-west Western Australia.
“A prominent example is the 2011 heat wave along WA’s reefs which led to coral bleaching and fish kills,” he said.
The international team found that the temperature gradient in the western Pacific was particularly strong after the late 1990s. The coral cores also reveal that this temperature gradient was intensified in the early and late 1800s, yet against a much lower background ocean temperature off WA.
The authors concluded that strong warming over the past 215 years made it easier for natural climate events, such as La Niña and West Pacific temperature gradient events, to exceed the critical temperature threshold for marine heat waves and mass coral bleaching to occur off Western Australia.
This will likely diminish the future ability of the coral reefs of Western Australia to serve as a climatically stable area for coral growth under future ocean warming.
Dr Janice Lough, AIMS Senior Principal Research Scientist, said it was likely that, given ongoing global climate change, future La Niña events coupled with a strong West Pacific temperature gradient would result in more extreme warming and high sea-level events with potentially significant consequences for the maintenance of WA’s unique marine ecosystems.
The researchers used core samples of massive Porites colonies from the Rowley Shoals, Ningaloo Reef and the Houtman-Abrolhos Islands off the Western Australian coastline which are directly in the path of warm water transport from the Western Pacific to the waters of southern Australia.
The researchers measured the chemical composition of the annual coral growth bands to reconstruct sea surface temperature of the West Australian shelf for 215 years, from 1795 to 2010.
Paper : Coral record of southeast Indian Ocean marine heatwaves with intensified Western Pacific temperature gradient by J. Zinke, A. Hoell, J. M. Lough, M. Feng, A. J. Kuret, H. Clarke, V. Ricca, K. Rankenburg & M. T. McCulloch is published in the journal, Nature Communications http://www.nature.com/ncomms/2015/151023/ncomms9562/full/ncomms9562.html
Professor Malcolm McCulloch – (+61 8) 6488 1921
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A group of acclaimed scientists from The University of Western Australia’s Oceans Institute and the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) will go where few others have gone before when they set out to unlock the secrets of a deep ocean canyon off Perth the size of the USA’s Grand Canyon.
A UWA team headed by Coral CoE Deputy Director, Professor Malcolm McCulloch, together with researchers from the Western Australian Museum, CSIRO and the Institute of Marine Sciences in Italy, will be among the first to explore life in the vast Perth Canyon, about 50km off Fremantle.
The underwater canyon formed over tens of millions of years and extends from the continental shelf edge of Western Australia to depths of more than four kilometres to the abyssal sea floor. Major up-swelling of essential nutrients in the canyon makes it a global marine hotspot, attracting blue whales and other large fauna that migrate to the waters seasonally to feed. Despite being so close to Perth and Fremantle, little is known about life in its deep abyss.
Professor McCulloch and his team will lead the research expedition on board the Schmidt Ocean Institute’s Research Vessel, R/V Falkor, during a 12-day trip departing on Sunday, 1 March.
Researchers will use a deep-diving remotely operated vehicle (ROV) to discover and collect deep-sea corals and sea water from the canyon. Chemical and biological analyses of these rare samples will provide critical new data about the canyon’s marine ecosystems. This will help determine the likely future impacts of warming seas and ocean acidification on the deep-sea life and waters in these remote and previously inaccessible habitats.
Professor McCulloch said that ROV exploration had never before been carried out there, making it a voyage of genuine discovery.
“The deep ocean is the largest habitat on earth but it’s the world’s least explored environment – we know more about the surface of the moon than we do about the deep sea floor,” Professor McCulloch said.
“The Perth Canyon is a great unknown. It is the largest submarine canyon along Australia’s shelf, less than a stone’s throw from WA’s capital city, yet has never been subject to rigorous scientific investigation.
“We plan to unlock its secrets using modern tools such as an ROV to collect samples, then utilise a suite of geochemical tools to investigate its longer-term history and future capacity to cope with the pressures of climate change.”
He said despite the challenges of exploration in such remote environments, it was important to research such habitats because of their key role in the Earth’s climate system and in supplying the essential nutrients to sustain life in the oceans.
“By understanding these deep-water environments and their inhabitants’ sensitivity to ocean acidification, the expedition will provide important new data on the ocean’s role in sequestering CO2 and the degree to which coral species in the Perth Canyon are able to adapt to changing conditions.”
He said the team hoped to answer the larger question of how animals that calcify skeletons are likely to be affected under future climate change scenarios, and the ability of the deeper oceans to more permanently sequester rapidly rising levels of atmospheric CO2.
“We hope to not only reveal the ocean’s living treasures, but also to establish how critical seawater parameters necessary to sustain life are changing due to the combined forces of ocean warming and CO2-driven ocean acidification,” he said.
Besides giving researchers the chance to better understand the Perth Canyon, the work should also help to better understand the likely threats to other deep ecosystems in the region and similar environments worldwide.
Other UWA researchers involved in the expedition include Dr Jim Falter, Dr Julie Trotter, Professor Chari Pattiaratchi and research associate Lara Garcia-Corral.
To find out how they fare, visit the Schmidt Ocean Institute daily blog.
The project is being funded by the Australian Research Council, Schmidt Ocean Institute and The University of Western Australia.
Professor Malcolm McCulloch (UWA School of Earth and Environment and The UWA Oceans Institute) (+61 8) 6488 3074
David Stacey (UWA Media and Public Affairs Manager) (+61 8) 6488 3229 / (+61 4) 32 637 716
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