Ocean Acidification Shakes the Foundation of Cold‐Water Coral Reefs

The longest‐ever simulation of future ocean conditions shows that the skeletons of deep‐sea corals change shape and become 20‐30% weaker, putting oases of deep‐sea biodiversity at risk.

Because the ocean absorbs much of the extra carbon dioxide produced by human activities, the chemistry of seawater is changing, a process known as ocean acidification. Scientists at Heriot‐Watt University, publishing in Proceedings of the Royal Society B, have simulated this process in the laboratory: while corals appear to feed and grow well, this hides fundamental changes in the structure of their skeletons. These changes put the whole reef structure at risk.

Few people are aware that more than half the coral species known to science are found in deep‐waters growing in chilly temperatures, and that spectacular reefs supporting a wealth of other marine life grow in the cold waters of the North Atlantic Ocean.

A greater forkbeard swimming over cold‐water coral reefs of the Logachev Mound, South Rockall. White coral, live; grey coral, dead. Credit: Changing Oceans.

Scientists at Heriot‐Watt University painstakingly kept Scottish deep‐water corals for a year in purpose‐built aquaria. Carefully designed experiments, of the highest international standard, made it possible to simulate precisely a range of future ocean conditions with higher carbon dioxide and warmer temperatures. They discovered that the coral skeleton changed in structure and shape, and that the dead coral became much more easily snapped and damaged.

“The very foundation of the reefs is where the biggest impacts may be seen. Live corals are standing on the shoulders of their dead parents and grandparents, and we see that ocean acidification can start to dissolve dead coral skeleton,” explains Dr. Sebastian Hennige, lead author of the new study. “This makes them weaker and more brittle, like bones with osteoporosis, and means that they may not be able to support the large reefs above them in the future”.

“This is bad news for deep‐coral reefs”, says Professor Murray Roberts, who led the project team, “There is no scope for dead coral to adapt to ocean acidification. Our results strongly suggest that deep coral reef structures as we know them may be at serious risk of disappearance within our children’s lifetimes – and the role these structures play in the ecosystem, providing habitat for thousands of other species, including places for sharks to lay their eggs, will be lost.”

“We know that ocean acidification can impact marine biodiversity in a variety of ways”, explains Dr. Phillip Williamson, coordinator of the UK Ocean Acidification research program(UKOA) that funded this work, and editor of the UN’s Convention on Biological Diversity recent report on ocean acidification, “but this study highlights just how much we still need to understand about important deep‐sea habitats, and how important our efforts are to reduce carbon dioxide emissions now”.

The study “Hidden impacts of ocean acidification to live and dead coral framework” was published in the Proceedings of the Royal Society B, on 19 August 2015 ‐ http://rspb.royalsocietypublishing.org. This work took place through the UK Ocean Acidification research program (UKOA).

UK Ocean Acidification research program (www.oceanacidification.org.uk)

UKOA is a £12m, 5 year research program funded by the Natural Environment Research Council (NERC), the Department for Environment, Food and Rural affairs (Defra) and the Department of Energy and Climate Change (DECC). UKOA outputs feed into the cross‐government Climate Change Adaptation program and the Living with Environmental Change (LWEC) program. UKOA has many international links and partnerships, including those with the German BIOACID program; the European research project MedSeA; the US Ocean Acidification Program; the Ocean Acidification International Coordination Centre; and the Convention on Biological Diversity.

Heriot‐Watt University (http://www.hw.ac.uk)

Heriot‐Watt led work on cold‐water corals and coralline algae for the UKOA program, groups that both play important roles in marine ecosystems that are threatened by ocean acidification. The work included extensive fieldwork in coastal and deep‐sea areas of the Atlantic Ocean. A highlight video of the Logachev deep‐sea coral mounds is available at: https://www.youtube.com/watch?v=Es_JmKURR9Q, and further video and still imagery are available on request.

In 2016 Heriot‐Watt University will expand its climate change research through the new Lyell Centre for Earth and Marine Science and Technology. This collaboration between Heriot‐Watt and the British Geological Survey (BGS) will create a new purpose‐built facility on the University’s Edinburgh campus in early 2016. The £20M Lyell Centre brings together the University’s experts in marine ecosystems, climate change and applied geoscience with the BGS’s world‐renowned capacities in marine geology, offshore survey and habitat mapping. Through the Lyell Centre, Heriot‐Watt aims to recruit up to 20 new research leaders and their teams to drive forward the University’s research in earth and marine science and technology. The Lyell Centre is supported by the Natural Environment Research Council and the Scottish Funding Council with additional funding from the Wolfson Foundation, Garfield Weston Foundation and the Binks Trust.

Marine ecosystem research: http://www.cmbb.hw.ac.uk

Cold‐water coral resource webpage: http://www.lophelia.org

The UN Convention on Biological Diversity report on the “An updated synthesis of the impacts of ocean acidification on marine biodiversity” was edited by S. Hennige, M. Roberts and P. Williamson, with their involvement supported by UKOA https://www.cbd.int/doc/publications/cbd-ts-75-en.pdf.