Past events reveal how future warming could harm cold-water corals

Sampling cold water corals in the depths of the Atlantic Ocean by the MARUM ROV Squid, Bremen, Germany. Credit: Dierk Hebbeln and Claudia Wienberg (CC-BY 4.0, https://creativecommons.org/licenses/by/4.0/)

What will be the impact of future global warming on cold-water corals? A new analysis of ancient evidence from the last major global warming event identifies food and oxygen supply as key environmental factors influencing the vitality of cold-water corals in the North Atlantic Ocean and Mediterranean Sea. Rodrigo da Costa Portilho-Ramos of the University of Bremen, Germany, and colleagues present these findings in the open-access journal PLOS Biology May 19.

Much like tropical corals in shallow waters, cold-water corals serve as crucial “engineers” for deep-sea reefs and mounds that support rich and unique ecosystems. As climate change progresses, researchers predict that cold-water corals are at risk of damage such as rising ocean temperatures, diminished food supply, declining oxygen levels and acidification. oceans. However, no extinctions of cold-water coral ecosystems have been documented in real time, so the precise factors that may determine their fate are unclear.

To shed new light, Portilho-Ramos and his colleagues turned to ancient evidence of past climate change captured in seafloor sediments. They analyzed sediments collected at or near six cold-water coral ecosystem sites in the North Atlantic Ocean and Mediterranean Sea, applying standard techniques to reconstruct ocean conditions and species abundance. of common coral Lophelia pertusa over the past 20,000 years. This period encompasses the last major global warming event on Earth.

The analysis revealed that the former abundance of L. pertusa was most strongly influenced by changes in the food supply, brought either vertically from shallower depths or by lateral water flow along the bottom. marine. Low oxygen concentration also appears to be a key stressor for L. pertusa. Meanwhile, changes in ocean temperature and salinity did not appear to be significantly associated with the proliferation or disappearance of L. pertusa over time.

These results suggest that climate change-induced alterations in ocean processes that affect food and oxygen supply may play a key role in the future health of cold-water coral ecosystems. In some cases, the data suggests that a high abundance of food can compensate for low oxygen levels.

The authors call for future research to further explore the role of food supplies and to account for ocean acidification, which could not be captured in this study.

Portilho-Ramos adds: “Marine sediment records from the North Atlantic and the Mediterranean Sea reveal that climate change-induced cold-water coral growth and mortality events over the past 20,000 years have been mainly triggered by food supply controlled by export and turbulent production. hydrodynamics rather than variations in bottom water temperature. Therefore, climate-induced changes in ocean processes regarding food supply are also likely to be the determining factors in the life and death of cold-water coral species in the coming decades.


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More information:
PLoS Biology (2022). DOI: 10.1371/journal.pbio.3001628

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Past events reveal how future warming could harm cold-water corals (2022, May 19)
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