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Coral Bleaching: Reef Recovering Faster Than Anticipated

In 2015/2016, high ocean temperatures led to global coral bleaching. A study under the leadership of the department of Marine Ecology at the University of Bremen now shows that coral reefs have the ability to recover from such disasters faster than anticipated – if humans leave them in peace.

This rate of recovery is among the fastest that has ever been observed for reefs,” says Christian Wild, head of the Marine Ecology working group. Anna Koester, PhD student in the working group, is the lead author of a study recently published in the Scientific Reports journal. The marine ecologist assumes that the remarkably fast recovery is mainly related to the special location of the reef: The research team investigated the condition of the corals in the Aldabra atoll, a sparsely populated archipelago located far out in the Indian Ocean. “There, human-made local factors such as nutrient pollution, marine pollution, and overfishing play virtually no role,” explains the scientist. That means it is the ideal location to investigate how the condition of damaged reefs changes when they are not exposed to human-induced stressors. 

The study of the researchers showed: The reefs located in the vast lagoon of the Aldabra atoll recovered in less than four years from the global coral bleaching of 2015/2016. At that time, up to two thirds of the corals had been damaged. The corals facing the open sea also recovered quickly, although not quite as fast as those in the protected lagoon. “Their exposure to currents and waves seems to play a role,” says Koester. In deeper waters, the recovery was much slower: In contrast to the reefs in shallow waters, the deeper corals recovered only gradually.

Koester’s and Wild’s conclusion: If local stressors, such as nutrient pollution, can be significantly reduced, coral reefs can recover well and quickly from bleaching and have a chance to survive. Nevertheless, it is still essential to reduce the causes of coral bleaching, especially ocean warming. Because not every reef regenerates equally fast – especially in less protected environments, it requires more time. “All models predict that the rate of coral bleaching will increase in the future,” emphasizes Wild. In this case, even the up to now privileged coral reefs in the Aldabra lagoon would face hard times.

Further Information:

Study: Koester A, Migani V, Bunbury N, Ford A, Sanchez C, Wild C (in press): Early trajectories of benthic coral reef communities following the 2015/16 coral bleaching event at remote Aldabra Atoll, Seychelles. Scientific Reports

Link to study: www.nature.com/articles/s41598-020-74077-x

Link to Marine Ecology working group: www.uni-bremen.de/en/marine-ecology

www.uni-bremen.de/en/

 

Contact:

Anna Koester
Marine Ecology
Faculty of Biology/Chemistry
University of Bremen
Phone: +49 421 218- 63358
Email: anna.koesteruni-bremen.de

Prof. Dr. Christian Wild
Marine Ecology
Faculty of Biology/Chemistry
University of Bremen
Phone: +49 421 218- 63367
Email: christian.wilduni-bremen.de

 

Korallenbleiche eines Riffes bei Mahé, Seychellen.
Coral bleaching of a reef near Mahé, Seychelles. Unusually warm water temperatures have caused these corals to lose their symbiotic partners, small algae in their tissue, which normally provide them with nutrients through photosynthesis. As a result, much of their color disappears and the corals appear white. Coral bleaching can lead to the death of entire reefs.