Published on 21 Apr 2020

​Key to corals' bleaching susceptibility lies in their diet shows new study co-authored by ASE/EOS PhD student

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Climate change and warming oceans are major threats tocoral reefs and can cause widespread coral bleaching. As coral scientists andconservationists work against the clock to restore and preserve coral reefs,new research has revealed some corals have a secret to help them tolerateclimate change. A study led by Dr. Inga Conti-Jerpe at the School of BiologicalSciences and Swire Institute of Marine Science, The University of Hong Kong,and co-authored by ASE PhD student Ms MollyMoynihan reveals that a key to corals’ susceptibilityto bleaching lies in their diet. The study is published in the highly rankedjournal Science Advances.

The researchers behind the study suspected diet might be animportant factor for how well corals tolerate warming, but this had never beenstudied before, partly due to the complicated nature of corals’ diets. Coralsare animals that can get their energy both from capturing prey with stingingcells called nematocysts and by providing a home to photosynthetic algae, whoshare nutrients with the coral in return. They can use both strategiessimultaneously, and the strategy they rely on most varies with species andenvironmental conditions. This makes it tricky for scientists to identify themain source of nutrients; a problem the researchers in this study solved byusing stable carbon (C) and nitrogen (N) isotopes to track the nutrients in thecoral tissue.

The results show that corals which rely more on capturingprey could cope better with warming waters, while those that rely onphotosynthetic algae are more vulnerable. This has important implications forconservation and restoration of coral reefs. “The results of our studyhelp predict which coral species are more likely to survive as oceans warm.Unfortunately, what we found is that the most susceptible species are thosethat are commonly used in coral reef restoration efforts. To ensure thelong-term success of reef rehabilitation, restoration initiatives should shifttheir focus to bleaching-resistant species.” said Dr. David Baker,Associate Professor at the School of Biological Sciences and Swire Institute ofMarine Science who supervised the study.

Unfortunately, while predatory nutrition can confer someprotection from bleaching, predatory corals are by no means immune to theeffects of warming oceans: The scientists note that given sustained elevatedtemperatures, all the species in the study eventually bleached. “Capturinga lot of food doesn’t save corals from bleaching,” explains Dr. Conti-Jerpe,“it just buys them a little more time – time that they desperately need.” Thefindings of this study will help scientists, conservationists and policy makersanticipate which corals will disappear first and how this will change reefecosystems overall, including the services they provide.

Ms. Molly Moynihan is currently a PhD student at theEarth Observatory of Singapore and Asian School of the Environment at NTUSingapore. She became involved in this research during an internship at theUniversity of Hong Kong and has continued to collaborate with Dr. Baker’s groupon this project, as well as for her own PhD research, while at NTU.

HKU Press release

Original publication in Science Advances