Researchers at the School of Biological Sciences and the Swire Institute of Marine Science, The University of Hong Kong have developed a new method for determining what corals eat, and demonstrated that reliance on certain nutritional sources underpins their bleaching susceptibility in warming oceans.
The research, published in the prestigious journal Science Advances, solves a conundrum scientists have struggled with for decades: determining the diet of a coral involves measuring how much prey it captures with stinging tentacles as well as how much food is provided by the photosynthetic algae inside their cells. To overcome this challenge, the team, led by Dr. Inga Conti-Jerpe, compared the stable isotope “fingerprint” of hundreds of corals collected in Hong Kong to that of their associated algae. The results showed that some corals have isotopic fingerprints that match that of their algae, indicating the two partners share nutrients. Other corals have fingerprints distinct from their algae due to a diet based on the capture and consumption of prey particles in the water. The researchers found that more predatory corals had significantly larger polyps (an individual coral unit—much like an anemone) than corals more dependent on photosynthesis, a previously contentious relationship first proposed in 1974.
“We knew that polyp size is a factor that affects the surface area to volume ratio of a coral, a trait that other scientists have observed might be linked to delayed bleaching in the field. We decided to run a warming experiment with our Hong Kong corals to see if their diet accurately predicted how long they could withstand elevated temperatures without bleaching—and it did,” explains Dr. Conti-Jerpe.
About the journal paper:
I. E. Conti-Jerpe, P. D. Thompson, C. W. M. Wong, N. L. Oliveira, N. N. Duprey, M. A. Moynihan, D. M. Baker, Trophic strategy and bleaching resistance in reef-building corals. Sci. Adv. 6, eaaz5443 (2020).