How do coral energy strategies influence their survival?

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Most reef-building corals harness autotrophic nutrition from their photosynthetic algalendosymbionts and heterotrophic nutrition via predation of plankton. This flexible trophic strategyis thought to underpin their ability to colonise a range of depths, habitats and oceanographiccontexts that vary in energetic resource supply (Williams et al. 2018 Mar Biol; Fox et al. 2018Current Biology). Laboratory experiments suggest heterotrophic feeding might explain the abilityof some corals to persist in challenging environments, including highly turbid reefs where sunlightis rapidly attenuated. This is because heterotrophy provides a valuable nutritional source thatsupports coral growth despite reduced autotrophic contributions from the algal endosymbionts(Grotolli et al. 2006 Nature). Coastal darkening, a consequence of increasingly turbid nearshorewaters, is impacting coral reefs worldwide. Nevertheless, we know very little about how coraltrophic strategies vary in response to spatial and temporal gradients in resource availability andwhether trophic plasticity enables some corals to persist under these increasingly challengingcoastal conditions. Identifying mechanisms that enable coral survival across gradients in resourceavailability is key to understanding whether and how coral reefs will adapt as our coastal waterssteadily grow darker (Williams & Graham 2019 Funct Ecol).