How do coral energy strategies influence their survival?

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