Modeling Symbiont Dynamics and Coral Regulation under Changing Temperatures*

Abstract

Corals provide important ecosystem services as protective coastal structures and as habitats for coastal biodiversity. Corals depend on their symbiotic relationship with algae, a relationship under threat from rising temperatures. To better understand the nature and resilience of this relationship, we provide a model in which two clades of algae (one efficient, the other resilient) compete over the nitrogen that the coral “chooses” to provide in a changing environment. This model is consistent with a wide range of empirical observations about observed bleaching episodes (when algal populations drop dramatically) and the observed algal composition over time, depending on environmental conditions.