Experimental evolution in coral photosymbionts as a tool to increase thermal tolerance

Abstract

Coral reefs are under major threat from ocean warming. When temperatures become too high corals bleach, expelling their symbiotic, photosynthetic microalgae (Symbiodinium), which they depend on for much of their nutritional requirements. Prolonged bleaching has led to widespread coral mortality and the severity and frequency of bleaching events are predicted to increase in the future. Coral bleaching tolerance is influenced by the thermal tolerance of the Symbiodinium harboured, and these microbial members of the coral holobiont may be able to evolve more rapidly than the coral host itself. Here, we examined the response of replicate cultures of five genetically distinct Symbiodinium strains..