Heat challenge elicits stronger physiological and gene expression responses than starvation in symbiotic Oculina arbuscula.

Heterotrophy has been shown to mitigate coral-algal dysbiosis (coral bleaching) under heat challenge, but the molecular mechanisms underlying this phenomenon remain largely unexplored. Here, we quantified coral physiology and gene expression of fragments from 13 genotypes of symbiotic Oculina arbuscula after a 28-d feeding experiment under (1) fed, ambient (24 °C); (2) unfed, ambient; (3) fed, heated (ramp to 33 °C); and (4) unfed, heated treatments. We monitored algal photosynthetic efficiency throughout the experiment, and after 28 d, profiled coral and algal carbohydrate and protein reserves, coral gene expression, algal cell densities, and chlorophyll-a and chlorophyll-c2 pigments.