Effects of Heat Stress on Phytopigments of Zooxanthellae (Symbiodinium spp.) Symbiotic with the Corals Acropora hyacinthus, Porites solida, and Favites complanata

Abstract

The question of whether global warming affects phytopigments within Symbiodinium spp. of coral is central to understanding the process of coral bleaching. In this study, corals Acropora hyacinthus, Porites solida, and Favites complanata were exposed to elevated temperatures (28, 30, 32, and 34oC) for 48 h and the responses of Symbiodinium chl a, chl c, total carotenoids, total phaeophytins, and fucoxanthins were examined. In A. hyacinthus, the phytopigment concentrations at 28 and 30oC were significantly different from 32 and 34oC, implying a step-function response initiated between 30 and 32oC. In P. solida, all phytopigments varied significantly between the temperatures, except in the case of total carotenoids which had no significant response. In F. complanata, all phytopigments decreased linearly as temperature increased. Our results indicate that decreases in Symbiodinium phytopigments in response to heat stress may be a need to adapt while their host coral may already be adapted (or exapted).