Temperature effects on coral bleaching: evaluation of potential bioindicators for global warming

Abstract

Bleaching is a process in which coral lose their coloration due to an interruption on their symbiotic relationship with zooxanthella algae. Several factors infl uence this phenomenon, high temperatures on water being the main cause. This study consists in analyzing temperature effects on bleaching of three species: the constructor coral reef Siderastrea stellata, and the zoanthids Palythoa caribaeorum and Zoanthus sociatus, in order the evaluate them as potential bioindicators of global warming. Species S. stellata displayed complete bleaching at 45ºC in 24 hours and at 40ºC in 72 hours. At 35ºC the experimental samples showed partial bleaching after a week, being thus considered as relatively resistant to this temperature. P. caribaeorum bleached completely after 48 hours when submitted to 45ºC, and in 72 hours at 40ºC. Species Z. sociatus was the most resistant to temperature, taking 48 to bleach at 45ºC and not showing complete bleaching after a week under temperatures as high as 40ºC. Among the three studied species it is suggested that S. stellata is employed as a bioindicator for global warming.