Fig. 5. Diel cycle of catalase (CAT) activity from coral tissue and symbiotic zooxanthellae at the 5-m depth in Eilat, Red Sea. Measurements were performed between 3 and 5 March 2002. Activity is presented as % activity [(U mg^-1 protein)/(max U mg^-1 protein)] for (A) F. favus (N=3), (B) G. lobata (N=2) and (C) P. sinuosa (N=3). The black bars represent CAT activity of the animal tissue and the gray bars represent CAT activity of the zooxanthellae. Values are represented as means ± s.d. (night=05.00 h; morning=08.00 h; mid.=10.00-14.00 h; afternoon= 16.00 h).