Figure 4: Effect of heat stress on symbiont cell density in Acropora millepora (a) and Pocillopora damicornis (b) incubated in control (filled triangles) and heat stress treatments (open triangles). Error bars represent SD; coral branches for caspase 3 activity and coral branches for PAM fluorometry. difference (post hoc LSD analysis, ) between treatment and control for the same time point.