t 1Department of Plant Biology, Carnegie Institution for Science,

system Aiptasia [11, 12] and aquarium-grown and field-collected corals to explore the effects of heat stress in the dark. Two strains of Aiptasia were used. Strain H2 is a clonal temperature and light intensity are varied will be needed to characterize the presumed interplay of heat and light stress on the rate, extent, and specific mechanisms of bleaching inof endogenous symbionts in Symbiodinium clade B [11]. Intive chlorophyll determinations (Figure 3B). Moreover, under4These authors contributed equally to this work the conditions and short duration of stress used in these*Correspondence