Bleaching condition varies among Acropora millepora color morphs

Understanding the mechanisms that underpinvariation in bleaching susceptibility in corals is central tothe conservation of reefs in the face of climate change.Fluorescent proteins (FPs) are pigments associated with the coral animal that are expressed by many coral species and govern color polymorphisms in the wild. FPs can play photoprotective and anti-oxidant roles in corals;however, it is unclear whether the abundance of FPs affects bleaching susceptibility in the wild.Here, we analyse the bleaching condition of three color morphs with different FP levels in Acropora millepora from the northern Great Barrier Reef (GBR). Colonies were surveyed at four sites during a cold winter and a warm summer. In winter, following unusually cold temperatures, proportionally fewer green (high FP) morphs paled (48%) than yellow(intermediate FP) and red (low FP) color morphs (66 and 60%, respectively). In the warm summer, proportionally fewer green colonies bleached (20%) than the other two color morphs (34 and 33% for yellow and red, respectively). This is the first demonstration of differential susceptibility to natural temperature stress among fluorescent color morphs from similar habitats and highlights the functional importance of subtle intraspecific differences in FP content