ABSTRACT Coral holobionts maintain complex symbioses, which can be influenced by global and local stressors. However, the role of coral‐associated bacterial and algal (Symbiodiniaceae) communities in facilitating coral persistence in variable and extreme, multi‐stressor environments is not fully understood. Multi‐stressor environments, such as semi‐enclosed inland bays, provide natural laboratories to study potential coral holobiont responses to future ocean conditions in situ. We investigated the role of Symbiodiniaceae and bacterial communities in coral holobiont persistence across habitats and dry versus wet seasons. We collected three Caribbean coral species ( Siderastrea siderea , Siderastrea radians , and branching Porites sp.) from two semi‐enclosed inland bays and two nearby fringing reefs in Curaçao across three seasonal timepoints. We show that all coral species hosted high proportions of stress‐tolerant Symbiodiniaceae in inland bays, likely facilitating the survival of their coral hosts in these turbid and highly variable and extreme environments. We also observed distinct differences in bacterial community composition across habitats, sites, and seasons in S. siderea and S. radians but not branching Porites sp. Bacterial communities of S. siderea and S. radians contained higher proportions of bacteria with the potential for diverse metabolisms, such as sulfur and nitrogen cycling, in inland bays and during wet seasons. Environmental conditions therefore strongly influence bacterial community composition, and bacterial diversity and metabolic flexibility are likely critical for coral holobiont success across environments and seasons. Our findings show how Caribbean coral holobionts persist in multi‐stressor environments and may respond as anthropogenic climate change continues to exacerbate and intensify these stressors.
Powell et al. (Mon,) studied this question.