Context-dependent effects of a Caribbean cleaner goby on coral reef microbial communities

Species-mediated transfer of microbes around ecosystems is an emerging topic in microbial ecology. Species aggregation hubs provide a useful way to study microbial transfer in ecosystems as they could spread beneficial or pathogenic microbes. In coral reefs, cleaner fish stations are iconic examples of aggregation hubs due to their well described cleaner-client interactions. Yet, it is unknown how these hubs influence reef microbial diversity. Because cleaners attract clients (and likely microbes) from the local environment, we expect cleaning station effects to be reef context-dependent. Here, we tested how the presence of cleaning gobies influences microbial (bacteria and archaea) diversity around cleaning stations on 2 geographically distinct reefs. We conducted a field manipulation of cleaning gobies and sequenced the 16S rRNA genes from the cleaning fish station substrate (coral and inert tiles) and resident client damselfish. We also quantified reef water nutrients and heterotrophic and photosynthetic microbial populations around corals with cleaners present versus removed. Consistent with our expectations, we found that cleaning gobies have context-dependent effects on client fish and substrate and that host-associated microbiomes are structured by host type and reef location. Our study is the first to highlight how cleaner fish stations can impact bacteria and archaea around reefs.