Functional Microbiomes at the Interface: Mediators in Marine Biofouling and Larval Settlement.

Natural and artificial marine surfaces are rapidly colonized by microscopic communities, including propagules of some macrofoulers, in a process called biofouling. These microbiomes play an important role in modulating the evolving microbial community, as well as the attachment and settlement of other invertebrate larvae. Microbiomes act as biochemical and biophysical interfaces in marine communities. This review explores the gene-level processes that underlie microbial functions relevant to biofouling and larval settlement, such as quorum sensing, extracellular polymeric substance (EPS), and innate immune system components, as well as biosynthetic and degradative processes that generate signaling molecules. We critically evaluate current knowledge on how microbial metabolites promote or inhibit larval recruitment in corals, barnacles, polychaetes, and bivalves, and how omics-based approaches are uncovering the functional potential of biofilm communities. We evaluate how these interactions influence ecosystem services, such as habitat structuring, reef resilience, and coastal infrastructure maintenance.