marine microbiome marine microbiome all animals on earth form associations with microorganisms, including protists, bacteria, archaea, fungi, and viruses. in the ocean, animal–microbial relationships were historically explored in single host–symbiont systems. however, new explorations into the diversity of marine microorganisms associating with diverse marine animal hosts is moving the field into studies that address interactions between the animal host and a more multi-member microbiome. the potential for microbiomes to influence the health, physiology, behavior, and ecology of marine animals could alter current understandings of how marine animals adapt to change, and especially the growing climate-related and anthropogenic-induced changes already impacting the ocean environment. marine animal host-microbiome relationship relationships are generally thought to exist in a symbiotic state, and are normally exposed to environmental and animal-specific factors that may cause natural variations. some events may change the relationship into a functioning but altered symbiotic state, whereas extreme stress events may cause dysbiosis or a breakdown of the relationship and interactions. in the oceans, it is challenging to find eukaryotic organisms that do not live in close relationship with a microbial partner. host-associated microbiomes also influence biogeochemical cycling within ecosystems with cascading effects on biodiversity and ecosystem processes. the microbiomes of diverse marine animals are currently under study, from simplistic organisms including sponges and ctenophores to more complex organisms such as sea squirts and sharks. background part of a series onmicrobiomes plant microbiomes endosphere phyllosphere rhizosphere laimosphere root microbiome soil microbiome spermosphere marine microbiomes seagrass coral cetacean marine microbial symbiosis human microbiomes human milk fecal transplant gut–brain axis placental salivary uterine necrobiome other microbiomes mycobiome phycosphere built environment drosophila gut microbiota plant endophyte epiphyte rhizobacteria human gut lung oral skin vaginal marine microbial community initial acquisition accessible carbohydrates flora (microbiology) holobionts plant holobiont marine holobiont coral crab seagrass sponge rhodolith hologenomics hologenome evolution viromes bat human mangrove viriome virosphere related biomass partitioning dysbiosis gnotobiosis phytobiome quorum sensing biological dark matter microbial population biology microbial cooperation metagenomics viral metatranscriptomics metabolomics pan-genome superorganism symbiogenesis projects human microbiome project earth microbiome project category