Fecal indicator bacteria and zoonotic pathogens in marine snow and California mussels (Mytilus californianus)

Pollution of nearshore waters with disease-causing microorganisms impacts ecosystems health through illness and deaths in people and wildlife, as well as negative socioeconomic consequences of impaired marine resources. Insight on pathogen ecology in coastal habitats is crucial for accurately mitigating inputs and impacts of microbial pollution. Three objectives were addressed to (i) compare fecal pollution in proximity to (a) freshwater runoff, and (b) endemic marine wildlife; (ii) evaluate presence and magnitude of fecal microorganisms in marine snow and mussels and (iii) determine if pathogens in mussels and FIB levels in seawater or mussels are correlated. Sampling during the wet season, proximity to freshwater, and FIB levels in mussel homogenates (but not seawater) were associated with pathogen presence in mussels. Pathogens and FIB were enriched in aggregate-rich fractions, further supporting an important role of marine snow in pathogen transmission. The lack of association between FIB in surrounding waters and presence of pathogens in mussels calls into question current regulations for insuring safe seafood to consumers in the United States, and alternative monitoring approaches such as direct testing for select pathogens should be further evaluated.