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A survey of marine pelagic coastal microbial communities was conducted over a large geographic latitude range, from Cape Mendocino in northern California USA to Queen Charlotte Sound in British Columbia Canada, during the spring to summer transition. DNA metabarcoding and flow cytometry were used to characterize microbial communities. Physical and chemical oceanography indicated moderate conditions during the survey with no widespread upwelling, marine heat wave, or other extreme conditions. However, four locations displayed features approaching acidified conditions: Heceta Head, Newport, Copalis Beach, and Cape Flattery. Although bacterial and archaeal communities at the Juan de Fuca canyon and northward had high similarity, those south of the Juan de Fuca canyon were well differentiated from each other. In contrast, eukaryotic microbial communities exhibited stronger geographic differentiation than bacterial and archaeal communities across the extent of the survey. Seawater parameters that were best predictors of bacterial and archaeal community structure were temperature, pH, and dissolved inorganic nutrients (nitrate, phosphate, silicate), while those that were best predictors of eukaryotic microbial community structure were salinity, dissolved oxygen, total alkalinity, and dissolved inorganic nutrients (nitrite, silicate). Although five bacterial and archaeal indicators for potentially corrosive waters were identified (Colwellia, Nitrosopumilus, Nitrosopelagicus, Sup05 cluster, Sva0996 marine group), no eukaryotic microbial indicators were found. Potentially pathogenic taxa detected in the survey included four disease-causing bacteria for mammals, finfish, and/or shellfish (Coxiella, Flavobacterium, Francisella, Tenacibaculum), sixteen genera of microalgae capable of producing biotoxins, and fifteen parasitic species. This study demonstrates the value of coordinating microbial sampling and analysis with broad-scale oceanographic surveys to generate insights into community structures of these important pelagic trophic levels.

Mucorales infections are increasing in frequency and are a One Health pathogen of concern. In humans and domestic animals, risk factors include being immunocompromised, elevated circulating serum iron, contaminated open wounds, or metabolic diseases such as ketoacidosis or uncontrolled diabetes. Mucormycosis was first identified in 2012 in Pacific Northwest marine mammals, predominantly in harbor porpoises. We performed an assessment to determine the overall qualitative risk, or risk score, of mucormycosis in harbor porpoises. Risk factors for this disease are unknown in aquatic mammals. In a separate risk factor analysis, potential risk factors such as pollutants, trace metals (e.g., iron), and co-infection with other pathogens (e.g., viruses and Brucella spp.) were examined in mucormycosis cases and noncases using a matched case-control study design, to determine the presence and strength of association of these factors with mucormycosis. Disease severity (gross and histopathology) and exposure scores were multiplied together to obtain the overall risk scores of 9 -16 which corresponded to moderate and severe, respectively. In the risk factor analysis, the factors most strongly associated with a mucormycosis case, relative to a control, were elevated liver iron, decreased blubber thickness, and the decreased ratio of the sum of PCB congeners/sum of PBDE congeners. The results of this study suggest that mucormycosis may pose an inordinately high risk to harbor porpoises (and potentially sympatric species in the Salish Sea such as southern resident killer whales) based on the detected prevalence and the severity of lesions observed at necropsy. However, the risk may be greater on an individual basis compared to the overall population, and is likely related to other factors such as increased POP and heavy metal burdens.