Environmental Controls of Oyster-Pathogenic Vibrio spp. in Oregon Estuaries and a Shellfish Hatchery.

spp. have been a persistent concern for coastal bivalve hatcheries, which are vulnerable to environmental pathogens in the seawater used for rearing larvae, yet the biogeochemical drivers of oyster-pathogenic spp. in their planktonic state are poorly understood. Here, we present data tracking oyster-pathogenic bacteria in Netarts Bay and Yaquina Bay in Oregon, USA, as well as in adjacent coastal waters and a local shellfish hatchery, through the 2015 upwelling season. populations were quantified using a culture-independent approach of high-throughput specific 16S rRNA gene sequencing paired with droplet digital PCR, and abundances were analyzed in the context of local biogeochemistry. The most abundant putative pathogen in our samples was Environmental concentrations of total spp. and were highest in Netarts Bay sediment samples and higher in seawater from Netarts Bay than from nearshore coastal waters or Yaquina Bay. In Netarts Bay, the highest concentrations were observed during low tide, and abundances increased throughout the summer. We hypothesize that the warm shallow waters in estuarine mudflats facilitate the local growth of the pathogen. Samples from larval oyster tanks in Whiskey Creek Shellfish Hatchery, which uses seawater pumped directly from Netarts Bay, contained significantly lower total species concentrations, but roughly similar concentrations, than did the bay water, resulting in a 30-fold increase in the relative abundance of the pathogen in hatchery tanks. This suggests that the pathogen is able to grow or persist under hatchery conditions. It has been argued that oyster-pathogenic spp. have contributed to recent mortality events in U.S. shellfish hatcheries (R. A. Elston, H. Hasegawa, K. L. Humphrey, I. K. Polyak, and C. Häse, Dis Aquat Organ 82:119-134, 2008, https://doi.org/10.3354/dao01982); however, these events are often sporadic and unpredictable. The success of hatcheries is critically linked to the chemical and biological composition of inflowing seawater resources; thus, it is pertinent to understand the biogeochemical drivers of oyster-pathogenic spp. in their planktonic state. Here, we show that Netarts Bay, the location of a local hatchery, is enriched in oyster-pathogenic compared to coastal seawater, and we hypothesize that conditions in tidal flats promote the local growth of this pathogen. Furthermore, appears to persist in seawater pumped into the local hatchery. These results improve our understanding of the ecology and environmental controls of the pathogen and could be used to improve future aquaculture efforts, as multiple stressors impact hatchery success.