Pathogenicity of Hatchery-Isolated Vibrio spp. to Eastern Oyster (Crassostrea virginica) Larvae

• Logan Lewis, Marine Science, University of Delaware

• Jennifer Biddle, School of Marine Science & Policy, University of Delaware

Eastern oyster (Crassostrea virginica) larvae grown in an aquaculture setting are susceptible to pathogenic infection, most commonly by species of Vibrio bacteria. Vibrio spp. are known to cause larval population crashes in hatcheries. These crashes decrease aquaculture output and harm human economic interests. However, there is limited research on which species and strains are most prevalent or most pathogenic in real-world aquaculture settings, particularly in the Mid-Atlantic. Previous research at the University of Delaware oyster hatchery sought to better understand which Vibrio species contribute to crashes by isolating and sequencing multiple Vibrio strains from larvae during both crash events and healthy periods. In this study, these strains were experimentally tested against eastern oyster larvae 48 hours post-spawn to compare their pathogenicity and determine which strains are true contributors to population crashes. The mortality rate of larvae was calculated after 48-hour exposure to each strain using a neutral red uptake assay. This will improve our understanding of why and how hatchery population crashes occur and can be used to improve the efficiency and efficacy of monitoring for dangerous Vibrio infection in hatcheries. The findings will also inform further research into genomic characterization of hatchery-associated Vibrio and the characterization of novel species of Vibrio.