Analyzing Commercial Shipping Docks as a Source for Human and Wildlife Pathogens in the St. Louis River Estuary

Abstract

Ballast-mediated emergence of aquatic invasive species has long posed a threat to aquatic ecosystems. Historically, concern has primarily been centered on macrofauna such as invasive mussels and fish and how to control the spread of these organisms among geographic isolated waters. It has been recognized just in the last several decades that the proliferation of emergent and harmful microorganisms needs to be minimized among harbors. Even so, the translocation of bacteria via ballast water and the effects these organisms have on the environment they are introduced to is still understudied. In this study, seventy-five sites around the St. Louis River estuary were sampled to characterize the surface water and sediment bacterial communities throughout the harbor, to determine the potential effects of ballast water discharge on these communities, and to establish a basic understanding of the potential pathogenic threats to humans and wildlife in various locations in the estuary. Ordination analyses showed a distinct clustering of bacterial communities found in the surface water at dock sites indicating short-term effects of dock habitats on the bacterial community compositions. Additionally, the sediment bacterial communities at the docks showed that dock sites were more likely to be habitats that contain greater amounts of pathogens compared to other estuary locations as well as when compared to surface water samples. Dock sites contained pathogen-containing genera such as Aeromonas, Corynebacterium_1, Staphylococcus, and Streptococcus, all of which were found in greater abundances at dock sites than elsewhere in the estuary. Overall, bacterial communities and the relative abundance of pathogen-containing bacterial genera were altered in areas with increased exposure to ballast water discharge.