The ecology of potentially pathogenicVibriospp. in a seagrass meadow ecosystem

Abstract

Seagrass meadow ecosystems offer several valuable ecosystem services in coastal regions around the world. Recent studies have suggested that one such important service is reduction of pathogenic bacteria and specificallyVibriospp. in adjacent waters. The specific mechanisms of pathogen reduction remain unclear, although increased sedimentation has been suggested as one likely process for pathogens to be quenched from the water column. WhetherVibriospp. persist in the sediment or in other compartments of the seagrass meadow is currently not known, but it has been shown that marine surface biofilms can function as reservoirs of pathogenic vibrios. This general feature may also apply to seagrass and sediment surfaces. In this study, we investigated the relative abundance and community ecology ofVibriospp. bacteria in Baltic Sea seagrass meadows using both culturing and culture-independent methods. While we did not detect a significant reduction ofVibriospp., the highest relative abundances ofVibriospp. were observed in the water column above unvegetated sites as compared to seagrass meadows. We also detected high relative abundances ofVibriospp. on seagrass roots, supporting previous observations that marine surfaces are selectively colonized byVibriospp., implying that these habitats are important for the persistence and possibly release ofVibriospp. into the water column. Our results emphasize the need to understand the interactions of pathogenic bacteria with coastal habitats, including interactions with host organisms such as seagrasses that provide biofilm microenvironments, in order to understand how diseases associated with these organisms develop.