Potentially Pathogenic spp. in Algal Wrack Accumulations on Baltic Sea Sandy Beaches.

The bacteria known to cause infections to humans and wildlife have been largely overlooked in coastal environments affected by beach wrack accumulations from seaweed or seagrasses. This study presents findings on the presence and distribution of potentially pathogenic species on coastal beaches that are used for recreation and are affected by red-algae-dominated wrack. Using species-specific primers and 16S rRNA gene amplicon sequencing, we identified , . (non-toxigenic), and . , along with 14 operational taxonomic units (OTUs) belonging to the genus in such an environment. . and . were most frequently found in water at wrack accumulation sites and within the wrack itself compared to sites without wrack. Several OTUs were exclusive to wrack accumulation sites. For the abundance and presence of . and the presence of , the most important factors in the water were the proportion of in the wrack, chl-a, and CDOM. Specific OTUs correlated with salinity, water temperature, cryptophyte, and blue-green algae concentrations. To better understand the role of wrack accumulations in abundance and community composition, future research should include different degradation stages of wrack, evaluate the link with nutrient release, and investigate microbial food-web interactions within such ecosystems, focusing on potentially pathogenic species that could be harmful both for humans and wildlife.