Identifying the drivers of microbial community changes and interactions in polluted coastal sediments

Despite over three decades of research into the composition and distribution of microbial communities, gaps remain in our mechanistic understanding of microbial community assembly processes, especially in benthic communities in coastal zones continuously exposed to anthropogenic pressures. We analyzed the microbial communities (prokaryotes, fungi, and protists) in sediment samples from ports and bays located along the Adriatic coast chronically exposed to chemical and nutrient pollution, and explored how selective pressures (pollutants, nutrients, and environmental conditions) and dispersal shape these communities. We found that biogeographic factors (i.e. location) play a key role in structuring microbial communities, with benthic fungi also being shaped by the presence of pollutants and nutrients. Strong correlations between nutrient loads and pollutants were observed, along with weakened interactions between microbial communities, particularly between prokaryotes and protists, in the presence of specific pollutants (bismuth, cadmium, copper, zinc, mercury). These results are an important step in disentangling the complex interactions between pollutants and microbial community dynamics in aquatic ecosystems. Further research is needed to assess how these shifts in microbial community dynamics may affect ecosystem services in vulnerable coastal zones.