The interaction between plastics and microalgae affects community assembly and nutrient availability

The presence of plastics and microplastics in water environments has raised concerns for potential negative impacts. The broader ecological implications for ecosystem functioning are, however, still unknown. The interaction between phytoplankton community and plastics has, for example, been overlooked. Here, we investigated the role of plastic as a substrate for biofilm growth and how this affects the dispersal of terrestrial microalgae, potentially altering the assembly of pelagic communities. When exposing an artificially assembled microalgae community to pristine and biofouled plastic under laboratory-controlled conditions, we found that only biofouled plastic affected the final community structure and the content of available nutrients in water. This is due to the exchanged algal species between the biofilm and the pelagic community. The results from this batchwise pilot scale study indicate that plastic can act as a substrate for benthic and pelagic species, potentially affecting ecosystem functions, which have been overlooked so far.