Unravelling the microalgal community in the plastisphere: preliminary results from the PhytoPlastic project

The ‘plastisphere’, the diverse microbial community growing on the surface of floating plastic debris, represents a new artificial habitat for drifting aquatic organisms. Despite the presence of microalgae within this epiplastic biofilm has been documented, it is still unclear how these materials influence the structure and dynamics of microalgae communities, in particular in freshwater ecosystems. Here, we present the first results of the 4th collaborative FreshProject "PhytoPlastic". The project is aimed at investigating the temporal establishment of phytobenthos on different plastic polymers in lakes over a wide geographical scale. We incubated two widely used plastic polymers (low-density polyethylene-LDPE, polyethylene terephthalate-PET) and glass substrates (as control) in 14 lakes across Europe. To assess the temporal and seasonal evolution of the colonisation, samples were collected in each season after 3, 7, 15, and 30 days. For each substrate, we assessed the phytobenthic biomass estimating the chlorophyll a, and the ash-free dry mass. Moreover, microalgae composition was taxonomically determined on a subset of samples. This project represents, to the best of our knowledge, the first coordinated experiment conducted at a large spatial scale that explores the microalgae-plastic interaction. We will thereby generate a unique dataset, providing additional knowledge about the key drivers of the processes involved. Besides the valuable scientific knowledge, the project represents a large collaboration among early career researchers in freshwater sciences and will set the basis for further partnerships.