Effects of conventional and biodegradable microplastics on marine microbial communities

Microplastics (MP) are ubiquitous in marine ecosystems and are suitable matrices for bacterial attachment and growth. Studies on the microbes growing on plastics are mainly done using flow cytometry and massive sequencing and do not allow quantification of specific groups. We here show the results of the participation in an international mesocosm experiment in the Marine… (SYKE) in Finland, designed to compare the effects of biodegradable and conventional microplastics on planktonic communities of the Baltic Sea. Our specific aim was to see the enhancement of bacterial activity and concentration using epifluorescence microscopy techniques, Specifically, we applied the novel technique BONCAT-FISH that allows simultaneously the identification and the detection of the activity for each bacterial cell. The experiment was run from the 26th August to the 6th September 2019. Mesocosms were filled with Baltic seawater and amended with MP at in situ concentrations (20 MP beads/ml) in triplicates: None (control), conventional, biodegradable, conventional + biodegradable MP. Our results show a low impact of the presence and quality of MP on marine bacterial communities and very weak differences between the composition and activity of bacterial communities growing with biodegradable or conventional MP additions