Seasonal and spatial distribution of trace metals and bacteria on beached plastics in the Adriatic sea

Marine plastic litter (MPL) is a significant threat to marine ecosystems, acting as a carrier for pollutants like trace metals (TM) and microbial communities whose distribution in intertidal zones’ sediment and seawater suggests potential environmental and health risk for coastal areas. The Adriatic Sea has been identified as a hotspot for MPL accumulation. This study is the first to investigate the interaction of MPL and sediment with TM and bacteria along the eastern Adriatic coast. MPL, sediment and seawater were collected from the intertidal zone of three beaches before and after the tourist season. A total of six different polymer types were detected, with polypropylene (PP) and polyethylene (PE) being the most prevalent. PP showed the greatest variability in metal adsorption, with Zn being the most adsorbed metal on all polymers and at all locations and seasons. Cd and Co exhibited the lowest amounts adsorbed. The amounts of adsorbed metals on plastics showed a similar pattern to the TM levels in seawater and sediment. The bacterial assemblages suggest that the distribution of certain bacterial genera on MPL and in the sediment was influenced by both location and season. The bacterial communities on plastics and in sediment showed different taxonomic compositions with the genera Bacillus, Exiguobacterium and Psychrobacter dominated on the plastic samples, while Vibrio species predominated in the sediment. This work elucidates the interaction and distribution of TM and bacteria between beached MPL and sediment in coastal environments of the Adriatic Sea and may contribute to similar studies in other coastal environments affected by MPL accumulation.