Photosynthesis enhancement in four marine microalgal species exposed to expanded polystyrene leachate

Due to its widespread use, large amounts of expanded polystyrene (EPS) have been released into the marine environment, where it is broken down into small pieces with large surface areas. As such, chemical additives may be released into the environment, which can affect marine organisms; however, studies of the effects of such additives are lacking. We assessed the effects of leachate from EPS on the photosynthetic activities of four microalgal species (Dunaliella sauna, Scenedesmus rubescens, Chlorella saccharophila, and Stichococcus bacillaris). They were exposed to EPS leachate for seven days and their photosynthetic activities were analyzed based on seven parameters. Overall, leachate exposure increased photosynthetic activity in all four species, albeit to different degrees and showing slightly different trends among the seven parameters. Based on chemical analysis, hexabromocyclododecane concentrations were higher in small-fragment leachate, whereas UV326 concentrations were higher in low-concentration-large-sphere leachate; bisphenol-A and total organic carbon showed no major differences among leachates. Thus, we speculate that exposure to trace chemicals influenced microalgal photosynthesis and overall growth. These results support further investigation of the impacts of plastic debris and chemical additives on marine ecosystems and organisms.