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Effects of polystyrene microplastics on the extracellular and intracellular dissolved organic matter released by Skeletonema costatum using a novel in situ method
Summary
Researchers studied how polystyrene microplastics affect the dissolved organic matter released by the marine diatom Skeletonema costatum. They found that microplastic exposure altered both the quantity and chemical composition of organic compounds released by the algae, which could in turn influence how other contaminants behave in seawater. The study reveals an indirect pathway through which microplastics may affect marine chemistry and pollutant cycling.
Microplastics (MPs) affect the physicochemical algal-dissolved organic matter properties, indirectly influencing the environmental behavior of contaminants including persistent organic pollutants and heavy metals. Limited research is available on the roles played by intracellular- and extracellular-dissolved organic matter (I-DOM and E-DOM) in the processes that affect the environmental behavior of contaminants. Furthermore, the effects of MPs on the production of I-DOM and E-DOM, as well as their environmental behaviors, remain uncertain. A critical issue lies in the challenge of quantitatively identifying I-DOM and E-DOM in situ. In this work, a new fluorescence ratio method was developed and applied to in situ examine the impacts of polystyrene (PS) MPs (50, 500 nm, and 5 μm) on the I-DOM and E-DOM released by Skeletonema costatum (S. costatum). The experimental results indicated that the detection limits were 0.06 mg L, with the respective minimum detectable proportions being 2% for both E-DOM and I-DOM. The suppressive effects of 10-50 mg L of 50 and 500 nm PS MPs on the cell proliferation of S. costatum and the E-DOM secretion were most pronounced on day 6. And the rates of suppression of E-DOM secretion were 10.1%-18.2% and 4.2%-13.9%, respectively. The exposure of algal cells to 50 mg L of 50 and 500 nm PS MPs led to cell rupture and the leakage of I-DOM on day 6. This suggests that the developed method in the laboratory could offer a promising approach for studying the generation of E-DOM and I-DOM in situ, as well as their environmental behaviors affected by MPs.