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Impact of facemask debris on marine diatoms: Physiology, surface properties, sinking rate, and copepod ingestion
Summary
Laboratory experiments showed that plastic debris shed by discarded surgical masks inhibits the growth of marine diatoms (microscopic algae that form the base of ocean food chains) and alters their cell surface properties at the nanoscale. Diatoms exposed to mask debris were eaten less by copepods and sank faster, disrupting the normal flow of carbon through the marine ecosystem. The findings reveal a novel pathway by which pandemic-era plastic waste can cascade through oceanic food webs.
Discarded surgical masks have become a new source of plastic waste in seawater capable of releasing numerous micro and nano plastic fragments. However, little information is available about how this waste impacts the ecological state of marine phytoplankton. Here, we exposed two model marine diatoms (Phaeodactylum tricornutum and Thalassiosira weissflogii) to mask-released debris (MD) that is characterized by various differently-charged functional groups. Although MD could only bind loosely to diatoms, it still inhibited their growth and significantly altered cell surface physicochemical properties. At the nanoscale, MD-exposed cell walls showed enhanced roughness and modulus, besides declined electrical potential, adhesion, and proportion of oxygen-containing compounds. As a result, diatom ingestion by copepods was reduced, and the sinking rate of the carbon pool consisting of MD plus diatoms decreased as well. Our study indicated that MD effects on diatoms have the potential to slow down carbon export from surface seawater to the deep sea. Since oxidation and generation of functional groups are common during the aging process of microplastics (MPs) in nature, the interactions between the diatom cell surface and MD have important environmental significance.