Effects of microplastics exposure on ingestion, fecundity, development, and dimethylsulfide production in Tigriopus japonicus (Harpacticoida, copepod)

The effects of microplastics pollution on the marine ecosystem have aroused attention. Copepod grazing stimulates dimethylsulfide (DMS) release from dimethylsulfoniopropionate (DMSP) in phytoplankton, but the effect of microplastics exposure on DMS and DMSP production during copepod feeding has not yet been revealed. Here, we investigated the effects of polyethylene (PE) and polyamide-nylon 6 (PA 6) microplastics on ecotoxicity and DMS/DMSP production in the copepod Tigriopus japonicus. The microplastics had detrimental effects on feeding, egestion, reproduction, survival, and DMS and DMSP production in T. japonicus and presented significant dose-response relationships. The 24 h-EC50 for ingestion rates (IRs) of female T. japonicus exposed to PE and PA 6 were 57.6 and 58.9 mg L, respectively. In comparison, the body size of the copepods was not significantly affected by the microplastics during one generation of culture. Ingesting fluorescently labeled microplastics confirmed that microplastics were ingested by T. japonicus and adhered to the organs of the body surface. T. japonicus grazing promoted DMS release originating from degradation of DMSP in algal cells. Grazing-activated DMS production decreased because of reduced IR in the presence of microplastics. These results provide new insight into the biogeochemical cycle of sulfur during feeding in copepods exposed to microplastics.