Fate and Effects of Macro- and Microplastics in Coastal Wetlands

Coastal wetlands trap plastics from terrestrial and marine sources, but the stocks of plastics and their impacts on coastal wetlands are poorly known. We evaluated the stocks, fate, and biological and biogeochemical effects of plastics in coastal wetlands with plastic abundance data from 112 studies. The representative abundance of plastics that occurs in coastal wetland sediments and is ingested by marine animals reaches 156.7 and 98.3 items kg(-1), respectively, 200 times higher than that (0.43 items kg(-1)) in the water column. Plastics are more abundant in mangrove forests and tidal marshes than in tidal flats and seagrass meadows. The variation in plastic abundance is related to climatic and geographic zones, seasons, and population density or plastic waste management. The abundance of plastics ingested by pelagic and demersal fish increases with fish length and dry weight. The dominant characteristics of plastics ingested by marine animals are correlated with those found in coastal wetland sediments. Microplastics exert negative effects on biota abundance and mangrove survival but positive effects on sediment nutrients, leaf drop, and carbon emission. We highlight that plastic pollution is widespread in coastal wetlands and actions are urged to include microplastics in ecosystem health and degradation assessment.

Automated summary

Coastal wetlands serve as traps for plastics, but little is known about the stocks and impacts of plastics in these areas. We conducted a comprehensive evaluation of plastic abundance in coastal wetlands, finding that the abundance of plastics in sediment and the ingestion by marine animals far exceeds that in the water column. The abundance of plastics varies across different types of coastal wetlands and is influenced by climate, geography, seasons, and population density or waste management. Plastic ingestion by fish increases with size and weight. Microplastics have negative effects on biota abundance and mangrove survival but positive effects on sediment nutrients, leaf drop, and carbon emission. It is crucial to include microplastics in assessing the health and degradation of coastal wetland ecosystems.