How Do Microplastics Distribute Through Freshwater Ecosystems? Which Biota, Feeding Groups, and Trophic Levels Are Most at Risk?

Freshwater environments were initially less investigated than marine environments for the presence of microplastics. This changed over the last decade as the distribution patterns of microplastics were more complicated than initially hypothesized. This raised the question of how microplastics are distributed in freshwater ecosystems and how many microplastics become transported from rivers into oceans. Microplastics have since been detected in multiple significant freshwater environments and biota (via ingestion). Environments, such as the Great Lakes in North America, the Nile, Danube, Rhine, and Amazon Rivers, have all been assessed and microplastic contamination confirmed. Critically, the biota found in these systems have been found to ingest microplastics. Microplastics become ingested by various benthic macroinvertebrates that form a large proportion of the bio-load in freshwater ecosystems. This creates a pathway for microplastics to bioaccumulate into larger predatory organisms, such as fish, birds, and even humans. Unfortunately, the distribution of microplastics through freshwater communities has been under-investigated, with many studies focusing solely on the environmental compartments and not on the biota. It is key to understand and determine how microplastics are distributed through ecosystems, as well as which species are most critically endangered by microplastics.