Bioavailability and ingestion of microplastic by zooplankton in the natural environment

Microplastics have been documented in marine environments worldwide where they pose a potential risk to biota. Zooplankton may be particular susceptible, as the microplastics overlap with the size range of their natural prey and can therefore be readily ingested. Laboratory studies have established that zooplankton, such as copepods, can consume microplastics, affecting their energy budget and negatively impacting upon reproduction, health and survival. As such, understanding the extent to which zooplankton encounter and ingest plastic particles and fibres within their natural environment is imperative, not least to reliably assess the risk that different microplastics pose to animals near the base of the marine food web. In this study, we sampled six sites in the western English Channel (United Kingdom) over the course of one year to determine the types and amount of anthropogenic debris available to and ingested by zooplankton in the natural environment. Over 12,000 zooplankton were processed, with ingested and waterborne microplastics characterised and counted. Our results demonstrate that zooplankton routinely encounter and ingest microplastics under natural conditions across a range of spatial and temporal points. The results show a sizable range in ingestion from 1 microplastic per 4.5 zooplankton to 1 microplastic per 300 zooplankton. We demonstrate a weak correlation between ingestion and encounter rate but a stronger correlation with Chla, suggesting a higher ingestion of microplastics in oligotrophic waters. The results also indicate that zooplankton may show a preference for longer more neutrally coloured fibers. The function of zooplankton in the plastic cycle will be discussed with regards to their role as a reservoir of microplastics in the marine environment. Also see: https://micro2024.sciencesconf.org/559615/document