Functional study of the ingestion and excretion of microplastics by marine coastal copepods

Zooplanktonic organisms, particularly copepods, play a critical role in marine food webs, linking primary producers to higher consumers and participating in the biogeochemical cycles of marine ecosystems. With increasing ocean pollution of microplastics, their ingestion by marine organisms as copepods is a growing problem of pollution in marine ecosystems and, indirectly and consequently, for human health. Copepods, as primary consumers, can be important vectors in the transfer and dispersion of these microplastics. Our study, conducted in Toulon Bay (NW Mediterranean Sea, France), targeted four dominant copepod genera: Oithona spp. (ambush feeding), Euterpina spp. (cruising filtration) and Acartia spp. and Centropages spp. (sweeping filtration), representing three different feeding behaviors. The study investigated how microplastic particles, size 5 and 10 μm diameter, influenced the ingestion, the excretion of these particles and the properties of faecal pellets. The results showed that microplastic ingestion in the presence of phytoplankton was more pronounced in filter-feeding and cruising copepods with 13 and 14 MP.cop-1.d-1, respectively, compared to ambush-feeding with 2 MP.cop-1.d-1. A preference for 10 μm microplastics in sweep-feeding copepods was shown with 9 MP.cop-1d-1 versus 3 MP.cop-1.d-1. Although no significant influence on faecal pellets production was observed, a decrease of the volume of fecal pellets produced by filter-feeding-cruising copepods was recorded with a decrease of 27.5%. These results highlight the importance of studying the impact of feeding behaviors on the incorporation of microplastics into trophic webs by copepods.