Capture, ingestion, and egestion of microplastics by suspension-feeding bivalves: a 40-year history

Abstract

In aquatic environments, suspension-feeding bivalve molluscs are exposed to a manifold of natural and anthropogenically derived particles, including micro- and nanoplastics. Plastic particles interact with feeding and digestive organs and can produce negative effects. As a result of these effects and the potential transfer of microplastics to higher trophic levels, including humans, there has been renewed interest in the ingestion of plastic particles by different species of bivalves. Many recent studies, however, have ignored the ability of bivalves to select among particles both pre- and post-ingestively. Neglecting to consider the factors that mediate particle capture, ingestion, and egestion can lead to erroneous data and conclusions. This paper outlines the current state of knowledge of particle processing by bivalves, and demonstrates how it relates to studies utilizing plastic particles. In particular, the effects of particle size, shape, and surface properties on capture, preferential ingestion, post-ingestive sorting, and egestion are summarized. The implications of particle selection for the use of bivalves as bioindicators of microplastic pollution in the environment are discussed. Only through a full understanding of the types of plastic particles ingested and egested by bivalves can internal exposure, toxic effects, and trophic transfer of microplastics be assessed adequately.