Bioavailability of Microplastics to Marine Zooplankton: Effect of Shape and Infochemicals

The underlying mechanisms that influence microplastic ingestion in marine zooplankton remain poorly understood. Here, we investigate how microplastics of a variety of shapes (bead, fiber, and fragment), in combination with the algal-derived infochemicals dimethyl sulfide (DMS) and dimethylsulfoniopropionate (DMSP), affect the ingestion rate of microplastics in three species of zooplankton, the copepods <i>Calanus helgolandicus</i> and <i>Acartia tonsa</i> and larvae of the European lobster <i>Homarus gammarus</i>. We show that shape affects microplastic bioavailability to different species of zooplankton, with each species ingesting significantly more of a certain shape: <i>C. helgolandicus</i>-fragments (<i>P</i> < 0.05); <i>A. tonsa</i>-fibers (<i>P</i> < 0.01); <i>H. gammarus</i> larvae-beads (<i>P</i> < 0.05). Thus, different feeding strategies between species may affect shape selectivity. Our results also showed significantly increased ingestion rates by <i>C. helgolandicus</i> on all microplastics that were infused with DMS (<i>P</i> < 0.01) and by <i>H. gammarus</i> larvae and <i>A. tonsa</i> on DMS-infused fibers and fragments (<i>P</i> < 0.05). By using a range of more environmentally relevant microplastics, our findings highlight how the feeding strategies of different zooplankton species may influence their susceptibility to microplastic ingestion. Furthermore, our novel study suggests that species reliant on chemosensory cues to locate their prey may be at an increased risk of ingesting aged microplastics in the marine environment.