Microplastics impede larval urchin selective feeding

Microplastics are emergent threats to marine organisms as ingestion can cause a multitude of physiological problems. Suspension feeders, including marine invertebrate larvae, are particularly susceptible to ingesting microplastics due to similarities in physical appearance to algal cells. Larval feeding involves multiple stages: the capture and subsequent selection of particles followed by ingestion from the mouth to the stomach, digestion, and finally, egestion. Yet, little is known about which aspect of the feeding process is disrupted by microplastics. Here, we determine if prior exposure to microplastics alters the feeding behavior of the larval sea urchin Heliocidaris crassispina. We conducted two experiments: a food handling experiment studied larval survival, growth, and time required to fill and vacate the stomach; and a particle selection experiment analyzed changes in the ability of the larvae to selectively ingest algal cells over microplastics. In both experiments, larvae were pre-exposed to algae only (control), the addition of 10 mmpolystyrene beads at 1 bead mL(-1) or 1000 beads mL(-1) until 3- or 7-days post-fertilization. Previous exposure to microplastics lengthened stomach filling time and impaired particle selection. While there was no significant change in survivorship and larval arm length, these sub-lethal impacts on larval feeding likely have more severe ramifications in vivo where food is limited, and thus, potentially threaten post-settlement success.