Microplastics, plastic pieces smaller than five millimeters, are of growing concern in marine ecosystems because they cause multiple negative effects, including decreased survivorship and direct developmental defects. Sea urchin larvae are a target for microplastic studies because they easily ingest microplastics and are an important component of marine zooplankton communities. Prior studies examining the survival and development of Tripneustes gratilla larvae exposed to 5µm polyethylene beads found no effect on larval survivorship and only a small effect on body width development in five-day old larvae. However, it is unclear how generalizable these findings are to other sea urchin species and for other types of plastic. Our research aims to discover the effects of polystyrene microplastics on larval survivorship and body-size development in Lytechinus variegatus following the same procedures used with T. gratilla. In this study, L. variegatus larvae were divided among three treatments: treatment one had 300 algae/ml, treatment two had 150 algae and 150 5μm polystyrene beads/ml and treatment three had 300 5µm polystyrene beads/ml. Larvae were kept at a concentration of 5 larvae/ml. Percent survivorship was estimated from 5ml samples and were taken daily for 21 days. Body measurements were taken on five-day-old larvae using ImageJ. Five different body measurements were made: post-oral arm length (POA), body width, body length, the ratio of POA length to body width, and the ratio of POA length to body length. Treatments were replicated two times for survivorship and three times for arm length measurements because data were collected from larvae created during two, independent lab-spawning events. Survivorship estimates so far suggest that treatment one had the highest survivorship, treatment two had intermediate survivorship, and treatment three had the lowest survivorship. However, these results are based on only two replicates and will be repeated. Body measurements had two significant differences among treatments. Body width was significantly larger in treatment one than treatment two (p=0.005) or treatment three. Body length was significantly smaller for treatment three than treatment one (p<0.001) or treatment two (p=.005). Our results suggest that microplastic effects on sea urchin larvae may not be generalizable among species or type of plastic.

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