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THE EFFECTS OF MICROPLASTICS ON SEA URCHIN LARVAL SURVIVORSHIP AND DEVELOPMENT**

Abstract

Microplastics, plastic pieces smaller than five millimeters, are of growing concerns 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 limited effects on body width development at five days post feeding (dpf). However, it is unclear how generalizable these findings are to other sea urchin species and for other types of plastic. Our research aims to understand the effects of polystyrene microplastics on larval survivorship and body-size development in Lytechinus variegatus and Arbacia punctulata following similar procedures as used with T. gratilla. In this study, L. variegatus and A. punctulata larvae were divided among three treatments that varied in microplastic concentration but were consistent in total particle concentration. The treatments were 1) 300 algae/ml; 2) 150 algae and 150 5μm polystyrene beads/ml; 3) 300 5µm polystyrene beads/ml. Larvae were kept at a concentration of 5 larvae/ml for all treatments. Percent survivorship was estimated from 5ml samples taken daily until survivorship was around zero. Body measurements were taken at 5 dpf for both species and 9 dpf for just A. punctulata larvae. 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. Current results suggest that for L. variegatus there is lower survivorship in the treatments with beads relative to the 300 algae/ml treatment, but replication is needed for statistical analysis. Survivorship for A. punctulata was statistically lower in the treatments with beads at 5 dpf. For both species, initial results suggest limited effects on body measurements, but replication is needed. So far, our results suggest that it may be a general trend among sea urchin larvae that there are limited effects of microplastics on development, but microplastics have a larger effect on larval survivorship.

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