Assessment of polystyrene microplastic exposure in the sea anemone, Exaiptasia pallida

Microplastics are among the most common forms of pollution found in marine environments, and their small size allows them to be easily ingested by marine biota. Exaiptasia pallida is a solitary anemone native to the western Atlantic that harbors symbiotic dinoflagellates, like those of reef-building corals, and passively feeds on prey, like brine shrimp. To assess the influence of microplastics on E . pallida , laboratory experiments were conducted in which symbiotic and aposymbiotic anemones were exposed to 100 Âμm red polystyrene microplastic beads with and without brine shrimp. The ingestion of microplastics by the anemones was measured after 3 hr, and egestion of microplastics was measured after 24 and 48 hr following initial exposure. Oxidative stress and photosynthetic impairment have been reported in sea anemones following contaminant exposure; therefore, the quantum yield of photosystem II (YPSII) and maximum electron transport rate (ETRmax) were assessed in symbiotic anemones at 0, 24, and 48 hr. Antioxidant enzymes (glutathione peroxidase and catalase) were assessed in both symbiotic and aposymbiotic anemones 48 hr following the initial exposure. Exaiptasia pallida consumed polystyrene in every treatment, and both the presence of brine shrimp and symbiotic state significantly increased the microplastic ingestion. Unfed, symbiotic anemones ingested 5% of the microplastics offered, whereas symbiotic anemones fed brine shrimp consumed 16% of the microplastics offered. Likewise, aposymbiotic anemones consumed 16%–18% of the microplastics offered to them, independent of the presence of brine shrimp. No changes in YPSII or ETRmax were observed in symbiotic anemones exposed to microplastics. Aposymbiotic anemones had a greater ingestion rate of polystyrene microbeads than symbiotic anemones, and catalase activity was increased in aposymbiotic anemones exposed to microplastics. These results suggest that bleached (aposymbiotic) E . pallida may be more vulnerable to polystyrene exposure in the environment. This is the first study to demonstrate the effects of polystyrene in E . pallida . These findings can be used in future studies to assess the environmental impacts of polystyrene on cnidarians.