Distribution and biological implications of plastic pollution on the fringing reef of Mo’orea, French Polynesia

Plastic pollution has been recognized as a major pollutant of the open ocean, but the extent and impact of plastic pollution on the coral reef environment has yet to be fully understood. In this study, the distribution of both macro- (>5mm) and micro- plastic (<5mm) of a typical coral reef ecosystem— the fringing reef of an isolated South Pacific island, Mo’orea, French Polynesia—was quantified. During the course of the study, macroplastic was found on every beach on the island, and distribution of plastic was categorized by site type and the presence of Turbinaria oranata, a common macroalgae of Mo’orea. Microplastic (plastic pieces <5mm) was found in the water column of the fringing reef of the island, at a concentration of 0.74 plastic pieces per square meter. To test the impact on coral reef organisms of the plastic pollution found in the fringing reef, microplastic was exposed to a species of soft coral, Discosoma spp.in a laboratory setting. The resilience of Discosoma spp.in fluctuating temperatures and rising CO 2 levels is well understood, but the effect of plastic pollution on Discosoma spp. and other corallimorphs has never before been analyzed. This study reports for the first time the ingestion of microplastic by the soft coral Discosoma spp . Positively buoyant and negatively buoyant microplastic were both ingested over different time frames. In addition, wild (not experimentally introduced) microplastic was found in the stomach cavity of the organism. These findings indicate that plastic debris are being ingested by Discosoma spp. and may impair the health of this prevalent coral reef organism.