Abstract
Microplastics are increasing in marine environments worldwide, but their fate is not fully understood. Reef-building corals are suggested to serve as sinks for microplastics via active removal through ingestion and passive removal by adhesion. However, it is unknown which type of plastics are more likely to be ingested or adhered to corals and whether water flow or coral morphology affects these processes. We exposed the corals, Leptoseris sp., Montipora capitata, Montipora digitata, and Pocillopora acuta to weathered polyester fibers, acrylic fibers, and polystyrene fragments under three unidirectional flow regimes (2.6, 5.0 and 7.5 cm s− 1). Adhesion rates were 3.9 times higher than ingestion rates and fibers were the dominant type of microplastics for both ingestion and adhesion. Flow significantly affected adhesion but not ingestion. Species was a significant factor for both ingestion and adhesion, but we did not find a significant correlation to morphological traits for either process. Moreover, on M. capitata, we observed higher adhesion rates on exposed skeleton than live tissue, suggesting that M. capitata actively removes microplastics from its surface and that non-living sections of reefs may also serve as an important sink for microplastic pollution. Our data revealed that processes that influence coral and microplastic interactions are complex but appear to be species-specific and are likely influenced by feeding strategies and other characteristics of corals. We also highlight the potential for non-living structures on reefs to serve as microplastic sinks.