Microplastic ingestion by scleractinian corals

Microplastics (i.e. plastic fragments <5 mm in diameter) are a widespread form of contamination in marine ecosystems around the globe (Moore 2008). Coastal ecosystems, such as inshore coral reefs, are likely to be particularly heavily impacted by microplastics because these contaminants often enter the marine environment through fragmentation of larger plastic items from terrestrial sources (Thompson et al. 2004), including via water treatment plant effluent (Browne et al. 2011; Fendall and Sewell 2009). Additionally, coral reefs are popular sites for short and long-term visits by tourists, as well as trawlers and recreational vessels, which carry many components that are composed of various forms of plastic (Claessens et al. 2011). Routine boating, fishing and other recreational activities can potentially introduce plastic debris into the marine environment through minor damage to boat hulls that releases paint chips into the ocean, and/or inadvertent loss of ropes and rigging lines, fishing floats and marker buoys (Ivar do Sul and Costa 2014). At present, the impacts of the accumulation of persistent plastic products in the environment remain poorly understood. In some cases, microplastics may be considered a harmful pollutant because they can act as both a sink (Mato et al. 2001) and a source (Laist 1987; Teuten et al. 2009; Zitko and Hanlon 1991) of environmental contamination. That is, plastics adsorb and transport other contaminants in seawater such as heavy metals (Ashton et al. 2010) and persistent organic pollutants (Endo et al. 2005; Mato et al. 2001; Teuten et al. 2007). Neither plastics nor these contaminants easily degrade in the environment, or during digestion by organisms, enabling them to bioaccumulate in the food chain (Gregory 1996; Rios et al. 2007), and ultimately reach higher trophic levels (Carpenter and Smith Abstract We report for the first time the ingestion of microplastics by scleractinian corals, and the presence of microplastics in coral reef waters adjacent to inshore reefs on Australia’s Great Barrier Reef (GRE, 18°31′S 146°23′E). Analysis of samples from sub-surface plankton tows conducted in close proximity to inshore reefs on the central GBR revealed microplastics, similar to those used in marine paints and fishing floats, were present in low concentrations at all water sampling locations. Experimental feeding trials revealed that corals mistake microplastics for prey and can consume up to ~50 μg plastic cm−2 h−1, rates similar to their consumption of plankton and Artemia nauplii in experimental feeding assays. Ingested microplastics were found wrapped in mesenterial tissue within the coral gut cavity, suggesting that ingestion of high concentrations of microplastic debris could potentially impair the health of corals.