Widespread microplastic pollution across the Caribbean Sea confirmed using queen conch

The Caribbean Sea is reported to have one of the highest levels of plastic pollution of any marine ecosystem. Much less is known about the levels of microplastics as an emerging pollutant in the marine environment, especially in the water column and benthic substrates where they can be easily ingested by marine organisms. This study was carried out to quantify marine microplastics in the Wider Caribbean using the mollusk, queen conch (Aliger gigas). We analyzed feces collected from queen conch, a non-lethal method of sampling, to investigate microplastic pollution in eleven sites across the Wider Caribbean. Microplastics were extracted by degradation of organic matter from feces with peroxide (30%) over 48 h. Microplastics were then analyzed by stereomicroscope and scanning electron microscope. Microplastics were found to be present in the feces of all 175 queen conch sampled, and in statistically different abundances among sites, but with no obvious geographical pattern. The highest and lowest levels were found in Central America; the highest being in Belize (270 ± 55 microplastics/queen conch) and Alacranes, Mexico (203 ± 29 microplastics/queen conch), whilst the lowest levels were found in Puerto Morelos, Mexico. Fibers, mostly between 1000 and 1500 μm in size, were the most frequent microplastic particle types at every site and represented between 60 and 98% of all microplastic particles found. Our results suggest that the use of queen conch feces is a suitable method for detecting benthic microplastic pollution, and have confirmed that microplastic pollution of marine benthos is widespread across the Wider Caribbean.