Microplastics in the digestive systems of groundfish in the Monterey Bay

Microplastic contamination has been recognized as a growing problem in marine ecosystems that can limit an organism’s access to nutrients as well as transport organic toxins through absorption and release. Microplastics are particles (<5mm) that are either manufactured or created by the degradation of larger plastics, and enter the marine food web at various stages. Recent research indicates the presence of microplastics in the Monterey Bay National Marine Sanctuary both in beach sediments and deep in the Monterey Submarine Canyon, but research is only beginning to examine microplastic consumption by fish species in Monterey Bay. This study documents microplastic ingestion in lingcod and several rockfish species from Monterey Bay. Fish digestive tracts were obtained from local fishermen in 2018 and 2019. The number of microplastics found in the digestive tracts of each fish was compared with fish size and species. Species determinations were made from gut tissue using DNA barcoding of the mt CO1 gene. The study examined microplastic prevalence in fish and whether a species’ position in the water column influences the amount or type of microplastics consumed. Preliminary studies showed that ~70% of all fish species had ingested some sort of microplastic and that the dominant type was microfibers. This study adds to the expanding data sets on microplastic ingestion in fish species, and provides evidence of the increasing presence of microplastics in marine environments.