Occurrence and Amount of Microplastics Ingested by Fishes in the Watersheds of the Gulf of Mexico
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Occurrence and types of microplastics in the digestive system of freshwater fishes could be an emerging environmental crisis because of the proliferation of plastic pollution in aquatic environments. Recent studies report increasing amounts of microplastics in marine systems and in the gut tracts of marine fishes. To date, only one study has reported percent occurrence of microplastics (12%) in the digestive system of freshwater fishes. Purposes of this study were to quantify occurrences and types of microplastics ingested by fishes within the western freshwater drainages of the Gulf Mexico and an estuary of the Gulf of Mexico. My study objectives were (1) to enumerate and identify microplastics from fishes taken from 10 sites and nine freshwater drainages of Texas and harbor, bay, and gulf sites within or near the Laguna Madre of southeast Texas, (2) to compare percent occurrence of microplastics among habitat and trophic guilds of fishes, and (3) to compare percent occurrence of microplastics between urbanized and non-urbanized streams and thus test the hypothesis that fishes from urbanized streams will have greater percent occurrence of microplastics than fishes from non-urbanized streams. Among 535 fishes examined in this study, percent occurrence of microplastics was 8% in freshwater fishes and 10% in marine fishes. Plastic types included polyester, polystyrene, polypropylene, acrylate, and nylon. Percent occurrence of microplastics ingested by fishes in non-urbanized streams (5%) was less than that of one urbanized streams (Neches River; 29%). Percent occurrence by habitat (i.e., benthic, pelagic) and trophic guilds (herbivore/omnivore, invertivore, carnivore) were similar. Percent occurrences of microplastics reported herein are similar for freshwater fishes and towards the lower end of the range of microplastic ingestion in marine fishes (range: 8 - 33%). Occurrences of microplastics in the fishes pose several environmental concerns. For fish health, microplastics absorb toxins and can be passed through the digestive system, into the circulatory system, and accumulate in tissue. Long-term effects are unknown for the fish or the effects on human consumers.