The abundance and localization of environmental microplastics in gastrointestinal tract and muscle of Atlantic killifish (Fundulus heteroclitus)

Abstract Microplastics (MPs) have been found in a diverse range of organisms across trophic levels. While a majority of the information on organismal exposure to plastics in the environment comes from gastrointestinal (GI) data, the prevalence of MP particles in other tissues is not well understood. Additionally, many studies have not been able to detect the smallest, most prevalent, MPs (1 µm – 5mm) that are the most likely to distribute to tissues in the body. To address these knowledge gaps, MPs in the GI tract and muscle of Atlantic killifish (Fundulus heteroclitus) collected from two sites on Buzzards Bay, Cape Cod, MA were quantified down to 2 µm in size. Fourier-transform infrared spectroscopy and Raman spectroscopy were used to identify all particles. Of the 2,008 particles analyzed in various fish tissue samples, only 3.4 % (69 particles) were identified as plastic; polymers included nylon, polyethylene, polypropylene, and polyurethane. MP abundance in the GI tract was greater than in the muscle. MPs detected in the GI tract samples also tended to be more diverse in both size and polymer type than those found in the muscle. We found that MPs <50 µm, which are often not analyzed in the literature, were the most common in both the GI tract and muscle samples. There was not a significant correlation between the MP content in the muscle compared to the GI tract, indicating that GI tract MP abundance cannot be used to predict non-GI tract tissue MP content; however, MP abundance in muscle correlated with fish total length, suggesting potential bioaccumulation of these small MPs.