Presence of Plastics in the Gastrointestinal Tract of Sharks in Texas Bays
Plastics in the marine environment have become an important topic in the recent decade due to its ubiquitous presence, long lasting impacts, and detrimental health effects. Plastics have been observed affecting marine organisms by causing gastrointestinal or respiratory blockages or tears. Other consequences of plastic ingestion include exposure to endocrine disrupting compounds, persistent organic pollutants, and toxic trace metals. Few studies have investigated the presence of plastics in shark gastrointestinal tracts, and nothing is known for sharks in Texas bays. This study assessed the presence, abundance, and type of plastics present in the gastrointestinal tracts (cardiac stomach, pyloric stomach, and spiral valve intestine) of three shark species [blacktip shark (Carcharhinus limbatus), bonnethead shark (Sphyrna tiburo), and bull shark (Carcharhinus leucas)] in four bays (Sabine Lake, Aransas Bay, Corpus Christi Bay, and Lower Laguna Madre) along the Texas coast using a stereomicroscope and Fourier transform infrared spectroscopy (FTIR). Young-of-the-year, juvenile, and adult individuals were examined in this study. Of the total number of sharks examined (n = 240) only eight individuals (two blacktip sharks, two bonnethead sharks, and four bull sharks) were found to contain plastic pieces, and a total of nine pieces of plastic were found. Each plastic piece was found in the cardiac stomach. Monofilament fishing line and hooks were commonly found, meaning that fishing practices, not plastic ingestion through diet is the main problem. The most frequently found polymers were polyethylene (PE) and nylon 6. Due to the low number of plastics found in these sharks, plastics do not appear to pose a threat to these species in these bay systems, however, future studies should include smaller fibers which were omitted from this study and investigate nanoplastics which could cross the gastrointestinal tract lining and be remobilized around the body.
Wulf, D. (2023). Presence of plastics in the gastrointestinal tract of sharks in Texas bays (Unpublished thesis). Texas State University, San Marcos, Texas.