Suspected microplastic counts and characteristics in fish muscle and gastrointestinal tissue

<p>Microplastics, or particles &lt;5mm in diameter, comprise a significant portion of marine plastic pollution. These particles can be directly or indirectly taken up by fish and have been detected in multiple fish tissues. Ingestion of plastic particles was recently reported for free-ranging bottlenose dolphins (<em>Tursiops</em> <em>truncatus</em>) inhabiting Sarasota Bay, FL, USA, a community that also has prevalent exposure to plasticizers (i.e., phthalates) at concentrations higher than human reference populations. The sources of these exposures for Sarasota Bay bottlenose dolphins are currently unknown, but plastic-contaminated prey could be a possible vector. To test this hypothesis, muscle and the contents and tissues of the gastrointestinal tract (GIT) from prey fish collected in Sarasota Bay were screened for suspected plastic particles, and particle properties (e.g., color, shape, surface texture) were compared to those observed in gastric samples from bottlenose dolphins.  In total, 29 fish across four species (hardhead catfish, <em>Ariopsis</em> <em>felis</em> (n=2); pigfish, <em>Orthopristis</em> <em>chrysoptera</em> (n=12); pinfish, <em>Lagodon</em> <em>rhomboides</em> (n=10); and Gulf toadfish, <em>Opsanus</em> <em>beta</em> (n=5)) were collected from two sampling stations in Sarasota Bay, FL during September 2022. Suspected plastic particles were observed in 97% of fish (n=28), and particle abundance was higher for GIT tissue than muscle. Fish and dolphin samples contained fibers and films; however, foams were most abundant in dolphin samples and not observed in fish. Fragments, including tire wear particles (TWP), were not observed in dolphin samples, TWP fragments were not observed in bottlenose dolphin gastric samples, but 23.1% and 32.0% of fish muscle and GIT samples, respectively, contained at least one TWP fragment. While some similarities in particle properties were shared between dolphins and fish, small sample sizes and incongruent findings for foams and TWP particles suggest that further investigation is warranted to understand the potential for trophic transfer.</p>