Suspected microplastic counts and characteristics in fish muscle and gastrointestinal tissue

Microplastics, or particles <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 (Tursiops truncatus) 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 acro..., Microplastic screening of fish tissues followed methods used in Lusher et al., (2017) and Hart et al., (2022). Briefly, muscle and gastrointestinal (i.e., stomach and intestine) tissue from each fish were placed into a glass beaker, and organic (non-plastic) material in the samples was digested by adding a 10% potassium hydroxide (KOH) solution and incubated at 60°C for 24–72 hours (Karami et al., 2017). Following digestion, samples were vacuum filtered onto GF/A 1.6 µm glass fiber filters in a fume hood and left to dry in covered glass petri dishes. Particles of at least 35 µm were characterized visually using a dissection microscope (Leica EZ4, magnification 8-35x) according to physical attributes including shape (e.g., fiber, film, fragment, foam), surface texture (e.g., smooth, rough, rubber), and color (e.g., transparent, blue, black; Shim et al., 2017). Various parameters were used to identify potential plastic material. For example, suspected plastic fibers were indicated by a sm..., , ## Fish Microplastics Data\_Repository

Twenty-nine fish across four species (hardhead catfish, Ariopsis felis (n=2); pigfish, Orthopristis chrysoptera (n=12); pinfish, Lagodon rhomboides (n=10); and Gulf toadfish, Opsanus beta (n=5)) were collected from two sampling stations in Sarasota Bay, FL during September 2022. Both muscle and gastrointestinal (GIT) samples were screened for microplastics in 21 fish, while 10 fish were screened using either muscle (n=5) or GIT (n=5). Particles of at least 35 µm were characterized visually using a dissection microscope (Leica EZ4, magnification 8-35x) according to physical attributes including shape (e.g., fiber, film, fragment, foam), surface texture (e.g., smooth, rough, rubber), and color (e.g., transparent, blue, black; Shim et al., 2017). All particles at least 100 µm in size and with characteristics previously described were tested with a hot needle (250°C) and suspected to be of plastic origin if the needle left a mark on or melted the par...