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 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. 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.