Paper Provides New Insights on How Microplastics are Moving From Prey to Predator

A new research paper based on studies conducted in Sarasota Bay is providing insights on how microplastics are moving from prey to predator — indicating that dolphins are ingesting microplastics contained in the fish they eat and potentially providing new insights into the implications for human seafood consumers.

The paper “An analysis of suspected microplastics in the muscle and gastrointestinal tissues of fish from Sarasota Bay, FL: Exposure and implications for apex predators and seafood consumers” in the peer-reviewed journal Environments analyzed prey fish tissues and dolphins’ gastrointestinal fluid for microplastics contamination.

The research team found tiny particles suspected to be microplastics — particles 5 mm or less, about the size of a pencil eraser or smaller — in the gastrointestinal fluid of Sarasota Bay dolphins, suggesting contaminated fish as a food source. Looking at dolphin prey species, the team:

  • Screened 94 fish — two to 24 individuals per species — for microplastics.
  • Fish species sampled are known prey items of Sarasota Bay dolphins and included hardhead catfish (Ariopsis felis), sheepshead (Archosargus probatocephalus), menhaden (Brevoortia tyrannus), spotted seatrout (Cynoscion nebulosus), ladyfish (Elops saurus), scaled sardine (Harengula jaguana), pinfish (Lagodon rhomboides), spot (Leiostomus xanthurus), striped mullet (Mugil cephalus), Gulf toadfish (Opsanus beta), pigfish (Orthopristis chrysoptera), and Atlantic thread herring (Opisthonema oglinum).
  • Suspected microplastics were found in 82% of prey fish muscle samples and 97% of fish gastrointestinal samples.
  • Particle abundance and shape varied by fish species, possibly because of their feeding habits, including whether they are omnivores or carnivores and where and how they typically feed.
  • The highest particle loads were found in pinfish, Atlantic thread herring and Gulf toadfish, with pinfish having the highest abundance of microplastic particles.

“Our oceans contain roughly 171 trillion plastic particles thanks to the breakdown of plastic litter, direct contamination from human products and from sewage and wastewater discharge,” said study co-author, Elizabeth Berens McCabe, Senior Researcher at SDRP who focuses on the relationship between dolphins and their prey. “Given the ubiquity of plastics in the environment, it’s critical that we gain a better understanding of their impacts and what that means for dolphin and human communities.”

The work builds on a 2022 study — “Microplastics in gastric samples from common bottlenose dolphins (Tursiops truncatus) residing in Sarasota Bay FL (USA)” in Frontiers in Marine Science — that found microplastic contamination in the stomach contents of seven Sarasota Bay dolphins sampled during a Sarasota Dolphin Research Program health assessment. “Those findings were consistent with microplastics studies focused on other cetacean species worldwide,” said SDRP research partner and study co-author Dr. Leslie Hart, an environmental epidemiologist at the College of Charleston who focuses on microplastics and phthalate exposures in dolphins and humans. Phthalates are chemicals that can be released when plastics break down in the environment.

The high level of contaminants in this new study could be in-part attributed to Sarasota Bay’s location in an urban setting that receives runoff from a highly developed environment with more opportunities for plastics to enter the water. And since contaminants are known to accumulate in animals that feed at higher trophic levels, Sarasota Bay’s dolphins could be at even greater risk of exposure to microplastics and phthalates.

“We don’t yet know the full impacts of microplastic exposure for dolphins and other marine mammals, but laboratory and human studies suggest that exposure could lead to neurological and reproductive impairment, as well as inflammation and metabolic issues,” Dr. Hart said. “The high-levels of particles in fish tissues that we found also has implications for humans who eat seafood. The most contaminated species in our study — pinfish — are commonly used as bait to catch larger fish, such as seatrout. So, if microplastics move through the food web from prey to predator, seafood consumers could be eating microplastics and the chemicals they are made of (i.e., phthalates).”

The study’s lead author was Eric Conger, College of Charleston undergraduate student, and additional co-authors were Dr. Miranda Dziobak, Instructor, College of Charleston and University of South Carolina-Columbia, students Tita Curtin and Ayushi Gaur, College of Charleston, Dr. Randall S. Wells, SDRP Director, and Dr. John E. Weinstein, Professor of Physiology and Head of the Department of Biology, The Citadel.

—Funding for this study was provided by the National Institute of Environmental Health Sciences of the National Institutes of Health (Award # R15ES034169). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Citations

Conger, E.; Dziobak, M.; Berens McCabe, E.J.; Curtin, T.; Gaur, A.; Wells, R.S.; Weinstein, J.E.; Hart, L.B. An analysis of suspected microplastics in the muscle and gastrointestinal tissues of fish from Sarasota Bay, FL: Exposure and implications for apex predators and seafood consumers. Environments 2024, 11, 185. https://doi.org/10.3390/environments11090185

Hart, L. B., Dziobak, M., Wells, R. S., Ertel, B., & Weinstein, J. (2022). Microplastics in gastric samples from common bottlenose dolphins (Tursiops truncatus) residing in Sarasota Bay FL (USA). Frontiers in Marine Science, 9, 947124. https://doi.org/10.3389/fmars.2022.947124