How Does Plastic Pollution Impact Dolphins?
Worldwide, humans use an estimated 100 billion plastic bags every year; the average American uses more than 300, according to Environment America. All told, the U.N. Environment Program estimates that humans produce more than 400 million metric tons of plastic annually.
That’s a lot of plastic — and a lot of it is ending up in the ocean (170 trillion plastic particles, according to this study), where it impacts marine life in a variety of negative ways:
- Plastics, including braided micro-multifilament fishing line, can cause entanglements that lead to marine animal injuries and deaths (see a few examples of the entangled dolphins we’ve rescued here).
- Animals can ingest plastics either by mistake, thinking plastics were prey items, or accidentally, while feeding on other items. Emerging studies are also showing that plastics are prevalent in the food web and that predators are unwittingly consuming plastic when they eat their traditional prey items. The plastic can cause stomach or intestinal blockages that lead to starvation and death.
- Emerging studies indicate that marine animals can inhale microplastics.
- Exposure to the chemicals used in plastic production — called phthalates, or plasticizers — that are released as plastics break down in the environment can also harm animals at a more basic level, impacting their reproduction, growth, metabolism and heart and lung function.
Plastics Research
Since 2016, SDRP and its partners at The College of Charleston have studied indicators of plastic pollution exposure in Sarasota Bay dolphins. Following the methodologies used for human health studies, our initial exploratory project focused on whether we could detect metabolites of plastic-associated chemical additives — called phthalates — in urine.
Our findings from this early research indicated widespread exposure to these chemicals: 75% of Sarasota Bay dolphins are exposed to phthalates and they have significantly higher concentrations of some of these chemicals than humans.
Dolphins and Phthalates
Although phthalate exposure is common among dolphins in Sarasota Bay, the sources for these exposures are currently unknown. As part of a three-year project funded by the National Institutes of Health’s (NIH) National Institute of Environmental Health Sciences (NIEHS), we are investigating microplastic contamination in prey fish as a potential source of phthalate exposure and looking for evidence of microplastic ingestion in Sarasota Bay dolphins and common prey fish (for example, menhaden, spot, sheepshead, Gulf toadfish, pigfish, pinfish). The study involves collecting gastric and fecal samples from dolphins, as well as gastrointestinal tracts and muscle tissue from fish, and comparing characteristics such as color, type and texture of ingested microplastics between dolphins and fish. We’re also:
- Examining phthalate metabolite concentrations in dolphins and fish relative to individual particle abundance. This analysis will help us understand whether high quantities of ingested plastic are correlated with high concentrations of chemical plasticizers.
- Comparing microplastic abundance and physical properties among different fish tissues (for example, muscle/filet vs. gastrointestinal tract), so that we can better understand exposure risks for human seafood consumers.
Read More About Dolphins and Plastics
Microplastics Detected in Dolphin Breath
Every Breath They Take? New Study Suggests Dolphins are Inhaling Plastics A member of the SDRP research team holds a petri dish over a dolphin's blowhole to collect a breath
A Tangled Food Web
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
Stow it! Don’t Throw It!
Creating Monofilament Collectors to Help Save Dolphins from Entanglement Did you know that monofilament fishing line can take up to 600 years to decompose and that it
Plastic and Plastic Compounds in Dolphins
Studying the Impacts of Plastics and Plastic Compounds in Sarasota Bay Dolphins The oceans are estimated to contain more than 170 trillion plastic particles — with more
Dolphins and Microplastics
Study Finds Evidence that Dolphins are Ingesting Microplastics A new study in the peer-reviewed journal Frontiers in Marine Science has found evidence that members of the Sarasota Bay dolphin community are inadvertently ingesting
Join Our Marine Debris Team
One of the simplest ways to help wild dolphins — and all other marine life — is to make sure you’re not leaving plastics or other trash in our waterways or allowing garbage to
Research Publications
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.; Berens McCabe, E.; Conger, E.; Curtin, T.; Knight, M.; Weinstein, J. Plastic, It’s What’s for Dinner: A Preliminary Comparison of Ingested Particles in Bottlenose Dolphins and Their Prey. Oceans 2023, 4, 409–422. https://doi.org/10.3390/oceans4040028
Dziobak, M.K.; Wells, R.S.; Pisarski, E.C.; Wirth, E.F.; Hart, L.B. A Correlational Analysis of Phthalate Exposure and Thyroid Hormone Levels in Common Bottlenose Dolphins (Tursiops truncatus) from Sarasota Bay, Florida (2010–2019). Animals 2022, 12, 824. https://doi.org/10.3390/ani12070824
Dziobak, M.K.; Balmer, B.C.; Wells, R.S.; Pisarski, E.C.; Wirth, E.F.; Hart, L.B. Temporal and Spatial Evaluation of Mono(2-ethylhexyl) Phthalate (MEHP) Detection in Common Bottlenose Dolphins (Tursiops truncatus) from Sarasota Bay, Florida, USA. Oceans 2022, 3, 231–249. https://doi.org/10.3390/oceans3030017
Dziobak, M. K., Wells, R. S., Pisarski, E. C., Wirth, E. F., & Hart, L. B. (2021). Demographic assessment of mono(2-ethylhexyl) phthalate (MEHP) and monoethyl phthalate (MEP) concentrations in common bottlenose dolphins (Tursiops truncatus) from Sarasota Bay, FL, USA. GeoHealth, 5, e2020GH000348. https://doi.org/10.1029/2020GH000348
Hart LB, Dziobak MK, Pisarski EC, Wirth EF, Wells RS (2020) Sentinels of synthetics – a comparison of phthalate exposure between common bottlenose dolphins (Tursiops truncatus) and human reference populations. PLoS ONE 15 (10): e0240506. https://doi.org/10.1371/journal. pone.0240506
Hart, L. B., Beckingham, B., Wells, R. S., Alten Flagg, M., Wischusen, K., Moors, A., et al. (2018). Urinary phthalate metabolites in common bottlenose dolphins (Tursiops truncatus) from Sarasota Bay, FL, USA. GeoHealth, 2. https://doi.org/10.1029/2018GH000146
