Will Changes in Weather Expose Dolphins to More Chemicals?

Since 2016, the College of Charleston and its partners at the Sarasota Dolphin Research Program (SDRP) have been studying plastics pollution exposure in Sarasota Bay’s bottlenose dolphins. The studies have found plastics in dolphin stomach contents and breath, as well as chemicals used to make them – called phthalates – in their urine.

Now, a new study is investigating how climate-influenced events like major storms, rainfall and red tides impact phthalate exposure and health of Sarasota Bay dolphins.

Phthalates – used to make plastics flexible and more durable and also used as solvents and stabilizers – have been nicknamed the “everywhere chemical” because they’re so widespread in our daily lives. These chemicals are easily released as plastics deteriorate and are found in everything from PVC pipes, to food packaging and even cosmetics and perfumes. Exposure is so common that more than 95% of humans have detectible levels in their urine.

The research has shown that approximately 75% of Sarasota Bay dolphins have detectable levels of phthalates in their bodies. The levels in Sarasota Bay dolphins are higher than concentrations found during human studies.

This phthalate exposure is a concern for dolphins because these ubiquitous chemicals are known endocrine disruptors that impact mammals’ hormone systems. Hormonal changes can cause problems with growth, fertility and reproduction, which could have population-level impacts on dolphins. Human studies have also shown that phthalates can lead to heart problems and even neurological disorders.

By analyzing urine samples collected over three decades, the College of Charleston and SDRP aim to identify environmental influences on phthalate exposure and links to dolphin endocrine disruption, reproductive issues, growth abnormalities and cardiovascular health. This study will provide valuable insights into how environmental changes can impact dolphin exposure to these chemicals of emerging concern.

“In previous studies, we found that there were unexplained differences in phthalate concentrations in Sarasota Bay dolphins, depending on when urine samples were collected and what part of the bay the dolphins frequented,” says Leslie Hart, associate professor at the College of Charleston and the project’s lead researcher. “Through this study, we’re trying to tease out the factors that could account for some of the differences.”

Previous environmental studies in other parts of the world have shown that phthalate contamination can increase when rainfall causes excess runoff and flooding, so the team is comparing tropical storm and rainfall records for the Sarasota Bay area to the phthalate levels in the bay’s dolphins using archived urine samples from 202 animals.

And, because previous SDRP studies have shown that dolphins are forced to eat different prey items when fish populations decline during red tides – which could also impact phthalate levels – the team is comparing the urine samples with archived cell counts of the dinoflagellate that causes red tide blooms (Karenia brevis).

“Long-term forecasts predict increasingly warmer ocean temperatures, which provide fuel for tropical storms and hurricanes that can bring flooding and excess runoff from land,” Hart says. “As these waters drain into our local bays, they carry nutrients and chemicals, including phthalates and plastics, from the land, increasing the risk of contaminant exposure for local dolphin populations. Additionally, red tide blooms, driven by nutrient inputs, often lead to fish die-offs, potentially increasing trophic-associated exposure to phthalates and plastics.”

The study is funded by Sea Grant (Award No. NA22OAR4170655 – CFDA #11.417) and made possible thanks to the data gathered about the long-term resident dolphins of Sarasota Bay over more than 55 years through the Sarasota Dolphin Research Program, the world’s longest-running dolphin conservation research program. The SDRP, which has been operated by Brookfield Zoo Chicago since 1989, conducts periodic catch-and-release health assessments to monitor the bay’s dolphins. During these veterinary check-ups, the researchers gather a variety of biological samples used for various studies. Unused samples are stored for future work as new research questions arise.

“As phthalates have become ubiquitous in our environment, there’s a growing concern over what the impacts could be,” says Randy Wells, director of the SDRP and vice president of marine mammal conservation at Brookfield Zoo Chicago. “If humans are causing disturbances to things like dolphin reproduction because of plastics and chemicals from plastics, wildlife managers need to know that so they can work to mitigate the risks. Over more than five decades, Sarasota Bay has served as a natural laboratory where we can answer critically important questions like this.”

Additional investigators on the project are Krystan Wilkinson, staff scientist, Sarasota Dolphin Research Program; Miranda Dziobak, public health instructor, College of Charleston; Nadine Slimak, Vetted Communications; and Kylie Warden, graduate student at the College of Charleston.

Take Our Survey

The public can help be a part of this research by taking a short survey being conducted by the Sarasota Dolphin Research Program and the College of Charleston. The study is looking at how plastics and the chemicals added to plastics (called phthalates) in the environment impact bottlenose dolphins in Sarasota Bay and what this could mean for people living near the coast. By taking this survey, the public will help the research team understand how much people know about dolphins and plastics and use that information to create materials teaching people how to protect dolphins in Sarasota Bay and other locations.

Take the survey now at bit.ly/phthalate-survey. For the Spanish-language survey, visit bit.ly/encuesta-ftalatos