12-03-2025
Experts alarmed after researching bottlenose dolphins off coast of Florida: 'There's a growing concern'
A new study is looking at how rain and red tides affect plastic exposure in Florida's bottlenose dolphins, with concerning early findings that could impact dolphin health and reproduction, Oceanographic Magazine reported.
Researchers from the College of Charleston and the Sarasota Dolphin Research Program have discovered alarming levels of plastic particles in dolphin stomach contents and breath. Even more troubling, chemicals used to make plastic, known as phthalates, have been found in dolphin urine.
About 75% of Sarasota Bay dolphins now have detectable phthalate levels in their bodies, exceeding concentrations found in humans. This has prompted scientists to launch a bold investigation into how rainfall and red tides (toxic algae blooms) influence dolphin exposure to these plastic-derived chemicals.
"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," said Leslie Hart, associate professor at the College of Charleston and the project's lead researcher.
These plastic chemicals damage mammal hormone systems, causing problems with growth, fertility, and reproduction that could threaten entire dolphin populations.
The situation might get worse as ocean temperatures rise. Warmer waters fuel tropical storms that wash more plastic pollution into marine environments.
"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 said.
"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."
These same chemicals affect humans, too, with studies linking phthalates to heart problems, breast cancer, and brain disorders.
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Scientists are analyzing urine samples collected over 30 years to track how storms, rainfall, and red tide events affect phthalate exposure in dolphins.
The Sea Grant-funded study builds on data from 55-plus years of research on Sarasota Bay's resident dolphins, creating an unmatched historical record that helps answer these pressing questions.
"As phthalates have become ubiquitous in our environment, there's a growing concern over what the impacts could be," said Randy Wells, director of the Sarasota Dolphin Research Program.
"If humans are causing disturbances to things like dolphin reproduction because of plastics and chemicals from plastics, wildlife managers need to know so they can work to mitigate the risks."
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