Several drugs, including fentanyl, found in bottlenose dolphins in Gulf of Mexico, scientists say

Scientists have detected fentanyl and other drugs in dozens of dolphins from the Gulf of Mexico, which could have large implications on the overall health of the oceans, they say.

The research began in September 2020, when marine biologists conducting a routine boating survey to monitor the dolphin population in the Gulf of Mexico came across a deceased dolphin floating in the water, Dara Orbach, an assistant professor at Texas A&M University-Corpus Christi's marine biology program and co-author of the study, told ABC News.

The scientists could tell that the dolphin had just died because its tail was still moving, Orbach said. So, they decided to tow it back to campus to study.

Years later, when graduate student Makayla Guinn needed dolphin tissue samples for her research on hormones, the biologists retrieved some blubber from that dolphin to study, Orbach said.

The researchers then teamed up with Texas A&M-Corpus Christi biochemist, Hussain Abdulla, who lent out his laboratory for the marine biologists to run an untargeted analysis to see just what was inside these tissues. An untargeted analysis involves an instrument to indicate whether there are chemicals in the tissue, Christiana Wittmaack a toxicologist at Precision Toxicological Consultancy and co-author of the paper, told ABC News.

Although they were just looking for hormones, thousands of compounds were generated within the analysis. The researchers were especially shocked when they selected three specific compounds that they thought would be unlikely to find in a dolphin -- fentanyl, a muscle relaxant and a sedative -- and found that the sample tissue contained traces of all three.

For her honor student undergraduate project, Anya Ocampos then ran 89 dolphin samples through a mass spectrometer -- 83 of which were from biopsies of live dolphins located in Laguna Madre, a shallow lagoon near Corpus Christi Bay in South Texas. Fentanyl was the most prevalent of the drugs tested, found in 24 of the samples, the researchers found.

Not only did all of the dead samples test positive for at least one of the drugs, but some of them were from historic samples taken from the Mississippi Sound in 2013, which suggests that the drugs have been in the Gulf of Mexico's waterways for a long period of time, Orbach said.

In addition, dolphins don't drink water, Orbach said. The marine mammal obtains the majority of its hydration from its prey, therefore those animals would likely also have these contaminants in their system.

"So it's possible that this is a widespread and longstanding prevalent issue that simply has not been addressed," she said.

The drugs and other contaminants could be coming from a number of places, including dermal contact or the water itself, Wittmaack said.

Drugs being thrown overboard, since they are located so close to the Mexican border, agricultural runoff, or human wastewater could also be sources of the chemicals, Orbach said.

The dolphin found in 2020 was located adjacent to Robstown County, the location of the largest liquid fentanyl drug bust in U.S. history in 2023.

"This is something that we really need to monitor with time, so that we need to make sure that we're not seeing increases in in fentanyl concentrations," Wittmaack said.

There have never been any studies to show what the long-term effects of pharmaceuticals are in marine mammals, Orbach said.

Although the traces found were low amounts, the water pollution is the latest in a series of stressors that marine animals are facing.

"These are animals are subjected to constant noise pollution, vessel traffic, dredging, algal blooms, oil spills, chemical spills," Orbach said. "...When you add more and more factors, at some point the animal is so susceptible that they can't respond it."