• Posted June 14, 2024

Dolphins Off Florida, Georgia Have High Levels of Mercury

Dolphins living off the coasts of Georgia and Florida have elevated levels of mercury in their bodies, new research shows.

That could have implications for people, said a team led by Colleen Bryan, a research biologist at the National Institute of Standards and Technology in Charleston, S.C.

“As a sentinel species, the bottlenose dolphin data presented here can direct future studies to evaluate mercury exposure to human residents,” said the team that published its findings recently in the journal Toxics.

Mercury is a byproduct of human industry, but it also appears in nature. Animals, including large ocean-going fish and mammals, are at special risk since they rank high in the food chain and consume fish that have retained higher mercury levels.

As mercury builds up in the body, it can trigger a host of issues such as reproductive failure, behavioral changes and even death, the researchers said.

In the new study, the researchers analyzed 175 skin samples collected from common bottlenose dolphins between 2005 and 2019.  The samples came from St. Joseph, Choctawhatchee and Biscayne Bays in Florida and the Skidaway and Turtle/Brunswick river estuaries and Sapelo Island in Georgia.

After measuring mercury levels in the dolphin's skin, St. Joseph Bay dolphins had especially high levels of mercury -- averaging 14,193 nanograms of mercury per gram (ng/g) of skin -- including the highest they had ever recorded. 

The researchers also pointed to previous research from others. Those studies showed that dolphins in the Charleston area had the lowest average levels -- 509 ng/g -- while dolphins in the Florida Coastal Everglades had the highest -- 10,916 ng/g. 

The low rates of mercury in Charleston's waters could be based on the fact that tidal flows "flush out" mercury when the tide goes out. 

According to the U.S. Environmental Protection Agency “for most people, the risk from eating fish and shellfish is not a health concern," and the agency says that fish remains part of a healthy diet.

However, “Our research adds to other studies that have consistently shown elevated levels of mercury in dolphins in the Southeast,” Bryan said in a Penn State news release. “We hope it will lead to a better understanding of what’s happening in our oceans.”

More information

Find out more about mercury's effect on health at the NRDC.

SOURCE: Penn State University, news release, June 13, 2024