Everglades dolphins have record-high mercury levels, FIU study shows

By Tyler Treadway
December 26, 2016
TC Palm

Dolphins in the Everglades and the Indian River Lagoon are sending us a warning about how mercury accumulates in their bodies and ours.

A study Florida International University scientists published in the scientific journal Environmental Pollution in October found bottlenose dolphins in the Everglades, particularly along the northeastern shore of Florida Bay, had the highest levels of mercury concentration ever recorded: an average of 11 parts per million. That’s like a pinch of salt in 20 pounds of potato chips.

The discovery echoed research by scientists at Florida Atlantic University’s Harbor Branch Oceanographic Institute in 2012 that found mercury levels in Indian River Lagoon dolphins that weren’t much lower.

“We had levels of 7.0 (parts per million),” said Adam Schaefer, a Harbor Branch research professor who studies diseases in wildlife. “The Everglades is a primary location for mercury accumulation, and the conditions in the lagoon are very similar. So it makes sense our mercury levels are comparable.”

Dolphins are a “sentinel species,” Schaefer said. “High levels of mercury in dolphins shows that there are high levels of mercury in animals throughout the food chain. Dolphins are telling us there is mercury throughout lagoon species and throughout Everglades species.”


The Harbor Branch researchers followed their dolphin study in 2014 by finding high levels of mercury in people who live along the Indian River Lagoon and eat fish from there. Hair samples from 135 residents showed those who ate seafood three times a week were three times as likely to have more than 1 part per million of mercury in their systems, the limit the federal Environmental Protection Agency recommends for human health. People who had seafood daily were four times as likely to exceed the threshold, researchers found.

The mercury typically doesn’t kill dolphins or humans, said Jeremy Kiszka, an FIU marine scientist who co-authored that school’s study, but it can affect their livers, kidneys, immune systems and their ability to reproduce.

“It doesn’t kill on its own so much as make you susceptible to diseases that you normally could fight off,” Schaefer agreed.

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