Elevated Levels Of Mercury Have Been Found In Dolphins Across The Southeastern United States, Threatening Their Survival And Serving As A Warning Sign Of Health Hazards To Humans
For years, mercury contamination in marine environments has been a significant public health concern. Now, dolphins have emerged at the forefront of this issue.
In a new study, researchers have found elevated levels of mercury in dolphins across the southeastern United States, particularly along the Florida and Georgia coasts.
As apex predators at the top of the ocean’s food chain, dolphins accumulate mercury and other pollutants in their tissues through the consumption of a variety of smaller fish that make up their diet, including croaker, spot, squid, and shrimp. All of these species are vulnerable to the toxic element and are consumed by people as well.
The accumulation of mercury in dolphins not only threatens their survival but also serves as a warning sign of health hazards to humans from the ocean and the broader ecological impacts of mercury pollution.
“As a sentinel species, the bottlenose dolphin data presented here can direct future studies to evaluate mercury exposure to human residents,” wrote the authors of the study.
The team of researchers examined 175 samples of skin that were collected from bottlenose dolphins in estuaries between 2005 and 2019. The dolphins lived in the St. Joseph, Choctawhatchee, and Biscayne Bays in Florida, Sapelo Island, and Skidaway and Turtle/Brunswick River estuaries in Georgia.
The measured mercury in dolphin skin correlates directly with the methylmercury in their other organs and tissues. Mercury is converted to methylmercury by bacteria in the water. The methylmercury is then eaten or absorbed by small fish and passed up the food chain to larger species like dolphins.
In St. Joseph Bay, dolphins averaged 14,193 nanograms of mercury per gram in the skin. They had the highest recorded mercury levels out of all the dolphins that were tested.
According to Mackenzie Griffin, the lead author of the study and a biologist at the National Oceanic and Atmospheric Administration (NOAA), the high mercury levels in the bay may be partially due to industrial activities.
willyam – stock.adobe.com – illustrative purposes only, not the actual dolphins
The bay also isn’t flushed out with fresh water from other waterways, which would help reduce the amount of mercury present.
Previous studies have found that dolphins near Charleston, South Carolina, had lower average levels of mercury contamination than dolphins in the Florida Coastal Everglades, which had the highest. When the tide goes out at Charleston Harbor, mercury gets flushed away.
The study couldn’t confirm the mercury levels of Florida and Georgia residents. Still, the research offers valuable insights that can help guide future directions.
For humans, we know that consuming too much mercury can have adverse effects on the body. Eating smaller fish is the way to go if you’re concerned about mercury exposure.
Smaller fish, such as sardines, salmon, and herring, typically have much less mercury than bigger animals like sharks, whales, and dolphins.
Mercury is also a naturally occurring element, so it cannot be completely removed from certain food sources.
The issue with mercury is that when it enters our food supply unnaturally through mining, chemical manufacturing, and the burning of fossil fuels.
The study was published in the journal Toxics.
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