Contaminants in dolphins suggest ecosystem woes

When Gregory Bossart began studying lesions on Atlantic bottlenose dolphin (Tursiops truncatus) populations over 10 years ago, he didn’t know the extent to which they would point to negative impacts in the ecosystem.

In two studies published in the journal Diseases in Aquatic Organisms, Bossart, the lead author of one study and coauthor of another, and his colleagues reviewed 12 years of data they had collected on two populations of the species — one in Florida’s Indian River Lagoon and one near Charleston, S.C.

Both populations were facing emerging infectious diseases, tumors and antibiotic-resistant bacteria, they found, as well as alarmingly high levels of contaminants such as mercury in their systems.

“Dolphins are really trying to tell us something, but we’re not too good at listening at this point,” said Bossart, senior vice president of Animal Health, Research and Conservation at the Georgia Aquarium.

From 2003 to 2015, the researchers collected blood samples, gastric fluid, fecal matter, blowhole samples, biopsies and other biological material from a total of 360 dolphins. The team found elevated levels of mercury in the Florida dolphins and elevated levels of industrial toxins in the South Carolina dolphins. Dolphins in both populations had their immune systems chronically activated, Bossart said, putting them at greater risk of infectious disease.

The findings raise concerns not only about the dolphins’ health, Bossart said, but about the health of the ecosystem and possible threats to human health.

“It’s the concept of the canary in the coalmine,” he said. “Sentinel species tell us what’s happening in the environment and how that can potentially impact public health.”

In the Indian River Lagoon where mercury was prevalent in dolphins, the team also recently found mercury levels were high in the hair of recreational fishermen.

“The hair samples exceeded mercury guidelines established by the EPA,” he said, raising concerns particularly about pregnant women, whose fetuses can be affected by the toxin.

Dolphins can also serve as sentinel species for ecosystem health, Bossart said.

“I think the study is kind of a microcosm of a much larger ocean problem right now,” he said.