ORLANDO, Fla., Aug. 10 (UPI) -- Dolphins and whales stranded on beaches in the southeastern United States had high levels of toxins, including mercury and chemicals found in plastic, according to a study published in the journal Frontiers in Marine Science.
Scientists who led the study said the data provides new, troubling information about the impact of pollution on marine mammals -- knowledge that could help save vulnerable and declining species.
The findings also could be a warning for humans, because whales and dolphins eat seafood that people also eat, researchers said.
"We must do our part to reduce the amount of toxicants that enter into our marine environment, which have important health and environmental implications not just for marine life, but for humans," lead author Annie Page-Karjian said.
"Dolphins eat a variety of fish and shrimp in these marine environments and so do humans," said Page-Karjian, an assistant research professor of marine wildlife at Harbor Branch Oceanographic Institute in Fort Pierce, Fla.
Besides plastic chemicals, the study found toxins in the animals that included mercury, triclosan -- an antibacterial agent used in consumer products like in soap and toothpaste -- and atrazine, an herbicide.
The study, published last week, examined tissue from 83 dolphins and whales that became stranded from North Carolina to south Florida and died from 2012 to 2018. Eleven animal species were tested for 17 toxins.
The study is the first to report concentrations of toxicants in a white-beaked dolphin and in Gervais' beaked whales, species for which the scientific literature remains sparse.
The researchers involved in the study are licensed to retrieve bodies of marine mammals nationally and internationally as part of a network to respond to the stranding of marine animals.
Such science collected from the dead animals is difficult to collect from live animals, and the stranded animals often are in stages of sickness or decay, said Justin Perrault, another study participant, who is director of research at Loggerhead Marinelife Center Juno Beach, Fla.
"Some of the mercury levels we found were the highest found anywhere in the world," Perrault said. "It is eye-opening. To see the levels of some of these contaminants is alarming."
Despite those high levels, the study was unable to determine if the toxins caused the animals to beach themselves, said James Sullivan, executive director at Harbor Branch.
"It's really hard to judge, when an animal strands, if the toxins in the animal were related to why it stranded," Sullivan said. "But these health problems do stack up. The animal is much more susceptible to succumbing to natural disease and environmental problems, just like humans are more likely to get ill from coronavirus if they have underlying conditions."
Although the study focused on the Southeast, it has broader implications for marine mammal conservation, said John Calambokidis, senior research biologist with Olympia, Wash.-based Cascadia Research.
"There are many things we do not know about how many contaminants accumulate and might impact marine mammals," Calambokidis said. "This is valuable especially because there are so many chemicals that are used by humans and enter the environment and many are not tested for."