Heavy Metals and Other Toxins Found in Stranded Whales and Dolphins

A new study has detected heavy metals and other toxins in whales and dolphins that became stranded in Florida and Georgia over a 15-year timeframe.

Researchers analyzed tissue and fecal samples of 90 odontocetes (toothed whales), spanning nine different species, that had stranded in Florida and Georgia from 2007 to 2021. In total, the team led by the Harbor Branch Oceanographic Institute at Florida Atlantic University analyzed over 319 samples of blubber, kidney, liver, skeletal muscle, skin and feces for 12 trace elements: cobalt, copper, iron, manganese, molybdenum, selenium, zinc, arsenic, cadmium, lead, mercury and thallium.

The results revealed that the animals did experience bioaccumulation of heavy metals in varying amounts, which they could be exposed to through their diets. 

The study, published in the journal Cell Press: Heliyon, revealed that the highest concentrations for mercury, cadmium and lead were in two species, Risso’s dolphins (Grampus griseus) and short-finned pilot whales (Globicephala macrorhynchus).

The research also unveiled that heavy metal exposure may be increasing over time. According to the study, researchers found higher concentrations of several trace elements, including arsenic, copper, iron, lead, manganese, selenium, thallium and zinc, for adult pygmy (Kogia breviceps) and dwarf sperm whales (Kogia sima) that stranded from 2019 to 2021 compared to the same species that stranded earlier, in 2010 to 2018.

“When we separated phylogenetic groups into age classes and compared median concentrations of heavy metals in specific tissue types between adult specimens of species, we found some interesting trends,” Annie Page, senior author of the study, associate research professor and clinical veterinarian at Harbor Branch, said in a statement. 

Another trend the authors noted in the study was that the highest concentrations for several elements were found in fecal matter. Why is this important? It showed how beneficial the data collected in a non-invasive way can be, according to the authors.

While mercury and other toxins can impact many species in marine food webs, these elements can be especially harmful for those at the top of the food chain, as reported by the Minamata Convention on Mercury. The heavy metals can accumulate as predators consume their prey, and the heavy metals can cause several health problems for whales, dolphins, and other species.

“Exposure to heavy metal contaminants can result in oxidative stress, which can impair protein function, damage DNA and disrupt membrane lipids,” Page explained. “Heavy metal exposure has been linked to degenerative heart disease, immunodeficiency and increased parasite infestations, among other disease risks.”

The authors hope this research will contribute to baseline data on the risks of bioaccumulation of trace elements in whales and dolphins.

“This study illustrates the importance of monitoring toxic contaminants in stranded odontocetes, which serve as important sentinels of environmental contamination, and whose health may be linked to human health,” the study concluded.