High levels of toxic pollutants found in stranded whales, dolphins in Florida and North Carolina: Study

The highest-ever documented levels of toxins such as mercury and arsenic were present in the liver and fat tissue samples of these ocean giants, say researchers


                            High levels of toxic pollutants found in stranded whales, dolphins in Florida and North Carolina: Study
(Getty Images)

Harmful pollutants released from human activities found their way into the bodies of stranded whales and dolphins that washed ashore along the coasts of Florida and South Carolina, according to a new study. The highest-ever documented levels of toxins such as mercury and arsenic were present in the liver and fat tissue samples of these ocean giants, say researchers.

These pollutants in marine organisms could signal a potential risk for human health. "For example, many of the species in this study prey upon fishes that are also preferred species for human consumption -- so monitoring concentrations of contaminants in these animals provide a relatively low-cost snapshot of the potential exposure risk in humans, as well as other marine animals," says Annie Page-Karjian, the lead author from Harbor Branch Oceanographic Institute at Florida Atlantic University.

Plastics and other toxins clog our oceans and enter the food chain. Marine organisms end up consuming these pollutants unwittingly.  Previous studies have warned that plastics, and the chemicals used to make them, can severely harm animals' livers, kidneys and reproductive health. A recent study showed that a freshwater organism breaks down microplastics into nano-sized fragments, which are invisible to the naked eye. Dolphins and whales are the top predators, making them susceptible to the dangerous-effects of pollutants, say researches in their new study.

Thus Page-Karjian and her colleagues studied tissue samples of stranded whales and dolphins, in Florida and South Carolina, between 2012 and 2018. They studied 11 different species, including the rare white-beaked dolphin and Gervais' beaked whales. The researches also measured pollutant levels in both males and females, as well as fetal, young and adult animals. This allowed them to investigate how toxin levels varied with age and sex.

Adult female bottlenose dolphins had higher levels of arsenic and iron than their male counterparts. (Getty Images)

The measured levels of bisphenol A, a chemical used to make plastics. It is known to seep into packaged water and food. Additionally, they also looked at heavy metal contaminants such as arsenic, lead and mercury. At high concentrations, these toxins can damage animals' immune, reproductive and nervous systems.

The analysis showed that adult female bottlenose dolphins had higher levels of arsenic and iron than their male counterparts. As for differences in regions, dolphins stranded in Florida had accumulated higher amounts of toxins such as lead, mercury and selenium, and lower concentrations of iron, than those in North Carolina.

"While exposure to contaminants and toxic elements may not lead directly to stranding, such exposure is thought to impact animal survival through indirect effects on behavior, reproduction, and immunity," says Page-Karjian. "This study highlights the importance of marine mammal stranding response efforts and exemplifies why it is necessary to conduct necropsies of these animals and collect and archive tissue samples for future research. In the face of ever-growing consumer chemical industries, toxicology should be consistently integrated into standardized health assessments of free-ranging wildlife."

Besides pollutants, other human activities are also threatening the population of whales and dolphins. Some of the threats include bycatch ship strikes, noise pollution from shipping, oil, and gas industrial activities, and oil spills, according to the Wildlife Conservation Society, a non-governmental organization.

The study is published in Frontiers in Marine Science.

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