What seal pups can reveal about the effects of mercury exposure
Marine mammals living along the Pacific Coast of North America encounter more than the fish, crustaceans, cephalopods and other marine mammals that live around them. Because contaminants such as mercury can move through marine food webs and biomagnify—becoming more concentrated as they move from prey to predator—fish-eating marine mammals can be exposed to higher levels of these pollutants.
Seal pups offer valuable insights into the impacts of mercury exposure on marine life. Contaminants like mercury can magnify in marine food chains, affecting fish-eating mammals. Dr. Todd O'Hara and his team at Texas A&M University have studied marine mammals and their prey from Alaska to Mexico to understand these contaminant exposures and their health effects.
Seal and sea lion pups are crucial in this research due to their vulnerability to mercury exposure even before birth. Some contaminants, such as mercury and persistent organic pollutants like polychlorinated biphenyls (PCBs) and DDT, can be transferred from mothers to offspring during gestation and nursing. This study found that Steller sea lion pups from Alaska's western Aleutian Islands had higher mercury and PCB levels than adult females and sea lions from other locations.
Additionally, mercury levels in pups varied by location, likely due to differences in their mothers' diets. However, detecting mercury in an animal only reveals part of the story. Researchers also need to understand whether this exposure affects the animal's functioning, including potential neurologic effects. Developing a specialized neurological examination for harbor seal pups has been essential in assessing their nervous system health.
This 26-point examination, tailored to pinniped anatomy and behavior, allows veterinarians to identify neurological abnormalities quickly and accurately. By combining these examinations with other clinical assessments, researchers can better understand the effects of contaminants on marine mammals and guide appropriate treatment and rehabilitation.
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