Organochlorine Pesticides (OCPs) and Total Mercury in Stranded Harbor Seal (Phoca vitulina) Pups from the Northeast Atlantic

Contaminants that exhibit high bioaccumulation and biomagnification potentials are of great concern and pose significant health risks for both higher trophic species and their offspring. Organochlorine pesticides (OCPs) and methylmercury (MeHg) are compounds of concern. This study looks at the levels of OCPs, including o,p’-DDT, atrazine, chlorothalonil, acetochlor, hexacholorobenzene (HCB), dieldrin, among others as well as total mercury (THg) in stranded harbor seal (Phoca vitulina) pups. THg is used as a proxy for MeHg, because it accounts for the majority of Hg accumulated in tissues of marine pelagic predators. The pups were collected off the coasts of Maine, New Hampshire, and Rhode Island between the years 2013 and 2017. Tissue samples were archived following necropsy by the Mystic Aquarium stranding and animal care teams and subsampled for further chemical analyses. Gas chromatography/mass spectrometry (GC/MS) was used to determine OCPs in the blubber, and THg was determined for brain, hair, kidney, muscle, and liver samples using MA-3000, a direct mercury analyzer. THg concentrations varied among tested tissues in the following order: kidneys > liver = hair > muscle > brain. Moreover, THg concentrations in kidneys and liver increased with animal body size, and remained constant in hair, muscle, and brain. Among the targeted pesticides, endrin, heptachlor, and lindane were found at significant concentrations. It is critical to continue to monitor the levels of these contaminants in the environment as they can biomagnify in humans as well as impact marine ecosystems as is clear in these infant pup chemical burdens.