Mercury Accumulation in Harbour Seals from the Northeastern Pacific Ocean: The Role of Transplacental Transfer, Lactation, Age and Location

Abstract

Mercury (Hg) bioaccumulates in the aquatic food chain in the form of methylmercury, a compound well known for its neurotoxicity. We analyzed total mercury (THg) in hair collected from 209 harbour seals captured at 10 sites in British Columbia (Canada) and Washington State (USA) between 2003 and 2010. In addition, laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) allowed for a highly refined analysis of THg accumulation over time by examining nine whiskers taken from 4- to 6-week-old pups. We estimate that THg concentrations in pups increased sharply at a point corresponding to mid- to late gestation of their time in utero (4.7 ± 0.8 and 6.6 ± 1.3 µg/g dry weight (dw), respectively), and then again at the onset of nursing (8.1 ± 1.3 µg/g dw). These abrupt changes highlight the importance of both pre- and post-natal THg transfer from the mother to the growing fetus and the newborn pup. While THg levels varied among sites, hair analyses from seals collected at the same site demonstrated the influence of age in THg accumulation with pups (5.3 ± 0.3 µg/g) and juveniles (4.5 ± 0.5 µg/g) having lower levels than those in adults (8.3 ± 0.8 µg/g). Our results revealed that 33 % of the pups sampled (n = 167) had THg levels that surpassed a mammalian hair threshold for neurochemical alterations. This study suggests that Hg could represent a health concern to marine wildlife, especially as atmospheric emissions of this toxic element from human activities in the Pacific Rim and worldwide continue.

Stable isotope composition and parasitic infections of harbor seal young‐of‐the‐year used as prey‐based diet indicators

“…, Noël et al . ). Further, the Δδ 15 N between young‐of‐the‐year and adults gradually decreases from May to August that might be explained by the postweaning fast and the transition period between lactation and prey‐based diet (Hobson et al .…”

Climate change–contaminant interactions in marine food webs: Toward a conceptual framework

“…New research on mercury contamination of the oceanic mesopelagic environment and food webs from the Northeastern Pacific has been evidenced by the detection of high total mercury (THg) concentrations (i.e., 5.8–7.0 μg/g) in muscle of deeper‐diving and offshore foraging Northern elephant seals ( Mirounga angustirostris ) (Peterson et al., ). Similarly, mercury was recently detected in relatively high concentrations in hair of harbor seals ( P. vitulina ) from British Columbia and Washington State (USA), with a THg concentrations in the order of 5.3 ± 0.3 μg/g in pups, 4.5 ± 0.5 μg/g in juveniles, and 8.3 ± 0.8 μg/g in adults, exhibiting the highest THg levels relative to other marine mammal species from the Northeastern Pacific (Noël et al., ). In muscle tissues of marine mammals and fish, MeHg generally accounts for an average between 80 and 100% of THg (Kannan et al., ; Magalhães et al., ; Storelli, Stuffler & Marcotrigiano, ; Wagemann, Trebacz, Boila & Lockhart, ; Wagemann, Trebacz, Hunt & Boila, ).…”

The role of metallothioneins, selenium and transfer to offspring in mercury detoxification in Franciscana dolphins ( Pontoporia blainvillei )

“…However the values of Hg in Franciscan dolphin brains were lower than those mentioned above, The organic form could efficiently cross the placental barrier (Noël et al, 2016) and demethylating mechanisms develop with increasing age (Wintle et al, 2011), leaving fetal and very young dolphins more vulnerable to organic Hg toxic effects when compared to adult mammals (Correa et al, 2014).…”