Mercury contamination in polar fish: Bioaccumulation and trophic transfer in Notothenia coriiceps from Admiralty Bay, maritime Antarctic

Mercury (Hg) contamination in marine ecosystems poses a significant environmental and health concern, particularly in Antarctica where data remain scarce. This study investigates total mercury (THg) and methylmercury (MeHg) concentrations in muscle tissues of Notothenia coriiceps from Admiralty Bay (King George Island, Antarctica) to investigate bioaccumulation patterns and ecological drivers. Stable isotope analyses of carbon (δ¹³C) and nitrogen (δ¹⁵N) were used to determine trophic positioning and dietary sources and selenium (Se) concentrations and Se:Hg molar ratios were measured to assess potential detoxification. THg in N. coriiceps ranged from 100.2 to 670.3 ng/g d.w., with MeHg comprising approximately 79% of THg. A strong positive correlation between both THg and MeHg and δ¹⁵N confirmed trophic biomagnification (TMS = 0.22 for THg, 0.18 for MeHg), with a 1.6-1.8-fold increase in mercury concentration per trophic level. Notably, considerable inter-individual variability in Hg burdens was observed, particularly among the smallest individuals, which exhibited relatively high THg concentration despite their diminutive size. This counterintuitive pattern likely reflects diet, foraging habitat, and trophic ecology appears to overshadow body size alone in determining Hg accumulation. All studied fish had Se:Hg ratios >1, suggesting mitigated toxicity. This study provides critical data on mercury bioaccumulation and biomagnification in Antarctic fish, emphasizing the necessity for continued monitoring of Hg contamination in polar marine ecosystems.