Littoral Environnement et Sociétés (LIENSs), UMR 7266 CNRS-La Rochelle Université, 2 rue Olympe de Gouges, 17000 La Rochelle, France; Universite de Pau et des Pays de l'Adour, E2S UPPA, CNRS, IPREM, Institut des Sciences Analytiques et de Physico-chimie pour l'Environnement et les Matériaux, Pau, France.
Littoral Environnement et Sociétés (LIENSs), UMR 7266 CNRS-La Rochelle Université, 2 rue Olympe de Gouges, 17000 La Rochelle, France; Institut Universitaire de France (IUF), 1 rue Descartes, 75005 Paris, France.
Sci Total Environ. 2020 Nov 10;742:140499. doi: 10.1016/j.scitotenv.2020.140499. Epub 2020 Jun 27.
Since mercury (Hg) biogeochemistry in the Southern Ocean is minimally documented, we investigated Hg stable isotopes in the blood of seabirds breeding at different latitudes in the Antarctic, Subantarctic and Subtropical zones. Hg isotopic composition was determined in adult penguins (5 species) and skua chicks (2 species) from Adélie Land (66°39'S, Antarctic) to Crozet (46°25'S, Subantarctic) and Amsterdam Island (37°47'S, Subtropical). Mass-dependent (MDF, δHg) and mass-independent (MIF, ΔHg) Hg isotopic values separated populations geographically. Antarctic seabirds exhibited lower δHg values (-0.02 to 0.79 ‰, min-max) than Subantarctic (0.88 to 2.12 ‰) and Subtropical (1.44 to 2.37 ‰) seabirds. In contrast, ΔHg values varied slightly from Antarctic (1.31 to 1.73 ‰) to Subtropical (1.69 to 2.04 ‰) waters. The extent of methylmercury (MeHg) photodemethylation extrapolated from ΔHg values was not significantly different between locations, implying that most of the bioaccumulated MeHg was of mesopelagic origin. The larger increase of MDF between the three latitudes co-varies with MeHg concentrations. This supports an increasing effect of specific biogenic Hg pathways from Antarctic to Subtropical waters, such as Hg biological transformations and accumulations. This "biogenic effect" among different productive southern oceanic regions can also be related to different mixed layer depth dynamics and biological productivity turnover that specifically influence the vertical transport between the mesopelagic and the photic zones. This study shows the first Hg isotopic data of the Southern Ocean at large scale and reveals how regional Southern Ocean dynamics and productivity control marine MeHg biogeochemistry and the exposure of seabirds to Hg contamination.
由于南大洋的汞（Hg）生物地球化学过程记录甚少，我们研究了在南极、亚南极和亚热带地区不同纬度繁殖的海鸟血液中的 Hg 稳定同位素。我们测定了来自阿德雷地（66°39'S，南极）到克罗泽群岛（46°25'S，亚南极）和阿姆斯特丹岛（37°47'S，亚热带）的成年企鹅（5 种）和贼鸥雏鸟（2 种）的 Hg 同位素组成。受质量影响的（MDF，δHg）和与质量无关的（MIF，ΔHg）Hg 同位素值将种群在地理上区分开来。南极海鸟的 δHg 值（-0.02 至 0.79‰，最小值至最大值）低于亚南极（0.88 至 2.12‰）和亚热带（1.44 至 2.37‰）海鸟。相比之下，ΔHg 值在南极（1.31 至 1.73‰）到亚热带（1.69 至 2.04‰）水域之间变化不大。从 ΔHg 值推断出的甲基汞（MeHg）光脱甲基化的程度在不同地点之间没有显著差异，这意味着大部分生物积累的 MeHg 来自中层水。这三个纬度之间的 MDF 差异较大，与 MeHg 浓度呈正相关。这支持了从南极到亚热带水域特定的生物成因 Hg 途径的生物累积效应，例如 Hg 的生物转化和积累。这种不同的富有生产力的南大洋区域之间的“生物效应”也与特定影响中层水和透光层之间垂直传输的混合层深度动态和生物生产力更替有关。本研究显示了南大洋大范围 Hg 同位素数据的首次结果，并揭示了区域南大洋动力学和生产力如何控制海洋 MeHg 生物地球化学和海鸟对 Hg 污染的暴露。
