Elevated methylmercury in Antarctic surface seawater: The role of phytoplankton mass and sea ice

Fange Yue; Yanbin Li; Yanxu Zhang; Longquan Wang; Dan Li; Peipei Wu; Hongwei Liu; Lijin Lin; Dong Li; Ji Hu; Zhouqing Xie

doi:10.1016/j.scitotenv.2023.163646

Elevated methylmercury in Antarctic surface seawater: The role of phytoplankton mass and sea ice

Sci Total Environ. 2023 Jul 15:882:163646. doi: 10.1016/j.scitotenv.2023.163646. Epub 2023 Apr 22.

Authors

Fange Yue¹, Yanbin Li², Yanxu Zhang³, Longquan Wang¹, Dan Li⁴, Peipei Wu³, Hongwei Liu¹, Lijin Lin⁵, Dong Li⁶, Ji Hu⁶, Zhouqing Xie⁷

Affiliations

¹ Institute of Polar Environment & Anhui Key Laboratory of Polar Environment and Global Change, Department of Environmental Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, China.
² Frontiers Science Center for Deep Ocean Multispheres and Earth System, and Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China; College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100, China.
³ School of Atmospheric Sciences, Nanjing University, Nanjing, Jiangsu 210023, China.
⁴ College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China.
⁵ College of Oceanic and Atmospheric Sciences, Ocean University of China, Qingdao 266100, China.
⁶ Second Institute of Oceanography, Ministry of Natural Resources (MNR), Hangzhou 310000, China.
⁷ Institute of Polar Environment & Anhui Key Laboratory of Polar Environment and Global Change, Department of Environmental Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, China. Electronic address: zqxie@ustc.edu.cn.

PMID: 37094685
DOI: 10.1016/j.scitotenv.2023.163646

Abstract

Methylmercury is a neurotoxin that is biomagnified in marine food webs. Its distribution and biogeochemical cycle in Antarctic seas are still poorly understood due to scarce studies. Here, we report the total methylmercury profiles (up to 4000 m) in unfiltered seawater (MeHg_T) from the Ross Sea to the Amundsen Sea. We found high MeHg_T levels in oxic unfiltered surface seawater (upper 50 m depth) in these regions. It was characterized by an obviously higher maximum concentration level of MeHg_T (up to 0.44 pmol/L, at a depth of 3.35 m), which is higher than other open seas (including the Arctic Ocean, the North Pacific Ocean and the equatorial Pacific), and a high MeHg_T average concentration in the summer surface water (SSW, 0.16 ± 0.12 pmol/ L). Further analyses suggest that the high phytoplankton mass and sea-ice fraction are important drivers of the high MeHg_T level that we observed in the surface water. For the influence of phytoplankton, the model simulation showed that the uptake of MeHg by phytoplankton would not fully explain the high levels of MeHg_T, and we speculated that high phytoplankton mass may emit more particulate organic matter as microenvironments that can sustain Hg in-situ methylation by microorganisms. The presence of sea-ice may not only harbor a microbial source of MeHg to surface water but also trigger increased phytoplankton mass, facilitating elevation of MeHg in surface seawater. This study provides insight into the mechanisms that impact the content and distribution of MeHg_T in the Southern Ocean.

Keywords: Methylation; Methylmercury; Phytoplankton; Sea ice; Southern Ocean; Water mass.

MeSH terms

Antarctic Regions
Ice Cover
Methylmercury Compounds* / analysis
Oceans and Seas
Phytoplankton
Seawater / chemistry
Water

Substances

Methylmercury Compounds
Water