Shallow methylmercury production in the marginal sea ice zone of the central Arctic Ocean

Understanding persistent high levels of mercury in arctic biota has been an elusive goal for nearly two decades. Little is known about where exactly inorganic Hg inputs into the Arctic generate the toxic methylmercury (MeHg) form that bioaccumulates in biota. Lars-Eric Heimbürger and colleagues (2015, see reference below) present the first full-depth high resolution profiles (> 5200 m-depth) of total mercury (tHg) and MeHg in the central Arctic Ocean (79-90°N). MeHg maxima occur in the pycnocline waters, although noticeably shallower than in the other oceans (150 m in the Arctic versus roughly 1000 m in the Atlantic). These shallow maxima are probably due to the accumulation of settling biogenic particles slowed down by the strong density barrier of the arctic pycnocline, which in turn will favor their microbial degradation and MeHg production. The shallow MeHg maxima likely result in enhanced biological uptake at the base of the marine food web, yielding elevated MeHg levels in Arctic wildlife. For this study the authors developed a new double isotope-dilution MeHg detection method with exceptional precision and low detection limit. These new findings will be guide future Arctic Hg research, notably the international Arctic GEOTRACES multi-ship survey planned for summer 2015 by American, Canadian and German teams.

15 Heimburger l

Figure: Total mercury (tHg) and methylmercury (MeHg) profiles in picomoles per litre (pM) at the coastal influenced open water Laptev Sea station (PS78/280:79°N; brown triangles), the open water Amundsen Basin station at the sea ice edge (PS78/273:81°N; red dots), the > 75% sea ice covered Makarov Basin station (PS78/245:85°N; green squares), and the permanently sea ice-covered North Pole station (PS78/218:90°N, purple diamonds). The white line indicates the sea ice extent during the time of sampling. The blue line shows the general oceanic circulation of intermediate and Atlantic waters after Rudels, 2012. Click here to view the figure larger.

 

References:

Heimbürger, L.-E., Sonke, J. E., Cossa, D., Point, D., Lagane, C., Laffont, L., Galfond, B.T., Nicolaus, M., Rabe, B., van der Loeff, M. R. (2015). Shallow methylmercury production in the marginal sea ice zone of the central Arctic Ocean. Sci. Rep., 5. DOI: 10.1038/srep10318. Click here to access the paper.

Rudels, B. Arctic Ocean circulation and variability – advection and external forcing encounter constraints and local processes. Ocean. Sci. 8 261–286 (2012).

 

Latest highlights

Science Highlights

Quantifying the weathered fluxes to the ocean is far from over: the overlooked role of rock coast erosion

This study reveals that cliff derived sediment supply is only three times less than the solid discharge of rivers for Europe.

21.01.2022

Science Highlights

Contrasting distributions of dissolved manganese, nickel, cadmium and zinc in the Mediterranean Sea

Extensive trace metal clean sampling during the Dutch GEOTRACES cruise in the Mediterranean Sea allowed Middag and his colleagues to establish the basin scale distribution of these trace metals.

19.01.2022

Science Highlights

Specific features characterize the dissolved iron distribution in the North Western Indian Ocean

Venkatesh Chinni and Sunil Kumar Singh propose dissolved iron profiles along two meridional transects realized during spring and fall seasons between the Arabian Sea and the sub-tropical western Indian Ocean…

07.01.2022

Science Highlights

Anthropogenic aerosol has become a dominant source of zinc in the deep water of the Northern South China Sea

Liao and colleagues determined zinc concentrations and isotope compositions in sinking particles collected in the Northern South China Sea…

24.11.2021

Rechercher