Aarhus University Seal / Aarhus Universitets segl

Effects of microbial processes and CaCO3 dynamics on inorganic carbon cycling in snow-covered Arctic winter sea ice

New publication by Dorte Haubjerg Søgaard, Jody W. Deming, Lorenz Meire, Søren Rysgaard

2019.03.27 | Peter Schmidt Mikkelsen

Abstract:

Few combined measurements of primary and bacterial productivity exist for Arcticsea ice, particularly during winter, making it difficult to assess the relative importance of thesemicrobial processes for carbon cycling in sea ice. Furthermore, the occurrence of calcium carbon-ate (CaCO3), though well-documented in sea ice, is poorly described for the overlying snow. Toaddress these gaps, we investigated primary and bacterial productivity and carbon dynamics at 2contrasting locations: (1) a landfast site, with thick snow-covered first-year sea ice, and (2) apolynya site, with thin snow-covered young (<1 wk) sea ice. Comparisons of bacterial carbondemand and primary production indicated net heterotrophy in the sea ice at both locations, witha net carbon consumption rate of 0.87 to 1.86 mg C m−2d−1derived from sea ice bacterial carbondemand of 0.93 to 2.00 mg C m−2d−1and gross primary production of 0.06 to 0.14 mg C m−2d−1. Asthese microbial rates are very low, physical processes largely account for the observed CO2deple-tion in the ice. High CaCO3concentrations of 250 to 430 μmol kg−1were measured in the snowcovers which, though similar to concentrations in the underlying ice, are orders of magnitudehigher than those reported from the few studies available on CaCO3in snow. Together theseresults suggest that the role of biology in modulating inorganic carbon cycling in ice, which can beimportant in spring, is minor as compared to abiotic processes.  

 Mar Ecol Prog Ser.  Vol. 611: 31– 44, 2019https://doi.org/10.3354/meps12868  

Arctic Research Centre