Oxygen fluxes beneath Arctic land-fast ice and pack ice: towards estimates of ice productivity


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Christian.Katlein [ at ] awi.de

Abstract

Sea-ice ecosystems are among the most extensive of Earth’s habitats; yet its autotrophic and heterotrophic activities remain poorly constrained. We employed the in situ aquatic eddy-covariance (AEC) O2 flux method and laboratory incubation techniques (H14CO3−, [3H] thymidine and [3H] leucine) to assess productivity in Arctic sea-ice using different methods, in conditions ranging from land-fast ice during winter, to pack ice within the central Arctic Ocean during summer. Laboratory tracer measurements resolved rates of bacterial C demand of 0.003–0.166 mmol C m−2 day−1 and primary productivity rates of 0.008–0.125 mmol C m−2 day−1 for the different ice floes. Pack ice in the central Arctic Ocean was overall net autotrophic (0.002–0.063 mmol C m−2 day−1), whereas winter land-fast ice was net heterotrophic (− 0.155 mmol C m−2 day−1). AEC measurements resolved an uptake of O2 by the bottom-ice environment, from ~ − 2 mmol O2 m−2 day−1 under winter land-fast ice to~ − 6 mmol O2 m−2 day−1 under summer pack ice. Flux of O2-deplete meltwater and changes in water flow velocity masked potential biological-mediated activity. AEC estimates of primary productivity were only possible at one study location. Here, productivity rates of 1.3 ± 0.9 mmol O2 m−2 day−1, much larger than concurrent laboratory tracer estimates (0.03 mmol C m−2 day−1), indicate that ice algal production and its importance within the marine Arctic could be underestimated using traditional approaches. Given careful flux interpretation and with further development, the AEC technique represents a promising new tool for assessing oxygen dynamics and sea-ice productivity in ice-covered regions.



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ISI/Scopus peer-reviewed
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Published
Eprint ID
47399
DOI 10.1007/s00300-018-2350-1

Cite as
Attard, K. M. , Søgaard, D. H. , Piontek, J. , Lange, B. A. , Katlein, C. , Sørensen, H. L. , McGinnis, D. F. , Rovelli, L. , Rysgaard, S. , Wenzhöfer, F. and Glud, R. N. (2018): Oxygen fluxes beneath Arctic land-fast ice and pack ice: towards estimates of ice productivity , Polar Biology . doi: 10.1007/s00300-018-2350-1


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