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

Attard, Karl M., Søgaard, Dorte H., Piontek, Judith, Lange, Benjamin A., Katlein, Christian, Sørensen, Heidi L., McGinnis, Daniel F., Rovelli, Lorenzo, Rysgaard, Søren, Wenzhöfer, Frank and Glud, Ronnie N. (2018) Oxygen fluxes beneath Arctic land-fast ice and pack ice: towards estimates of ice productivity. Open Access Polar Biology, 41 (10). pp. 2119-2134. DOI 10.1007/s00300-018-2350-1.

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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.

Document Type: Article
Keywords: Sea-ice; Primary production; Bacterial production; Carbon cycling; Eddy-covariance
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BI Biological Oceanography
AWI
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1007/s00300-018-2350-1
ISSN: 0722-4060
Projects: PACES
Expeditions/Models/Experiments:
Date Deposited: 27 Jun 2018 10:31
Last Modified: 01 Feb 2019 15:02
URI: http://oceanrep.geomar.de/id/eprint/43510

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