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

• Published in: Polar Biology
• Main Authors: 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, Glud, Ronnie N.
• Other Authors: Ecosystems and Environment Research Programme, Tvärminne Zoological Station, Marine Ecosystems Research Group, Tvärminne Benthic Ecology Team
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer 2018
• Subjects: 1172 Environmental sciences; 1171 Geosciences; Sea-ice; Primary production; Bacterial production; Carbon cycling; Eddy-covariance; AQUATIC EDDY-CORRELATION; MELTING SEA-ICE; HETEROTROPHIC ACTIVITY; PERMEABLE SEDIMENTS; O-2 MICROSENSORS; DISSOLVED-OXYGEN; PAM FLUOROMETER; FRAM STRAIT; UPPER OCEAN; HEAT-FLUX; Arctic; Arctic Ocean; Fram Strait; Polar Biology; Sea ice
• Online Access: http://hdl.handle.net/10138/251199

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) O-2 flux method and laboratory incubation techniques ((HCO3-)-C-14, [H-3] thymidine and [H-3] 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 0.003-0.166mmolCm(-2)day(-1) and primary productivity rates of 0.008-0.125mmolCm(-2)day(-1) for the different ice floes. Pack ice in the central Arctic Ocean was overall net autotrophic (0.002-0.063mmolCm(-2)day(-1)), whereas winter land-fast ice was net heterotrophic (-0.155mmol C m(-2) day(-1)). AEC measurements resolved an uptake of O-2 by the bottom-ice environment, from similar to-2mmolO(2)m(-2) day(-1) under winter land-fast ice to similar to-6mmolO(2)m(-2)day(-1) under summer pack ice. Flux of O-2-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 +/- 0.9mmolO(2)m(-2)day(-1), much larger than concurrent laboratory tracer estimates (0.03mmolCm(-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. Peer reviewed