Observations of late-winter marine productivity in an ice-covered fjord, West Greenland

• Main Authors: Chandler, David, Mackie, Shona
• Format: Text
• Language: English
• Published: 2019
• Subjects: Arctic; Greenland; polar night; Sea ice
• Online Access: https://doi.org/10.5194/essd-2019-181; https://www.earth-syst-sci-data-discuss.net/essd-2019-181/

Direct observations of marine microbial metabolism are sparse in the Arctic, particularly under sea ice during winter. This paper presents the first observations of Arctic winter microbial activity under sea ice in a west Greenland fjord (Lillefjord, ∼70° N). Here, measured changes in dissolved oxygen (DO) content in light and dark in-situ incubations were used to calculate net community productivity, respiration and photosynthesis rates. Data were collected at two fully ice-covered sites during February 2013, shortly after the end of the polar night. Averaged over the full study period, dark incubations showed statistically significant decreases in DO of −0.36 ± 0.24 (near shore) and -0.09 ± 0.07 gO 2 m −3 d −1 (fjord centre), which are 2–20 times greater than rates previously reported under sea ice in the Arctic. The data provide no significant evidence for photosynthesis or any temporal change in metabolism rates over the study period; however, ambient sea water DO increased significantly at the fjord centre (0.023 ± 0.013 gO 2 m −3 d −1 ), possibly attributable to sea ice algal photosynthesis. These incubation data may improve our understanding of microbial activity in the fjord during winter, and their contribution to Arctic ecosystems under present and future conditions. The data are available online at https://doi.pangaea.de/10.1594/PANGAEA.906332 .