Enhanced bottom-ice algal biomass across a tidal strait in the Kitikmeot Sea of the Canadian Arctic

• Published in: Elementa: Science of the Anthropocene
• Main Authors: Laura A. Dalman, Brent G.T. Else, David Barber, Eddy Carmack, William J. Williams, Karley Campbell, Patrick J. Duke, Sergei Kirillov, Christopher J. Mundy
• Format: Article in Journal/Newspaper
• Language: English
• Published: BioOne 2019
• Subjects: Ice algae; Fast ice; Tidal strait; Nutrients; Under-ice current; envir; geo; Arctic; Nunavut; Dease Strait; ice algae; Kitikmeot; Sea ice
• Online Access: https://doi.org/10.1525/elementa.361; https://doaj.org/article/72e1b327a459483c96747293c1c95d18

Sea ice algae are an important contributor of primary production in the Arctic ecosystem. Within the bottom-ice environment, access to nutrients from the underlying ocean is a major factor controlling production, phenology, and taxonomic composition of ice algae. Previous studies have demonstrated that tides and currents play an important role in driving the flux of nutrients to bottom-ice algal communities when biological demand during the spring bloom is high. In this study we investigate how surface currents under landfast first-year ice influence nutrient supply based on stoichiometric composition, algal chlorophyll a biomass and species composition during spring 2016, in Dease Strait, Nunavut. Stronger water dynamics over a shoaled and constricted strait dominated by tidal currents (tidal strait) supported turbulent flow more than 85% of the deployment duration in comparison to outside the tidal strait in an embayment where turbulent flow was only evidenced a small percentage (<15%) of the time. The system appeared to be nitrate-depleted with surface water concentrations averaging 1.3 μmol L–1. Increased currents were correlated significantly with a decrease in ice thickness and an increase in ice algal chlorophyll a. Furthermore, pennate diatoms dominated the ice algal community abundance with greater contribution within the strait where currents were greatest. These observations all support the existence of a greater nutrient flux to the ice bottom where currents increased towards the center of the tidal strait, resulting in an increase of bottom ice chlorophyll 'a' biomass by 5–7 times relative to that outside of the strait. Therefore, expanding beyond the long identified biological hotspots of open water polynyas, this paper presents the argument for newly identified hotspots in regions of strong sub-ice currents but persistent ice covers, so called “invisible polynyas”.