Phytoplankton and dimethylsulfide dynamics at two contrasting Arctic ice edges

• Published in: Biogeosciences
• Main Authors: M. Lizotte, M. Levasseur, V. Galindo, M. Gourdal, M. Gosselin, J.-É. Tremblay, M. Blais, J. Charette, R. Hussherr
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2020
• Subjects: Ecology; QH540-549.5; Life; QH501-531; Geology; QE1-996.5; Arctic; Barrow Strait; Nares; Nares strait; Phytoplankton; Sea ice
• Online Access: https://doi.org/10.5194/bg-17-1557-2020; https://doaj.org/article/cd107d3815544cb6a2702e74c1c5b07b

Arctic sea ice is retreating and thinning and its rate of decline has steepened in the last decades. While phytoplankton blooms are known to seasonally propagate along the ice edge as it recedes from spring to summer, the substitution of thick multiyear ice (MYI) with thinner, ponded first-year ice (FYI) represents an unequal exchange when considering the roles sea ice plays in the ecology and climate of the Arctic. Consequences of this shifting sea ice on the phenology of phytoplankton and the associated cycling of the climate-relevant gas dimethylsulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) remain ill constrained. In July–August 2014, two contrasting ice edges in the Canadian High Arctic were explored: a FYI-dominated ice edge in Barrow Strait and a MYI-dominated ice edge in Nares Strait. Our results reveal two distinct planktonic systems and associated DMS dynamics in connection to these diverging ice types. The surface waters exiting the ponded FYI in Barrow Strait were characterized by moderate chlorophyll a (Chl a , <2.1 µ g L −1 ) as well as high DMSP (115 nmol L −1 ) and DMS (12 nmol L −1 ), suggesting that a bloom had already started to develop under the markedly melt-pond-covered (ca. 40 %) FYI. Heightened DMS concentrations at the FYI edge were strongly related to ice-associated seeding of DMS in surface waters and haline-driven stratification linked to ice melt (Spearman's rank correlation between DMS and salinity, <math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>r</mi><mi mathvariant="normal">s</mi></msub><mo>=</mo><mo>-</mo><mn mathvariant="normal">0.91</mn></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="52pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="83f93b87ef5255dd38ed375dd9451a5f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" ...