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- Title
Phytoplankton and dimethylsulfide dynamics at two contrasting Arctic ice edges.
- Authors
Lizotte, Martine; Levasseur, Maurice; Galindo, Virginie; Gourdal, Margaux; Gosselin, Michel; Tremblay, Jean-éric; Blais, Marjolaine; Charette, Joannie; Hussherr, Rachel
- Abstract
Arctic sea ice is retreating, 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 multi-year 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 µg 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 with ice-associated seeding of DMS in surface waters and haline-driven stratification linked to ice melt (Spearman's rank correlation between DMS and salinity, rs = 0.91, p < 0.001, n = 20). However, surface waters exiting the MYI edge at the head of Nares Strait were characterized by low concentrations of Chl a (< 0.5 µg L-1), DMSP (< 16 nmol L-1) and DMS (< 0.4 nmol L-1), despite the nutrient-replete conditions characterizing the surface waters. The increase in autotrophic biomass and methylated sulfur compounds took place several km (ca. 100 km) away from the MYI ice edge suggesting the requisite for ice-free, light-sufficient conditions for a phytoplankton bloom to fully develop and for sulfur compound dynamics to follow and expand. In light of the ongoing and projected climate-driven changes to Arctic sea ice, results from this study suggest that the early onset of autotrophic blooms under thinner, melt pond-covered ice may have vast implications for the timing and magnitude of DMS pulses in the Arctic.
- Subjects
ALGAL blooms; ICE; ARCTIC climate; WATER; PHYTOPLANKTON; EDGES (Geometry); SEA ice
- Publication
Biogeosciences Discussions, 2019, p1
- ISSN
1810-6277
- Publication type
Article
- DOI
10.5194/bg-2019-422