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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2019-422
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-422
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 25 Oct 2019

Submitted as: research article | 25 Oct 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

Phytoplankton and dimethylsulfide dynamics at two contrasting Arctic ice edges

Martine Lizotte1, Maurice Levasseur1, Virginie Galindo2, Margaux Gourdal1, Michel Gosselin2, Jean-Éric Tremblay1, Marjolaine Blais3, Joannie Charette4, and Rachel Hussherr1 Martine Lizotte et al.
  • 1Département de biologie, Québec-Océan, Université Laval, Québec, Québec, G1V 0A6, Canada
  • 2Institut des sciences de la mer de Rimouski (ISMER), Université du Québec à Rimouski, Rimouski, Québec, G5L 3A1, Canada
  • 3Maurice Lamontagne Institute, Fisheries and Oceans Canada, Mont-Joli, Québec, G0J 2L0, Canada
  • 4Fisheries and Oceans Canada, Winnipeg, Manitoba, R3T 2N6, Canada

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.

Martine Lizotte et al.
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Martine Lizotte et al.
Data sets

CTD data collected by the CCGS Amundsen in the Canadian Arctic Amundsen Science Data Collection https://doi.org/10.5884/12713

Martine Lizotte et al.
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Short summary
This study brings further support to the premise that the prevalence of younger and thinner icescapes over older and thicker ones in the Canadian High Arctic favors the early development of under-ice microorganisms as well as their production of the climate-relevant gas dimethylsulfide (DMS). Given the rapid rate of climate-driven changes in Arctic sea ice, our results suggest implications for the timing and magnitude of DMS pulses in the Arctic, with ramifications for climate forecasting.
This study brings further support to the premise that the prevalence of younger and thinner...
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