Patterns and drivers of carbohydrate budgets in ice algal assemblages from first year Arctic sea ice

Shazia N Aslam,Andrea Niemi,Graham J C Underwood,Christine Michel

doi:10.1002/lno.10260

Shazia N Aslam, Andrea Niemi + Show 2 more

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https://doi.org/10.1002/lno.10260

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Abstract

AbstractOngoing changes in sea ice distribution will have major implications for the ecology of the Arctic Ocean. First year ice (FYI) supports abundant ice‐algae communities that produce dissolved and particulate carbohydrates, including extracellular polymeric substances (EPS), which are significant carbon sources, influence ice formation and microbial survival within sea ice, and water column carbon cycling following ice melt. Key drivers of the distribution and composition of these carbohydrates are poorly characterised. Carbohydrates and chlorophyll a concentrations were linearly related in springtime bottom FYI at 36 sites in the Canadian Archipelago region, with high levels of spatial heterogeneity. Nanoeukaryote cell density and phosphate concentration were strong drivers of total and dissolved carbohydrate and uronic acid concentrations. Particulate carbohydrates were strongly related to total bacterial abundance. Dissolved carbohydrates contributed 77% of total carbohydrate: the most abundant (51%) size fraction being dissolved carbohydrates < 8 kDa in size, with dissolved EPS contributing 7% to total carbohydrate. Carbohydrate fractions differed in monosaccharide profiles; dissolved components being glucose rich; particulate EPS containing more mannose, xylose, fucose and arabinose. These profiles corresponded to those of cultured sea‐ice diatoms. Microbial abundance, silicate, nitrate and phosphate concentration and ice thickness were important environmental drivers, with thicker ice containing relatively more particulate EPS, with thinner ice containing high amounts of glucose‐rich smaller‐sized carbohydrate moieties. Changes in ice characteristics will alter the relative balance of labile and refractory carbohydrates generated within bottom ice layers, with implications for food webs and carbon turnover in the warming Arctic Ocean.

Highlights

IntroductionThe physical presence of ice and the productivity of ice-associated algae, support significant components of the marine polar food web (Carmack and Wassman 2006; Hop et al 2006) such that the shift from thick multiyear to thinner first year ice (Stroeve et al 2014; Swart et al 2015)
Ongoing changes in sea ice distribution will have major implications for the ecology of the Arctic Ocean
The important role played by carbohydrate-rich constituents in sea ice ecology and biogeochemistry has been increasingly recognised in the last few years (Krembs et al 2011; Underwood et al 2013; Vancoppenolle et al 2013)

Summary

Introduction

The physical presence of ice and the productivity of ice-associated algae, support significant components of the marine polar food web (Carmack and Wassman 2006; Hop et al 2006) such that the shift from thick multiyear to thinner first year ice (Stroeve et al 2014; Swart et al 2015) Abundant autotrophic and heterotrophic microbiological communities, associated with high concentrations of dissolved (DOM) and particulate organic matter (POM), grow in sea ice, especially near the ice-water interface of first year ice (FYI) where freezing seawater forms a semi-solid matrix permeated by millimetre to submillimetre pores and channels (Thomas et al 2010; Ewert and Deming 2013; Vancoppenolle et al 2013). Recent work has shown a role for EPS in the formation of atmospherically active polar aerosols (Leck et al 2013; Wilson et al 2015) during the open water summer period

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