Carbon and nitrogen uptake rates and macromolecular compositions of bottom-ice algae and phytoplankton at Cambridge Bay in Dease Strait, Canada

Kwanwoo Kim,C J Mundy,Sang Heon Lee,Kathleen M Gough,Bo Kyung Kim,Sun-Yong Ha,Nicole M Pogorzelec

doi:10.1017/aog.2020.17

Abstract

AbstractOur understanding of ice algal responses to the recent changes in Arctic sea ice is impeded by limited field observations. In the present study, environmental characteristics of the landfast sea-ice zone as well as primary production and macromolecular composition of ice algae and phytoplankton were studied in the Kitikmeot Sea near Cambridge Bay in spring 2017. Averaged total chlorophyll-a(Chl-a) concentration was within the lower range reported previously for the same region, while daily carbon uptake rates of bottom-ice algae were significantly lower in this study than previously reported for the Arctic. Based on various indicators, the region's low nutrient concentrations appear to limit carbon uptake rates and associated accumulation of bottom-ice algal biomass. Furthermore, the lipids-dominant biochemical composition of bottom-ice algae suggests strong nutrient limitation relative to the distinctly different carbohydrates-dominant composition of phytoplankton. Together, the results confirm strong nitrate limitation of the local marine system.

Highlights

Ice algae within or attached to the sea-ice bottom provide an important food source in arctic marine food webs from sympagic and pelagic zooplankton to marine mammals as well as seabirds (Søreide and others, 2010; Daase and others, 2013; Van Leeuwe and others, 2018; others therein)
The ammonium relative nitrogen preference index (RPI) (RPINH4) of bottom-ice algae (1.7 ± 0.5) and phytoplankton (2.6 ± 0.7) in this study indicate that ammonium was potentially preferred compared to nitrate throughout the study period (McCarthy and others, 1977)
Lower assimilation rates and a greater lipid-dominant biochemical composition suggest bottom-ice algae were under greater nutrient limitation in a likely post-bloom state relative to the more carbohydrate-dominant phytoplankton that had yet to undergo their spring bloom

Summary

Introduction

Ice algae within or attached to the sea-ice bottom provide an important food source in arctic marine food webs from sympagic and pelagic zooplankton to marine mammals as well as seabirds (Søreide and others, 2010; Daase and others, 2013; Van Leeuwe and others, 2018; others therein). A potential fall bloom after the phytoplankton blooms in late summer can extend the short arctic summer production period and provide lateseason food complements before the long dark winter (Lee and others, 2011). These spring and fall blooms of ice algae prolong the production season of overwintering grazers in the Arctic Ocean (Michel and others, 1996; Lee and others, 2008, 2011; Fernández-Méndez and others, 2014). The diatom-dominant ice algal community contains large amounts of high-quality polyunsaturated fatty acids which can be critical for successful egg production, hatching and larval development of sympagic herbivores (Leu and others, 2010)

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