Changes in Sea-Ice Protist Diversity With Declining Sea Ice in the Arctic Ocean From the 1980s to 2010s

Hop, Haakon; Vihtakari, Mikko; Bluhm, Bodil A.; Assmy, Philipp; Poulin, Michel; Gradinger, Rolf; Peeken, Ilka; Quillfeldt, Cecilie von; Olsen, Lasse Mork; Житина, Л. С.; Melnikov, I. A.

doi:10.3389/fmars.2020.00243

Cited by 51 publications

(52 citation statements)

References 108 publications

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“…Furthermore, MYI can act as long-term storage for carbon and other elements, given internal biomass layers (e.g., Lange et al, 2015) and its potential for seeding spring bottomice algal communities in the following year (Olsen et al, 2017;Kauko et al, 2018), compared to FYI that undergoes a complete annual cycle of growth and melt. The different biochemical signatures of the upper and bottom layers of the ice and the partly contrasting signatures of bottom FYI and MYI found in our study (25% of identified FAs, d 15 N and d 13 C in 22:6n-3 with significant differences) support our hypothesis that FYI and MYI can host different sea-ice inhabitants and are consistent with previous studies reporting differences in community composition between the two ice types (Hardge et al, 2017;Hop et al, 2020). MYI protist communities are particularly rich in species diversity (Melnikov, 2009;Hop et al, 2020), suggesting that the loss of Arctic MYI will impact the complex interaction between primary producers, immediate consumers, and consequently top predators.…”

Section: Discussionsupporting

confidence: 93%

“…The different characteristics of MYI and FYI provide evidence that known ecosystem structures are not only threatened by the general reduction of available seaice habitat but also by changes in the occurrence of different ice types. Potential differences in their support of different algal assemblages (e.g., Hop et al, 2020) might yield important consequences for highly specialized seaice grazers, the entire dependent ecosystem, and the flow of energy within it.…”

Section: Introductionmentioning

confidence: 99%

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Fatty acids and stable isotope signatures of first-year and multiyear sea ice in the Canadian High Arctic

et al. 2020

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Ice algae are critical components to the lipid-driven Arctic marine food web, particularly early in the spring. As little is known about these communities in multiyear ice (MYI), we aimed to provide a baseline of fatty acid (FA) and stable isotope signatures of sea-ice communities in MYI from the Lincoln Sea and compare these biomarkers to first-year ice (FYI). Significant differences in the relative proportions of approximately 25% of the identified FAs and significantly higher nitrogen stable isotope values (δ15N) in bottom-ice samples of FYI (δ15N = 6.4 ± 0.7%) compared to MYI (δ15N = 5.0 ± 0.4%) reflect different community compositions in the two ice types. Yet, the relative proportion of diatom- and dinoflagellate-associated FAs, as well as their bulk and most of the FA-specific carbon stable isotope compositions (δ13C) were not significantly different between bottom FYI (bulk δ13C: –28.4% to –26.7%, FA average δ13C: –34.4% to –31.7%) and MYI (bulk δ13C: –27.6% to –27.2%, FA average δ13C: –33.6% to –31.9%), suggesting at least partly overlapping community structures and similar biochemical processes within the ice. Diatom-associated FAs contributed, on average, 28% and 25% to the total FA content of bottom FYI and MYI, respectively, indicating that diatoms play a central role in structuring sea-ice communities in the Lincoln Sea. The differences in FA signatures of FYI and MYI support the view that different ice types harbor different inhabitants and that the loss of Arctic MYI will impact complex food web interactions with ice-associated ecosystems. Comparable nutritional quality of FAs, however, as indicated by similar average levels of polyunsaturated FAs in bottom FYI (33%) and MYI (28%), could help to ensure growth and reproduction of ice-associated grazers despite the shift from a MYI to FYI-dominated sea-ice cover with ongoing climate warming.

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Section: Discussionsupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Fatty acids and stable isotope signatures of first-year and multiyear sea ice in the Canadian High Arctic

et al. 2020

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“…However, maximum centric diatom abundances in 1975 were two orders of magnitude lower and about one month later (late August) than during the North Pole expedition 2015. The general trend toward stronger dominance of cryopelagic and pelagic diatom species in the more recent years is also supported by a study covering the MYI to FYI transition in the central AO over the last 40 years (Hop et al, 2020).…”

Section: Variability In Uib Biomass and Community Compositionmentioning

confidence: 57%

“…The general patterns described above are consistent with observations of UIBs in Baffin Bay in 2015 and 2016 during the Green Edge project (Oziel et al, 2019) with dominance of pennate diatoms and dinoflagellates during the early stages of UIBs and dominance of pelagic centric diatoms during the peak of the UIB. Notable exceptions are cryopelagic species belonging to the pennate diatom genera Fragilariopsis and Pseudo-nitzschia, which thrive both in sea ice and the water column (Hop et al, 2020), but are nevertheless usually outnumbered by centric diatoms of the genera Chaetoceros and Thalassiosira during the peak UIB phase.…”

Section: Variability In Uib Biomass and Community Compositionmentioning

confidence: 99%

Under-Ice Phytoplankton Blooms: Shedding Light on the “Invisible” Part of Arctic Primary Production

et al. 2020

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The growth of phytoplankton at high latitudes was generally thought to begin in open waters of the marginal ice zone once the highly reflective sea ice retreats in spring, solar elevation increases, and surface waters become stratified by the addition of sea-ice melt water. In fact, virtually all recent large-scale estimates of primary production in the Arctic Ocean (AO) assume that phytoplankton production in the water column under sea ice is negligible. However, over the past two decades, an emerging literature showing significant under-ice phytoplankton production on a pan-Arctic scale has challenged our paradigms of Arctic phytoplankton ecology and phenology. This evidence, which builds on previous, but scarce reports, requires the Arctic scientific community to change its perception of traditional AO phenology and urgently revise it. In particular, it is essential to better comprehend, on small and large scales, the changing and variable icescapes, the under-ice light field and biogeochemical cycles during the transition from sea-ice covered to ice-free Arctic waters. Here, we provide a baseline of our current knowledge of under-ice blooms (UIBs), by defining their ecology and their environmental setting, but also their regional peculiarities (in terms of occurrence, magnitude, and assemblages), which is shaped by a complex AO. To this end, a multidisciplinary approach, i.e., combining expeditions and modern autonomous technologies, satellite, and modeling analyses, has been used to provide an overview of this pan-Arctic phenological feature, which will become increasingly important in future marine Arctic biogeochemical cycles.

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“…A: Sea ice reductions entail an increasing seasonal ice zone and ultimate replacement of multiyear ice (MYI) with single-year ice (SYI) (Stroeve and Notz, 2018), with consequences for sympagic biodiversity (Vincent, 2010;Hop et al, 2020). Are some diazotrophs reliant on MYI and/or SYI habitats, and which are thus the biogeochemical consequences when SYI is expanding on behalf of MYI?…”

Section: Cyanobacterial Diazotrophs May Be Of Higher Relative Abundanmentioning

confidence: 99%

Nitrogen Fixation in a Changing Arctic Ocean: An Overlooked Source of Nitrogen?

Friesen

Riemann

2020

Front. Microbiol.

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The Arctic Ocean is the smallest ocean on Earth, yet estimated to play a substantial role as a global carbon sink. As climate change is rapidly changing fundamental components of the Arctic, it is of local and global importance to understand and predict consequences for its carbon dynamics. Primary production in the Arctic Ocean is often nitrogen-limited, and this is predicted to increase in some regions. It is therefore of critical interest that biological nitrogen fixation, a process where some bacteria and archaea termed diazotrophs convert nitrogen gas to bioavailable ammonia, has now been detected in the Arctic Ocean. Several studies report diverse and active diazotrophs on various temporal and spatial scales across the Arctic Ocean. Their ecology and biogeochemical impact remain poorly known, and nitrogen fixation is so far absent from models of primary production in the Arctic Ocean. The composition of the diazotroph community appears distinct from other oceans – challenging paradigms of function and regulation of nitrogen fixation. There is evidence of both symbiotic cyanobacterial nitrogen fixation and heterotrophic diazotrophy, but large regions are not yet sampled, and the sparse quantitative data hamper conclusive insights. Hence, it remains to be determined to what extent nitrogen fixation represents a hitherto overlooked source of new nitrogen to consider when predicting future productivity of the Arctic Ocean. Here, we discuss current knowledge on diazotroph distribution, composition, and activity in pelagic and sea ice-associated environments of the Arctic Ocean. Based on this, we identify gaps and outline pertinent research questions in the context of a climate change-influenced Arctic Ocean – with the aim of guiding and encouraging future research on nitrogen fixation in this region.

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Changes in Sea-Ice Protist Diversity With Declining Sea Ice in the Arctic Ocean From the 1980s to 2010s

Cited by 51 publications

References 108 publications

Fatty acids and stable isotope signatures of first-year and multiyear sea ice in the Canadian High Arctic

Fatty acids and stable isotope signatures of first-year and multiyear sea ice in the Canadian High Arctic

Under-Ice Phytoplankton Blooms: Shedding Light on the “Invisible” Part of Arctic Primary Production

Nitrogen Fixation in a Changing Arctic Ocean: An Overlooked Source of Nitrogen?

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