Earlier sea-ice melt extends the oligotrophic summer period in the Barents Sea with low algal biomass and associated low vertical flux

Kohlbach, Doreen; Goraguer, Lucie; Bodur, Yasemin; Müller, Oliver; Amargant-Arumí, Martí; Blix, Katalin; Bratbak, Gunnar; Chierici, Melissa; Dąbrowska, A.; Dietrich, Ulrike; Edvardsen, Bente; García, Laura M.; Gradinger, Rolf; Hop, Haakon; Jones, Elizabeth M.; Lundesgaard, Øyvind; Olsen, Lasse Mork; Reigstad, Marit; Saubrekka, Karoline; Tatarek, Agnieszka; Wiktor, Józef; Wold, Anette; Assmy, Philipp

doi:10.1016/j.pocean.2023.103018

Cited by 16 publications

(9 citation statements)

References 130 publications

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“…In 2019, parts of the Barents Sea shelf were still ice-covered and water temperature at the study stations was overall lower. In the ice-free summer of 2018, the microbial community in the study area was in a late post-bloom stage, while in 2019, remnants of a marginal ice-zone bloom were still observed (Kohlbach et al, 2023;Amargant-Arumı́et al, 2024). Even though the microbial community in 2018 was in a later seasonal succession stage than in 2019, both communities sustained comparable primary production averaged across the transect (Amargant-Arumı́et al, 2024).…”

Section: Effect Of Interannual Variation Of Seaice Cover On Copepod S...mentioning

confidence: 95%

“…There were no significant interannual differences in secondary production of small copepods, but variations were observed between locations, with highest production occurring in warm waters in the southernmost part of the transect. In 2018, water temperatures in the study area were overall higher, less sea-ice was present and chlorophyll a concentrations were low (Kohlbach et al, 2023). In August 2018, the protist community was in a late-summer oligotrophic state, dominated by small-sized autotrophic and heterotrophic protists, predominantly flagellates and ciliates (Kohlbach et al, 2023).…”

Section: Factormentioning

confidence: 98%

“…In 2018, water temperatures in the study area were overall higher, less sea-ice was present and chlorophyll a concentrations were low (Kohlbach et al, 2023). In August 2018, the protist community was in a late-summer oligotrophic state, dominated by small-sized autotrophic and heterotrophic protists, predominantly flagellates and ciliates (Kohlbach et al, 2023). Highest primary production in 2018 was observed at the southernmost station of the transect (P1), where the growth of small pico-and nano-flagellated cells was sustained by nutrient input through Atlantic Water inflow (Amargant-Arumıé t al., 2024).…”

Section: Factormentioning

confidence: 98%

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Response of the copepod community to interannual differences in sea-ice cover and water masses in the northern Barents Sea

Gawinski,

Daase,

Primicerio

et al. 2024

Front. Mar. Sci.

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The reduction of Arctic summer sea ice due to climate change can lead to increased primary production in parts of the Barents Sea if sufficient nutrients are available. Changes in the timing and magnitude of primary production may have cascading consequences for the zooplankton community and ultimately for higher trophic levels. In Arctic food webs, both small and large copepods are commonly present, but may have different life history strategies and hence different responses to environmental change. We investigated how contrasting summer sea-ice cover and water masses in the northern Barents Sea influenced the copepod community composition and secondary production of small and large copepods along a transect from 76°N to 83°N in August 2018 and August 2019. Bulk abundance, biomass, and secondary production of the total copepod community did not differ significantly between the two years. There were however significant spatial differences in the copepod community composition and production, with declining copepod abundance from Atlantic to Arctic waters and the highest copepod biomass and production on the Barents Sea shelf. The boreal Calanus finmarchicus showed higher abundance, biomass, and secondary production in the year with less sea-ice cover and at locations with a clear Atlantic water signal. Significant differences in the copepod community between areas in the two years could be attributed to interannual differences in sea-ice cover and Atlantic water inflow. Small copepods contributed more to secondary production in areas with no or little sea ice and their production was positively correlated to water temperature and ciliate abundance. Large copepods contributed more to secondary production in areas with extensive sea ice and their production was positively correlated with chlorophyll a concentration. Our results show how pelagic communities might function in a future ice-free Barents Sea, in which the main component of the communities are smaller copepods, and the secondary production they generate is available in energetically less resource-rich portions.

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Section: Effect Of Interannual Variation Of Seaice Cover On Copepod S...mentioning

confidence: 95%

Section: Factormentioning

confidence: 98%

Section: Factormentioning

confidence: 98%

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Response of the copepod community to interannual differences in sea-ice cover and water masses in the northern Barents Sea

Gawinski,

Daase,

Primicerio

et al. 2024

Front. Mar. Sci.

Self Cite

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“…This difference could indicate that the position of the ice cover in the Barents Sea during the autumn is relevant for the hydrographic conditions over the saddle at this time of the year. According to Kohlbach et al (2023), the marginal ice zone had retreated beyond the shelf break into the Nansen Basin in August 2018, while in August 2019 large parts of the northwestern Barents Sea shelf were still covered by sea ice, resulting in lower temperatures and a fresher surface layer (Kohlbach et al, 2023). These differences in the large-scale conditions at the end of the melting seasons of 2018 and 2019 must also have affected the following winter conditions of 2018-2019 and 2019-2020 observed at our mooring site.…”

Section: Eastward Transport Of Positive Temperature Anomaliesmentioning

confidence: 99%

An emerging pathway of Atlantic Water to the Barents Sea through the Svalbard Archipelago: drivers and variability

Kalhagen,

Skogseth,

Baumann

et al. 2024

Preprint

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Abstract. The Barents Sea, an important component of the Arctic Ocean, is experiencing shifts in ocean currents, stratification, sea-ice variability, and marine ecosystems. Inflowing Atlantic Water (AW) is known to be a key driver of change. Although AW predominantly enters the Barents Sea via the Barents Sea Opening, other pathways exist but remain relatively unexplored. Summer climatology fields of temperature in the last century compared to 2000–2019 indicate warming in the trench Storfjordrenna and the shallow banks Hopenbanken and Storfjordbanken in the Svalbard Archipelago, and shoaling of AW, extending further into the "channel" between Edgeøya and Hopen islands. This region emerges as a pathway of AW into the northwestern Barents Sea. One year-long records from a mooring deployed between September 2018 and November 2019 at a saddle in this channel, show the flow of Atlantic-origin waters into the Arctic domain of the northwestern Barents Sea. The average current is directed eastward, into the Barents Sea, but is dominated by large variability throughout the year. Here, we investigate this variability on time scales from hours to months. Wind forcing mediates the currents and the water and heat exchange through the channel through geostrophic adjustment to Ekman transport. The main drivers for the AW inflow and the cross-saddle transport of positive temperature anomalies are persistent strong semidiurnal tidal currents, intermittent wind-forced events, and wintertime warm water intrusions forced by upstream conditions. We propose that similar topographic constraints where the Polar Front acts like a barrier may become more important for AW inflow and heat exchange in the future. The ongoing warming and possible shoaling of AW together with changes in the large-scale weather patterns would likely increase inflow and heat transport through the processes identified in this study.

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“…Decadal records of sinking particles in the Arctic Ocean revealed long‐lasting effects of a warm‐water anomaly; stimulating small phytoplankton while larger diatoms decreased in abundance, coincident with shifting bacterial composition (Cardozo‐Mino et al, 2023). These dynamics have major consequences for carbon export and benthopelagic coupling (Jacquemot et al, 2022; Kohlbach et al, 2023; Salter et al, 2023). Future ocean scenarios predict substantial ecosystem shifts in the Arctic, supported by a changing microbiome structure at higher temperatures (Ahme et al, 2023).…”

Section: Introductionmentioning

confidence: 99%

The Arctic summer microbiome across Fram Strait: Depth, longitude, and substrate concentrations structure microbial diversity in the euphotic zone

Wietz,

Engel,

Ramondenc

et al. 2024

Environmental Microbiology

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The long‐term dynamics of microbial communities across geographic, hydrographic, and biogeochemical gradients in the Arctic Ocean are largely unknown. To address this, we annually sampled polar, mixed, and Atlantic water masses of the Fram Strait (2015–2019; 5–100 m depth) to assess microbiome composition, substrate concentrations, and oceanographic parameters. Longitude and water depth were the major determinants (~30%) of microbial community variability. Bacterial alpha diversity was highest in lower‐photic polar waters. Community composition shifted from west to east, with the prevalence of, for example, Dadabacteriales and Thiotrichales in Arctic‐ and Atlantic‐influenced waters, respectively. Concentrations of dissolved organic carbon peaked in the western, compared to carbohydrates in the chlorophyll‐maximum of eastern Fram Strait. Interannual differences due to the time of sampling, which varied between early (June 2016/2018) and late (September 2019) phytoplankton bloom stages, illustrated that phytoplankton composition and resulting availability of labile substrates influence bacterial dynamics. We identified 10 species clusters with stable environmental correlations, representing signature populations of distinct ecosystem states. In context with published metagenomic evidence, our microbial‐biogeochemical inventory of a key Arctic region establishes a benchmark to assess ecosystem dynamics and the imprint of climate change.

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Earlier sea-ice melt extends the oligotrophic summer period in the Barents Sea with low algal biomass and associated low vertical flux

Cited by 16 publications

References 130 publications

Response of the copepod community to interannual differences in sea-ice cover and water masses in the northern Barents Sea

Response of the copepod community to interannual differences in sea-ice cover and water masses in the northern Barents Sea

An emerging pathway of Atlantic Water to the Barents Sea through the Svalbard Archipelago: drivers and variability

The Arctic summer microbiome across Fram Strait: Depth, longitude, and substrate concentrations structure microbial diversity in the euphotic zone

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