Arctic (Svalbard islands) active and exported diatom stocks and cell health status

Abstract. Diatoms tend to dominate the Arctic spring phytoplankton bloom, a key event in the ecosystem including a rapid decline in surface-water pCO2. While a mass sedimentation event of diatoms at the bloom terminus is commonly observed, there are few reports on the status of diatoms' health during Arctic blooms and its possible role on sedimentary fluxes. Thus, we examine the idea that the major diatom-sinking event which occurs at the end of the regional bloom is driven by physiologically deteriorated cells. Here we quantify, using the Bottle-Net, Arctic diatom stocks below and above the photic zone and assess their cell health status. The communities were sampled around the Svalbard islands and encompassed pre- to post-bloom conditions. A mean of 24.2±6.7 % SE (standard error) of the total water column (max. 415 m) diatom standing stock was found below the photic zone, indicating significant diatom sedimentation. The fraction of living diatom cells in the photic zone averaged 59.4±6.3 % but showed the highest mean percentages (72.0 %) in stations supporting active blooms. In contrast, populations below the photic layer were dominated by dead cells (20.8±4.9 % living cells). The percentage of diatoms' standing stock found below the photic layer was negatively related to the percentage of living diatoms in the surface, indicating that healthy populations remained in the surface layer. Shipboard manipulation experiments demonstrated that (1) dead diatom cells sank faster than living cells, and (2) diatom cell mortality increased in darkness, showing an average half-life among diatom groups of 1.025±0.075 d. The results conform to a conceptual model where diatoms grow during the bloom until resources are depleted and supports a link between diatom cell health status (affected by multiple factors) and sedimentation fluxes in the Arctic. Healthy Arctic phytoplankton communities remained at the photic layer, whereas the physiologically compromised (e.g., dying) communities exported a large fraction of the biomass to the aphotic zone, fueling carbon sequestration to the mesopelagic and material to benthic ecosystems.

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Arctic (Svalbard Islands) Active and Exported Diatom Stocks and Cell Health Status

10.5194/bg-2018-459 ◽

2018 ◽

Cited By ~ 1

Author(s):

Susana Agustí ◽

Jeffrey W. Krause ◽

Israel A. Marquez ◽

Paul Wassmann ◽

Svein Kristiansen ◽

...

Keyword(s):

Health Status ◽

Large Fraction ◽

The Arctic ◽

Total Water ◽

Photic Layer ◽

Cell Mortality ◽

Phytoplankton Communities ◽

The Status ◽

Benthic Ecosystems ◽

Living Diatoms

Abstract. Diatoms tend to dominate the Arctic spring bloom, a key event in the ecosystem. Large sinking of diatoms is expected at the end of the bloom driven by deteriorated cell status associated to nutrients (silicon) depletion. However, there are few reports on the status of diatoms' health during Arctic blooms and its possible role on sedimentary fluxes. Here we quantify, using the Bottle-Net, Arctic diatom stocks below and above the photic layer and assess their cell health status. The communities were sampled around the Svalbard Islands and encompassed a broad diversity of conditions and bloom stages. About 1/4 (mean±SE 24.2 ± 6.7 %) of the total water column (max. 415 m) diatom stock was found below the photic layer, indicating significant sinking of diatoms in the area. The fraction of living diatom cells in the photic layer averaged 59.4 ± 6.3 % but showed the highest percentages (72.0 %) in stations supporting active blooms. In contrast, populations below the photic layer were dominated by dead cells (20.8 ± 4.9 % living cells). The percentage of diatom’s stock found below the photic layer was negatively related to the percentage of living diatoms in the surface, indicating that healthy populations remained in the surface layer. An experiment on board in a tall (1.35 m) sedimentation column confirmed that dead diatom cells from the Arctic community sink faster that living ones. Also, diatoms cell mortality increased in darkness, showing an averaged half life of 1.025 ± 0.075 d−1. The results conform to a conceptual model where diatoms grow during the bloom until silicic acid stocks are depleted, and support a link between diatom cell health status and sedimentation fluxes in the Arctic. Healthy arctic phytoplankton communities remained at the photic layer, whereas dying communities exported a large fraction of the biomass to the aphotic zone, fuelling carbon sequestration and benthic ecosystems.

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Spatial Distribution of Arctic Bacterioplankton Abundance Is Linked to Distinct Water Masses and Summertime Phytoplankton Bloom Dynamics (Fram Strait, 79°N)

Frontiers in Microbiology ◽

10.3389/fmicb.2021.658803 ◽

2021 ◽

Vol 12 ◽

Author(s):

Magda G. Cardozo-Mino ◽

Eduard Fadeev ◽

Verena Salman-Carvalho ◽

Antje Boetius

Keyword(s):

Water Column ◽

Phytoplankton Bloom ◽

Standing Stock ◽

The Arctic ◽

Fram Strait ◽

Arctic Water ◽

Entire Water Column ◽

Taxonomic Groups ◽

Card Fish ◽

Bacterioplankton Communities

The Arctic is impacted by climate warming faster than any other oceanic region on Earth. Assessing the baseline of microbial communities in this rapidly changing ecosystem is vital for understanding the implications of ocean warming and sea ice retreat on ecosystem functioning. Using CARD-FISH and semi-automated counting, we quantified 14 ecologically relevant taxonomic groups of bacterioplankton (Bacteria and Archaea) from surface (0–30 m) down to deep waters (2,500 m) in summer ice-covered and ice-free regions of the Fram Strait, the main gateway for Atlantic inflow into the Arctic Ocean. Cell abundances of the bacterioplankton communities in surface waters varied from 105 cells mL–1 in ice-covered regions to 106 cells mL–1 in the ice-free regions. Observations suggest that these were overall driven by variations in phytoplankton bloom conditions across the Strait. The bacterial groups Bacteroidetes and Gammaproteobacteria showed several-fold higher cell abundances under late phytoplankton bloom conditions of the ice-free regions. Other taxonomic groups, such as the Rhodobacteraceae, revealed a distinct association of cell abundances with the surface Atlantic waters. With increasing depth (>500 m), the total cell abundances of the bacterioplankton communities decreased by up to two orders of magnitude, while largely unknown taxonomic groups (e.g., SAR324 and SAR202 clades) maintained constant cell abundances throughout the entire water column (ca. 103 cells mL–1). This suggests that these enigmatic groups may occupy a specific ecological niche in the entire water column. Our results provide the first quantitative spatial variations assessment of bacterioplankton in the summer ice-covered and ice-free Arctic water column, and suggest that further shift toward ice-free Arctic summers with longer phytoplankton blooms can lead to major changes in the associated standing stock of the bacterioplankton communities.

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Spatial dynamics in Arctic bacterioplankton community densities are strongly linked to distinct physical and biological processes (Fram Strait, 79°N)

10.1101/2020.09.02.277574 ◽

2020 ◽

Author(s):

Magda G. Cardozo Mino ◽

Eduard Fadeev ◽

Verena Salman-Carvalho ◽

Antje Boetius

Keyword(s):

Water Column ◽

Surface Waters ◽

Phytoplankton Bloom ◽

Standing Stock ◽

The Arctic ◽

Fram Strait ◽

Entire Water Column ◽

Free Region ◽

Taxonomic Groups ◽

Bacterioplankton Communities

AbstractThe Arctic is impacted by climate warming faster than any other oceanic region on Earth. Assessing the baseline of microbial communities in this rapidly changing ecosystem is vital for understanding the imminent implications of Arctic warming and sea ice retreat on ecosystem functioning. Using CARD-FISH and semi-automated counting, we quantified 14 ecologically relevant taxonomic groups of bacterioplankton (Bacteria and Archaea) from surface (0– 30 m) down to deep waters (2500 m) in summerly ice-covered and ice-free regions of the Fram Strait, the main gateway for Atlantic inflow into the Arctic Ocean. Cell abundances of the bacterioplankton communities in surface waters varied from 105 cells mL−1 in ice-covered region to 106 cells mL−1 in the ice-free region and were overall driven by variations in phytoplankton bloom conditions across the Strait. In surface waters the bacterial classes Bacteroidia and Gammaproteobacteria showed several-fold higher cell abundances under late phytoplankton bloom conditions of the ice-free regions. Other taxonomic groups, such as the Rhodobacteraceae, revealed a distinct association of cell abundances with the surface Atlantic waters. With depth (> 500 m) the total cell abundances of the bacterioplankton communities decreased by one to two orders of magnitude, while largely unknown taxonomic groups (e.g., SAR324 and SAR202 clades) maintained constant cell abundances throughout the entire water column (103 cells mL−1). This suggests that some enigmatic taxonomic groups may occupy a specific ecological niche in the entire water column. Our results provide the first quantitative spatial variations assessment of bacterioplankton in summerly ice-covered and ice-free Arctic water column, and suggest that further shift towards ice-free Arctic summers with longer phytoplankton blooms can lead to major changes in the associated standing stock of the bacterioplankton communities.

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The impact of sea ice regime on meiobenthic structure and function north of Svalbard

10.7287/peerj.preprints.26650 ◽

2018 ◽

Author(s):

Katarzyna Grzelak ◽

Monika Kędra ◽

Klaudia Gregorczyk ◽

Nathalie Morata ◽

Magdalena Blazewicz

Keyword(s):

Sea Ice ◽

Phytoplankton Bloom ◽

Standing Stock ◽

Arctic Region ◽

The Arctic ◽

Life Strategy ◽

Nematode Diversity ◽

Rapid Transition ◽

And Function ◽

The Impact

Eight stations located in the seasonal sea ice zone north of Svalbard were investigated during ‘TRANSSIZ’ cruise within Arctic in Rapid Transition initiative. Nematodes were used as a key group within the meiofauna. Our study provides previously unavailable data on nematode diversity for this Arctic region during ecologically important spring to summer transition time. Phytoplankton bloom development is crucial for the Arctic marine ecosystems functioning, yet data from this time of year, particularly for the deep-sea basins north of Svalbard are still scarce. The obtained results suggest that nematode community differences are attributed to prevailing environmental conditions, ice-edge related bloom-phase. Three distinct nematode assemblages were observed and were related to bloom stage. Nematodes standing stock and diversity was the lowest at stations where pre-bloom phase occurred. Community was dominated by opportunistic genera belonging to Monhysteridae and by Acantholaimus. Conditions at stations with already developed bloom promoted enhanced abundance and biomass of nematodes and almost two time higher number of nematode genera in comparison to pre-bloom stations. Communities at those stations were characterized by genera of Desmoscolecidae family. Stations with early-bloom conditions appeared as transitional, with conditions in which relatively high number of genera with different life strategy can co-exist. The study was completed thanks to funding provided by the National Science Centre, Poland (grant no. 2016/20/S/NZ8/00432 and 2015/19/B/NZ8/03945). Presented material was collected during R/V Polarstern TRANSSIZ cruise (ARK XXIX/1; PS92), carried out under grant number AWI_PS92_00 and organized by Arctic in Rapid Transition (ART).

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The impact of sea ice regime on meiobenthic structure and function north of Svalbard

10.7287/peerj.preprints.26650v1 ◽

2018 ◽

Author(s):

Katarzyna Grzelak ◽

Monika Kędra ◽

Klaudia Gregorczyk ◽

Nathalie Morata ◽

Magdalena Blazewicz

Keyword(s):

Sea Ice ◽

Phytoplankton Bloom ◽

Standing Stock ◽

Arctic Region ◽

The Arctic ◽

Life Strategy ◽

Nematode Diversity ◽

Rapid Transition ◽

And Function ◽

The Impact

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Spectral Characterization of Dissolved Organic Matter in Seawater and Sediment Pore Water from the Arctic Fjords (West Svalbard) in Summer

Water ◽

10.3390/w13020202 ◽

2021 ◽

Vol 13 (2) ◽

pp. 202

Author(s):

Meilian Chen ◽

Ji-Hoon Kim ◽

Sungwook Hong ◽

Yun Kyung Lee ◽

Moo Hee Kang ◽

...

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Pore Water ◽

Phytoplankton Bloom ◽

Ocean Surface ◽

The Arctic ◽

Sediment Pore Water ◽

Ice Edge ◽

Accumulation Trend ◽

Arctic Fjords

Fjords in the high Arctic, as aquatic critical zones at the interface of land-ocean continuum, are undergoing rapid changes due to glacier retreat and climate warming. Yet, little is known about the biogeochemical processes in the Arctic fjords. We measured the nutrients and the optical properties of dissolved organic matter (DOM) in both seawater and sediment pore water, along with the remote sensing data of the ocean surface, from three West Svalbard fjords. A cross-fjord comparison of fluorescence fingerprints together with downcore trends of salinity, Cl−, and PO43− revealed higher impact of terrestrial inputs (fluorescence index: ~1.2–1.5 in seawaters) and glaciofluvial runoffs (salinity: ~31.4 ± 2.4 psu in pore waters) to the southern fjord of Hornsund as compared to the northern fjords of Isfjorden and Van Mijenfjorden, tallying with heavier annual runoff to the southern fjord of Hornsund. Extremely high levels of protein-like fluorescence (up to ~4.5 RU) were observed at the partially sea ice-covered fjords in summer, in line with near-ubiquity ice-edge blooms observed in the Arctic. The results reflect an ongoing or post-phytoplankton bloom, which is also supported by the higher levels of chlorophyll a fluorescence at the ocean surface, the very high apparent oxygen utilization through the water column, and the nutrient drawdown at the ocean surface. Meanwhile, a characteristic elongated fluorescence fingerprint was observed in the fjords, presumably produced by ice-edge blooms in the Arctic ecosystems. Furthermore, alkalinity and the humic-like peaks showed a general downcore accumulation trend, which implies the production of humic-like DOM via a biological pathway also in the glaciomarine sediments from the Arctic fjords.

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Assessing Phytoplankton Bloom Phenology in Upwelling-Influenced Regions Using Ocean Color Remote Sensing

Remote Sensing ◽

10.3390/rs13040675 ◽

2021 ◽

Vol 13 (4) ◽

pp. 675

Author(s):

Afonso Ferreira ◽

Vanda Brotas ◽

Carla Palma ◽

Carlos Borges ◽

Ana C. Brito

Keyword(s):

Climate Change ◽

Remote Sensing ◽

Phytoplankton Bloom ◽

Ocean Color ◽

Coastal Region ◽

Coastal Areas ◽

Ocean Color Remote Sensing ◽

Chl A ◽

Peak Biomass ◽

Phytoplankton Communities

Phytoplankton bloom phenology studies are fundamental for the understanding of marine ecosystems. Mismatches between fish spawning and plankton peak biomass will become more frequent with climate change, highlighting the need for thorough phenology studies in coastal areas. This study was the first to assess phytoplankton bloom phenology in the Western Iberian Coast (WIC), a complex coastal region in SW Europe, using a multisensor long-term ocean color remote sensing dataset with daily resolution. Using surface chlorophyll a (chl-a) and biogeophysical datasets, five phenoregions (i.e., areas with coherent phenology patterns) were defined. Oceanic phytoplankton communities were seen to form long, low-biomass spring blooms, mainly influenced by atmospheric phenomena and water column conditions. Blooms in northern waters are more akin to the classical spring bloom, while blooms in southern waters typically initiate in late autumn and terminate in late spring. Coastal phytoplankton are characterized by short, high-biomass, highly heterogeneous blooms, as nutrients, sea surface height, and horizontal water transport are essential in shaping phenology. Wind-driven upwelling and riverine input were major factors influencing bloom phenology in the coastal areas. This work is expected to contribute to the management of the WIC and other upwelling systems, particularly under the threat of climate change.

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Implications of sea-ice biogeochemistry for oceanic production and emissions of dimethyl sulfide in the Arctic

Biogeosciences ◽

10.5194/bg-14-3129-2017 ◽

2017 ◽

Vol 14 (12) ◽

pp. 3129-3155 ◽

Cited By ~ 17

Author(s):

Hakase Hayashida ◽

Nadja Steiner ◽

Adam Monahan ◽

Virginie Galindo ◽

Martine Lizotte ◽

...

Keyword(s):

Sea Ice ◽

Water Column ◽

Dimethyl Sulfide ◽

Phytoplankton Bloom ◽

Model Simulation ◽

Field Measurements ◽

Sulfur Cycle ◽

The Arctic ◽

Model Parameters ◽

Ocean Ecosystem

Abstract. Sea ice represents an additional oceanic source of the climatically active gas dimethyl sulfide (DMS) for the Arctic atmosphere. To what extent this source contributes to the dynamics of summertime Arctic clouds is, however, not known due to scarcity of field measurements. In this study, we developed a coupled sea ice–ocean ecosystem–sulfur cycle model to investigate the potential impact of bottom-ice DMS and its precursor dimethylsulfoniopropionate (DMSP) on the oceanic production and emissions of DMS in the Arctic. The results of the 1-D model simulation were compared with field data collected during May and June of 2010 in Resolute Passage. Our results reproduced the accumulation of DMS and DMSP in the bottom ice during the development of an ice algal bloom. The release of these sulfur species took place predominantly during the earlier phase of the melt period, resulting in an increase of DMS and DMSP in the underlying water column prior to the onset of an under-ice phytoplankton bloom. Production and removal rates of processes considered in the model are analyzed to identify the processes dominating the budgets of DMS and DMSP both in the bottom ice and the underlying water column. When openings in the ice were taken into account, the simulated sea–air DMS flux during the melt period was dominated by episodic spikes of up to 8.1 µmol m−2 d−1. Further model simulations were conducted to assess the effects of the incorporation of sea-ice biogeochemistry on DMS production and emissions, as well as the sensitivity of our results to changes of uncertain model parameters of the sea-ice sulfur cycle. The results highlight the importance of taking into account both the sea-ice sulfur cycle and ecosystem in the flux estimates of oceanic DMS near the ice margins and identify key uncertainties in processes and rates that should be better constrained by new observations.

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Loss of natriuretic peptide receptor C enhances sinoatrial node dysfunction in aging and frail mice

The Journals of Gerontology Series A ◽

10.1093/gerona/glab357 ◽

2021 ◽

Author(s):

Hailey J Jansen ◽

Motahareh Moghtadaei ◽

Sara A Rafferty ◽

Robert A Rose

Keyword(s):

Health Status ◽

Natriuretic Peptide ◽

Recovery Time ◽

Sinoatrial Node ◽

Optical Mapping ◽

Frailty Index ◽

Age Groups ◽

Rapid Decline ◽

Natriuretic Peptide Receptor ◽

Peptide Receptor

Abstract Heart rate is controlled by the sinoatrial node (SAN). SAN dysfunction is highly prevalent in aging; however, not all individuals age at the same rate. Rather, health status during aging is affected by frailty. Natriuretic peptides regulate SAN function in part by activating natriuretic peptide receptor C (NPR-C). The impacts of NPR-C on HR and SAN function in aging and as a function of frailty are unknown. Frailty was measured in aging wildtype (WT) and NPR-C knockout (NPR-C -/-) mice using a mouse clinical frailty index (FI). HR and SAN structure and function were investigated using intracardiac electrophysiology in anesthetized mice, high-resolution optical mapping in intact atrial preparations, histology and molecular biology. NPR-C -/- mice rapidly became frail leading to shortened lifespan. HR and SAN recovery time were increased in older vs. younger mice and this was exacerbated in NPR-C -/- mice; however, there was substantial variability among age groups and genotypes. HR and SAN recovery time were correlated with FI score and fell along a continuum regardless of age or genotype. Optical mapping demonstrates impairments in SAN function that were also strongly correlated with FI score. SAN fibrosis was increased in aged and NPR-C -/- mice and was graded by FI score. Loss of NPR-C results in accelerated aging due to a rapid decline in health status in association with impairments in HR and SAN function. Frailty assessment was effective and often better able to distinguish aging-dependent changes in SAN function in the setting of shorted lifespan due to loss of NPR-C.

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Observational evidence for the formation of ocean DMS-derived aerosols during Arctic phytoplankton blooms

10.5194/acp-2016-1161 ◽

2017 ◽

Author(s):

Ki-Tae Park ◽

Sehyun Jang ◽

Kitack Lee ◽

Young Jun Yoon ◽

Min-Seob Kim ◽

...

Keyword(s):

Dimethyl Sulfide ◽

Phytoplankton Bloom ◽

The Arctic ◽

Size Distributions ◽

Particle Size Distributions ◽

Phytoplankton Blooms ◽

Mixing Ratios ◽

Arctic Haze ◽

Aerosol Particle Size ◽

Arctic Atmosphere

Abstract. The connection between marine biogenic dimethyl sulfide (DMS) and the formation of aerosol particles in the Arctic atmosphere was evaluated by analyzing atmospheric DMS mixing ratios, aerosol particle size distributions and aerosol chemical composition data that were concurrently collected at Ny-Ålesund, Svalbard (78.5° N, 11.8° E) during April and May 2015. Measurements of aerosol sulfur (S) compounds showed distinct patterns during periods of Arctic haze (April) and phytoplankton blooms (May). Specifically, during the phytoplankton bloom period the contribution of DMS-derived SO42− to the total aerosol SO42− increased by 7-fold compared with that during the proceeding Arctic haze period, accounting for up to 70 % of fine SO42− particles (

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