Bioavailable iron produced through benthic cycling in glaciated Arctic fjords (Svalbard)

Abstract The Arctic has the highest warming rates world-wide. Glaciated fjord ecosystems, which are known hotspots of carbon cycling and burial, are predicted to be extremely sensitive to this warming. Glaciers are important sources of iron, an essential nutrient for phytoplankton, to high-latitude marine ecosystems. However, up to 95% of the glacially-sourced iron settles in sediments close to the glacial source. We found that only 0.6-12% of the total glacially-sourced iron is potentially bioavailable. Our results also show that biogeochemical cycling in fjord sediments converts the unreactive glacial iron into more reactive and bioavailable phases, leading to an up to 9-fold increase in the amount of potentially bioavailable iron. Arctic fjord sediments therefore likely are an important source of bioavailable iron. However, once glaciers retreat onto land, the flux of iron from sediments into the water column is reduced, such that glacial retreat could exacerbate iron limitation in polar oceans.

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Potentially bioavailable iron produced through benthic cycling in glaciated Arctic fjords of Svalbard

Nature Communications ◽

10.1038/s41467-021-21558-w ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Katja Laufer-Meiser ◽

Alexander B. Michaud ◽

Markus Maisch ◽

James M. Byrne ◽

Andreas Kappler ◽

...

Keyword(s):

Fold Increase ◽

Marine Ecosystems ◽

The Arctic ◽

Iron Cycling ◽

Glacial Retreat ◽

Coastal Marine ◽

Essential Nutrient ◽

Coastal Marine Ecosystems ◽

Arctic Fjord ◽

Fjord Sediments

AbstractThe Arctic has the highest warming rates on Earth. Glaciated fjord ecosystems, which are hotspots of carbon cycling and burial, are extremely sensitive to this warming. Glaciers are important for the transport of iron from land to sea and supply this essential nutrient to phytoplankton in high-latitude marine ecosystems. However, up to 95% of the glacially-sourced iron settles to sediments close to the glacial source. Our data show that while 0.6–12% of the total glacially-sourced iron is potentially bioavailable, biogeochemical cycling in Arctic fjord sediments converts the glacially-derived iron into more labile phases, generating up to a 9-fold increase in the amount of potentially bioavailable iron. Arctic fjord sediments are thus an important source of potentially bioavailable iron. However, our data suggests that as glaciers retreat onto land the flux of iron to the sediment-water interface may be reduced. Glacial retreat therefore likely impacts iron cycling in coastal marine ecosystems.

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Complex Microbial Communities Drive Iron and Sulfur Cycling in Arctic Fjord Sediments

Applied and Environmental Microbiology ◽

10.1128/aem.00949-19 ◽

2019 ◽

Vol 85 (14) ◽

Cited By ~ 13

Author(s):

J. Buongiorno ◽

L. C. Herbert ◽

L. M. Wehrmann ◽

A. B. Michaud ◽

K. Laufer ◽

...

Keyword(s):

Organic Matter ◽

Primary Production ◽

Sulfate Reduction ◽

The Arctic ◽

Sulfur Cycling ◽

Glacial Retreat ◽

Sulfate Reducing ◽

Glacial Runoff ◽

Sulfate Reduction Rates ◽

Fjord Sediments

ABSTRACTGlacial retreat is changing biogeochemical cycling in the Arctic, where glacial runoff contributes iron for oceanic shelf primary production. We hypothesize that in Svalbard fjords, microbes catalyze intense iron and sulfur cycling in low-organic-matter sediments. This is because low organic matter limits sulfide generation, allowing iron mobility to the water column instead of precipitation as iron monosulfides. In this study, we tested this with high-depth-resolution 16S rRNA gene libraries in the upper 20 cm at two sites in Van Keulenfjorden, Svalbard. At the site closer to the glaciers, iron-reducingDesulfuromonadales, iron-oxidizingGallionellaandMariprofundus, and sulfur-oxidizingThiotrichalesandEpsilonproteobacteriawere abundant above a 12-cm depth. Below this depth, the relative abundances of sequences for sulfate-reducingDesulfobacteraceaeandDesulfobulbaceaeincreased. At the outer station, the switch from iron-cycling clades to sulfate reducers occurred at shallower depths (∼5 cm), corresponding to higher sulfate reduction rates. Relatively labile organic matter (shown by δ13C and C/N ratios) was more abundant at this outer site, and ordination analysis suggested that this affected microbial community structure in surface sediments. Network analysis revealed more correlations between predicted iron- and sulfur-cycling taxa and with uncultured clades proximal to the glacier. Together, these results suggest that complex microbial communities catalyze redox cycling of iron and sulfur, especially closer to the glacier, where sulfate reduction is limited due to low availability of organic matter. Diminished sulfate reduction in upper sediments enables iron to flux into the overlying water, where it may be transported to the shelf.IMPORTANCEGlacial runoff is a key source of iron for primary production in the Arctic. In the fjords of the Svalbard archipelago, glacial retreat is predicted to stimulate phytoplankton blooms that were previously restricted to outer margins. Decreased sediment delivery and enhanced primary production have been hypothesized to alter sediment biogeochemistry, wherein any free reduced iron that could potentially be delivered to the shelf will instead become buried with sulfide generated through microbial sulfate reduction. We support this hypothesis with sequencing data that showed increases in the relative abundance of sulfate reducing taxa and sulfate reduction rates with increasing distance from the glaciers in Van Keulenfjorden, Svalbard. Community structure was driven by organic geochemistry, suggesting that enhanced input of organic material will stimulate sulfate reduction in interior fjord sediments as glaciers continue to recede.

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Climate-Associated Changes in Mercury Sources in the Arctic Fjord Sediments

ACS Earth and Space Chemistry ◽

10.1021/acsearthspacechem.1c00095 ◽

2021 ◽

Author(s):

Ju Hyeon Lee ◽

Sae Yun Kwon ◽

Hoin Lee ◽

Seung-Il Nam ◽

Jung-Hyun Kim ◽

...

Keyword(s):

The Arctic ◽

Arctic Fjord ◽

Fjord Sediments

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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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Paleocene-Eocene volcanic segmentation of the Norwegian-Greenland seaway reorganized high-latitude ocean circulation

Communications Earth & Environment ◽

10.1038/s43247-021-00249-w ◽

2021 ◽

Vol 2 (1) ◽

Author(s):

Jussi Hovikoski ◽

Michael B. W. Fyhn ◽

Henrik Nøhr-Hansen ◽

John R. Hopper ◽

Steven Andrews ◽

...

Keyword(s):

Ocean Circulation ◽

High Latitude ◽

Seismic Reflection ◽

Arctic Region ◽

Climatic Conditions ◽

The Arctic ◽

Early Eocene ◽

Subaerial Exposure ◽

Thermal Maximum ◽

Volcanic Facies

AbstractThe paleoenvironmental and paleogeographic development of the Norwegian–Greenland seaway remains poorly understood, despite its importance for the oceanographic and climatic conditions of the Paleocene–Eocene greenhouse world. Here we present analyses of the sedimentological and paleontological characteristics of Paleocene–Eocene deposits (between 63 and 47 million years old) in northeast Greenland, and investigate key unconformities and volcanic facies observed through seismic reflection imaging in offshore basins. We identify Paleocene–Eocene uplift that culminated in widespread regression, volcanism, and subaerial exposure during the Ypresian. We reconstruct the paleogeography of the northeast Atlantic–Arctic region and propose that this uplift led to fragmentation of the Norwegian–Greenland seaway during this period. We suggest that the seaway became severely restricted between about 56 and 53 million years ago, effectively isolating the Arctic from the Atlantic ocean during the Paleocene–Eocene thermal maximum and the early Eocene.

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Airborne Hyperspectral Data Acquisition and Processing in the Arctic: A Pilot Study Using the Hyspex Imaging Spectrometer for Wetland Mapping

Remote Sensing ◽

10.3390/rs13061178 ◽

2021 ◽

Vol 13 (6) ◽

pp. 1178

Author(s):

Jordi Cristóbal ◽

Patrick Graham ◽

Anupma Prakash ◽

Marcel Buchhorn ◽

Rudi Gens ◽

...

Keyword(s):

Maximum Likelihood ◽

Pilot Study ◽

Data Processing ◽

High Latitude ◽

Hyperspectral Images ◽

The Arctic ◽

Wetland Mapping ◽

Kappa Index ◽

Spectral Angle Mapper ◽

Spectral Angle

A pilot study for mapping the Arctic wetlands was conducted in the Yukon Flats National Wildlife Refuge (Refuge), Alaska. It included commissioning the HySpex VNIR-1800 and the HySpex SWIR-384 imaging spectrometers in a single-engine Found Bush Hawk aircraft, planning the flight times, direction, and speed to minimize the strong bidirectional reflectance distribution function (BRDF) effects present at high latitudes and establishing improved data processing workflows for the high-latitude environments. Hyperspectral images were acquired on two clear-sky days in early September, 2018, over three pilot study areas that together represented a wide variety of vegetation and wetland environments. Steps to further minimize BRDF effects and achieve a higher geometric accuracy were added to adapt and improve the Hyspex data processing workflow, developed by the German Aerospace Center (DLR), for high-latitude environments. One-meter spatial resolution hyperspectral images, that included a subset of only 120 selected spectral bands, were used for wetland mapping. A six-category legend was established based on previous U.S. Geological Survey (USGS) and U.S. Fish and Wildlife Service (USFWS) information and maps, and three different classification methods—hybrid classification, spectral angle mapper, and maximum likelihood—were used at two selected sites. The best classification performance occurred when using the maximum likelihood classifier with an averaged Kappa index of 0.95; followed by the spectral angle mapper (SAM) classifier with a Kappa index of 0.62; and, lastly, by the hybrid classifier showing lower performance with a Kappa index of 0.51. Recommendations for improvements of future work include the concurrent acquisition of LiDAR or RGB photo-derived digital surface models as well as detailed spectra collection for Alaska wetland cover to improve classification efforts.

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Relatively high antibiotic resistance among heterotrophic bacteria from arctic fjord sediments than water – Evidence towards better selection pressure in the fjord sediments

Polar Science ◽

10.1016/j.polar.2015.10.002 ◽

2015 ◽

Vol 9 (4) ◽

pp. 382-388 ◽

Cited By ~ 7

Author(s):

A.A. Mohamed Hatha ◽

C.S. Neethu ◽

S.M. Nikhil ◽

K.M. Mujeeb Rahiman ◽

K.P. Krishnan ◽

...

Keyword(s):

Antibiotic Resistance ◽

Selection Pressure ◽

Heterotrophic Bacteria ◽

Arctic Fjord ◽

Fjord Sediments

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Pliocene ostracods (Crustacea) from the Togakushi area, central Japan; palaeobiogeography of trans-Arctic taxa and Japan Sea endemic species

Journal of Micropalaeontology ◽

10.1144/jm.27.2.161 ◽

2008 ◽

Vol 27 (2) ◽

pp. 161-175 ◽

Cited By ~ 6

Author(s):

Hirokazu Ozawa ◽

Hideaki Nagamori ◽

Tomotaka Tanabe

Keyword(s):

High Latitude ◽

Endemic Species ◽

Japan Sea ◽

Kuroshio Current ◽

The Arctic ◽

Northwestern Pacific ◽

Arctic Seas ◽

Central Japan ◽

The Japan Sea ◽

Northern Atlantic

Abstract. Pliocene strata (4–3 Ma) in the Togakushi area, central Japan, yield significant ostracods, which allow investigation of the origins of high-latitude (Arctic–Atlantic) taxa and the Japan Sea endemic species, together with their post-Miocene history of extinction-speciation and migration. Three types of extinct species are found here: (1) cryophilic species in common with, or closely related to, species in Plio-Pleistocene assemblages described from the Japan Sea; (2) species closely related to, or comparable with, species that characterize Miocene Japan; and (3) species endemic to the Pliocene Japan Sea. Type (1) contains species closely related to high-latitude species known from the Arctic and northern Atlantic Oceans. Their presence suggests migration from the northwestern Pacific to the northern Atlantic through the Arctic seas since the Late Pliocene after the opening of the Bering Strait. Both Types (2) and (3) contain genera originating in the south, which show high specific diversity in regions affected by the modern warm Kuroshio Current. Ancestral ostracods of Types (2) and (3) invaded the Japan Sea from the Pacific from the Middle Miocene, and diversified to produce closely related species in the semi land-locked Japan Sea until the Early Pliocene. Two new species Aurila togakushiensis sp. nov. and Aurila shigaramiensis sp. nov. are described.

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Tropopause height at 78° N 16° E: average seasonal variation 2007–2010

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-39-2011 ◽

2011 ◽

Vol 11 (1) ◽

pp. 39-52

Author(s):

C. M. Hall ◽

G. Hansen ◽

F. Sigernes ◽

K. M. Kuyeng Ruiz

Keyword(s):

Climate Change ◽

Seasonal Variation ◽

Air Temperature ◽

High Latitude ◽

Column Density ◽

Surface Air Temperature ◽

The Arctic ◽

Tropopause Height ◽

Vhf Radar ◽

Ozone Column

Abstract. We present a seasonal climatology of tropopause altitude for 78° N 16° E derived from observations 2007–2010 by the SOUSY VHF radar on Svalbard. The spring minimum occurs one month later than that of surface air temperature and instead coincides with the maximum in ozone column density. This confirms similar studies based on radiosonde measurements in the arctic and demonstrates downward control by the stratosphere. If one is to exploit the potential of tropopause height as a metric for climate change at high latitude and elsewhere, it is imperative to observe and understand the processes which establish the tropopause – an understanding to which this study contributes.

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Upper tropospheric water vapour variability at high latitudes – Part 1: Influence of the annular modes

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-22291-2015 ◽

2015 ◽

Vol 15 (16) ◽

pp. 22291-22329 ◽

Cited By ~ 2

Author(s):

C. E. Sioris ◽

J. Zou ◽

D. A. Plummer ◽

C. D. Boone ◽

C. T. McElroy ◽

...

Keyword(s):

Water Vapour ◽

Atmospheric Chemistry ◽

High Latitude ◽

Lower Stratosphere ◽

Southern Annular Mode ◽

The Arctic ◽

Boreal Winter ◽

High Latitudes ◽

Annular Mode ◽

Annular Modes

Abstract. Seasonal and monthly zonal medians of water vapour in the upper troposphere and lower stratosphere (UTLS) are calculated for both Atmospheric Chemistry Experiment (ACE) instruments for the northern and southern high-latitude regions (60–90 and 60–90° S). Chosen for the purpose of observing high-latitude processes, the ACE orbit provides sampling of both regions in eight of 12 months of the year, with coverage in all seasons. The ACE water vapour sensors, namely MAESTRO (Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) and the Fourier Transform Spectrometer (ACE-FTS) are currently the only satellite instruments that can probe from the lower stratosphere down to the mid-troposphere to study the vertical profile of the response of UTLS water vapour to the annular modes. The Arctic oscillation (AO), also known as the northern annular mode (NAM), explains 64 % (r = −0.80) of the monthly variability in water vapour at northern high-latitudes observed by ACE-MAESTRO between 5 and 7 km using only winter months (January to March 2004–2013). Using a seasonal timestep and all seasons, 45 % of the variability is explained by the AO at 6.5 ± 0.5 km, similar to the 46 % value obtained for southern high latitudes at 7.5 ± 0.5 km explained by the Antarctic oscillation or southern annular mode (SAM). A large negative AO event in March 2013 produced the largest relative water vapour anomaly at 5.5 km (+70 %) over the ACE record. A similarly large event in the 2010 boreal winter, which was the largest negative AO event in the record (1950–2015), led to > 50 % increases in water vapour observed by MAESTRO and ACE-FTS at 7.5 km.

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