scholarly journals Geophysical and geochemical controls on the megafaunal community of a high Arctic cold seep

2018 ◽  
Author(s):  
Arunima Sen ◽  
Emmelie K. L. Åström ◽  
Wei-Li Hong ◽  
Alexey Portnov ◽  
Malin Waage ◽  
...  
Keyword(s):  
Barents Sea ◽  
High Arctic ◽  
Cold Seep ◽  
Snow Crab ◽  
Seismic Profiles ◽  
Community Members ◽  
Gas Reservoirs ◽  
Biological Communities ◽  
Methane Seepage ◽  
Gas Source

Abstract. Cold seep communities around gas hydrate mounds (pingos) in the Western Barents Sea (76°N, 16°E, ~400 m depth) were investigated with high resolution, geographically referenced images acquired with an ROV and towed camera. Four pingos associated with seabed methane release hosted diverse biological communities of mainly non-seep (background) species including commercially important fish and crustaceans, as well as a species new to this area (the snow crab Chionoecetes opilio). We attribute the presence of most benthic community members to habitat heterogeneity and the occurrence of hard substrates (methane derived authigenic carbonates), particularly the most abundant phyla (Cnidaria and Porifera), though food availability and exposure to a diverse microbial community is also important for certain taxa. Only one chemosynthesis based species was confirmed, the siboglinid frenulate polychaete, Oligobrachia haakonmosbiensis. Overall, the pingo communities formed two distinct clusters, distinguished by the presence or absence of frenulates. Methane gas advection through sediments was absent below the single pingo that lacked frenulates, while seismic profiles indicated gas saturated sediment below the other frenulate colonized pingos. The absence of frenulates could not be explained by sediment sulfide concentrations, despite these worms likely containing sulfide oxidizing symbionts. We propose that high levels of seafloor methane seepage linked to sub-surface gas reservoirs support an abundant and active sediment methanotrophic community that maintains high sulfide fluxes and serves as a carbon source for frenulate worms. The pingo currently lacking a sub-surface gas source and lower methane concentrations has lower sulfide flux rates and limited amounts of carbon insufficient to support frenulates. Two previously undocumented behaviors were visible through the images: grazing activity of snow crabs on bacterial mats, and seafloor crawling of Nothria conchylega onuphid polychaetes.

scholarly journals Geophysical and geochemical controls on the megafaunal community of a high Arctic cold seep

2018 ◽  
Vol 15 (14) ◽  
pp. 4533-4559 ◽  
Author(s):  
Arunima Sen ◽  
Emmelie K. L. Åström ◽  
Wei-Li Hong ◽  
Alexey Portnov ◽  
Malin Waage ◽  
...  
Keyword(s):  
Barents Sea ◽  
High Arctic ◽  
Cold Seep ◽  
Snow Crab ◽  
Seismic Profiles ◽  
Community Members ◽  
Gas Reservoirs ◽  
Biological Communities ◽  
Methane Seepage ◽  
Large Populations

Abstract. Cold-seep megafaunal communities around gas hydrate mounds (pingos) in the western Barents Sea (76∘ N, 16∘ E, ∼400 m depth) were investigated with high-resolution, geographically referenced images acquired with an ROV and towed camera. Four pingos associated with seabed methane release hosted diverse biological communities of mainly nonseep (background) species including commercially important fish and crustaceans, as well as a species new to this area (the snow crab Chionoecetes opilio). We attribute the presence of most benthic community members to habitat heterogeneity and the occurrence of hard substrates (methane-derived authigenic carbonates), particularly the most abundant phyla (Cnidaria and Porifera), though food availability and exposure to a diverse microbial community is also important for certain taxa. Only one chemosynthesis-based species was confirmed, the siboglinid frenulate polychaete Oligobrachia cf. haakonmosbiensis. Overall, the pingo communities formed two distinct clusters, distinguished by the presence or absence of frenulate aggregations. Methane gas advection through sediments was low, below the single pingo that lacked frenulate aggregations, while seismic profiles indicated abundant gas-saturated sediment below the other frenulate-colonized pingos. The absence of frenulate aggregations could not be explained by sediment sulfide concentrations, despite these worms likely containing sulfide-oxidizing symbionts. We propose that high levels of seafloor methane seepage linked to subsurface gas reservoirs support an abundant and active sediment methanotrophic community that maintains high sulfide fluxes and serves as a carbon source for frenulate worms. The pingo currently lacking a large subsurface gas source and lower methane concentrations likely has lower sulfide flux rates and limited amounts of carbon, insufficient to support large populations of frenulates. Two previously undocumented behaviors were visible through the images: grazing activity of snow crabs on bacterial mats, and seafloor crawling of Nothria conchylega onuphid polychaetes.

scholarly journals Geochemistry, faunal composition and trophic structure in reducing sediments on the southwest South Georgia margin

2016 ◽  
Vol 3 (9) ◽  
pp. 160284 ◽  
Author(s):  
James B. Bell ◽  
Alfred Aquilina ◽  
Clare Woulds ◽  
Adrian G. Glover ◽  
Crispin T. S. Little ◽  
...  
Keyword(s):  
Trophic Structure ◽  
Cold Seep ◽  
Biological Communities ◽  
Isotopic Signatures ◽  
South Georgia ◽  
Methane Seepage ◽  
Bottom Waters ◽  
Report Data ◽  
High Dominance

Despite a number of studies in areas of focused methane seepage, the extent of transitional sediments of more diffuse methane seepage, and their influence upon biological communities is poorly understood. We investigated an area of reducing sediments with elevated levels of methane on the South Georgia margin around 250 m depth and report data from a series of geochemical and biological analyses. Here, the geochemical signatures were consistent with weak methane seepage and the role of sub-surface methane consumption was clearly very important, preventing gas emissions into bottom waters. As a result, the contribution of methane-derived carbon to the microbial and metazoan food webs was very limited, although sulfur isotopic signatures indicated a wider range of dietary contributions than was apparent from carbon isotope ratios. Macrofaunal assemblages had high dominance and were indicative of reducing sediments, with many taxa common to other similar environments and no seep-endemic fauna, indicating transitional assemblages. Also similar to other cold seep areas, there were samples of authigenic carbonate, but rather than occurring as pavements or sedimentary concretions, these carbonates were restricted to patches on the shells of Axinulus antarcticus (Bivalvia, Thyasiridae), which is suggestive of microbe–metazoan interactions.

scholarly journals Effectiveness of Fluorescent Viability Assays in Studies of Arctic Cold Seep Foraminifera

2021 ◽  
Vol 8 ◽  
Author(s):  
Katarzyna Melaniuk
Keyword(s):  
Water Depth ◽  
Rose Bengal ◽  
Gas Hydrate ◽  
Barents Sea ◽  
Fluorescence Probe ◽  
Isotopic Signature ◽  
Cold Seep ◽  
Cold Seeps ◽  
Gas Reservoirs ◽  
The Past

Highly negative δ13C values in fossil foraminifera from methane cold seeps have been proposed to reflect episodes of methane release from gas hydrate dissociation or free gas reservoirs triggered by climatic changes in the past. Because most studies on live foraminifera are based on the presence of Rose Bengal staining, that colors the cytoplasm of both live and recently dead individuals it remains unclear if, and to what extent live foraminifera incorporate methane-derived carbon during biomineralization, or whether the isotopic signature is mostly affected by authigenic overgrowth. In this paper, modern foraminiferal assemblages from a gas hydrate province Vestnesa Ridge (∼1,200 m water depth, northeastern Fram Strait) and from Storfjordrenna (∼400 m water depth in the western Barents Sea) is presented. By using the fluorescent viability assays CellTrackerTM Green (CTG) CMFDA and CellHunt Green (CHG) together with conventional Rose Bengal, it was possible to examine live and recently dead foraminifera separately. Metabolically active foraminifera were shown to inhabit methane-enriched sediments at both investigated locations. The benthic foraminiferal faunas were dominated by common Arctic species such as Melonis barleeanus, Cassidulina neoteretis, and Nonionellina labradorica. The combined usage of the fluorescence probe and Rose Bengal revealed only minor shifts in species compositions and differences in ratios between live and recently dead foraminifera from Storfjordrenna. There was no clear evidence that methane significantly affected the δ13C signature of the calcite of living specimens.

Summer phytoplankton of the northern Barents Sea (75–80º N)

2019 ◽  
pp. 8-19
Author(s):  
Larisa A. Pautova ◽  
Vladimir A. Silkin ◽  
Marina D. Kravchishina ◽  
Valeriy G. Yakubenko ◽  
Anna L. Chultsova
Keyword(s):  
Barents Sea ◽  
Weighted Average ◽  
Arctic Basin ◽  
High Arctic ◽  
Alexandrium Tamarense ◽  
Warm Water ◽  
The Arctic ◽  
Absolute Maximum ◽  
Deep Trench ◽  
Maximum Biomass

The structure of the summer planktonic communities of the Northern part of the Barents sea in the first half of August 2017 were studied. In the sea-ice melting area, the average phytoplankton biomass producing upper 50-meter layer of water reached values levels of eutrophic waters (up to 2.1 g/m3). Phytoplankton was presented by diatoms of the genera Thalassiosira and Eucampia. Maximum biomass recorded at depths of 22–52 m, the absolute maximum biomass community (5,0 g/m3) marked on the horizon of 45 m (station 5558), located at the outlet of the deep trench Franz Victoria near the West coast of the archipelago Franz Josef Land. In ice-free waters, phytoplankton abundance was low, and the weighted average biomass (8.0 mg/m3 – 123.1 mg/m3) corresponded to oligotrophic waters and lower mesotrophic waters. In the upper layers of the water population abundance was dominated by small flagellates and picoplankton from, biomass – Arctic dinoflagellates (Gymnodinium spp.) and cold Atlantic complexes (Gyrodinium lachryma, Alexandrium tamarense, Dinophysis norvegica). The proportion of Atlantic species in phytoplankton reached 75%. The representatives of warm-water Atlantic complex (Emiliania huxleyi, Rhizosolenia hebetata f. semispina, Ceratium horridum) were recorded up to 80º N, as indicators of the penetration of warm Atlantic waters into the Arctic basin. The presence of oceanic Atlantic species as warm-water and cold systems in the high Arctic indicates the strengthening of processes of “atlantificacion” in the region.

scholarly journals Distribution of rorquals and Atlantic cod in relation to their prey in the Norwegian high Arctic

Polar Biology ◽  
2021 ◽  
Author(s):  
Hiroko K. Solvang ◽  
Tore Haug ◽  
Tor Knutsen ◽  
Harald Gjøsæter ◽  
Bjarte Bogstad ◽  
...  
Keyword(s):  
Prey Species ◽  
Barents Sea ◽  
Atlantic Cod ◽  
Spatial Association ◽  
High Arctic ◽  
Humpback Whales ◽  
Predatory Fish ◽  
Detection Range ◽  
Minke Whales ◽  
Acoustic Methods

AbstractRecent warming in the Barents Sea has led to changes in the spatial distribution of both zooplankton and fish, with boreal communities expanding northwards. A similar northward expansion has been observed in several rorqual species that migrate into northern waters to take advantage of high summer productivity, hence feeding opportunities. Based on ecosystem surveys conducted during August–September in 2014–2017, we investigated the spatial associations among the three rorqual species of blue, fin, and common minke whales, the predatory fish Atlantic cod, and their main prey groups (zooplankton, 0-group fish, Atlantic cod, and capelin) in Arctic Ocean waters to the west and north of Svalbard. During the surveys, whale sightings were recorded by dedicated whale observers on the bridge of the vessel, whereas the distribution and abundance of cod and prey species were assessed using trawling and acoustic methods. Based on existing knowledge on the dive habits of these rorquals, we divided our analyses into two depth regions: the upper 200 m of the water column and waters below 200 m. Since humpback whales were absent in the area in 2016 and 2017, they were not included in the subsequent analyses of spatial association. No association or spatial overlap between fin and blue whales and any of the prey species investigated was found, while associations and overlaps were found between minke whales and zooplankton/0-group fish in the upper 200 m and between minke whales and Atlantic cod at depths below 200 m. A prey detection range of more than 10 km was suggested for minke whales in the upper water layers.

scholarly journals Thermogenic hydrocarbons fuel a redox stratified subseafloor microbiome in deep sea cold seep sediments

2020 ◽  
Author(s):  
Xiyang Dong ◽  
Jayne E. Rattray ◽  
D. Calvin Campbell ◽  
Jamie Webb ◽  
Anirban Chakraborty ◽  
...  
Keyword(s):  
Deep Sea ◽  
Hydrogen Oxidation ◽  
Sulfide Oxidation ◽  
Cold Seep ◽  
Reductive Dehalogenation ◽  
Cold Seeps ◽  
Community Members ◽  
Metabolic Potential ◽  
Near Surface ◽  
Fumarate Addition

AbstractAt marine cold seeps, gaseous and liquid hydrocarbons migrate from deep subsurface origins to the sediment-water interface. Cold seep sediments are known to host taxonomically diverse microorganisms, but little is known about their metabolic potential and depth distribution in relation to hydrocarbon and electron acceptor availability. In this work, we combined geochemical, metagenomic and metabolomic measurements in distinct sediment redox regimes to profile microbial activities within the uppermost 350 cm of a newly discovered cold seep in the NW Atlantic deep sea (2.3 km water depth). Depth-resolved metagenomic profiling revealed compositional and functional differentiation between near-surface sediments (dominated by Proteobacteria) and deeper subsurface layers (dominated by Atribacteria, Chloroflexi, Euryarchaeota and Lokiarchaeota). Metabolic capabilities of community members were inferred from 376 metagenome-assembled genomes spanning 46 phyla (including five novel candidate phyla). In deeper sulfate-reducing and methanogenic sediments, various community members are capable of anaerobically oxidizing short-chain alkanes (alkyl-CoM reductase pathway), longer-chain alkanes (fumarate addition pathway), and aromatic hydrocarbons (fumarate addition and subsequent benzoyl-CoA pathways). Geochemical profiling demonstrated that hydrocarbon substrates are abundant in this location, thermogenic in origin, and subject to biodegradation. The detection of alkyl-/arylalkylsuccinate metabolites, together with carbon isotopic signatures of ethane, propane and carbon dioxide, support that microorganisms are actively degrading hydrocarbons in these sediments. Hydrocarbon oxidation pathways operate alongside other deep seabed metabolisms such as sulfide oxidation, hydrogen oxidation, carbon fixation, fermentation and reductive dehalogenation. Upward migrated thermogenic hydrocarbons thus sustain diverse microbial communities with activities that affect subseafloor biogeochemical processes across the redox spectrum in deep sea cold seeps.

scholarly journals Geophysical imaging of permafrost in the SW Svalbard – the result of two high arctic expeditions to Spitsbergen

2020 ◽  
Author(s):  
Mariusz Majdanski ◽  
Artur Marciniak ◽  
Bartosz Owoc ◽  
Wojciech Dobiński ◽  
Tomasz Wawrzyniak ◽  
...  
Keyword(s):  
Surface Waves ◽  
Active Layer ◽  
High Arctic ◽  
The Arctic ◽  
Seismic Profiles ◽  
Frozen Ground ◽  
Near Surface ◽  
Seismic Processing ◽  
Reflection Seismic ◽  
Sea Coast

<p>The Arctic regions are the place of the fastest observed climate change. One of the indicators of such evolution are changes occurring in the glaciers and the subsurface in the permafrost. The active layer of the permafrost as the shallowest one is well measured by multiple geophysical techniques and in-situ measurements.</p><p>Two high arctic expeditions have been organized to use seismic methods to recognize the shape of the permafrost in two seasons: with the unfrozen ground (October 2017) and frozen ground (April 2018). Two seismic profiles have been designed to visualize the shape of permafrost between the sea coast and the slope of the mountain, and at the front of a retreating glacier. For measurements, a stand-alone seismic stations has been used with accelerated weight drop with in-house modifications and timing system. Seismic profiles were acquired in a time-lapse manner and were supported with GPR and ERT measurements, and continuous temperature monitoring in shallow boreholes.</p><p>Joint interpretation of seismic and auxiliary data using Multichannel analysis of surface waves, First arrival travel-time tomography and Reflection imaging show clear seasonal changes affecting the active layer where P-wave velocities are changing from 3500 to 5200 m/s. This confirms the laboratory measurements showing doubling the seismic velocity of water-filled high-porosity rocks when frozen. The same laboratory study shows significant (>10%) increase of velocity in frozen low porosity rocks, that should be easily visible in seismic.</p><p>In the reflection seismic processing, the most critical part was a detailed front mute to eliminate refracted arrivals spoiling wide-angle near-surface reflections. Those long offset refractions were however used to estimate near-surface velocities further used in reflection processing. In the reflection seismic image, a horizontal reflection was traced at the depth of 120 m at the sea coast deepening to the depth of 300 m near the mountain.</p><p>Additionally, an optimal set of seismic parameters has been established, clearly showing a significantly higher signal to noise ratio in case of frozen ground conditions even with the snow cover. Moreover, logistics in the frozen conditions are much easier and a lack of surface waves recorded in the snow buried geophones makes the seismic processing simpler.</p><p>Acknowledgements               </p><p>This research was funded by the National Science Centre, Poland (NCN) Grant UMO-2015/21/B/ST10/02509.</p>

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