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 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 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.

The role of bacteria in the formation of cold seep carbonates: geological evidence from Monferrato (Tertiary, NW Italy)

1999 ◽  
Vol 126 (1-4) ◽  
pp. 253-270 ◽  
Author(s):  
Simona Cavagna ◽  
Pierangelo Clari ◽  
Luca Martire
Keyword(s):  
Cold Seep ◽  
Geological Evidence ◽  
Nw Italy

scholarly journals Mechanisms of dissolved and labile particulate iron supply to shelf waters and phytoplankton blooms off South Georgia, Southern Ocean

2018 ◽  
Vol 15 (16) ◽  
pp. 4973-4993 ◽  
Author(s):  
Christian Schlosser ◽  
Katrin Schmidt ◽  
Alfred Aquilina ◽  
William B. Homoky ◽  
Maxi Castrillejo ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Water Column ◽  
Mixed Layer ◽  
Surface Mixed Layer ◽  
Pore Waters ◽  
Phytoplankton Blooms ◽  
Faecal Pellets ◽  
South Georgia ◽  
Shelf Sediments ◽  
Bottom Waters

Abstract. The island of South Georgia is situated in the iron (Fe)-depleted Antarctic Circumpolar Current of the Southern Ocean. Iron emanating from its shelf system fuels large phytoplankton blooms downstream of the island, but the actual supply mechanisms are unclear. To address this, we present an inventory of Fe, manganese (Mn), and aluminium (Al) in shelf sediments, pore waters, and the water column in the vicinity of South Georgia, alongside data on zooplankton-mediated Fe cycling processes, and provide estimates of the relative dissolved Fe (DFe) fluxes from these sources. Seafloor sediments, modified by authigenic Fe precipitation, were the main particulate Fe source to shelf bottom waters as indicated by the similar Fe ∕ Mn and Fe ∕ Al ratios for shelf sediments and suspended particles in the water column. Less than 1 % of the total particulate Fe pool was leachable surface-adsorbed (labile) Fe and therefore potentially available to organisms. Pore waters formed the primary DFe source to shelf bottom waters, supplying 0.1–44 µmol DFe m−2 d−1. However, we estimate that only 0.41±0.26 µmol DFe m−2 d−1 was transferred to the surface mixed layer by vertical diffusive and advective mixing. Other trace metal sources to surface waters included glacial flour released by melting glaciers and via zooplankton egestion and excretion processes. On average 6.5±8.2 µmol m−2 d−1 of labile particulate Fe was supplied to the surface mixed layer via faecal pellets formed by Antarctic krill (Euphausia superba), with a further 1.1±2.2 µmol DFe m−2 d−1 released directly by the krill. The faecal pellets released by krill included seafloor-derived lithogenic and authigenic material and settled algal debris, in addition to freshly ingested suspended phytoplankton cells. The Fe requirement of the phytoplankton blooms ∼ 1250 km downstream of South Georgia was estimated as 0.33±0.11 µmol m−2 d−1, with the DFe supply by horizontal/vertical mixing, deep winter mixing, and aeolian dust estimated as ∼0.12 µmol m−2 d−1. We hypothesize that a substantial contribution of DFe was provided through recycling of biogenically stored Fe following luxury Fe uptake by phytoplankton on the Fe-rich shelf. This process would allow Fe to be retained in the surface mixed layer of waters downstream of South Georgia through continuous recycling and biological uptake, supplying the large downstream phytoplankton blooms.

scholarly journals Ecological and Evolutionary Processes Shaping Viral Genetic Diversity

Viruses ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 220 ◽  
Author(s):  
Cas Retel ◽  
Hanna Märkle ◽  
Lutz Becks ◽  
Philine Feulner
Keyword(s):  
Joint Effect ◽  
Genomic Variation ◽  
Genomic Diversity ◽  
Model Systems ◽  
Evolutionary Processes ◽  
Biological Communities ◽  
Generation Times ◽  
Inference Methods ◽  
Genetic Inference

The contemporary genomic diversity of viruses is a result of the continuous and dynamic interaction of past ecological and evolutionary processes. Thus, genome sequences of viruses can be a valuable source of information about these processes. In this review, we first describe the relevant processes shaping viral genomic variation, with a focus on the role of host–virus coevolution and its potential to give rise to eco-evolutionary feedback loops. We further give a brief overview of available methodology designed to extract information about these processes from genomic data. Short generation times and small genomes make viruses ideal model systems to study the joint effect of complex coevolutionary and eco-evolutionary interactions on genetic evolution. This complexity, together with the diverse array of lifetime and reproductive strategies in viruses ask for extensions of existing inference methods, for example by integrating multiple information sources. Such integration can broaden the applicability of genetic inference methods and thus further improve our understanding of the role viruses play in biological communities.

scholarly journals Structured report data can be used to develop deep learning algorithms: a proof of concept in ankle radiographs

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Daniel Pinto dos Santos ◽  
Sebastian Brodehl ◽  
Bettina Baeßler ◽  
Gordon Arnhold ◽  
Thomas Dratsch ◽  
...  
Keyword(s):  
Deep Learning ◽  
Language Processing ◽  
Learning Algorithms ◽  
Area Under The Curve ◽  
Learning Networks ◽  
Report Data ◽  
Structured Reports ◽  
Picture Archiving And Communication ◽  
Using Data

Abstract Background Data used for training of deep learning networks usually needs large amounts of accurate labels. These labels are usually extracted from reports using natural language processing or by time-consuming manual review. The aim of this study was therefore to develop and evaluate a workflow for using data from structured reports as labels to be used in a deep learning application. Materials and methods We included all plain anteriorposterior radiographs of the ankle for which structured reports were available. A workflow was designed and implemented where a script was used to automatically retrieve, convert, and anonymize the respective radiographs of cases where fractures were either present or absent from the institution’s picture archiving and communication system (PACS). These images were then used to retrain a pretrained deep convolutional neural network. Finally, performance was evaluated on a set of previously unseen radiographs. Results Once implemented and configured, completion of the whole workflow took under 1 h. A total of 157 structured reports were retrieved from the reporting platform. For all structured reports, corresponding radiographs were successfully retrieved from the PACS and fed into the training process. On an unseen validation subset, the model showed a satisfactory performance with an area under the curve of 0.850 (95% CI 0.634–1.000) for detection of fractures. Conclusion We demonstrate that data obtained from structured reports written in clinical routine can be used to successfully train deep learning algorithms. This highlights the potential role of structured reporting for the future of radiology, especially in the context of deep learning.

Understanding the role of soil erosion on co 2 -c loss using 13 c isotopic signatures in abandoned Mediterranean agricultural land

2016 ◽  
Vol 550 ◽  
pp. 330-336 ◽  
Author(s):  
Agata Novara ◽  
Saskia Keesstra ◽  
Artemio Cerdà ◽  
Paulo Pereira ◽  
Luciano Gristina
Keyword(s):  
Soil Erosion ◽  
Agricultural Land ◽  
Isotopic Signatures

New data on recently described Chilean trophonines (Gastropoda: Muricidae), description of a new species and notes of their occurrence at a cold seep site

Zootaxa ◽  
2006 ◽  
Vol 1222 (1) ◽  
pp. 53 ◽  
Author(s):  
ROLAND HOUART ◽  
JAVIER SELLANES
Keyword(s):  
New Species ◽  
Type Species ◽  
Cold Seep ◽  
Central Chile ◽  
Methane Seepage ◽  
South Central ◽  
New Material ◽  
A New Species ◽  
Seep Site

Additional specimens of three newly described Chilean species of Trophon s.l. Monfort, 1810 have been dredged recently off south-central Chile, and we here list the new data and illustrate the radulae. Another species, Trophon wilhelmensis Ramírez-Bohme, 1981, is combined with Coronium Simone, 1996. Pagodula concepcionensis n. sp. is described and another species remains unidentified. A type species is designated for Pagodula Monterosato, 1884. Part of the new material comes from an area of methane seepage located northwest of the Bay of Concepción, from 726 to 930 m depth. Many drilled valves of two species of chemosymbiotic clams (Calyptogena gallardoi Sellanes & Krylova, 2005 and Thyasira methanophila Oliver & Sellanes, 2005) were also obtained at the seep site. We assume that this holes document attacks of this trophonines to the clams.

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