scholarly journals The influence of methane fluxes on the sulfate/methane interface in sediments from the Rio Grande Cone Gas Hydrate Province, southern Brazil

2017 ◽  
Vol 47 (3) ◽  
pp. 369-381 ◽  
Author(s):  
Luiz Frederico Rodrigues ◽  
João Marcelo Ketzer ◽  
Rogerio Véscia Lourega ◽  
Adolpho Herbert Augustin ◽  
Gesiane Sbrissa ◽  
...  
Keyword(s):  
Gas Hydrate ◽  
Rio Grande ◽  
Methane Flux ◽  
Concentration Profiles ◽  
Southern Brazil ◽  
Methane Fluxes ◽  
Stratigraphic Position ◽  
Seismic Records ◽  
Pelotas Basin ◽  
Gas Chimneys

ABSTRACT: Much research has been published regarding the relation between major gas hydrate accumulations and the global carbon cycle. In this context, the determination of the sulfate/methane interface (SMI) depth is of primary importance in order to understand the dynamics of methane flux in the shallow section. This paper identifies the depth of the SMI in sediments based on sulfate and methane concentration profiles in cores recovered in the Rio Grande Cone Gas Hydrate Province, Pelotas Basin, southern Brazil. The shape of methane and sulfate concentration profiles in the sediments can be linked to the local methane flux rate as follows: (i) near linear, high upward-diffusing methane flux coupled with high sulfate diffusion from seawater; (ii) irregular, variable methane flux rates; and (iii) kink-type profile, which is indicative of variable rather than strictly high upward methane flux. The areas in which a high methane flux was identified are spatially associated with gas chimneys in sediments within pockmarks, whereas profiles with low methane flux are present in adjacent areas. These chimneys appear as acoustic blankings in seismic records and can therefore be mapped in subsurface. The wavy-like seismic reflection following the SMI coincides with the occurrence of authigenic carbonate nodules and concretions. In addition, high methane fluxes and the occurrence of concretions and nodules carbonates were correlated by stratigraphic position of the concretions bearing intervals and sulfate profiles.

Seasonal variability of natural methane seepage offshore Western Svalbard

2021 ◽  
Author(s):  
Manuel Moser ◽  
Knut Ola Dølven ◽  
Bénédicte Ferré
Keyword(s):  
Gas Hydrate ◽  
Bottom Water ◽  
Methane Flux ◽  
Mixing Rate ◽  
Bottom Water Temperature ◽  
Acoustic Data ◽  
Methane Seepage ◽  
Continental Shelves ◽  
Water Conditions ◽  
Methane Fluxes

<p>Natural methane seepage from the seafloor to the water column occurs worldwide in marine environments, from continental shelves to deep-sea basins. Depending on water depth, methane fluxes, and mixing rate of the seawater, methane may partially reach the atmosphere, where it could contribute to the global greenhouse effect. Estimates of annual marine methane fluxes are commonly calculated from hydro-acoustic data collected during single research surveys. These snapshot estimates neglect short (i.e., tide) and long (seasonal) variations.</p><p>Here we compare the seepage activity along the upper limit of the gas hydrate stability zone offshore Western Svalbard in August 2017 (bottom water temperature (BT) ~3.46°C), June 2020 (BT ~1.75°C), and November 2020 (BT ~3.96°C) using high-resolution vessel-based multibeam data. Our results complete annual methane flux estimates by Ferré et al. (2020) and confirm a significantly reduced seepage activity during the cold bottom-water conditions. We investigate short-term variation by comparing a 7.5 km long multibeam section at three phases of the lunar semidiurnal (M2) tide. We will discuss how these processes affect annual methane fluxes estimates offshore Svalbard and further Arctic methane fluxes estimates.</p><p>The research is part of the Centre for Arctic Gas Hydrate, Environment and Climate (CAGE) and is supported by the Research Council of Norway through its Centres of Excellence funding scheme grant No. 223259 and UiT.</p><p> </p><p>Ferré, B., Jansson, P. G., Moser, M., Serov, P., Portnov, A., Graves, C. A., et al. (2020). Reduced methane seepage from Arctic sediments during cold bottom-water conditions. Nat. Geosci. 13, 144–148. DOI: 10.1038/s41561-019-0515-3</p>

scholarly journals Post Miocene Ostracodes From Pelotas Basin, Southern Brazil. Taxonomy - Part I

1991 ◽  
Vol 18 (2) ◽  
pp. 138
Author(s):  
YVONE SANGUINETTI ◽  
LILIA DE ORNELLAS ◽  
JOÃO COIMBRA
Keyword(s):  
Rio Grande ◽  
Southern Brazil ◽  
Rio Grande Do Sul ◽  
Pelotas Basin

O estudo taxonômico dos ostracodes do intervalo Pós-Mioceno, contidos em sete perfurações, 2-MO-1-RS, 2-CI-1-RS, 2-CA-1-RS, 2-PS-1-RS, 2-PN-1-RS, 2-GA-1-RS e 2-GA-2-RS realizadas pela Petróleo Brasileiro S.A., PETROBRAS, na Bacia de Pelotas no Rio Grande do Sul, permitiu a determinação de Brasilicythere reticulispinosa gen. et sp. nov. e de nove outras espécies novas: Argenticytheretta levipunctata, A. variabilis, Caudites posdiagonalis, Ambostracon crucicostatum, Coquimba bertelsae, Bradleya pelotensis, Henryhowella rectangulata e H. spinosa. Permitiu, ainda, registrar a ocorrência de Cytheretta punctata, Coquimba tenuireticulata, Callistocythere litoralensis e C. marginalis. São apresentadas, também, duas espécies indeterminadas, Protocytheretta sp. e Quadracythere sp.

scholarly journals Post Miocene Ostracodes From Pelotas Basin, Southern Brazil. Taxonomy-Part II

1992 ◽  
Vol 19 (2) ◽  
pp. 155 ◽  
Author(s):  
YVONE SANGUINETTI ◽  
LILIA DE ORNELLAS ◽  
JOÃO COIMBRA ◽  
MARIA INÊS RAMOS
Keyword(s):  
Rio Grande ◽  
Southern Brazil ◽  
Rio Grande Do Sul ◽  
Pelotas Basin

O presente trabalho compreende o estudo taxonômico dos ostracodes pós-miocênicos contidos em perfurações realizadas pela Petróleo Brasileiro S. A. (PETROBRAS) na Bacia de Pelotas, no Rio Grande do Sul. São descritas seis espécies novas que ocorrem nas perfurações 2-CA-1-RS, 2-CI-1-RS, 2-MO-1-RS e 2-PN-1-RS: Cypris cassinensis, Cyprideis maxipunctata, C. mostardensis, C. posteroinflata, C. sparsopunctata e Costa riograndensis. É registrada a ocorrência de Cyprideis salebrosa, Perissocytheridea kroemmelbeini, e da espécie indeterminada Krithe sp.

scholarly journals Distinct methane-driven biogeochemical regimes in Arctic seafloor gas hydrate mounds

2020 ◽  
Author(s):  
Scott Klasek ◽  
Wei-Li Hong ◽  
Marta Torres ◽  
Stella Ross ◽  
Katelyn Hostetler ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Gas Hydrate ◽  
Methane Flux ◽  
High Arctic ◽  
Community Diversity ◽  
Sulfate Reducing ◽  
Recent Increase ◽  
Gas Seepage ◽  
Microbial Responses ◽  
Methane Fluxes

Abstract Archaea mediating anaerobic methane oxidation are key in preventing methane produced in marine sediments from reaching the hydrosphere; however, a complete understanding of how microbial communities in natural settings respond to changes in methane flux remains largely uncharacterized. We investigate microbial communities in gas hydrate-bearing seafloor mounds at Storfjordrenna, offshore Svalbard in the high Arctic, where distinct methane flux regimes ranging from steady-state dynamics, recent increase in subsurface diffusive flux, and gas seepage were identified. Populations of anaerobic methanotrophs and sulfate-reducing bacteria were highest at the seep site, while a recent increase in methane influx was associated with decreased community diversity. Despite high methane fluxes and methanotroph doubling times estimated at 5-9 months, microbial community responses were largely synchronous with the advancement of methane into shallower sediment horizons. Together, these provide a framework for interpreting subseafloor microbial responses to methane escape in a changing Arctic.

scholarly journals Methane flux and gas hydrate accumulations in the Sea of Okhotsk and their ecological aspects

2021 ◽  
Vol 43 (3) ◽  
Author(s):  
N.L. Sokolova ◽  
Yu. A. Telegin ◽  
A.I. Obzhirov
Keyword(s):  
Natural Gas ◽  
Gas Hydrates ◽  
Gas Hydrate ◽  
Sea Of Okhotsk ◽  
World Ocean ◽  
Direct Methods ◽  
Methane Flux ◽  
Methane Cycle ◽  
The Sea Of Okhotsk ◽  
Methane Fluxes

Methane is one of the important representatives of the organic substances in the atmosphere (for example, an increase of methane content in the atmosphere can affect enhancing the greenhouse effect). Gas hydrates are an essential part of links in the methane cycle and the accompanying fluxes of other gases. The research object in this paper is the Sea of Okhotsk, where gas hydrate fields and active submarine gas discharge areas were found. The study of methane fluxes is relevant both for the Sea of Okhotsk and the World Ocean. From 1984 to 2015, the background and anomalous methane fields were explored in the Sea of Okhotsk as a result of gas geochemical research carried out by scientists of the Gasgeochemistry Laboratory (POI FEB RAS). The flux of natural gas became stronger from the sources to the seafloor, from the seafloor to the water, and, finally, to the atmosphere due to renew of fault zones. Moreover, the amount of methane vents on the Sakhalin slope has increased from 2-3 vents to more than 400. The most representative hydroacoustic anomalies “flares” mapped direct methods study methane hydrates. The received outcomes indicate the urgency of the study of methane fluxes and the formation-dissociation mechanism of gas hydrates, and the influence of natural gas from hydrocarbon sources on the environment.

MICROBIAL COMMUNITIES AND DIFFERENTIAL METHANE FLUX IN ARCTIC GAS HYDRATE MOUNDS

2017 ◽  
Author(s):  
Stella C. Ross ◽  
◽  
Scott Klasek ◽  
Wei-Li Hong ◽  
Marta E. Torres ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Gas Hydrate ◽  
Methane Flux

A 12-year study of fungal infections in Rio Grande do Sul, Southern Brazil

2019 ◽  
Vol 36 (2) ◽  
pp. 55-60 ◽  
Author(s):  
Vanessa da Silva Fay ◽  
Tatiana Schäffer Gregianini ◽  
Ana Beatriz Gorini da Veiga ◽  
Stela Maris Bottin Gonçalves ◽  
Diana Mara Rodrigues ◽  
...  
Keyword(s):  
Fungal Infections ◽  
Rio Grande ◽  
Southern Brazil ◽  
Rio Grande Do Sul

Molecular Detection of Trypanosoma kaiowa in Tabanus triangulum (Diptera: Tabanidae) from the Coastal Plain of Rio Grande do Sul, Southern Brazil

2021 ◽  
Author(s):  
Gratchela D. Rodrigues ◽  
Eduardo Blodorn ◽  
Ândrio Zafalon-Silva ◽  
William Domingues ◽  
Roberta Marques ◽  
...  
Keyword(s):  
Coastal Plain ◽  
Molecular Detection ◽  
Rio Grande ◽  
Southern Brazil ◽  
Rio Grande Do Sul

scholarly journals Habitat use patterns of franciscana dolphins (Pontoporia blainvillei) off southern Brazil in relation to water depth

2009 ◽  
Vol 89 (5) ◽  
pp. 943-949 ◽  
Author(s):  
Daniel Danilewicz ◽  
Eduardo R. Secchi ◽  
Paulo H. Ott ◽  
Ignacio B. Moreno ◽  
Manuela Bassoi ◽  
...  
Keyword(s):  
Habitat Use ◽  
Rio Grande ◽  
Limiting Factors ◽  
Small Scale ◽  
Southern Brazil ◽  
Rio Grande Do Sul ◽  
Use Patterns ◽  
Management Procedures ◽  
By Catch ◽  
Pontoporia Blainvillei

The patterns of habitat use by the franciscana dolphins (Pontoporia blainvillei) along its distribution are poorly known. This study investigates the patterns of habitat use with respect to depth for 181 individuals of different age, size, gender and reproductive condition off Rio Grande do Sul, southern Brazil. The results reveal that franciscanas are very homogeneously distributed according to depth. Individuals from all lengths utilize nearly the entire range of depths of the surveyed area. Larger or older animals do not use deeper waters than younger animals, indicating that body size and age are not limiting factors for franciscanas that occupy deeper or offshore waters. Gestation seems to not cause a change in the distribution of females. Although the sex-ratio of the overall data did not vary from 1:1 in different depth intervals, a small-scale comparison between the northern and southern coast demonstrated the existence of some kind of sexual segregation. Franciscana by-catch in Rio Grande do Sul is not sustainable and it is agreed that management procedures are needed. Nevertheless, the available data on species distribution do not allow the designing of a protected area in order to minimize the by-catches of a particular sex/reproductive class.

scholarly journals Herpetofauna from an urban Pampa fragment in southern Brazil: composition, structure and conservation

Check List ◽  
2016 ◽  
Vol 12 (5) ◽  
pp. 1964
Author(s):  
Omar Machado Entiauspe-Neto ◽  
Tângela Denise Perleberg ◽  
Marco Antonio de Freitas
Keyword(s):  
Natural History ◽  
Urban Areas ◽  
Rio Grande ◽  
Southern Brazil ◽  
Rio Grande Do Sul ◽  
Faunal Composition ◽  
Diversity Patterns ◽  
Reptile Species ◽  
History Of ◽  
Composition Structure

Faunistic inventories regarding natural history of amphibians and reptiles are considered scarce and very little is known about their assemblages in urban areas; the Pampas morphoclimatic domain, also known as Uruguayan Savannah or Southern Grasslands, is also poorly known regarding their faunal composition.  Herein, we present a checklist of 16 amphibian and 20 reptile species recorded over a course of four years in the Instituto Federal de Educação, Ciências e Tecnologia, Câmpus Pelotas-Visconde da Graça, in Pelotas, Rio Grande do Sul, Brazil. We also present data on natural history and discuss conservation efforts to be undertaken in the area, in one of the least preserved and known Brazilian morphoclimatic domains, providing insights into urban herpetofaunal diversity patterns and showing the importance of modified areas in its conservation.

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