scholarly journals Methane concentration in water column and in pore water of a coastal lagoon (Cabiúnas lagoon, Macaé, RJ, Brazil)

2004 ◽  
Vol 47 (2) ◽  
pp. 301-308 ◽  
Author(s):  
André Luiz dos Santos Fonseca ◽  
Murilo Minello ◽  
Claudio Cardoso Marinho ◽  
Francisco de Assis Esteves
Keyword(s):  
Water Column ◽  
Pore Water ◽  
Coastal Lagoon ◽  
Aquatic Macrophytes ◽  
Methane Concentration ◽  
Typha Domingensis ◽  
Littoral Region ◽  
High Influence

The aim of this study was to evaluate methane concentration in water column and pore water at limnetic and littoral regions of a coastal lagoon. At the littoral region samples were taken from three monospecific macrophytes stands (Typha domingensis, Eleocharis interstincta and Potamogeton stenostachys). The methane concentration in the pore water at the littoral region was higher than the concentration found at the limnetic region in each fraction of the sediment. The higher methane concentration in the superficial fraction of the sediment (0-2 cm) was shown at the P. stenostachys stand (3.7 mM). It was the only significantly different (p<0.05) from the limnetic region. The pore water methane concentration increased with depth at the aquatic macrophytes stands. The methane concentration in the water column did not vary significantly among the sampling sites (p>0.05). It could be concluded that there was a high influence of aquatic macrophytes on the pore water methane concentration.

scholarly journals Vertical segregation of two species of Hyphessobrycon(Characiformes: Characidae) in the Cabiúnas coastal lagoon, southeastern Brazil

2008 ◽  
Vol 6 (4) ◽  
pp. 683-688 ◽  
Author(s):  
Sergio M. Q. Lima ◽  
André A. Cunha ◽  
Jorge I. Sánchez-Botero ◽  
Érica P. Caramaschi
Keyword(s):  
Water Column ◽  
Coastal Lagoon ◽  
Rio De Janeiro ◽  
Predation Pressure ◽  
Southeastern Brazil ◽  
Congeneric Species ◽  
Nutrient Distribution ◽  
Vertical Segregation ◽  
Macrophyte Cover

Segregation in the use of the water column by two congeneric species of Characidae, Hyphessobrycon bifasciatus and H. luetkenii, was investigated through underwater observations in the Cabiúnas coastal lagoon in northeastern Rio de Janeiro, Brazil. The use of the water column by the two species differed significantly. Hyphessobrycon luetkenii occupied mainly the uppermost stratum, with 79% of the observations within 20 cm of the surface; whereas H. bifasciatus was more common between 20 cm and 40 cm below the surface (55% of the observations). Predation pressure, macrophyte cover and nutrient distribution may influence this vertical segregation.

scholarly journals Correlation of <i>Virgulinella fragilis</i> Grindell & Collen (benthic foraminiferid) with near-anoxia in Aso-kai Lagoon, central Japan

2005 ◽  
Vol 24 (2) ◽  
pp. 159-167 ◽  
Author(s):  
Hiroyuki Takata ◽  
Koji Seto ◽  
Saburo Sakai ◽  
Satoshi Tanaka ◽  
Katsumi Takayasu
Keyword(s):  
Cluster Analysis ◽  
Pore Water ◽  
Coastal Lagoon ◽  
Bottom Water ◽  
Low Oxygen ◽  
Central Japan ◽  
Reactive Iron ◽  
Predominant Species ◽  
Oxygen Conditions ◽  
Cluster A

Abstract. The distribution of Virgulinella fragilis and the hydro-environment of Aso-kai Lagoon, central Japan, were studied to clarify the foraminifer’s adaptation to low-oxygen conditions. The hypolimnion of the lagoon is oxygen-poor during much of the year. Two faunas (A and B) are recognized, based on cluster analysis. Cluster A fauna consists of species common in brackish lagoons, such as the genera Trochammina and Ammonia, and occurs in seasonally oxygenated waters. Virgulinella fragilis, the predominant species of Cluster B fauna, dominates the central part of the lagoon. This species can tolerate more severe oxygen deficiencies than the typical brackish foraminifers (e.g. Trochammina spp.) and can adapt to long periods of oxygen-poor conditions in coastal lagoon environments, as well as in pelagic to hemi-pelagic settings. In order to survive in the near-anoxia of Aso-kai Lagoon, V. fragilis may have adapted to environments in which little reactive iron is available in the sediment, leaving pore-water and bottom-water sulphide available for symbionts, or may utilize sulphur denitrification processes.

On the lack of widespread bottom simulating reflectors in the Mediterranean Basin

2021 ◽  
Author(s):  
Cristina Corradin ◽  
Angelo Camerlenghi ◽  
Michela Giustiniani ◽  
Umberta Tinivella ◽  
Claudia Bertoni
Keyword(s):  
Water Column ◽  
Pore Water ◽  
Mediterranean Basin ◽  
Stability Field ◽  
Hydrocarbon Gases ◽  
Wide Range ◽  
Bottom Simulating Reflectors ◽  
Messinian Evaporites ◽  
The Mediterranean ◽  
The Mediterranean Basin

&lt;p&gt;In the Mediterranean Basin, gas hydrate bottom simulating reflectors (BSR) are absent, with very few and spatially limited exceptions occurring in Eastern Mediterranean mud volcanoes and in the Nile deep sea fan. This is in spite of widespread occurrence of hydrocarbon gases in the subsurface, mainly biogenic methane, from a wide range of stratigraphic intervals.&lt;br&gt;In this study we model the methane hydrate stability field using all available information on DSDP and ODP boreholes in the Western Mediterranean and in the Levant Basin, including the downhole changes of pore water salinity. The models take into account the consequent pore water density changes and use known estimates of geothermal gradient. None of the drilled sites were located on seismic profiles in which a BSR is present.&lt;br&gt;The modelled base of the stability field of methane hydrates is located variably within, below, or even above the drilled sedimentary section (the latter case implies that it is located in the water column). We discuss the results in terms of geodynamic environments, areal distribution of Messinian evaporites, upward ion diffusion from Messinian evaporites, organic carbon content, and the peculiar thermal structure of the Mediterranean water column. &lt;br&gt;We conclude that the cumulative effects of geological and geochemical environments make the Mediterranean Basin a region that is unfavorable to the existence of BSRs in the seismic record, and most likely to the existence of natural gas hydrates below the seabed.&lt;br&gt;&lt;br&gt;&lt;/p&gt;

Biogeochemical processes in the Barents sea

2021 ◽  
pp. 287-306
Author(s):  
A.Yu. Lein ◽  
◽  
A.S. Savvichev ◽  
Keyword(s):  
Organic Matter ◽  
Water Column ◽  
Methane Concentration ◽  
Barents Sea ◽  
Biogeochemical Processes ◽  
Total Abundance ◽  
The North ◽  
The Barents Sea ◽  
Continental Origin ◽  
Biomass Of Microorganisms

Biogeochemical processes involving microorganisms play an important role in marine sedimentogenesis. The study of biogeochemical processes in the Barents Sea was carried out from 1997 with interruptions until 2019. Using a complex of geological-geochemical, microbiological, radioisotope and stable isotope methods, it was possible to obtain a quantitative estimate of the total abundance and biomass of microorganisms, rates of biogeochemical processes, methane content and organic matter suspended. In the course of work in four expeditions, it was found that in the surface (0–10 m) water column south of 74° N the magnitude of the total abundance and the biomass of microorganisms increased by 2019 by about 5 times compared to 1998. To the north, in colder waters, the total abundance and the biomass of organisms were lower than in the southern region of the sea. The methane concentration in the surface layer of the water column at the border with the atmosphere did not change much for 20 years (1976–1997) and increased noticeably from 1997 to 2017, from 3.3 to 15.8 nM. The increase in FFM, the biomass of organisms and the concentration of methane in the water column is associated with the melting of glaciers, with the release of organic matter of continental origin released from ice into the water. The results of the work indicate changes in the ecosystem of the Barents Sea.

scholarly journals Seasonal dynamics of methane in the water column of two subtropical lakes differing in trophic status

2009 ◽  
Vol 69 (2) ◽  
pp. 281-287 ◽  
Author(s):  
CC. Marinho ◽  
C. Palma Silva ◽  
EF. Albertoni ◽  
CR. Trindade ◽  
FA. Esteves
Keyword(s):  
Water Column ◽  
Methane Concentration ◽  
Trophic Status ◽  
Rio Grande ◽  
Aquatic Systems ◽  
Subtropical Lakes ◽  
Production And Consumption ◽  
Higher Temperature ◽  
Methane Concentrations ◽  
Methane Dynamics

Alterations in methane concentration in the water column of aquatic systems is closely linked to the processes of production and consumption of this gas, i.e., methanogenesis and methanotrophy respectively. The aim of this research is to evaluate methane dynamics through diurnal variation in the concentration of this gas in the water column of two lakes differing in trophic status at the campus of Fundação Universidade do Rio Grande (FURG). In two sampling periods (November 2001 and July 2002) methane concentrations in the water column were significantly higher (3.66 and 0.41 μmoles.L-1, respectively) at Lago dos Biguás, with mesoeutrophic features when related to Lago Polegar (1.43 and 0.19 μmoles.L-1, respectively) which has oligotrophic features. The higher methane concentrations were detected in November 2001 when higher temperature was also detected. The results highlighted the importance of trophic status as well as seasonality for the methane dynamics in these ecosystems.

scholarly journals Effects of surface loading on groundwater flow and skeletal deformation

2019 ◽  
Vol 20 (1) ◽  
pp. 287-295
Author(s):  
Qingyang Yu ◽  
Chengbin Wang ◽  
Zhenxue Dai ◽  
Xinglong Ran ◽  
Mohammad Amin Amooie ◽  
...  
Keyword(s):  
Water Column ◽  
Pore Water ◽  
Land Subsidence ◽  
Water Storage ◽  
Column Height ◽  
Surface Load ◽  
Surface Loading ◽  
Water Head ◽  
Storage Rate ◽  
Water Column Height

Abstract This paper proposes a relationship for the physics and mechanics constants of porous media related to water storage rate and ground settlement under a surface load variation condition. This provides the basis for accurate calculation of ground subsidence. Traditional equations for vertical deformation, groundwater flow and land subsidence due to surface loading were developed using Jacob's assumptions. This paper derives a skeletal elastic specific storage rate. The new deformation and flow equations are similar to the traditional ones based on Jacob's assumptions except that the pore-water head in the traditional equations corresponds with the margin between the pore-water head and the water-column height given in the proposed equations representing the surface load. The analysis show that increasing the surface loading leads to land subsidence, rise in pore-water head and decrease in elastic water storage capacity. The maximum subsidence is equivalent to the subsidence triggered by lowering the water head to the equivalent water column height. The maximum rise of the water head is also equal to the equivalent water column height. The maximum water released to a specific volume of porous medium is close to that resulting from reduction in the water head by the equivalent column height.

Molecular differences between water column and sediment pore water SPE-DOM in ten Swedish boreal lakes

2020 ◽  
Vol 170 ◽  
pp. 115320 ◽  
Author(s):  
Juliana Valle ◽  
Mourad Harir ◽  
Michael Gonsior ◽  
Alex Enrich-Prast ◽  
Philippe Schmitt-Kopplin ◽  
...  
Keyword(s):  
Water Column ◽  
Pore Water ◽  
Boreal Lakes ◽  
Sediment Pore Water
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