USGS Science⌕ Search

SEARCH · USGS Science

Results for “Anaerobe”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14Linked to original sources
USGS1987

Effects of cover materials on leaching of constituents from dolomitic lead mine tailings

Five raised-bed test plots were used to study the effects of cover materials on the leaching of constituents from dolomitic Pb mine tailings over a 2-yr period. The cover materials studied were a fertilizer and seed mixture, anaerobically digested sewage sludge, loam and sod, and fallen leaves from silver maples ( Acer Saccharinum ); one plot was not covered. Fresh leachates and receiving pool waters were analyzed for ten metals, Si, P, inorganic anions, filterable organic carbon (FOC), and alkalinity. The mixture of fertilizer and seed decreased leaching of Pb and Zn during the first year. The leaf cover increased leaching of Pb during both years; this effect decreased as the leaves weathered. Sludge caused some increase in Pb leaching during the first year, and increased Cd leaching during both years. Concentrations of most leachate constituents decreased, and pH increased in the receiving pools. Concentrations of Pb remained higher in the receiving pool for the leaf-covered plot than in the other pools. Increases in leaching of Pb and Cd with a sludge cover were moderate, and the ability of the material to support plant growth on the tailings suggested that it may be a good medium for inducing growth of vegetative cover on the dolomitic tailings. Other organic materials may cause pronounced increase in the concentration of toxic trace metals in leachate from the tailings.

Missouri↗
USGS2000

Geochemical investigations by the U.S. Geological Survey on uranium mining, milling, and environmental restoration

Recent research by the U.S. Geological Survey has characterized contaminant sources and identified important geochemical processes that influence transport of radionuclides from uranium mining and milling wastes. 1) Selective extraction studies indicated that alkaline earth sulfates and hydrous ferric oxides are important hosts of 226 Ra in uranium mill tailings. The action of sulfate-reducing and ironreducing bacteria on these phases was shown to enhance release of radium, and this adverse result may temper decisions to dispose of uranium mill tailings in anaerobic environments. 2) Field studies have shown that although surface-applied sewage sludge/wood chip amendments aid in revegetating pyritic spoil, the nitrogen in sludge leachate can enhance pyrite oxidation, acidification of groundwater, and the consequent mobilization of metals and radionuclides. 3) In a U.S. Environmental Protection Agencyfunded study, three permeable reactive barriers consisting of phosphate-rich material, zero-valent iron, or amorphous ferric oxyhydroxide have been installed at an abandoned uranium upgrader facility near Fry Canyon, UT. Preliminary results indicate that each of the permeable reactive barriers is removing the majority of the uranium from the groundwater. 4) Studies on the geochemistry of rare earth elements as analogues for actinides such as uranium and thorium in acid mine drainage environments indicate high mobility under acid-weathering conditions but measurable attenuation associated with iron and aluminum colloid formation. Mass balances from field and laboratory studies are being used to quantify the amount of attenuation. 5) A field study in Colorado demonstrated the use of 234 U/ 238 U isotopic ratio measurements to evaluate contamination of shallow groundwater with uranium mill effluent.

Utah↗
USGS1990

Transformation of Monoaromatic hydrocarbons to organic acids in anoxic groundwater environment

The transformation of benzene and a series of alkylbenzenes was studied in anoxic groundwater of a shallow glacial-outwash aquifer near Bemidji, Minnesota, U.S.A. Monoaromatic hydrocarbons, the most water-soluble components of crude oil, were transported downgradient of an oil spill, forming a plume of contaminated groundwater. Organic acids that were not original components of the oil were identified in the anoxic groundwater. The highest concentrations of these oxidized organic compounds were found in the anoxic plume where a decrease in concentrations of structurally related alkylbenzenes was observed. These results suggest that biological transformation of benzene and alkylbenzenes to organic acid intermediates may be an important attenuation process in anoxic environments. The transformation of a complex mixture of hydrocarbons to a series of corresponding oxidation products in an anoxic subsurface environment provides new insight into in situ anaerobic degradation processes.

Minnesota↗
USGS2000

Influence of dissimilatory metal reduction on fate of organic and metal contaminants in the subsurface

Geobacter become dominant members of the microbial community when Fe(III)-reducing conditions develop as the result of organic contamination, or when Fe(III) reduction is artificially stimulated. These results suggest that further understanding of the ecophysiology of Geobacter species would aid in better prediction of the natural attenuation of organic contaminants under anaerobic conditions and in the design of strategies for the bioremediation of subsurface metal contamination.

Hydrogeology Journal↗
USGS1996

Geovibrio ferrireducens, a phylogenetically distinct dissimilatory Fe(III)-reducing bacterium

A new, phylogenetically distinct, dissimilatory, Fe(III)-reducing bacterium was isolated from surface sediment of a hydrocarbon-contaminated ditch. The isolate, designated strain PAL-1, was an obligately anaerobic, non-fermentative, motile, gram-negative vibrio. PAL-1 grew in a defined medium with acetate as electron donor and ferric pyrophosphate, ferric oxyhydroxide, ferric citrate, Co(III)-EDTA, or elemental sulfur as sole electron acceptor. PAL-1 also used proline, hydrogen, lactate, propionate, succinate, fumarate, pyruvate, or yeast extract as electron donors for Fe(III) reduction. It is the first bacterium known to couple the oxidation of an amino acid to Fe(III) reduction. PAl-1 did not reduce oxygen, Mn(IV), U(VI), Cr(VI), nitrate, sulfate, sulfite, or thiosulfate with acetate as the electron donor. Cell suspensions of PAL-1 exhibited dithionite-reduced minus air-oxidized difference spectra that were characteristic of c -type cytochromes. Analysis of the 16S rRNA gene sequence of PAL-1 showed that the strain is not related to any of the described metal-reducing bacteria in the Proteobacteria and, together with Flexistipes sinusarabici, forms a separate line of descent within the Bacteria. Phenotypically and phylogenetically, strain PAl-1 differs from all other described bacteria, and represents the type strain of a new genus and species, Geovibrio ferrireducens .

Archives of Microbiology↗
USGS2014

Insights into biodegradation through depth-resolved microbial community functional and structural profiling of a crude-oil contaminant plume

Small-scale geochemical gradients are a key feature of aquifer contaminant plumes, highlighting the need for functional and structural profiling of corresponding microbial communities on a similar scale. The purpose of this study was to characterize the microbial functional and structural diversity with depth across representative redox zones of a hydrocarbon plume and an adjacent wetland, at the Bemidji Oil Spill site. A combination of quantitative PCR, denaturing gradient gel electrophoresis, and pyrosequencing were applied to vertically sampled sediment cores. Levels of the methanogenic marker gene, methyl coenzyme-M reductase A (mcrA), increased with depth near the oil body center, but were variable with depth further downgradient. Benzoate degradation N (bzdN) hydrocarbon-degradation gene, common to facultatively anaerobic Azoarcus spp., was found at all locations, but was highest near the oil body center. Microbial community structural differences were observed across sediment cores, and bacterial classes containing known hydrocarbon degraders were found to be low in relative abundance. Depth-resolved functional and structural profiling revealed the strongest gradients in the iron-reducing zone, displaying the greatest variability with depth. This study provides important insight into biogeochemical characteristics in different regions of contaminant plumes, which will aid in improving models of contaminant fate and natural attenuation rates.

Minnesota↗
USGS1999

Distribution of microbial physiologic types in an aquifer contaminated by crude oil

We conducted a plume-scale study of the microbial ecology in the anaerobic portion of an aquifer contaminated by crude-oil compounds. The data provide insight into the patterns of ecological succession, microbial nutrient demands, and the relative importance of free-living versus attached microbial populations. The most probable number (MPN) method was used to characterize the spatial distribution of six physiologic types: aerobes, denitrifiers, iron-reducers, heterotrophic fermenters, sulfate-reducers, and methanogens. Both free-living and attached numbers were determined over a broad cross-section of the aquifer extending horizontally from the source of the plume at a nonaqueous oil body to 66 m downgradient, and vertically from above the water table to the base of the plume below the water table. Point samples from widely spaced locations were combined with three closely spaced vertical profiles to create a map of physiologic zones for a cross-section of the plume. Although some estimates suggest that less than 1% of the subsurface microbial population can be grown in laboratory cultures, the MPN results presented here provide a comprehensive qualitative picture of the microbial ecology at the plume scale. Areas in the plume that are evolving from iron-reducing to methanogenic conditions are clearly delineated and generally occupy 25-50% of the plume thickness. Lower microbial numbers below the water table compared to the unsaturated zone suggest that nutrient limitations may be important in limiting growth in the saturated zone. Finally, the data indicate that an average of 15% of the total population is suspended.

Microbial Ecology↗
USGS2023

Functional gene composition and metabolic potential of deep-sea coral-associated microbial communities

Over the past decade, an abundance of 16S rRNA gene surveys have provided microbiologists with data regarding the prokaryotes present in a coral-associated microbial community. Functional gene studies that provide information regarding what those microbes might do are fewer, particularly for non-tropical corals. Using the GeoChip 5.0S microarray, we present a functional gene study of microbiomes from five species of cold-water corals collected from depths of 296–1567 m. These species included two octocorals, Acanthogorgia aspera and Acanthogorgia spissa , and three stony corals: Desmophyllum dianthus , Desmophyllum pertusum (formerly Lophelia pertusa ), and Enallopsammia profunda . A total of 24,281 gene sequences (representing different microbial taxa) encoding for 383 functional gene families and representing 9 metabolic gene categories were identified. Gene categories included metabolism of carbon, nitrogen, phosphorus, and sulfur, as well as virulence, organic remediation, metal homeostasis, secondary metabolism and phylogeny. We found that microbiomes from Acanthogorgia spp. were the most functionally distinct but also least diverse compared against those from stony corals. Desmophyllum spp. microbiomes were more similar to each other than to E. profunda . Of 383 total gene families detected in this study, less than 20% were significantly different among these deep-water coral species. Similarly, out of 59 metabolic sub-categories for which we were able to make a direct comparison to microbiomes of tropical corals, only 7 were notably different: anaerobic ammonium oxidation (anammox), chitin degradation, and dimethylsulfoniopropionate (DMSP) degradation, all of which had higher representations in deep-water corals; and chromium homeostasis/resistance, copper homeostasis/resistance, antibiotic resistance, and methanogenesis, all of which had higher representation in tropical corals. This implies a broad-scale convergence of the microbial functional genes present within the coral holobiont, independent of coral species, depth, symbiont status, and morphology.

Coral Reefs↗
USGS2012

Desulfohalophilus alkaliarsenatis gen. nov., sp. nov., an extremely halophilic sulfate- and arsenate-respiring bacterium from Searles Lake, California

A haloalkaliphilic sulfate-respiring bacterium, strain SLSR-1, was isolated from a lactate-fed stable enrichment culture originally obtained from the extreme environment of Searles Lake, California. The isolate proved capable of growth via sulfate-reduction over a broad range of salinities (125–330 g/L), although growth was slowest at salt-saturation. Strain SLSR-1 was also capable of growth via dissimilatory arsenate-reduction and displayed an even broader range of salinity tolerance (50–330 g/L) when grown under these conditions. Strain SLSR-1 could also grow via dissimilatory nitrate reduction to ammonia. Growth experiments in the presence of high borate concentrations indicated a greater sensitivity of sulfate-reduction than arsenate-respiration to this naturally abundant anion in Searles Lake. Strain SLSR-1 contained genes involved in both sulfate-reduction ( dsrAB ) and arsenate respiration ( arrA ). Amplicons of 16S rRNA gene sequences obtained from DNA extracted from Searles Lake sediment revealed the presence of close relatives of strain SLSR-1 as part of the flora of this ecosystem despite the fact that sulfate-reduction activity could not be detected in situ. We conclude that strain SLSR-1 can only achieve growth via arsenate-reduction under the current chemical conditions prevalent at Searles Lake. Strain SLSR-1 is a deltaproteobacterium in the family Desulfohalobiacea of anaerobic, haloalkaliphilic bacteria, for which we propose the name Desulfohalophilus alkaliarsenatis gen. nov., sp. nov.

California↗
USGS2008

Geochemical characterisation of seepage and drainage water quality from two sulphide mine tailings impoundments: Acid mine drainage versus neutral mine drainage

Seepage water and drainage water geochemistry (pH, EC, O 2 , redox, alkalinity, dissolved cations and trace metals, major anions, total element concentrations) were studied at two active sulphide mine tailings impoundments in Finland (the Hitura Ni mine and Luikonlahti Cu mine/talc processing plant). The data were used to assess the factors influencing tailings seepage quality and to identify constraints for water treatment. Changes in seepage water quality after equilibration with atmospheric conditions were evaluated based on geochemical modelling. At Luikonlahti, annual and seasonal changes were also studied. Seepage quality was largely influenced by the tailings mineralogy, and the serpentine-rich, low sulphide Hitura tailings produced neutral mine drainage with high Ni. In contrast, drainage from the high sulphide, multi-metal tailings of Luikonlahti represented typical acid mine drainage with elevated contents of Zn, Ni, Cu, and Co. Other factors affecting the seepage quality included weathering of the tailings along the seepage flow path, process water input, local hydrological settings, and structural changes in the tailings impoundment. Geochemical modelling showed that pH increased and some heavy metals were adsorbed to Fe precipitates after net alkaline waters equilibrated with the atmosphere. In the net acidic waters, pH decreased and no adsorption occurred. A combination of aerobic and anaerobic treatments is proposed for Hitura seepages to decrease the sulphate and metal loading. For Luikonlahti, prolonged monitoring of the seepage quality is suggested instead of treatment, since the water quality is still adjusting to recent modifications to the tailings impoundment.

Mine Water and the Environment↗
USGS2009

Description of Tessaracoccus profundi sp.nov., a deep-subsurface actinobacterium isolated from a Chesapeake impact crater drill core (940 m depth)

A novel actinobacterium, designated CB31 T , was isolated from a 940 m depth sample of a drilling core obtained from the Chesapeake meteor impact crater. The strain was isolated aerobically on R2A medium agar plates supplemented with NaCl (20 g l -1 ) and MgCl 2 ???6H 2 O (3 g l -1 ). The colonies were circular, convex, smooth and orange. Cells were slightly curved, rod-shaped in young cultures and often appeared in pairs. In older cultures cells were coccoid. Cells stained Gram-positive, were non-motile and did not form endospores. The diagnostic diamino acid of the peptidoglycan was ll-diaminopimelic acid. The polar lipids included phosphatidylglycerol, diphosphatidglycerol, four different glycolipids, two further phospholipids and one unidentified lipid. The dominant menaquinone was MK-9(H 4 ) (70%). The major cellular fatty acid was anteiso C15:0 (83%). The DNA G + C content was 68 mol%. The strain grew anaerobically by reducing nitrate to nitrite or by fermenting glucose. It was catalase positive and oxidase negative. It grew between 10 and 45??C, with an optimum between 35 and 40??C. The pH range for growth was 5.7-9.3, with an optimum at pH 7.5. The closest phylogenetic neighbors based on 16S rRNA gene sequence identity were members of the genus Tessaracoccus (95-96% identity). On the basis of phenotypic and phylogenetic distinctiveness, strain CB31 T is considered to represent a novel species of the genus Tessaracoccus, for which we propose the name Tessaracoccus profundi sp. nov.. It is the first member of this genus that has been isolated from a deep subsurface environment. The type strain is CB31 T (=NCIMB 14440 T = DSM 21240 T ). ?? 2009 Springer Science+Business Media B.V.

Antonie van Leeuwenhoek↗
USGS2005

Part 1: Vadose-zone column studies of toluene (enhanced bioremediation) in a shallow unconfined aquifer

The objectives of the laboratory study described in this paper were (1) to determine the effectiveness of four nutrient solutions and a control in stimulating the microbial degradation of toluene in the unsaturated zone as an alternative to bioremediation methodologies such as air sparging, in situ vitrification, or others (Part I), and (2) to compare the effectiveness of the addition of the most effective nutrient solution from Part I (modified Hoagland type, nitrate-rich) and hydrogen peroxide (H 2 O 2 ) on microbial degradation of toluene for repeated, simulated spills in the unsaturated zone (Part II). For Part 1, fifteen columns (30-cm diameter by 150-cm height), packed with air-dried, 0.25-mm, medium-fine sand, were prepared to simulate shallow unconfined aquifer conditions. Toluene (10 mL) was added to the surface of each column, and soil solution and soil gas samples were collected from the columns every third day for 21 days. On day 21, a second application of toluene (10 mL) was made, and the experiment was run for another 21 days. Solution 4 was the most effective for microbial degradation in Part I. For Part II, three columns were designated nutrient-rich 3-day toluene columns and received toluene injections every 3 days; three columns were designated as nutrient-rich 7-day columns and received toluene injections every 7 days; and two columns were used as controls to which no nutrient was added. As measured by CO 2 respiration, the initial benefits for aerobic organisms from the O 2 enhancement were sustained by the bacteria for only a short period of time (about 8 days). Degradation benefits from the nutrient solution were sustained throughout the experiment. The O 2 and nutrient-enhanced columns degraded significantly more toluene than the control columns when simulating repeated spills onto the unsaturated zone, and demonstrated a potentially effective in situ bioremediation technology when used immediately or within days after a spill. The combined usage of H 2 O 2 and nitrate-rich nutrients served to effectively maximize natural aerobic and anaerobic metabolic processes that biodegrade hydrocarbons in petroleum-contaminated media. Applications of this technology in the field may offer economical advantages to other, more intrusive abatement technologies.

Water, Air, & Soil Pollution↗
USGS2014

Marsh soils as potential sinks for Bacteroides fecal indicator bacteria, Waccamaw National Wildlife Refuge, Georgetown, SC, USA

A soil core collected in a tidal freshwater marsh in the Waccamaw National Wildlife Refuge (Georgetown, SC) exuded a particularly strong odor of cow manure upon extrusion. In order to test for manure and determine its provenance, we carried out microbial source tracking using DNA markers for Bacteroides, a noncoliform, anaerobic bacterial group that represents a broad group of the fecal population. Three core sections from 0-3 cm, 9-12 cm and 30-33 were analyzed for the presence of Bacteroides. The ages of core sediments were estimated using 210Pb and 137Cs dating. All three core sections tested positive for Bacteroides DNA markers related to cow or deer feces. Because cow manure is stockpiled, used as fertilizer, and a source of direct contamination in the Great Pee Dee River/Winyah Bay watershed, it is very likely the source of the Bacteroides that was deposited on the marsh. The mid-points of the core sections were dated as follows: 0-3 cm: 2009; 9-12 cm: 1999, and 30-33 cm: 1961. The presence of Bacteroides at different depths/ages in the soil profile indicates that soils in tidal freshwater marshes are, at the least, capable of being short-term sinks for Bacteroides and, may have the potential to be long-term sinks of stable, naturalized populations.

South Carolina↗
USGS2023

Attenuation of acid rock drainage by stimulating sulfur-reducing bacteria

Iron-sulfide minerals found in shale formations are stable under anaerobic conditions. However, in the presence of oxygen and water, acid-loving chemolithotrophic bacteria can transform the iron-sulfide minerals into a toxic solution of sulfuric acid and dissolved iron and minerals known as acid rock drainage (ARD). The objective of this study was to disrupt chemolithotrophic bacteria responsible for ARD using chemical treatments and to foster an environment favorable for competing microorganisms to attenuate the biologically induced ARD. Chemical treatments were injected into flow-through microcosms consisting of 501 g of pyrite-rich shale pieces inoculated with ARD bacteria. Three treatments were tested in the microcosms: (1) a sodium hydroxide-bleach mix, (2) a sodium lactate solution, and (3) a sodium lactate-soy infant formula mix. The effectiveness of the treatments was assessed by monitoring pH, dissolved iron, and other geochemical constituents in the discharge waters. The optimal treatment was a sequential injection of 1.5 g sodium hydroxide, followed by 0.75 g lactate and 1.5 g soy formula dissolved in 20 mL water. The pH of the discharge water rose to 6.0 within 10 days, dissolved iron concentrations dropped below 1 mg/L, the median alkalinity increased to 98 mg/L CaCO 3 , and sulfur-reducing and slime-producing bacteria populations were stimulated. The ARD attenuating benefits of this treatment were still evident after 231 days. Other treatments provided a number of ARD attenuating effects but were tempered by problems such as high phosphate concentrations, short longevity, or other shortcomings. The results of these laboratory microcosm experiments were promising for the attenuation of ARD. Additional investigations and careful selection of treatment methods will be needed for field application.

Tennessee↗
USGS2017

Changes in community-level riparian plant traits over inundation gradients, Colorado River, Grand Canyon

Comparisons of community-level functional traits across environmental gradients have potential for identifying links among plant characteristics, adaptations to stress and disturbance, and community assembly. We investigated community-level variation in specific leaf area (SLA), plant mature height, seed mass, stem specific gravity (SSG), relative cover of C4 species, and total plant cover over hydrologic zones and gradients in years 2013 and 2014 in the riparian plant community along the Colorado River in the Grand Canyon. Vegetation cover was lowest in the frequently inundated active channel zone, indicating constraints on plant establishment and production by flood disturbance and anaerobic stress. Changes in trait values over hydrologic zones and inundation gradients indicate that frequently inundated plots exhibit a community-level ruderal strategy with adaptation to submergence (high SLA and low SSG, height, seed mass, C4 relative cover), whereas less frequently inundated plots exhibit adaptation to drought and infrequent flood disturbance (low SLA and high SSG, height, seed mass, C4 relative cover). Variation in traits not associated with inundation suggests niche differentiation and multiple modes of community assembly. The results enhance understanding of future responses of riparian communities of the Grand Canyon to anticipated drying and changes in hydrologic regime.

Arizona↗
USGS1982

Low-temperature formation of hydrocarbon gases in San Francisco Bay sediment (California, U.S.A.)

To understand the processes responsible for the presence of low-molecular-weight hydrocarbons (C1-C4) in anoxic environments, we studied sediments collected from an anaerobic estuarine mudflat. In these sediments methane (C1) was several orders of magnitude more abundant than all other C2-C4 hydrocarbons; the C1 (C2 + C3) ratio was ??? 13,000. Mean ethane/ethene and propane/propene ratios were 0.4 and 0.7, respectively. Production of C1-C4 hydrocarbons was monitored during prolonged incubation (7 months) of sediments at 27?? and 4??C. Samples stored at 27??C generated significant quantities of C1-C4 hydrocarbon gases. Incubation at 4??C inhibited production of these gases. Several bactericides were tested with respect to their ability to inhibit formation of gaseous hydrocarbons. Sodium azide, chloroform, and 2-bromoethanesulfonic acid effectively inhibited methane formation, but not ethene formation in dilute continuously-shaken sediment slurries. Zephiran chloride only caused partial inhibition of methanogenesis (46%) and ethene generation (34%) in these slurries. In experiments with more concentrated unshaken sediment slurries, however, zephiran chloride and sodium azide did not block formation of methane, ethane, or propane. Only storage at -10??C prevented production of these gases. These results indicate that C1-C4 hydrocarbons can be formed by low-temperature reactions, possibly mediated by microorganisms. ?? 1982.

Chemical Geology↗
USGS1983

Distribution, abundance and carbon isotopic composition of gaseous hydrocarbons in Big Soda Lake, Nevada: An alkaline, meromictic lake

Distribution and isotopic composition (δ 13 C) of low molecular weight hydrocarbon gases were studied in Big Soda Lake (depth = 64 m), an alkaline, meromictic lake with permanently anoxic bottom waters. Methane increased with depth in the anoxic mixolimnion (depth = 20–35 m), reached uniform concentrations (55 μM/l) in the monimolimnion (35–64 m) and again increased with depth in monimolimnion bottom sediments (>400 μM/kg below 1 m sub-bottom depth). The μ 13 C [ CH 4 ] values in bottom sediment below 1 m sub-bottom depth (<−70 per mil) increased with vertical distance up the core ( δ 13 C [ CH 4 ] = −55 per mil at sediment surface). Monimolimnion δ 13 C [ CH 4 ] values (−55 to −61 per mil) were greater than most δ 13 C [ CH 4 ] values found in the anoxic mixolimnion (92% of samples had δ 13 C [ CH 4 ] values between −20 and −48 per mil). No significant concentrations of ethylene or propylene were found in the lake. However ethane, propane, isobutane and n -butane concentrations all increased with water column depth, with respective maximum concentrations of 260, 80, 23 and 22 nM/l encountered between 50–60 m depth. Concentrations of ethane, propane and butanes decreased with depth in the bottom sediments. Ratios of CH 4 [C 2 H 6 + C 3 H 8 ] "> CH 4 [C 2 H 6 + C 3 H 8 ] were high (250–620) in the anoxic mixolimnion, decreased to ~161 in the monimolimnion and increased with depth in the sediment to values as high as 1736. We concluded that methane has a biogenic origin in both the sediments and the anoxic water column and that C 2 -C 4 alkanes have biogenic origins in the monimolimnion water and shallow sediments. The changes observed in δ 13 C [ CH 4 ] and CH 4 (C 2 H 6 + C 3 H 8 ) "> CH 4 (C 2 H 6 + C 3 H 8 ) with depth in the water column and sediments are probably caused by bacteria] processes. These might include anaerobic methane oxidation and different rates of methanogenesis and C 2 to C 4 alkane production by microorganisms.

Geochimica et Cosmochimica Acta↗
USGS1983

An interpretation of carbon and sulfur relationships in Black Sea sediments as indicators of environments of deposition

Syngenetic iron sulfides in sediments are formed from dissolved sulfide resulting from sulfate reduction and catabolism of organic matter by anaerobic bacteria. It has been shown that in recent marine sediments deposited below oxygenated waters there is a constant relationship between reduced sulfur and organic carbon which is generally independent of the environment of deposition. Reexamination of data from recent sediments from euxinic marine environments ( e.g. , the Black Sea) also shows a linear relationship between carbon and sulfur, but the slope is variable and the line intercepts the S axis at a value between 1 and 2 percent S. It is proposed that the positive S intercept is due to watercolumn microbial reduction of sulfate using metabolizable small organic molecules and the sulfide formed is precipitated and accumulates at the sediment-water interface. The variation in slope and intercept of the C to S plots for several cores and for different stratigraphic zones for the Black Sea can be interpreted in relation to thickness of the aqueous sulfide layer or thinness of the oxygen containing layer and to deposition rate, but also may be influenced by availability of iron, and perhaps the type of organic matter (Leventhal, 1979).

Geochimica et Cosmochimica Acta↗