Marine anoxic

Bacterially produced elemental sulfur can also react with hydrogen sulfide form polysulnde ions. Thus, polysulfide ions should constitute a significant fraction of sulfur nudeophiles in reducing sediments especially where sulfide oxidation is incomplete, such as in intertidal and salt marsh sediments (31321. The polysulfide ions should also be important at redox boundaries (anoxic/ suboxic) in the water column of marine anoxic basins, such as the Black Sea. 

Wei, C.L., and Murray, J.W. (1994) The behavior of scavenged isotopes in marine anoxic environments 210Pb and 210Po in the water column of the Black Sea. Geochim. Cosmochim. Acta 58, 1795-1811. 

Algeo T. J. and Scheckler S. E. (1998) Terrestrial—marine teleconnections in the Devonian links between the evolution of land plants, weathering processes, and marine anoxic events. Roy. Soc. London Phil. Trans. B 353, 113—130. 

Sulfides and disulfides can be produced by bacterial reactions in the marine environment. 2-Dimeth-ylthiopropionic acid is produced by algae and by the marsh grass Spartina alternifolia, and may then be metabolized in sediment slurries under anoxic conditions to dimethyl sulfide (Kiene and Taylor 1988), and by aerobic bacteria to methyl sulfide (Taylor and Gilchrist 1991). Further details are given in Chapter 11, Part 2. Methyl sulfide can also be produced by biological methylation of sulfide itself (HS ). Carbon radicals are not the initial atmospheric products from organic sulfides and disulfides, and the reactions also provide an example in which the rates of reaction with nitrate... 

Kiene RP, BF Taylor (1988) Demethylation of dimethylsulfoniopropionate and production of thiols in anoxic marine sediments. Appl Environ Microbiol 54 2208-2212. 

Holser, W.T. and Kaplan, I.R. (1966) Isotope geochemistry of sedimentary sulfates. Chem. Geol., 1, 93-135. Huerta-Diaz and Morse, J.W. (1992) Pyritization of trace metals in anoxic marine sediments. Geochim. Cosmochim. Acta, 56, 2681-2702. 

Anderson RF (1987) Redox behavior of uranium in an anoxic marine basin. Uranium 3 145-164 Anderson RF, Fleisher MQ, LeHuray AP (1989) Concentration, oxidation state, and particulate flux of uranium in the Black Sea. Geochim Cosmochim Acta 53 2215-2224 Back W, Hanshaw BB, Pyler TE, Plummer LN, Weiede AE (1979) Geochemical significance of groundwater discharge in Caleta Xel Ha, Quintana Roo, Mexico. Water Res 15 1521-1535 Barnes CE, Cochran JK (1990) Uranium removal in oceanic sediments and the oceanic U balance. Earth. Planet. Sci. Lett 97 94-101... 

Molecular hydrogen is an important intermediate in the degradation of organic matter by microorganisms in anoxic habitats such as freshwater and marine sediments, wet land soils, and the gastrointestinal tract of animals. In these particular conditions H2 is produced during fermentation of carbohydrates, lipids, nucleic acids, and proteins by anaerobic bacteria and,... 

Copper concentrations in sediment interstitial pore waters correlate positively with concentrations of dissolved copper in the overlying water column and are now used to predict the toxicity of test sediments to freshwater amphipods (Ankley et al. 1993). Sediment-bound copper is available to deposit-feeding clams, especially from relatively uncontaminated anoxic sediments of low pH (Bryan and Langston 1992). The bioavailability of copper from marine sediments, as judged by increased copper in sediment interstitial waters, is altered by increased acid volatile sulfide (AYS)... 

Iron sulphides are ubiquitous in marine and freshwater sediments. They are usually present either as pyrite or as monosulphides, which can be liberated by hydrochloric acid. These acid volatile sulphides give rise to an intense black colour that is characteristic of anoxic sediments. They play an important role in recent diagenetic processes in sediments and the ratio of pyrite to acid volatile sulphides has been used as an historical indicator to determine whether sediments were formed in marine or freshwater conditions. They can be present over a wide range of... 

Kiene RP, Taylor BF (1988) Demethylation of dimethylsulfoniopropionate and production of thiols in anoxic marine sediments. Appl Environ Microbiol 54 2208-2212 Kiene RP, Visscher P, Keller M, Kirst GO (1996) Biological and environmental chemistry of DMSP and related sulfonium compounds. Plenum, New York Kirst G (1989) Salinity tolerance of eukaryotic marine algae. Ann Rev Plant Physiol Plant Mol Biol 40 21-53... 

At the oxic-anoxic boundaries a rapid turnover of iron takes place. This oxic-anoxic boundary may occur in deeper layers of the water column of fresh and marine waters, at the sediment-water interface or within the sediments. 

Cowie, G.L., J.I. Hedges, and S.E. Calvert. 1992. Sources and relative reactivities of amino acids, neutral sugars, and lignin in an intermittently anoxic marine environment. Geochimica et Cosmochimica Acta 56 1963-1978. 

It is apparent that the aquatic echinoderm and terrestrial mammal deal with a chemical probe by very different metabolic pathways. The exclusive formation of oxidized ((T-demethylated) product in the mouse may partly reflect the animal s highly oxidizing environment, while the relatively anoxic marine environment is represented in the observed reduced metabolites of the sea urchin. 

Hoehler TM, Albert DB, Alperin MJ, Martens CS. 1999. Acetogenesis from CO2 in an anoxic marine sediment. Limnol Oceanogr 44 662-7. 

Because of its high organic content, the marine snow acts as a microhabitat that supports enhanced rates of heterotrophic microbial activity. The associated nutrient remineralization causes the seawater within and aroimd the marine snow to be characterized by elevated nitrogen and phosphorus concentrations and low levels of O2. The importance of these suboxic and anoxic microzones to the marine cycling of the biolimiting elements is unknown but potentially significant. 

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