Biogeochemistry of sulfur and iron in Thioploca-colonized surface sediments in the upwelling area off central chile

What Do We Really Know about the Role of Microorganisms in Iron Sulfide Mineral Formation?

“…Sulfur-disproportionating bacteria that can produce sulfide and sulfate from thiosulfate, sulfite (Bak and Pfennig, 1987), or elemental sulfur (Thamdrup et al, 1993), as well as sulfide oxidizing bacteria that can excrete polysulfides (Griesbeck et al, 2000;Prange et al, 2004), both produce reduced sulfur products that may contribute to sulfide mineralization. Iron sulfides, notably pyrite, can indeed form as a result of S(0)-disproportionation in microbial cultures and in marine sediments (Canfield et al, 1998;Finster et al, 1998;Zopfi et al, 2008). Microbially produced organosulfides and even complexation of metals by microbially-produced organic matter may also be relevant, including at conditions where high temperatures preclude direct microbial involvement.…”

“…As newly precipitated iron sulfide particles are generally in the nm-size range, transmission electron microscopy (TEM) imaging and associated techniques, such as electron energy loss spectroscopy (EELS) and SAED, are essential to characterize the morphology and crystal structure of sulfide mineral crystals at the sub-micron scale (Posfai et al, 2013a). While bulk sulfur isotopic analyses provide the best line of evidence regarding the provenance of sulfide in sulfide minerals, e.g., chemical sulfide vs. sulfide from sulfate reduction or from sulfur disproportionation (Chambers and Trudinger, 1979;Zopfi et al, 2008), considerable variations in isotopic compositions between-and even within-individual pyrite grains can occur (Kohn et al, 1998). In future studies, more spatially precise work using SIMS and nanoSIMS may provide critical information at the sub-micron scale to understand small spatial scale isotope fractionation and its possible causes (Fike et al, 2008;Orphan and House, 2009;Wacey et al, 2010).…”

Extrapolations of Standing-Stocks of Big Bacteria in Humboldt Eastern Boundary Current Ecosystem (HEBCE)

“…This is a feature that needs to be acknowledged for the HS and probably for other such systems under oxygen minimum zones [22]. Their potential to determine an important portion of the primary productivity of the HEBCE through the conservation of N by reducing nitrate to ammonium which is readily brought up to the photic zone through upwelling, has already been pointed out by Zopfi, et al [21,23].…”

“…The varying oceanographic conditions in the HS could probably determine many possible combinations at the food web and the biogeochemical pathway. At present there is more information on the biogeochemical related issues for off central Peru [38] and for off central Chile [23], than on the former condition. To assess the potential ecological significance for the Humboldt marine ecosystem of the extrapolated CM-DMM's standing-stock figures consideration must also be taken of the possible number of replications of the CM-DMM standing stock during a year cycle.…”

Hydrogen Cyanide Accumulation and Transformations in Non-polluted Salt Marsh Sediments

“…Thiosulfate concentrations in pore-water were measured by derivatization with monobromobimane, followed by HPLC separation with fluorescent detection according to Zopfi et al (2008) with minor changes in the stationary phase and gradient program. Prevail C18 Alltech reverse phase column (250 mm 9 4.6 mm 9 5 lm) was used for HPLC separation of thiosulfate.…”