Inorganic and Organic Sulfur Cycling in Salt-Marsh Pore Waters

Abstract

Sulfur species in pore waters of the Great Marsh, Delaware, were analyzed seasonally by polarographic methods. The species determined (and their concentrations in micromoles per liter) included inorganic sulfides (</=3360), polysulfides (</=326), thiosulfate (</=104), tetrathionate (</=302), organic thiols (</=2411), and organic disulfides (</=139). Anticipated were bisulfide increases with depth due to sulfate reduction and subsurface sulfate excesses and pH minima, the result of a seasonal redox cycle. Unanticipated was the pervasive presence of thiols (for example, glutathione), particularly during periods of biological production. Salt marshes appear to be unique among marine systems in producing high concentrations of thiols. Polysulfides, thiosulfate, and tetrathionate also exhibited seasonal subsurface maxima. These results suggest a dynamic seasonal cycling of sulfur in salt marshes involving abiological and biological reactions and dissolved and solid sulfur species. The chemosynthetic turnover of pyrite to organic sulfur is a likely pathway for this sulfur cycling. Thus, material, chemical, and energy cycles in wetlands appear to be optimally synergistic.

Benthic fluxes of copper, complexing ligands and thiol compounds in shallow lagoon waters

“…The porewater concentrations of the thiols increase with depth, which is consistent with an in situ production by reaction of sulfide with sedimentary organic matter (Vairavamurthy and Mopper, 1987). Similar trends but at higher levels (0.1-2.5 mM organic thiol) have been observed previously in salt-marsh porewaters (Luther III et al, 1986). Our benthic chamber experiments demonstrate that the porewaters are the main source of thiols in the overlying waters, and that the steady state level of thiols is a balance of porewater releases and biological uptake and photochemical reactions in the surface waters.…”

“…Thiol compounds are known to form strong complexes with copper (Leal and van den Berg, 1998) and have been shown to exist in estuarine waters (Laglera and van den Berg, 2003;Tang et al, 2000) and salt marsh sediments (Luther III et al, 1986). For this reason a method (Laglera and van den Berg, 2003) was used in this work that identifies thiol-type ligands directly from their specific voltammetric response.…”

“…Sediments can act as a source of copper (Klinkhammer, 1980), copper complexing ligands (Skrabal et al, 2000), sulfur species and thiol compounds (Luther III et al, 1986). Metal complexing ligands (Croot et al, 2000;Moffett and Brand, 1996) and thiol compounds are also known to be released by marine phytoplankton (Dupont and Ahner, 2005;Leal et al, 1999) into surface waters.…”

Particulate thiols in coastal waters: The effect of light and nutrients on their planktonic production

“…Significant concentrations of thiols such as methanethiol and 3-mercaptopropionate are present in anoxic marine waters and sediments, where they react to form disulfide and polysulfide bridges and strong complexes with metal ions (Luther et al 1986;Mopper and Taylor 1986). It is likely that such reactions promote molecular weight enhancement of organic matter in sediments and mobilization of metals (Boulegue et al 1982).…”

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

“…The DGM is a salt marsh, dominated by Spartina alterniflora (saltmarsh cordgrass) and has an active annual cycle of sulfur and iron (Lord et al 1983;Luther et al 1986;Ferdelman et al 1991;Luther et al 1991;Luther 1994, 1995). From midsummer to mid-spring, the iron-sulfide transition zone in the pore-waters is relatively shallow (at 0-10 cm depth).…”