Impact of fiddler crabs and plant roots on sediment biogeochemistry in a Georgia saltmarsh

Anaerobic Metabolism: Linkages to Trace Gases and Aerobic Processes

“…Compared to previous compilations, -50% of the amount attributed to 0 2 reduction is now credited to Fe(III) reduction, while the contribution of S0 4 reduction is unchanged (Thamdrup, 2000). Fe(III) reduction can also be the dominant carbon oxidation pathway in salt marsh sediments (Kostka et al, 2002c;Gribsholt et al, 2003).…”

“…Plants, bioturbation, or physical mixing have this effect. In salt marshes, bioturbation by crabs may be more important to Fe(III) regeneration than radial 0 2 loss from roots in some cases (Kostka et al, 2002c), but not in others (Gribsholt et al, 2003). In marine sediments, there is very little Fe(III) or Mn(IV) reduction in the absence of mixing (Thamdrup, 2000).…”

“…Indeed, Fe(III)-reducing and Fe(II)-oxidizing bacteria occur on the same 1-cm lengths of plant roots (Weiss et al, 2003). Burrowing animals influence sediments in much the same manner as roots (Kostka et al, 2002c;Gribsholt et al, 2003), and water table fluctuations can cause sediments to shift rapidly between reducing and oxidizing conditions. Although the processes discussed here have been demonstrated, their individual contributions to regulating Fe(III) cycling at an ecosystem level is largely unknown.…”

“…Oxidant regeneration is stimulated dramatically by the presence of animals and plants. The burrowing activity of animals (i.e., bioturbatiori) is a particularly important agent of Fe(III) and Mn(IV) regeneration in marine sediments and salt marshes (Thamdrup, 2000;Kostka et al, 2000c;Gribsholt et al, 2003;Gribsholt and Kristensen, 2002). Wetland plants promote regeneration by serving as conduits of 0 2 infusion deep into the soil profile.…”

Natural-abundance radiocarbon as a tracer of assimilation of petroleum carbon by bacteria in salt marsh sediments

“…Among these, iso-and anteiso-branched monoenoic and saturated C 15 and C 17 acids, 10-methyl-C 16 (10-Me-C 16 ) and monoenoic C 16 (e.g., C 16:1ω7c ) and C 18 (e.g., C 18:1ω7c ) acids are characteristic of many bacteria (Ratledge and Wilkinson, 1988;Kaneda, 1991), especially Gram-negative sulfate-reducing bacteria (Taylor and Parkes, 1983;Edlund et al, 1985;Dowling et al, 1986;Kohring et al, 1994;Vainshtein et al, 1992), and iron(III)-reducing bacteria (Moule and Wilkinson, 1987;Nichols et al, 1992;Coleman et al, 1993;Teece et al, 1999;Venkateswaran et al, 1999;Zhang et al, 2003). In salt marsh sediments inhabited by the tall form of Spartina, sulfate-and Fe(III)-reducing bacteria are abundant (10 6 to 10 8 cells/ml) and anaerobic decomposition predominates over aerobic decomposition (Lowe et al, 2000;Kostka et al, 2002a,b;Gribsholt et al, 2003;Furukawa et al, 2004).…”