The role of sulfur in salt marsh metabolism
Howarth, Robert W.
MetadataShow full item record
LocationGreat Sippewissett Salt Marsh, Buzzards, MA
The rate of sulfate reduction in stands of dwarf Spartina alterniflora in the Great Sippewissett Salt Marsh is approximately 75 moles S04 m2 year-1. This is the highest rate reported for any natural ecosystem. Sulfate reduction is the most important form of respiration in the marsh and results in the annual consumption of 1800 g C m-2, approximately equivalent to net primary production. Sulfate reduction rates in the peat are high for at least three reasons: 1) the below-ground production of Spartina alterniflora provides a large, annual input of organic substrates over a depth of some 20 cm, 2) sulfate is rapidly resupplied to the peat in infiltrating tidal waters, so low sulfate concentrations never limit the rate of sulfate reduction, and 3) sulfide concentrations remain below toxic levels. The stable mineral pyrite is a major end-product of sulfate reduction in salt marsh peat while iron mono-sulfides are not. This is unlike most anoxic marine sediments and apparently results because iron mono-sulfides are undersaturated. The iron mono-sulfides are undersaturated in part because of the relatively low concentration of total soluble sulfides and in part because of the fairly low pH of the peat. Both of these conditions probably result from the activity of the Spartina roots. If the incorporation of 35S into pyrite were not measured, the S3504 reduction measurements would greatly underestimate the true rate of sulfate reduction. Pyrite acts largely as a temporary store of reduced. sulfur. The pyrite concentration of the peat undergoes seasonal changes. On an annual basis, the reduced sulfur which results from sulfate reduction is either re-oxidized to sulfate within the peat or is exported, much of it as thiosulfate or a similar intermediately reduced compound. Most of the energy which is originally in organic matters is stored in reduced sulfur compounds when the organic matter is respired by sulfate reducing bacteria. Consequently, the export of reduced sulfur compounds from the peat represents an energy export. The export of energy as reduced inorganic sulfur compounds is probably larger than the net above-ground production by Spartina. This is an important vector for moving some of the energy trapped by the below-ground production of Spartina to zones where it is available for coastal food webs.
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 1979
Showing items related by title, author, creator and subject.
Distribution of hydrocarbons in a salt marsh ecosystem after an oil spill and physiological changes in marsh animals from the polluted environment Burns, Kathryn A. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1975-06)The studies described in this thesis were designed to answer several problems relating to the recovery of a salt marsh heavily polluted by an accidental spill of Number 2 fuel oil. Field and laboratory studies were ...
Gulmann, Lara K. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2004-09)Digestive associations between marine invertebrates and resident (attached) microbial communities may playa critical role in host physiology and involve previously unidentified microbial species. The overarching goal of ...
Hamersley, Michael R. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2001-12)I used direct measurements of nitrogen gas (N2) fluxes and a 15N stable isotope tracer to determine the contribution of denitrification to salt marsh sediment N cycling. Denitrification in salt marsh tidal creekbottoms ...