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- Title
Benthic metabolism and sulfur cycling along an inundation gradient in a tidal Spartina anglica salt marsh.
- Authors
Gribsholt, Britta; Kristensen, Erik
- Abstract
Central aspects of carbon and sulfur biogeochemistry were studied along a transect extending from an unvegetated mudflat into a Spartina anglica salt marsh. Conditions along the transect differed with respect to tidal elevation, sediment characteristics, vegetation coverage, and benthic macrofauna abundance. Dark sediment O[sub2] uptake and CO[sub2] emission at the highly bioturbated mudflat were low and relatively unaffected by tidal coverage. Sulfate reduction accounted for 30-60% of the daily CO[sub2] emission from the open mudflat sediment. Sediment O[sub2] uptake within the nonbioturbated and vegetated marsh was up to seven times higher during air exposure than during inundation, whereas the difference in CO[sub2] emissions always was less than a factor of 2. The contribution of sulfate reduction to CO[sub2] production was low <21%) and decreased progressively with tidal elevation as a result of the oxidizing capacity of S. anglica roots in the vegetated marsh. The boundary between the mudflat and the retreating marsh is a unique environment. High near-surface pore-water concentrations of dissolved organic carbon (DOC) above the marsh cliff and highly elevated total carbon dioxide (TCO[sub2]) pore-water concentrations at both sides of the cliff during air exposure coincided with extremely high TCO[sub2] emissions and apparent respiratory quotients (up to 14) only below the marsh cliff during inundation. We propose that substantial seepage of DOC-poor and HCO[sup-, sub3]-rich pore water may have occurred from the elevated marsh to the unvegetated sediment below during low tide followed by massive release of HCO[sup-, sub3] during high tide. Accordingly, sulfate reduction accounted for more than the TCO[sub2] release above the marsh cliff, but only for about 40% below the cliff. Mineralization rates and pathways in salt-marsh sediments vary considerably on small spatial and temporal scales and are dependent on inundation frequency as well as the...
- Subjects
BIOGEOCHEMISTRY; CARBON; SULFUR; SPARTINA anglica; SALT marshes
- Publication
Limnology & Oceanography, 2003, Vol 48, Issue 6, p2151
- ISSN
0024-3590
- Publication type
Article
- DOI
10.4319/lo.2003.48.6.2151