Impact of sampling methods on sulfate reduction rates and dissolved organic carbon (DOC) concentrations in vegetated salt marsh sediments
Gribsholt, B.; Kristensen, E. (2002). Impact of sampling methods on sulfate reduction rates and dissolved organic carbon (DOC) concentrations in vegetated salt marsh sediments. Wetlands Ecol. Manag. 10(5): 371-379
In: Wetlands Ecology and Management. Springer: Den Haag; Dordrecht; Hingham, MA; Amsterdam. ISSN 0923-4861; e-ISSN 1572-9834, more
The impact of sediment coring on measured rates of sulfate reduction (SRR) by the whole core super(35)S-injection technique was assessed in marsh sediment vegetated by Spartina anglica. Simultaneously, the role of extraction method (centrifugation vs. sippers) for determination of porewater DOC in vegetated sediment was evaluated. SRR was measured in situ with radiotracer injected directly into the sediment and in a time series from 1 to 24 h after coring. SRR incubations carried out within 6 h (June) or 12 h (August) of coring yielded up to an order of magnitude higher rates than measured in situ. The enhancement of SRR was instantaneous but temporary and correlated with measured porewater DOC concentrations. Cores sampled from rooted sediments should therefore not be used for sulfate reduction incubations within the first 12 h due to the effect of DOC leaching from roots cut during the coring procedure. The labile fraction of leached DOC appears to be exhausted after a pre-incubation period of at least 12 h. Measurement of porewater DOC is also problematic in vegetated sediment. Porewater extraction by centrifugation of sediment may result in up to one order of magnitude higher DOC concentrations than in porewater obtained by a nondestructive sipper technique. DOC is probably forced out of roots during centrifugation resulting in erroneously high porewater DOC concentrations.
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