Effects of sampling technique on measurements of porewater constituents in salt marsh sediments1

We examined the effect of three methods of porewater extraction on the measured concentrations of seven porewater constituents in vegetated salt marsh sediments. Porewater extraction by standard core sectioning followed by squeezing or centrifuging was compared with two less destructive methods of water collection. The core sectioning technique significantly increased the concentration of total dissolved organic carbon and dimethylsulfide presumably due to root damage by cutting. Sampling technique did not appear to influence interstitial salinity or concentrations of dissolved inorganic carbon, dissolved ammonium, soluble sulfides, and dissolved sulfate as long as proper precautions were taken to prevent the loss of reduced compounds.