Contribution of Methane Benthic and Atmospheric Fluxes of an Experimental Area (Sitka Stream)

Abstract

Contributions of methane benthic fluxes and methane emissions to the total methane amount were studied during the summer season for two consecutive years. Considering the fact that methane is produced in great amount within hyporheic sediments, we have expected that both methane released by the benthic fluxes into the overlying water and methane emitted to the atmosphere should significantly affect the total methane budget of the stream water within the experimental area. In order to asses this assumption, we measured methane concentrations within the vertical sediment profile of a hyporheic zone, direct benthic methane fluxes by static chambers, methane concentrations in the surface water, and methane emissions into the atmosphere simultaneously. The methane concentrations in interstitial water tended sharply to increase with sediment depth (0.54–734.99 μmol L−1) and were strongly correlated with benthic fluxes (r = 0.88, p < 0.05). We also found a considerable variability in the benthic methane fluxes (0–12.59 mmol m−2 day−1) and the spatial variability (0–71.43%) of the experimental area, suggesting that there may be various factors that affect the rate of benthic fluxes including methanotrophy in the top sediment layers. Generally, the contribution of benthic fluxes and methane emissions to the methane budgets of the experimental area was negligible (0.034 (0.45%) and 0.074 mol day−1 (0.98%), respectively).

Microbial Ecology of Methanotrophy in Streams Along a Gradient of CH4 Availability

“…This suggests that MOB in shallow stream sediments thrive on elevated CH 4 concentrations. CH 4 concentrations increased with sediment depth, a pattern that was noted earlier (Sanders et al, 2007;Rulík et al, 2013;Bednařík et al, 2015;Mach et al, 2015). The interface between oxygen-rich streamwater and CH 4enriched porewater may therefore represent a hot spot for MOX.…”

Methane formation and consumption by sediments in a cross-channel profile of a small river impoundment

“…Hence, this serves mainly for a comparison of the microbial activity between individual samples and not for calculation of the net CH 4 flux from the sediments. It would be necessary to measure in situ CH 4 benthic fluxes from the sediments to the surface water using the benthic chamber method in order to determine the net contribution of the sediments to the surface water CH 4 (sansone et al, 1998;Bednařík et al, 2015).…”