Anaerobic microbial metabolism in hyporheic sediment of a gravel bar in a small lowland stream

Abstract

Distribution of dissolved oxygen, nitrate, sulphate, carbon dioxide and dissolved organic carbon (DOC), acetate and lactate was studied in the stream and interstitial water along the subsurface flowpath in the hyporheic zone of a small lowland stream. Sediments were found to act as a source of nitrous oxide and methane. Interstitial methane concentrations were significantly much higher in comparison to those from surface water, and were significantly lower in the relatively well oxygenated downwelling zone than in the rather anoxic upwelling zone. The interstitial concentrations of O 2 , NO 3 À1 and SO 4 À2 showed significant decline along the subsurface flowpath, while concentrations of CO 2 , N 2 O, DOC, acetate and lactate remained unchanged. In addition to field measurements, ex situ incubation of sediments was carried out in the laboratory. Maximal methane production was found in the incubation assay using acetate (mean value 380 mg CH 4 kg DW À1 d À1 ). Mean value of the denitrification potential was 1.1 mg N 2 O kg DW À1 d À1. Nitrous oxide production potential reached 71-100% of denitrification potential. Our results demonstrate that respiration of oxygen, nitrate, sulphate and methanogenesis may coexist within the hyporheic zone and that anaerobic metabolism is an important pathway in organic carbon cycling in the Sitka stream sediments.

Methanogenic System of a Small Lowland Stream Sitka, Czech Republic

“…Similar pathway of methane cycling has been observed by Kuivila et al (1988) in well oxygenated sediments of Lake Washington, however, methane oxidation within the sediments would be rather normal in river sediments compared to lakes. All the above mentioned findings support our previous suggestions that coexistence of various metabolic processes in hyporheic sediments is common due to vertical and horizontal mixing of the interstitial water and occurrence of microbial biofilm (Hlaváčová et al 2005(Hlaváčová et al , 2006.…”

“…Availability of interstitial habitats for bacteria and archaea carrying out anaerobic processes has been confirmed by our previous (Hlaváčová et al 2005(Hlaváčová et al , 2006Cupalová & Rulík 2007) and contemporary findings. During this study we found relatively well developed populations of methanogenic archaea at all localities and that all localities also showed positive methanogenic potential.…”

“…temperature, pH, redox, conductivity, O2, CH4, NO3, SO4) patterns in the sediments and a schematic view of the site with sampling point positions have been published previously (Rulík et al 2000, Rulík & Spáčil 2004. Earlier measurements of a relatively high production of methane, as well as potential methanogenesis, confirmed the suitability of the field sites for the study of methane cycling (Rulík et al 2000, Hlaváčová et al 2005. …”

“…Since a relatively high production of methane has been measured in river sediments (e.g. Schindler & Krabbenhoft 1998, Hlaváčová et al 2005, Sanders et al 2007, Wilcock & Sorrell 2008, Sanz et al 2011, we proposed that river sediments may act as a considerable source of this greenhouse gas which is important in global warming (Hlaváčová et al 2006). …”

Benthic Uptake Rate due to Hyporheic Exchange: The Effects of Streambed Morphology for Constant and Sinusoidally Varying Nutrient Loads

“…In fact, stream water downwells into the alluvium in high-head zones and upwells into the stream in low-head zones [20]. Downwelling fluxes carry reactive solutes and DO, which is consumed by the microbial communities within the hyporheic zone [21][22][23][24], resulting in upwelling stream waters with lower DO concentrations than those of stream waters [21,23,[25][26][27][28][29][30].…”