Predictability of bacterial activity and denitrification in aquatic sediments with continuous measurements of redox potential

Abstract

ABSTRACT:Redox potential has been adopted as a qualitative parameter for interpreting solubility changes of nutrients and contaminants and the biological activity within wetland systems for several decades. The majority of studies considering the redox geochemistry in sediments used measurements of bulked material and single point measurement of biogeochemical parameters for interpretation, yet it remains questionable whether this information is reliable for environments that are very dynamic, such as wetlands. In this study it is evaluated whether variations in redox potential reflect dynamics of denitrification and overall bacterial respiration using continuous measurements of redox potential in time-series experiments in laboratory microcosms, in which the biogeochemical variation was enhanced by bioturbation. The results presented here suggest that measurements of redox potential have predictive potential in approximating rates of denitrification and overall bacterial respiration in aquatic sediments. The data clearly suggest that, while sediment bulk measurements and measurements of single profiles of redox potential, denitrification and bacterial activity often fail to provide ecological relevant information in dynamic systems, measurements of spatial and temporal redox potential profiles provide a useful parameter that reflects biogeochemical processes and functioning of sediments.

Contribution of bacteria to redox potential (E h) measurements in sediments

“…Taken together, measurements of E h in complex natural systems seem to reflect the metabolic activity of resident bacterial communities rather than concentrations of terminal electron acceptors in our microcosms. This complements previous studies that linked E h to bacterial activity and community structure (Bertics and Ziebis 2009;Hunting and Van der Geest 2011;Hunting et al 2012). Although it cannot be ruled out that E h measurements may still be overruled by redox couples unrelated to bacterial activity, quantitation of the electrochemical properties of the sediment may offer a potential indicator of bacterial processes in sediment systems.…”

Year-round N<sub>2</sub>O production by benthic NO<sub>x</sub> reduction in a monomictic south-alpine lake

“…In lacustrine sediments, microbial activity consumes O 2 rapidly in the topmost millimeters, leading to suboxic or anoxic conditions in deeper sediment horizons, where denitrification becomes an important redox process (Hunting and van der Geest, 2011). The O 2 penetration depth is closely related to the O 2 concentration in the overlying water and the sediment reactivity (Lehmann et al, 2009;Thibodeau et al, 2010).…”

From Saprotrophic to Clear Water Status: the Restoration Path of a Degraded Urban Lake

“…The water pH also influences the intensity of this phenomenon; the optimum is between pH 7.0 and pH 8.2. However, the most important factor is proper oxygen conditions (Hunting and Van der Geest 2011). In Długie Lake during artificial aeration, denitrification may have been the main process in sediment.…”