Microbial Ecology of the Hyporheic Zone: A Perspective Integrating Hydrology and Biology

Spatio‐temporal variations of hyporheic flow in a riffle‐step‐pool sequence

“…Since the formulation of the patch dynamics concept (Townsend, 1989), lotic ecologists and biogeochemists have developed an increased interest in these dynamics and the heterogeneity of hyporheic flows (Hendricks, 1993;Stanley et al, 1997;Lake, 2000;Brunke et al, 2003). Whereas patchiness makes hyporheic research difficult (Palmer, 1993), ecologists mostly identify such complexity as an enhancer of biogeochemical processes, e.g.…”

Methanogenic System of a Small Lowland Stream Sitka, Czech Republic

“…The river hyporheic zone, volume of saturated sediment beneath and beside streams containing some proportion of water from surface channel, plays a very important role in the processes of self-purification because the river bed sediments are metabolically active and are responsible for retention, storage and mineralization of organic matter transported by the surface water (Hendricks 1993;Jones & Holmes 1996, Baker et al 1999, Storey et al 1999, Fischer et al 2005. The seemingly well-oxygenated hyporheic zone contains anoxic and hypoxic pockets ("anaerobic microzones") associated with irregularities in sediment surfaces, small pore spaces or local deposits of organic matter, creating a 'mosaic' structure of various environments, where different microbial populations can live and different microbially mediated processes can occur simultaneously (Baker et al 1999, Morrice et al 2000, Fischer et al 2005.…”

“…Moreover, hyporheic-surface exchange and subsurface hydrologic flow patterns result in solute gradients that are important in microbial metabolism. Oxidation processes may occur more readily where oxygen is replenished by surface water infiltration, while reduction processes may prevail where surface-water exchange of oxygen is less, and the reducing potential of the environment is greater (Hendricks 1993). As water moves through the hyporheic zone, decomposition of the organic matter consumes oxygen, creating oxygen gradients along the flow path.…”

Nitrogen dynamics in rural streams : differences between geomorphologic units

“…4A & B). The sedimentation of organic and inorganic fine particles in pools may explain this nitrate depletion: fine sediments offer a large surface for the development of heterotrophic bacteria that consumed dissolved oxygen (Lock, 1993), and generated anaerobic micro-sites in which denitrification occurs (Hendricks 1993, Garcia-Ruiz et al 1998, Steinhart et al 2000. Negative correlations between denitrification and D50 and between denitrification and Oxygen content support this statement.…”

“…2006, 42 (1), [43][44][45][46][47][48][49][50][51][52] Nitrogen dynamics in rural streams : differences between geomorphologic units** Some effects of geomorphology on the processes that occur in shallow sediment can be predicted from bibliographic sources (Table 1): hydrological exchanges will be reduced in pools because of fine sediment deposition (Mermillot-Blondin et al 2000), nitrification will follow the same trend due to oxygen depletion (Hall 1986, Kemp & Dodds 2001, ammonium produced by ammonification will accumulate inside sediments (Lefebvre et al 2004), while nitrate will disappear because of a high denitrification (Dahm et al 1987). Reverse predictions can be made for riffles and sand bars, where vertical exchanges and oxygenation are higher (Hendricks 1993), nitrification stimulated by the available oxygen, ammonium will be both oxidized and flush out of the sediments (Lefebvre et al 2004), while nitrate content will be similar or slightly higher than in surface water (Christiensen et al 1990). …”