Interplay of hydrology, community ecology and pollutant attenuation in the hyporheic zone

Abstract

1) We describe the hierarchical interplay of hydrology, hyporheic ecology and transformation of nutrients and pollutants in the hyporheic zone (HZ). The exchange of water between the surface-subsurface generates the hyporheic exchange flow: the engine that drives the ecological functioning of the HZ. The magnitude and direction of hydrological fluxes in the HZ follow complex spatial patterns, strongly influenced by the temporal dynamics of surface flow in rivers. 2) The direction and magnitude of hydrological fluxes also shapes the structure of hyporheic communities (hyporheos). During surface disturbances such as flooding or drought, benthic organisms may also use the HZ as a refuge, although the importance of this role is debated. 3) Streambed organisms differ in their ability to colonise the HZ depending on the biological traits they possess. The reduction in oxygen concentration and pore size with increasing sediment depth imposes a limit on the distribution of macroinvertebrates, which are replaced by a suite of smaller organisms (meiofauna and protists) at deeper sediment layers. Therefore, a concomitant reduction in net biomass and productivity might be expected through depth. However, only a few studies have assessed the contribution of the hyporheos to whole system production, and they have focused only on the fraction of relatively large organisms. 4) The bioreactor ability of the HZ to transform nutrients and pollutants is an important ecosystem service sustained by the life activities of hyporheos. Biofilms have the key role in this process due to their capacity to metabolize a wide range of dissolved 3 compounds, including emerging pollutants. However, the residence time of water in pore sediments (resulting from hyporheic exchange flow) and the rest of the community (constantly reworking the sediments and grazing biofilms) are indirectly involved.

Comparing biotic drivers of litter breakdown across stream compartments

“…The dramatic reduction in biomass and α‐diversity of Protozoa and Eumetazoa invertebrates within the HZ in this study supports the widely reported pattern of simplification of streambed communities with increasing depth in the streambed (e.g. Schmid‐Araya, ; Sliva & Williams, ; Andrushchyshyn, Wilson, & Williams, ; Reynolds & Benke, , Peralta‐Maraver, ; Dunscombe, Robertson, Peralta‐Maraver, & Shaw, ). Results from our regional‐scale approach are also in agreement with previous experimental assessments (Cornut et al, ) and local‐scale survey studies (i.e.…”

Effect of Hyporheic Exchange on Macroinvertebrate Community in the Weihe River Basin, China

“…Many ecological processes are related to hyporheic exchange, because this affects the substrate properties and water quality and produces physicochemical gradients to which macroinvertebrates are sensitive [9,10]. Therefore, hyporheic exchange not only provides key ecological processes [11], but more importantly affects the development of macroinvertebrate communities in river ecosystems [10,12]. Actually,…”

Toward a conceptual framework of hyporheic exchange across spatial scales

“…vegetation density, riparian, and in-channel vegetation) is considered in this review as the main ecological factor that influences HEF (Heppell et al, 2009;Corenblit et al, 2007). Although not reported in this paper, we acknowledge that other ecological factors such as hyporheic freshwater invertebrates and biofilm have a major role in interacting with HEF (Peralta-Maraver et al, 2018).…”