Reconceptualizing the hyporheic zone for nonperennial rivers and streams
Citation:
DelVecchia, A., M. Shanafield, M. Zimmer, M. Busch, C. Krabbenhoft, R. Stubbington, K. Kaiser, R. Burrows, J. Hosen, T. Datry, S. Kampf, S. Zipper, K. Fritz, K. Costigan, AND D. Allen. Reconceptualizing the hyporheic zone for nonperennial rivers and streams. Freshwater Science. The Society for Freshwater Science, Springfield, IL, 41(2):167-182, (2022). https://doi.org/10.1086/720071
Impact/Purpose:
The subsurface environment of stream and river channels, the hyporheic zone, is important for supporting diverse aquatic communities and ecosystem functions. Traditionally, the hyporheic zone has been conceptualized to only consider saturated (from some mixture of surface and ground water) habitat within the bed and banks of stream channels. These conceptualizations exclude the subsurface environment of non-perennial streams (streams that periodically dry) which may periodically becomes unsaturated (humid to dry) despite still supporting comparable biodiversity and ecosystem functions in the hyporheic zone of perennial streams. This paper reviews how hydrology influences biogeochemistry and ecology of the hyporheic zone of non-perennial stream and proposes an interdisciplinary definition for the hyporheic zone inclusive of the spatio-temporal variation experienced in non-perennial streams.
Description:
Nonperennial streams dominate global river networks and are increasing in occurrence across space and time. When surface flow ceases or the surface water dries, flow or moisture can be retained in the subsurface sediments of the hyporheic zone, supporting aquatic communities and ecosystem processes. However, hydrological and ecological definitions of the hyporheic zone have been developed in perennial rivers and emphasize the mixing of water and organisms from both the surface stream and groundwater. The adaptation of such definitions to include both humid and dry unsaturated conditions could promote characterization of how hydrological and biogeochemical variability shape ecological communities within nonperennial hyporheic zones, advancing our understanding of both ecosystem structure and function in these habitats. To conceptualize hyporheic zones for nonperennial streams, we review how water sources and surface and subsurface structure influence hydrological and physicochemical conditions. We consider the extent of this zone and how biogeochemistry and ecology might vary with surface states. We then link these components to the composition of nonperennial stream communities. Next, we examine literature to identify priorities for hydrological and ecological research exploring nonperennial hyporheic zones. Lastly, by integrating hydrology, biogeochemistry, and ecology, we recommend a multidisciplinary conceptualization of the nonperennial hyporheic zone as the porous subsurface streambed sediments that shift between lotic, lentic, humid, and dry conditions in space and time to support aquatic–terrestrial biodiversity. As river drying increases in extent because of global change, we call for holistic, interdisciplinary research across the terrestrial and aquatic sciences to apply this conceptualization to characterize hyporheic zone structure and function across the full spectrum of hydrological states.
