Hyporheic invertebrate community response to flow permanence in a chalk stream

As the interface between surface water and groundwater, the hyporheic zone is recognised as a vital component of the fluvial environment and a unique habitat for invertebrates, with their distribution and abundance influenced primarily by interstitial water chemistry, flow permanence and direction of water exchange. The drivers of flow permanence and hyporheic zone depth were considered in the study, using a Bou-Rouch pump sampling programme at two sites on the River Lambourn. The results of the study indicated that flow permanence did have an effect on invertebrate metrics, with higher abundance and taxon richness at the intermittent and perennial sites respectively. Furthermore, invertebrate metrics differed between sampling depths, with a pattern of decreasing abundance in the deeper hyporheic zone. However, due to high variability between samples caused primarily by the sampling method, the observed relationships were not significant. The hyporheic zone remains under threat from anthropogenic stressors, mainly through fine sediment deposition and reduced flows, both of which act to reduce connectivity between surface and groundwater. While the results of the study highlighted potential hydrological drivers of hyporheic ecology, due to these increasing anthropogenic pressures, further investigation is required into the role of the hyporheic zone in the fluvial system and its response to potential future change.