The invertebrate community of the chalk stream hyporheic zone: spatio-temporal distribution patterns

This study examined the longitudinal distribution, vertical distribution and temporal dynamics of the invertebrate community inhabiting the chalk hyporheic zone of four catchments, which differed in their degree of eutrophication and sediment composition. We characterised the invertebrate community at two depths (20 and 35 cm), in the heads and tails of riffles at low and high groundwater levels. Taxon density declined significantly with increasing depth. The abundance of invertebrates did not differ significantly between the heads and tails of riffles and also did not respond to changes in groundwater level. The results suggest that the chalk hyporheic zone is a shallow habitat that is relatively homogenous at the riffle scale with respect to the distribution of fauna and potentially resilient to seasonal groundwater level fluctuations.