Influence of bed-sediment features on the interstitial habitat available for macroinvertebrates in 15 french streams

The interstitial space of bed-sediments is a major component of the stream system as it influences both physical and biological processes and patterns, such as exchanges between surface water and groundwater or the assemblage of invertebrates. To investigate the influence of grain-size distribution and vertical bed-packing on the interstitial habitat, we used 99 frozen cores collected from 15 French streams. On our data, overall invertebrate density, density of Chironomidae and taxon richness were more strongly related to effective porosity than to other physical variables describing bed-sediments. We built two models to quantify the influence of grain-size distribution and vertical bed-packing on effective porosity. The effective porosity decreased with increasing grain-size heterogeneity and was strongly related to grain-size distribution. These relationships differed with vertical bed-packing, but were consistent across three geologic types of sediments that varied in particle shape and particle texture. These general relationships suggest that effective porosity could be helpful to better understand the distribution patterns of invertebrates in bed-sediments.