Comparison of Benthic Macroinvertebrate Assemblages in Small Streams along a Gradient of Flow Permanence

Abstract

Benthic invertebrates were quantified in 6 small upland streams in Alabama for 2 y to examine the degree to which variation in assemblage structure was related to the hydrologic permanence of riffle habitats. Streams differed along a gradient of flow permanence: 2 were normally intermittent (i.e., riffles ceased flowing in normal rainfall years) in summer, 1 was rarely intermittent (i.e., normally perennial), and 3 streams were occasionally intermittent (i.e., riffles ceased flowing during dry years). Despite large differences in flow permanence among streams, invertebrate assemblages differed only slightly. Presence-absence data revealed that 75% of the species (171 total taxa, predominantly aquatic insects) were ubiquitous across the 6 streams or displayed no pattern with respect to permanence; 7% of the total species were found exclusively in the normally intermittent streams. Although somewhat variable, many of the community richness and diversity measures were positively correlated with stream perman...