Intermittent and perennial macroinvertebrate communities had similar richness but differed in species trait composition depending on flow duration

Abstract

While intermittent stream research has increased dramatically in recent decades, it remains difficult to predict traits that allow biota to persist in response to reduced flows and prolonged intermittent conditions. We quantified flow duration (FD) in ten reaches of six streams previously categorized as intermittent or perennial in north-central Arkansas. Macroinvertebrates were sampled in six streams in autumn and spring following a summer when six reaches did not maintain connected flow and four that maintained connected flow. Seasonal changes in discharge altered wetted habitat availability in all reaches and differences in FD influenced the magnitude of change in habitat availability. Richness increased in all reaches in spring due to more taxa that were poor dispersers, with traits such as low crawling rate and weak female dispersal. Richness was similar across reaches in both seasons but macroinvertebrate communities differed depending on FD. Perennial reaches were characterized by large predators and rheophilic taxa, while reaches with shorter FD were characterized by shredders and non-insect taxa. This study can inform conservation and restoration activities that aim to improve or maintain connectivity between intermittent and perennial habitats to increase local biodiversity.