Effects of Stream Drying, Season, and Distance to Refuges on Macroinvertebrate Community Structure in an Arid Intermittent Stream Basin

Abstract

Intermittent streams are globally ubiquitous and comprise a large percentage of stream networks. As climate changes in arid regions and increases the frequency and intensity of drying disturbances, it is important to understand how aquatic biota respond to such stressors and how it would impact biodiversity. To address these topics, we sampled 10 stream reaches in the Sycamore Creek drainage, an arid-land stream in central Arizona, with reach-scale flow regimes ranging from perennial to highly intermittent. We sampled aquatic macroinvertebrates across 10 reaches during 4 seasons to explore seasonal variability in community structure as habitat transitions through flowing and drying phases. We also collected continuous flow regime data at each reach with remote data loggers to explore the impacts of intermittency and distance to perennial refuges on species richness, taxonomic composition, and trait composition. Overall, richness was lower at intermittent reaches than perennial reaches, and richness values increased linearly as flow duration increased. We found no relationship between richness and distance to the nearest perennial refuge. Community assemblages differed significantly by season but were not distinct between perennial and intermittent reaches. Trait composition however was distinct between seasons as well as flow classification, with traits such as a lack of diapause, longer life span, and predatory feeding behaviors as indicators for perennial reaches. As climate change alters natural flow regimes, understanding the response of macroinvertebrate community structure to drying disturbances in an arid-land stream can help to provide insight on aquatic community responses to a drying climate at a larger scale.