THRESHOLD DISCHARGE EFFECTS ON MACROINVERTEBRATES ALONG AN URBANIZATION GRADIENT IN PIEDMONT HEADWATER STREAMS
Urban streams are characterized by altered hydrographs, increased nutrient concentrations, altered geomorphology, and decreased biodiversity. Threshold discharge (Qcritical) is the flow value that results in the mobilization of a specific sediment size and depends on 1) the median grain size and 2) the two-year flood discharge value. We asked how Qcritical impacts stream macroinvertebrates in Piedmont headwater streams to better understand the potential of Qcritical to integrate flow impacts on stream organisms. We sampled eight sites that ranged across watershed area (0.90 - 3.66 square miles) and percent impervious cover (0.81-33.3 %) in Mecklenburg County, North Carolina. Macroinvertebrates, background water quality (dissolved oxygen, specific conductivity, pH, temperature, nutrients), and Wolman pebble counts were collected during fall 2018 and winter 2019. Flow data were taken from nearby USGS gages for two years prior to sampling. The diversity of macroinvertebrates decreased along the impervious cover gradient. Qcritical did not vary systematically with %IC due to local variability in streambed D50. Linking sediment mobilization and macroinvertebrate diversity may provide insights into best practices for stream restoration design for controlling sediment transport and improving ecological health.
Rebecca Black (Primary Presenter/Author), UNC Charlotte , firstname.lastname@example.org;
Sandra Clinton, PhD (Co-Presenter/Co-Author), University of North Carolina at Charlotte, email@example.com;