Short term effect on colonized aquatic invertebrates at downstream site from waste water treatment plant

M.M. Mahato¹, J.H. Kennedy¹, W.T. Waller¹, L.P. Ammann², and K.E. Banks³. ¹Department of Biological Sciences, University of North Texas, Denton, TX 76203, ²University of Texas at Dallas, Richardson, TX, ³City of Denton, Denton, TX 76209

Urban streams in semi-arid regions of the Southwestern U.S. are often effluent dominated and there are no minimally impacted sites with comparable hydrologic regime either upstream of the potentially impacted site being studied or within the ecoregion. This presents challenges for monitoring water quality with benthic macroinvertebrates. This study evaluated the efficacy of detecting changes in water quality by transferring artificial substrates colonized at a reference site with minimal impacts to a potentially impacted urban stream. The results of these experiments were compared to a study in which substrates colonized in the urban stream are compared to undisturbed reference stream substrates. In the experiments, Hester-Dendy substrate samplers were anchored to racks for invertebrate colonization. One rack with 18 samplers was anchored in a minimally impacted reference stream and the other with five samplers was positioned 100 meters downstream of a waste water treatment plant. After 6 weeks, five colonized artificial samplers were transported from the reference to the downstream site. All samplers were retrieved one week after the transfer event. Collected invertebrates were identified to genus. Statistical comparisons and their statistical power will be made to evaluate changes in taxa abundance and composition between the various substrate treatments.