Evidence for Negative Effects of Drought on Baetis sp. (Small Minnow Mayfly) Abundance in a Southern California Stream

Abstract Benthic macroinvertebrate (BMI) sampling was conducted at two sites in Topanga Creek from 2003-2014. During this period, Southern California experienced extreme drought conditions (US Drought Monitor 2014). Examining trends in species composition over this period allows for a relatively long-term analysis of potential effects of drought on BMI communities. The Southern California Coastal Index of Biotic Integrity (SCC-IBI; Ode 2007) was applied to BMI samples from Topanga Creek to measure the effects of drought on quantitative biotic integrity. The following trends regarding the BMI community of Topanga Creek emerged during the course of this study: 1) Wet year rainfall in Topanga Creek Watershed positively correlated to relative and per sq. ft. springtime abundance of Baetis sp., relative abundance of Simulium sp. up to 78.7 cm (31) rain, and negatively correlated to relative abundance of Chironomidae n.d., 2) percent algae cover in April and May positvely correlated to abundance per sq. ft. Ba...