Influence of temporal variation of hydraulic parameters on the structure and function to the macroinvertebrate community in an Andean stream

In this study, we evaluated the response of the composition, structure, and function of the macroinvertebrate community regarding the hydraulic temporal variation in the Agua Blanca Stream. The 60 macroinvertebrate samples were collected in two reaches during two hydroclimatic periods with stratified random sampling. We measured the flow and channel width for each reach and the velocity, the depth, and the Froude number for each biological sample. The Kolmogorov-Smirnov test showed a significant increase in the values of velocity, flow, and Fr during the rainy season. The ANOSIM analysis showed a temporary variation in the composition and structure of the community: Leptohyphes, Smicridea, Helicopsyche, Nanomis, and Marilia genera were more abundant in the transition season while the Simuliidae and Sericostomatidae families in the rainy season. The dominant functional feeding group (FFG) in the transition season were the collectors and in the rain season, the fragmenters and collectors-filters. According to the CCA, Simuliidae and Metrichia were associated with high depth values, Mayobaetis with the width of the channel, and Sericostomatidae with the velocity and the Fr. Ostracods, Meridialis, and Triplectides had a negative association with velocity. According to the preference curves, the optimal velocity range for the Sericostomatidae family was 1,8 m.s-1 to 2,3 m.s-1 and the optimal depths for the Simuliidae family were between 0,3 m and 0,55 m. The role of the hydraulic variables evaluated was determinant for the presence of some genera and functional groups