No abstract

This research was conducted in the high‐Andean basin of the Zhurucay River in southern Ecuador. In 4 river reaches, 19 sampling campaigns were conducted per reach spread over a period of 35 months. The biotic samples were selected in the periods with greatest flow stability. Parallel to each sampling, 37 environmental variables grouped into 3 factors (riparian corridor, hydromorphology, and water quality) were recorded. The study aimed to analyse during periods of stable flow the influence of these environmental factors on the structure and density of the EPT community (Ephemeroptera, Plecoptera, Trichoptera) in a quasi‐pristine aquatic ecosystem. Multivariate statistical analysis revealed that the Froude number, gravel type, and width/depth ratio are the most relevant hydromorphological variables explaining variations in EPT density. Xiphocentronidae, Contulma, and Helicopsyche were observed to have a relationship with the order of the river, while Ochrotrichia, Nectopsyche, and Phylloicus varied with the type of riparian vegetation. Phylloicus, Ochrotrichia, and Nectopsyche were common in lentic sites, while the proportion of gravel and the width/depth ratio restricted the genus Helicopsyche. The only relevant water quality factor was the total phosphorus, which was related with 2 taxa. In conclusion, although macroinvertebrates are currently employed in water quality studies, riparian vegetation and hydromorphological factors are determinant for their communities in pristine Andean rivers. Such factors are therefore crucial in the study of environmental flows and the assessment of the ecological integrity.

This study assessed the effects of hydrological events on aquatic communities at the mesohabitat scale (pool, run, and riffle) in the high Andean region. Four headwater sites located in the Zhurucay microcatchment (southern Ecuador), with elevations higher than 3,500 m, were selected and monitored considering in each site a 50‐m‐long reach and within each reach five cross sections. In each of these reaches, 19 sampling campaigns were conducted in the period December 2011–October 2013, collecting macroinvertebrates and physical characteristics. A total of 27 hydrological indices were calculated using the daily flow rate as input. Large peak flow, small peak flow, and low flow (LF) events were defined based on discharge thresholds. Multivariate statistics showed that 14 hydrological indices were significantly related to the aquatic community. Further, the study revealed that (a) peak events produced stronger effects on communities than LF events, (b) the observed effects of LF events were weaker than those encountered in other latitudes, and (c) local benthic communities have more resilience than similar communities studied in other latitudes.