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Riparian and microhabitat factors determine the structure of the EPT community in Andean headwater rivers of Ecuador

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.