Aquatic entomofauna and biotic index along the Pindo Grande River, Montano Bajo Forest, in Pastaza Province, Ecuador

Abstract Pindo Grande River water quality was analyzed during rainy seasons of 2014 and 2017 and dry seasons of 2015 and 2016. Specimens were collected using surber net, kick net and manual stone collection, from five different sites along the river. In the laboratory, specimens were identified to the lowest possible taxonomic level. Taxon richness, abundance, diversity, trophic niches, and Biological Monitoring Working Party for Colombia (BMWP/Col) index were assessed. A total of 1,695 specimens belonging to 95 taxa were collected, including 57 taxa in rainy seasons and 38 taxa in dry seasons. Class Insecta was the most abundant (98.6%). Richness was highest (3,427) at M1000 collection sites in rainy and dry seasons and varied from moderate to high (13-35) at other sites. All sampling sites had medium diversity, and organisms belonged to three trophic categories: herbivores, detritivores, and predators. Environmental water quality was medium at most sites (BMWP/Col = 102-150). All sites exhibited good conservation status (BMWP/Col = 192-152) in the rainy season; only two sites presented medium conservation status (BMWP/col = 93-67) in the dry season. Principal component analysis indicated that main variables associated with sites were NO3 and COD in upstream areas in the rainy season and O2 in the dry season. Downstream areas were grouped based on depth and width of the river in the rainy season and on pH, PO4, and conductivity in the dry season. According to analysis, the Pindo Grande River has preserved epibenthic communities; it is an oxygenated stream, but its habitats have been gradually affected by anthropogenic activities.