Littoral macrobenthic communities and water quality in El Pañe Reservoir, Arequipa, Peru

Abstract

High Andean ponds and reservoirs are among the least-studied environments. We evaluated the composition of littoral macrobenthos and how it is affected by the physicochemical conditions of the water in El Pañe reservoir (Peru), located at 4,550 m.a.s.l. Samples were taken between November 2017 and October 2018 from three zones in the reservoir: low (downstream), middle and high (upstream); two of these zones with fish farms (low and middle) and one zone without fish farms (high). The following physicochemical parameters of the water were measured: dissolved oxygen, conductivity, pH and temperature. The macrobenthic community was analysed through diversity indices such as Shannon-Wiener (H’), Simpson’s dominance index (D), Pielou’s evenness (J’), true diversity (D1), and richness (S). The influence of the physicochemical variables on the macrobenthos was estimated by canonical correspondence analysis (CCA) and non-metric multidimensional scaling (NMDS). Dissolved oxygen was found to have lower values (<0.5 mg/l) than specified in the Environmental Quality Standards (EQS). Macroinvertebrate richness for the whole reservoir was 17 families, and the family with highest relative abundance was Chironomidae (42.24% in the low zone, 51% in the middle zone and 40.43% in the high zone). The indices showed greater species richness in the high zone, where there are no fish farms. Dissolved oxygen and conductivity were the main factors determining macrobenthos distribution and composition.