Benthic community of river Rocha related to pollutant input Cochabamba, Bolivia Comunidad bentonica del rio Rocha en relacion a la entrada de poluentes Cochabamba, Bolivia
Goitia, E.; Ayala, R.; Rossberg, M.; Romero, A.M.ria
Revista Boliviana de Ecologia y Conservacion Ambiental. Diciembre; 10: 3-16
2001
Document Number: 383954
This study evaluates the impact of pollutant input on the structure of the benthic community along the Rocha River. As the Rocha River flows from Sacaba to Capinota, it passes through Cochabamaba and Quillacollo, where it receives most of the waste discharge. Benthos samples were collected in places with very high pollutant input during nine months (1996-97) at nine sampling points along the river. At each point, six samples were obtained with a Surber net or a Van Veen dredge, depending on the substrate. In addition, some physical and chemical parameters were also measured. We identified32 morfospecies, with Chironomus sp. (37 623 ind m-2, 76%) being the most abundant, followed by Oligochaeta (5 565 ind m-2, 11%), and Tanypus sp. (4 616 ind m-2, 9%). All other organisms were present at low population densities. An ANOVA test showed highly significant spatial and temporal differences of the macroinvertebrate community due to environmental conditions that, in turn, were determined by the hydrologic cycle and waste discharge at the studied sites. Important spatial variations of BOD, QOD, DO, OM, and conductivity were observed. The variability of the system was strongly related to these factors, which, in turn, were determined by the waste discharge. The most polluted parts of the river were at Urkupina (R5) and Quiroz Rancho (R7), where the benthic community disappeared completely during the low water season, thus, these areas are considered highly polluted. Areas of the river within the city of Cochabamba are very polluted and the most abundant species are the species most tolerant to these conditions.