EL IMPACTO DE CONTAMINACIÓN POR HIDROCARBUROS SOBRE LA CALIDAD DE AGUAS Y SOBRE MACROINVERTEBRADOS BENTÓNICOS DEL RIO HONDO (CARRASCO, COCHABAMBA, BOLVIA)

Abstract

THE IMPACT OF PETROLEUM CONTAMINATION ON THE WATER AUALITY AND THE BENTHIC MACROINVERTEBRATES OF RIVER HONDO (CARRASCO, COCHABAMBA, BOLIVIA) El impacto que ejercen las descargas de residuos liquidos y solidos petroleros sobre los ecosistemas acuaticos de agua dulce es muy poco conocido. Este estudio investiga el impacto ambiental causado por la actividad petrolera en la provincia Carrasco del Departamento de Cochabamba (Bolivia). El estudio de caso es un derrame continuo de desechos liquidos con hidrocarburos, que afecta a al calidad de aguas superficiales y a la comunidad de macroinvertebrados bentonicos en el rio Hondo, un rio pequeno de bajo caudal, en dos periodos, epoca seca y epoca de Iluvias. El agua en el punto de descarga presento valores elevados de hidrocarburos totales. En la torrentera que recibe los desechos y en los tramos mas contaminados del rio Hondo no se encontro ningun organismo. La concentracion de los contaminantes disminuyo notablemente a lo largo del rio Hondo, principalmente por efecto de dilucion. En los tramos rio abajo, con contaminacion intermedia, se observo poco impacto sobre la diversidad de macroinvertebrados acuaticos, pero si sobre la densidad y sobre la estructura tropica de las comunidades. Los efectos de contaminacion fueron mas severos en epoca de estiaje que en epoca de lluvias, probablemente debido a una mayor dilucion en la ultima epoca. Palabras clave: Contaminacion, petroleo, bentos, bio-indicaccion, rio Hondo, Cochabamba, Bolivia. ABSTRACT The environmental impact of solid and liquid petroleum contamination on aquatic freshwater systems is poorly understood. The impact of small, continuous petroleum spills was studied in the province Carrasco in the department of Cochabamba (Bolivia) in the Hondo rivet; a river with small discharge. The impact of hydrocarbon waste on river water quality and on the macroinvertebrate community structure was studied during two periods, the dry season and the rainy season. In the small brook, which received hydrocarbon containing liquid waste and in the upper parts of Hondo rivet; no organisms were recorded as a result of hydrocarbon contamination. There was a downstream decrease of contamination levels due to dilution effects. In downstream segments with intermediate contamination levels, the impact of petroleum contamination on macroinvertebrate diversity was small, whereas the impact on the density of macroinvertebrates and on the trophic structure of the benthic communities was significant in both seasons. The effects of contamination were always more severe in the dry season than in the rainy season, probably because of dilution effect during the rainy season. Key words: Contamination, petroleum, benthos, bio-indication, Hondo river, Cochabamba, Bolivia.