Evaluación de la calidad del agua de la laguna San Martín, parroquia San Gerardo – Girón, utilizando diferentes enfoques cuantitativos

Abstract

Eutrophication is one of the most important threats to the ecological status and ecosystem services of lake systems; therefore, its assessment plays a key role in the management of these ecosystems. The present study was carried out to evaluate and verify the water quality and trophic status of the "San Martín" lagoon using different quantitative approaches. For this purpose, the National Sanitation Foundation (NSF) water quality index, the Oregon Water Quality Index (OWQI) and the Council of Ministers of the Environment (CCME) index were applied; additionally, the trophic status of the lagoon was categorized by applying the Organization for Economic Cooperation and Development (OECD) eutrophication index, the Carlson Eutrophication Index (ETI) and the TRIX trophic index. Three samplings were carried out in the summer season (August, September and October) and three in the winter season (February, March and April), at six sampling points around the accessible zone of the lagoon. To calculate the indices, the concentration of the following parameters was determined: phosphorus, nitrogen, transparency, chlorophyll-a, dissolved oxygen, fecal coliforms, pH, BOD, phosphates, nitrates, total nitrogen, temperature and turbidity. The results corresponding to the water quality indexes showed that according to the CCME index, the San Martín lagoon presented a regular water quality in which the low concentration of dissolved oxygen (DO) had a considerable influence on its condition. The NSF index classified the lagoon with a medium quality, while the Oregon index classified it with a very poor quality, this being the most demanding when classifying the quality of a body of water. On the other hand, the Carlson and TRIX trophic indices coincided in that the lagoon presents a hypereutrophic state, while the OECD and the trophic state related to phosphorus (IETPt) allowed the identification that the concentration of phosphorus, the depth and the availability of light condition the trophic state of the lagoon