Influencia de nutrientes sobre la diversidad de diatomeas epilíticas en cuatro tramos de los Ríos Chagrasacha y Quillopaccha del Sistema Lacustre Pisayambo

Abstract

The aim of the current research was to analyze the influence of nutrients on the diversity of epilithic diatoms in four sections of Chagrasacha and Quillopaccha rivers within Pisayambo lake system, this was carried out through the application of ecological indices such as: Shannon-Wiener Index, Margalef Index, Specific Sensitivity to Pollution Index and Canonical Correspondence Analysis. Three sampling sections were determined in Chagrasacha River and one section in Quillopaccha River. Protocols for collection, cleaning and identification of epilithic diatoms and standardized methods for the analysis of water nutrients were applied. Forty species concerning the abundance of epilithic diatoms were identified, they were: Eunotia minor (7.82%), Nitszchia incospicua (7.38%), Amphora pediculus (7%), Melosira varians (6.75%), Cymbella tumida (6.19%), and Stauroneis acuta (5.32%) was the most representative. According to the application of the Shannon-Wiener and Margalef indices, in section one there was greater diversity and abundance of epilithic diatoms. The canonical correspondence analysis revealed a high relationship of Fragilaria arcus and Nitzschia incognita species with presence of phosphates and Amphora pediculus and Melosira varians with presence of nitrates. In section three, which is located in Chagrasacha River, the concentration for nitrates was 9.74 mg/L and for phosphates 1.34 mg/L. In the analysis of the Specific Sensitivity Index to Pollution, a mean of 12.97±0.47 was registered, this indicates that the water quality in the entire study area was moderate in a range of 13-17. Thus, certain species of epilithic diatoms could be considered as biological indicators of the environmental conditions in the river due to their sensitivity and tolerance to environmental factors, so it is recommended to establish a permanent monitoring plan for the rivers in order to deepen the information about bioindicator species of water quality.