Benthic organisms as indicators of water quality in Lake Patzcuaro, Mexico

The water quality was evaluated in Lake Patzcuaro by biological methods using bacteria and macroinvertebrates as indicators, as well as physicochemical parameters. The bacteriological determinations showed critical areas near the two main villages, Patzcuaro and Janitzio. The bacterial ratio FC/FS indicated significant amounts of animal excreta throughout the lake. In areas with less urban influence where there was an abundance of immersed vegetation, the benthic macroinvertebrate community presented high Biotic, Diversity, and Equitability Indices, which were >2, >2, and >0.06, respectively. At the most polluted station, Oligochaetes, which are tolerant to organic matter, comprised 94% of the organisms.