Estrutura do fitoplâncton e a sua utilização como indicador de condições ecológicas no reservatório de Pedra, Bahia

Abstract

The present work had the objective of identifying the plankton algae species and relates their presence with the water quality in Pedra reservoir, in different seasonal periods and biannual scale. Eight quarterly surveys in 13 previously established stations and the samples collected throughout the euphotic zone. Algae densities, abundance and diversity, and ecological associations were determinated and water quality indexes calculated. The phytoplankton community was represented by 126 infrageneric taxa, distributed as follows: 41 Bacillariophyta; 41 Chlorophyta; 31 Cyanophyta; 8 Euglenophyta; 3 Cryptophyta; 1 Chrysophyta and 2 Dinophyta. The diversity was considered low, while the equitability was also low during the period of study. The algal density was low, and Aulacoseira granulat(Bacillariophyta) was the species with highest number in the period of study. Significant differences were not observed in densities during the first and the second years, neither between the sample stations. Regarding water quality, the indexes used showed Pedra reservoir as mesotrophic, throughout the different periods of the year. The use of phytoplanktonn in ecological indexes is a trustworthy tool for determining the trophyc state and monitoring environmental alterations in reservoirs, but the choice of brotec indexes is subject to environmental characteristics.