O fitoplâncton como bioindicador da qualidade da água do sistema de abastecimento público de água da Região Metropolitana de Belém (Pará, Brasil).

Abstract

This work had as its theme to approach the phytoplankton functional groups and the ecological indexes of the public water supply system in the Metropolitan Region of Belém (Amazon, Pará, Brazil). The system encompasses the reservoirs Água Preta, Bolonha and the Guamá River, since studies on these themes are scarce, and the answers of phytoplankton about the quality of the water in these environments are little known. The aim of this work was to identify the phytoplankton composition, density and biomass of the Belém supply system (reservoirs Bologna, Água Preta and Rio Guamá), through the study of algal biovolume, ecological indexes and functional groups in the interpretations of the dynamics of this community, of the limnological dynamics and their responses to possible changes in water quality. In the reservoirs, monthly collections (Jan, Feb, Mar, Apr, Jun, Jul and Oct / 2019) of water were carried out at four points. On the Guamá River, sampling took place monthly from May/2019 to April/2021, at the collection point of water to the public supply system, to determine the physico-chemical factors, density and biomass of phytoplankton. There was seasonal variation in turbidity, transparency and rainfall of the physical-chemical factors in the reservoirs and N-ammonia, STS, CV and transparency in the Guamá River. In the supply system, 262 phytoplankton species were identified, which showed space-time variations in density and biomass. In the reservoirs the main GF were W1, Lm and Q; GMF: 6a, 1a, 5b and 11c; GFBM: V, VI and VII. Species richness varied significantly between months. The Bolonha reservoir showed less richness, less diversity, greater dominance and less evenness, in relation to the Água Preta reservoir. In the Guamá River, GF P prevailed in the months of the study, chlorophyll-a followed variations in densities, chlorophyll-c was higher than chlorophyll-b, indicating the dominance of diatoms with more than 80% throughout the period, the ICF considered the waters varying from good to excellent. The IET classified the Guamá River as oligo-mesotrophic. This study recommends the functional groups of phytoplankton-GFs and ecological indexes as a tool for bioindication and monitoring of environmental quality as they are practical and representative of the environment.