Composição e riqueza de espécies de fitoplâncton de um trecho do baixo Rio Jari, sul do Amapá, Brasil

Abstract

The Jari river basin is a tributary on the left bank of the Amazon River, which has a section downstream of its mouth, called the lower course of the river, which suffers most from human intervention, such as urban expansion, sewage dumping and the presence of dam of the Santo Antônio do Jari Hydroelectric. Considering this, this study aimed to analyze the composition and richness of phytoplankton species in a stretch of the lower course of the Jari River, south of Amapá. For this, samples were collected at three different points on a stretch on the left bank of the Jari River. Subsequently, 10 slides of each sample were analyzed under an optical microscope, and the individuals observed were drawn and photographed for later identification through updated taxonomic literature. The Jaccard index was calculated to analyze the similarity of species occurring between the points, and using a similarity matrix, an order was made to verify the composition of phytoplankton between the points in terms of the formation of functional groups. 33 species of phytoplankton were identified, most belonging to the classBacillariophyceae. The species Phacus sp. occurred at the three sampled points; Eudorina elegans was common to points 1 and 3, while Cymatopleura sp. occurred at points 1 and 2. The species similarity between the three points was very low, ranging from 0.05 to 0.09, and the ordination showed that the points are distinct in terms of species composition, showing high beta diversity. The analysis of functional groups showed that the phytoplankton species occurring are characteristic of disturbed or polluted aquatic environments.