Composição do fitoplâncton, variação espaço-sazonal e correlação com variáveis ambientais da qualidade da água do rio Falsino-AP, Amazônia Oriental

Abstract

Water is an essential resource for sustaining life on the planet, and its quality is directly related to the balance and natural evolution of ecosystems. Phytoplankton, due to their high sensitivity to environmental changes, are widely used as bioindicators to assess water quality in natural ecosystems. This study aimed to identify the composition of the phytoplankton community, its spatiotemporal distribution, and its relationship with environmental variables in the Falsino River, located in the state of Amapá, Eastern Amazon. Six sampling sites were established, and two field campaigns were conducted in May and November 2019. Samples were collected using a 20 µm mesh plankton net, preserved in 5% formalin, and analyzed by optical microscopy. Environmental variables including pH, dissolved oxygen, electrical conductivity, and temperature were measured in situ using specific sensors. The results revealed the presence of 97 taxa, distributed across 12 classes and seven taxonomic divisions. The class Zygnematophyceae was the most representative, with 43 taxa, accounting for 44.33% of the total identified. Environmental variables did not show significant spatial fluctuations (p > 0.05). However, water temperature varied between seasonal periods, with higher values recorded during the dry season (p < 0.05). Spearman’s correlation matrix indicated a moderate association (r² = 0.44) between species richness and water temperature. This pattern was also confirmed by Principal Component Analysis (PCA), which showed a positive correlation between richness and temperature. This study provides an important contribution to the phycological knowledge of the Falsino River, allowing for a broader characterization of the phycoflora in the state of Amapá. The findings support further investigations in the region and other areas of the Amazon, fostering the management and conservation of its aquatic resources.