Efeito de parâmetros físico-químicos da água na composição e riqueza de espécies de macrófitas aquáticas em áreas sob palafitas em Laranjal do Jari, Amapá, Brasil

Abstract

The wetlands of the Amazon are located close to the banks of the great Amazonian rivers, being called wetlands. The municipality of Laranjal do Jari, Amapá, had its formation on the banks of the Jari river, thus, large flooded areas under stilts were formed with high levels of pollution due to domestic waste released directly into the water, this causes variations in the physical- water chemicals that can influence the composition, richness and abundance of aquatic macrophytes. This study aimed to analyze the effect of physical-chemical parameters of water on the composition, richness and percentage of coverage of aquatic macrophytes in areas under flooding in Laranjal do Jari. For this, 10 points were marked from the riverside to the mainland, at each point three plots of 1m² were established, equidistant from each other by 5m. The species and plots were photographed and later identified at a more specific level, in order to estimate the coverage percentage and to account for the number of species. Two water samples were collected at each point for analysis of the chemical and physical parameters of the water (nitrogen, phosphorus, pH, turbidity and electrical conductivity) and sent for laboratory analysis. Fifteen species of macrophytes were identified in 12 botanical families. The most representative families were Araceae (27.78%), Hydrocharitaceae and Salviniaceae (14.44%). The species with the highest coverage percentage were: Eichornia crassipes (26.38%), Pistia stratiotes (16.87%) and Limnobium laevigatum (15.57%). There was no significant relationship between the physicochemical variables of the water and the number of species in the sampled points. Canonical Correspondence Analysis (CCA) used to relate composition, percentage of coverage and physical-chemical variables of the water revealed that there was a gradient formed by the concentration of phosphorus and nitrogen related to a higher % of coverage of bioindicator species such as Eichhornia crassires, Pistia stratiotes and Limnolobium laevigatum; and greater turbidity, pH and conductivity, combined with pollution caused by phosphorus at all points, influenced a lower % coverage of C. blepharoleptos, N. alba, Brachiaria sp., Utricularia. However, the phosphorus-nitrogen gradient found indicates the action of bioindicator macrophytes in absorbing these loads of pollutants from the environment.

Keywords: Water quality bioindicators. Aquatic macrophytes. Physical-chemical parameters.