Distribuição espacial da comunidade perifítica no Rio São Mateus, Espírito Santo, Brasil

• Autor(a) principal: Pereira, Thais Almeida
• Data de Publicação: 2012
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Espírito Santo (riUfes)
• Texto Completo: http://repositorio.ufes.br/handle/10/5206
• topic: Ecologia; Perifíton; Distribuição longitudinal; Biomassa; 502

São Mateus River, the main water supplier for the city of São Mateus, has been used as receptor of domestic and industrial wastewater. Thus, because of the great importance of this river, this study evaluated the structure and dynamics of periphyton community, and the limnological characteristics of a stretch of São Mateus River subjected to different environmental conditions, and verified the differences of biotic and abiotic data between sampling sites. Four samplings with weekly intervals were performed in September and October 2010 (September 08th, 15th, 22th and October 1st) at six sampling sites: two upstream of the city of São Mateus (E1, E2), two along the city (E3, E4), and two downstream of the city of São Mateus (E5, E6). The variables measured for limnological characterization were: water transparency, lower limit of the euphotic zone, maximum depth, electric conductivity, turbidity, pH, concentration of total suspended solids, and the major nutrients (total nitrogen, nitrite, nitrate, ammonium, silicate, orthophosphate, and total phosphorus). The periphyton was scraped from roots of Eichhornia crassipes (Mart.) Solms. with the aid of brushes and jets of distilled water, fixed and preserved with 4%-formalin (qualitative analysis) and with 0.5%-acetic lugol (quantitative analysis). The structure of periphyton community was evaluated based on the attributes: taxa richness, total density and density per class, specific diversity, evenness, abundance, and dominance. The biomass was estimated through chlorophyll a, biovolume, dry matter, ash free dry matter, and ash. The Kruskal-Wallis non-parametric test was used to test significant differences (p < 0.05) between the mean values of biotic and abiotic variables along the sampling sites. The Principal Component Analysis (PCA) was employed to verify the longitudinal variation in relation to abiotic variables. The influence of abiotic factors on biotic variables was evaluated by the canonical correspondence analysis (CCA) with significance by the Monte Carlo test (p < 0.05). The São Mateus River presented neutral to slightly alkaline waters in all sampling sites. Turbidity, electric conductivity, total suspended solids, orthophosphate, total phosphorus, nitrite, ammonium, and total nitrogen of the sampling sites downstream of the city were different from those registered in the other sites, as evidenced by the Principal Component Analysis (PCA). Higher richness of taxa and total density of periphyton community were registered in the sampling sites along and downstream of the city of São Mateus, with greater contribution of the classes Bacillariophyceae (richness) and Cyanophyceae (total density) in all sampling sites. Higher values of chlorophyll a were observed at E1, while the total biovolume presented higher values in E4 ne E3. With regard to dry matter, the inorganic fraction (ash) was high especially at the sampling sites along and downstream of the city of São Mateus. The biomass and density were influenced by nutrients (phosphorus and nitrogen) and turbidity, as showed by the CCA, suggesting that the input of allochthonous material, largely derived from human activities (intensive fish farming and discharge of domestic and industrial wastewater) has changed the water quality (as evidenced by the PCA), as well as the periphytic communities.