Algas epilíticas em um reservatório tropical raso (Vitória, ES): estrutura e dinâmica em diferentes escalas temporais

• Autor(a) principal: Cavati, Bruna
• Data de Publicação: 2008
• 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/10/9980
• topic: Epilithic algae; Dry and rainy period; Succession; Shallow reservoir; Períodos seco e chuvoso; Sucessão; Agronomia; Reservatórios; Alga; 57

This research, developed in the Captation Lagoon of the water trucks supplying center of the City Prefecture of Vitória, a shallow tropical reservoir, aimed to evaluate changes in the structure and dynamics of the epilithics algae community in different temporal scales (succession and hydrological periods) in artificial limestone substratum. An experimental structure was confectioned, serving of support for limestone substrata, and implanted in the sampling site (located in the middle of the lagoon). The experiment had lasted 61 days in each season (dry and rainy). The measured abiotical variables were: wind velocity, light intensity, site depth, Secchi transparency, eufotic zone, air and water temperature, electric conductivity, total solids in suspension, turbidity, dissolved oxygen, pH, nitrite, nitrate, ammoniacal nitrogen, total nitrogen (kjeldahl), ortophosphate, total phosphorus dissolved and silica. The climatological data (precipitation and air temperature) had been obtained from the Incaper meteorological station. The structure and dynamics of the community had been evaluated based in the following attributes: specie richness, density, abundance, dominancy, diversity, evenness and biovolume. The chlorophylls a, b and c, carotenoids and phaeopigments concentrations had also been quantified in the epilithic algae. The lowest nitrogen-nutrients and electric conductivity values and the highest turbidity and phosphorus concentration values were reported in the higher precipitation period. According CONAMA resolution nº357/2005, the Captation lagoon can be classified as “water class 2” (destinated to parks and garden irrigation) and only the phosphorus values are higher than the resolution stardard quality values. 115 taxa were reported, with qualitative predominance of the Class Cyanophyceae, Chlorophyceae and Bacillariophyceae. In both periods, the density, biovolume and pigments concentrations were crescent; however, the most expressive density and pigments concentration increase occured in the dry season, as long as the biovolume increase occured in the rainy season. The diversity and evenness index showed temporal variations in short ans long-term. The succession standard was, quantitatively: initial colonization by Chlorophyceae, which was substituted by Cyanophyceae in the intermediary and final stages. Bacillariophyceae contributed in the intermediary stages, mainly in the dry season. Chlorophyceae showed the highest revelance to biovolume. Short-term community variability was determinated by autogenic process (competition and resources limitation), which were more accented in dry season. Pluviometric index and nitrogen and phosphorus-nutrients concentrations variation were determinants in long-term. The specie richness, density and pigments concentrations showed more sensible answers to nitrogen and to the disturbance features than the biovolume, which was masked in the rainy season by the taxonomic representation