Estrutura da comunidade algal perifítica de uma represa subtropical do sudoeste do Paraná

Abstract

The periphyton comprises a complex organization of microorganisms, small animals, and organic and inorganic matter residues that adhere to substrates. By virtue of their structural characteristic, they can accumulate and retain organic and inorganic substances. Thus, parallel to the trophic state, the periphyton is then an important bioindicator of the ecological quality of aquatic environments. The objective of this work was to evaluate the physical and chemical parameters of the water, to characterize the trophic state, to evaluate the temporal and spatial variations of the periphyton and to identify bioindicator taxa. The study area is the Represa da Trilha Ecológica da Universidade Tecnológica Federal do Paraná, Dois Vizinhos, Paraná. The experiment was installed in two points referring to the littoral and pelagic zones and in two periods of the year, dry and rainy season, with a sample in each period and sampling point. The climatic parameters were: temperature and precipitation, and physical and chemical characteristics of the water: pH, transparency, temperature, dissolved oxygen, orthophosphate, total phosphorus, nitrate and ammonium. Also the biomonitoring through the periphyton, we evaluated the biomass of the periphytic community, density of the taxa and calculated the biological indexes: Specific wealth (R), Diversity (H'), Dominance (D) and Equitability (J). Through the climatological, physical, chemical, biomass and density and total richness data, it is possible to verify a clear temporal separation between the rainy and dry periods, being the spatial variation not very significant. The forms of nitrogen and phosphorus that are the nutrients that are absorbed by aquatic organisms have presented relatively low values, which demonstrate that they are not available in large quantities in the environment. 89 taxa were identified, distributed in 39 genera and 5 classes. The average contribution of the general descriptive species during the evaluated period represented 51.31%. The data obtained from the climatological, physical, chemical and biological analyzes of the periphytic community show that Lake Ecological Trail is a natural oligotrophic ecosystem with low amounts of nutrients, a periphery with richness, diversity and low species dominance. With a separation between the rainy and dry period characteristic of the southern hemisphere of the globe that ends up influencing a small spatial variation between the littoral and pelagic zone, due to the specific characteristics of each region and the nutrient and organic matter contribution during the period of greatest precipitation.