Biodiversidade de cianobactérias perifíticas em ambiente lótico do Parque Nacional do Iguaçu - Paraná

Abstract

One of the major challenges of humanity today is to know and conserve existing biodiversity, especially in tropical and subtropical regions of the world where the number of species tends to be higher. Among the microorganisms, the microalgae, especially cyanobacteria, are primary producers of great importance, but can cause problems in ecosystem imbalance conditions such as contamination by toxins. To lotic environments, yet little is known of cyanobacteria biodiversity in southern Brazil. Thus, this study aimed to survey the periphytic cyanobacteria from stream Macuco, a preserved creek located within the boundaries of the Iguaçu National Park (Foz do Iguaçu - Paraná). The collection was held in december 2014 in three main segments: east, middle portion and mouth region. For each region was selected containing a segment 10 meters long. In each segment were selected 10 sample units with visible algal growth. The collection of cyanobacteria periphytic with macroscopic training was conducted by the method of quadrants. The microscopic sample of cyanobacteria has been made based on the scraping method, in this case, the stream trough epilithon. The qualitative laboratory analysis was performed under light microscopy using transects depletion, glass slide, from specimens preserved in 4% formaldehyde. The data were evaluated in spatial mode, using richness as a general descriptor of the community and the clustering method (cluster analysis), to seek grouping patterns. 25 species of cyanobacteria were identified, distributed in 13 genera. The Oscillatoria gender was more frequent than the other taxa (36%). It is inferred that the overlapping of Oscillatoria is due to their characteristics associated with periphytic habit, and its wide geographical distribution. The distribution of species at collection points was not homogeneous. In points 1 and 8 was not verified any cyanobacterial taxon, and point 7 showed the highest number of species. This point is characterized as top waterfall, and most species are not periphytic, with its adventitious presence due to the action of current stream. The similarity was higher between points 3 and 6 (100%), and points 4 and 7 (80%). It is justified by the presence of concomitant species in points whose composed these two groupings. The fragile environmental characteristics indicate the need to maintain the preservation of the area, for manteinance of cyanobacteria biodiversity.