Abstract
AIM: This research aimed to study the composition of epilithic diatom flora in headwater areas of the sub-basin of the Andreas stream, RS, Brazil, and their relation with eutrophication processes. METHODS: Quarterly excursions (March, June, September, December 2012 and Mach 2013) were performed in ten sampling points selected in the sub-basin, to collect samples for the identification and counting the organisms in the group of diatoms (Class Bacillariophyceae). RESULTS: The results indicated the occurrence of 243 taxa, distributed in 53 genera. Of these, 59 were considered abundant, being distributed in 29 genera. Seven species showed elevated tolerance levels to organic pollution and eutrophication: Adlafia drouetiana (R. M. Patrick) Metzeltin & Lange-Bertalot, Amphipleura lindheimeri Grunow; Fallacia monoculata (Hustedt) D. G. Mann, Navicula cryptotenella Lange-Bertalot, Navicula symmetrica R. M. Patrick, Nitzschia palea (Kützing) W. Smith and Sellaphora auldreekie D. G. Mann & S. M. McDonald in Mann et al. CONCLUSION: Although this research has been conducted in headwater areas, the occurrence of these seven species could be explained by considering the use of these areas for agricultural and livestock purposes, compromising the stability of these aquatic ecosystems, due to the significant contribution of fertilizer and organic matter, a condition that characterizes a process of eutrophication.
Highlights
Despite the extensive hydrographic network that characterizes Brazil, divided into eight major basins (Amazon, Tocantins River, North Atlantic and Northeast, San Francisco River, eastern Atlantic, Parana River, Uruguay River and Southeast Atlantic), there are few systems of monitoring water quality that have been implemented (Moresco and Rodrigues, 2013), considering that they are essential to increase understanding of the problems related to pollution of aquatic ecosystems (Bodo, 1992; Mohlenberg et al, 2007)
Concerning the methodologies for water quality evaluation, researchers worldwide (e. g., Cairns Junior and Pratt, 1993) argue that traditional techniques based on physical, chemical and bacteriological characteristics are not enough to meet their multiple uses, since they are deficient in the evaluation of aesthetics, recreation and ecological environmental conditions, being necessary an integrated quality analysis, considering the traditional valuation methodologies, but the biological aspects of the system
For qualitative and quantitative analysis, diatom samples were scrubbed off the upper surface of three to five submerged stones, 10 to 20 cm in diameter, using a toothbrush, and were fixed with formalin following the method described by Kobayasi and Mayama (1982)
Summary
Despite the extensive hydrographic network that characterizes Brazil, divided into eight major basins (Amazon, Tocantins River, North Atlantic and Northeast, San Francisco River, eastern Atlantic, Parana River, Uruguay River and Southeast Atlantic), there are few systems of monitoring water quality that have been implemented (Moresco and Rodrigues, 2013), considering that they are essential to increase understanding of the problems related to pollution of aquatic ecosystems (Bodo, 1992; Mohlenberg et al, 2007).Concerning the methodologies for water quality evaluation, researchers worldwide (e. g., Cairns Junior and Pratt, 1993) argue that traditional techniques based on physical, chemical and bacteriological characteristics are not enough to meet their multiple uses, since they are deficient in the evaluation of aesthetics, recreation and ecological environmental conditions, being necessary an integrated quality analysis, considering the traditional valuation methodologies, but the biological aspects of the system.Among the bioindicator organisms of the environmental conditions of lotic systems, the use of diatoms (Bacillariophyceae) has a long history (Stevenson and Pan, 1999). Diatoms are represented by about 100,000 species distributed in 250 genera and have a wide geographical distribution, occurring along rivers, estuaries, lakes, marine environments and a variety of substrates, natural or artificial, being observed in humid environment, ice and hot spring waters (Hoek et al, 1995) These organisms are one of the main dominant groups of periphytic algae in lotic systems and efficient indicators of environmental changes, since they respond sensitively to physical and chemical changes of water (Winter and Dunthie, 2000; Lobo et al, 2002), as well as to differences in geology, climate and land use between watersheds (Stoermer and Smol, 1999). Because they have a strongly silicified cell wall, these organisms can be mounted in permanent microscope slides, requiring no special treatment for preservation
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