Características da diatomoflórula em resposta as variações ambientais de um riacho na planície de inundação do Rio Paraná

Abstract

The streams have intrinsic relations influenced by drainage basin. Know the diversity and characteristics of Brazilian streams can bring explanations or important monitoring measures for water bodies. This paper presents the composition of the diatoms of Caracu stream, and analyzes its relationship to environmental, thus seeking to establish patterns and characterize. The collect occurs in June and July / 2001 (dry season) and December 2001 and January 2002 (rainy season). In two points of stream was collected pebbles and petioles of grass: mouth with Parana river (P2) and 200m upstream (P1). To analyze the diatoms, permanent slides were prepared. When collected it is measured pH, dissolved oxygen, turbidity, water temperature and conductivity. The species identification and counting were performed under an optical microscope, keeping area of 5.76 cm² per point. Environmental change was verified by a Principal Component Analysis (PCA) and the densities of valves by a Detrended Correspondence Analysis (DCA), and the dominance of each species by point and time. It recorded 164 species belonging to 42 genera. The rise in temperature observed between the periods favored some species as Fragilaria capucina and Brachusira vitreae, which increased its abundance. The species Achnanthes minutissima, Eolimna minima, Adlafia drouetiana and Navicula cryptocephala, which were species of higher density have become rare or absent. The species Achnhanthidium minuthissimum, Gomphonema parvulum, Gomphonema lagenula. Nitzschia palea, Nitzschia nana, Eunotia sudetica and Ulnaria ulna, demonstrate indifferent to changes of temperature, since they had reduced after the rainfall event and reestablished in the next month. It is concluded that the temperature and rain are determining factors in the development of species.