Epilithic diatoms in lotic systems of the Arroio Grande hydrographic sub-basin, Rio Grande do Sul, Brazil

Abstract

Epilithic diatoms are important components of freshwater periphyton. This study aimed to describe the composition and distribution of the epilithic diatom community in thirteen sampling sites in the Arroio Grande hydrographical sub-basin, RS, between October 2012 and March 2013. Samples were cleaned in oxygen peroxide and mounted on permanent slides for identifi cation. The diatom fl ora was composed of 106 species in 23 families and 41 genera. The most representative families and genera in taxa richness were Cymbellaceae (12 taxa), Naviculaceae (11), Sellaphoraceae (10), Gomphonema Ehreberg (10), Sellaphora Mereschkowsky, Nitzchia Hassall (seven), Navicula Bory, and Pinnularia C.G. Ehrenberg (six). Morphometric data for each species are presented. The upper reaches of the river basin presented greater specifi c richness than the lower stretches. This is the fi rst record of the diatom fl ora in this hydrographic basin.