Sequenciamento genético de espécies de diatomáceas epilíticas para aplicação na avaliação da qualidade da água em sistemas lóticos subtropicais e temperados brasileiros.

Abstract

Diatom algae have been widely used as bioindicators to assess water quality in lotic systems, due to their specific sensitivity to a variety of ecological conditions, responding quickly to environmental changes, highlighting that biotic indices are based on the relative abundance of species, whose taxonomic diagnosis uses frustule characters by means of conventional optical microscopy. However, obtaining such indices is time-consuming, expensive and requires excellent taxonomic expertise. This taxonomic diagnosis can be complemented using molecular tools. Thus, this research aimed to apply molecular techniques using 18S rRNA V4 and rbcL genes, to identify diatom species used in the biomonitoring of aquatic ecosystems. During 2020, water samples and epilithic diatom algae were collected in an upper reach of the Preto Stream Basin, Municipality of Santa Cruz do Sul, RS, Brazil, for environmental characterization and obtaining cultures of unialgal diatoms for morphological identification and molecular analysis. The results indicated the isolation of three ecologically important epilithic diatom species, identified molecularly as Gomphonema parvulum (Kützing) Kützing, Sellaphora seminulum (Grunow) D.G.Mann and Eolimna minima (Grunow) Lange-Bertalot. The comparison of the sequences with the GenBank database helped the morphological identification, and the rbcL gene showed better discriminatory capacity for the three sequenced species. This study contributes to increase the molecular data of diatom species available in the databases, highlighting the uses of the molecular approach as complementary taxonomical tool to evaluate the water quality of Brazilian subtropical and temperate lotic systems.