Taxonomy and ecology of Eunotia (Bacillariophyceae) in reservoirs of southern and southeastern regions of São Paulo State

Abstract

Eunotia Ehrenberg (Eunotiaceae, Eunotiales) is one of the largest genera of living diatoms, and is characteristic mainly by the rudimentary raphe system restricted to the poles and the presence of rimoportulae. In São Paulo State, around 87 species/varieties of Eunotia are presently known. However, most of the information was not yet published, and presently many species require taxonomic revision. Furthermore, ecological information on the species distribution of the genus in São Paulo State and in Brazil is almost inexistent. This study aims to expand taxonomic and ecological information of the genus Eunotia based on detailed study of populations from 31 reservoirs distributed in five hydrological basins in southern and southeastern regions of São Paulo State (Upper Tietê Basin and neighboring basins). These reservoirs cover a wide spectrum of trophic state (oligotrophic to hypereutrophic). Samplings include planktonic, periphytic and surface sediments materials, as well as the reservoir's physical and chemical parameters, according to a broader project that this proposal belongs (AcquaSed). To date this project has about 300 permanent slides of diatoms (without repetition) corresponding to 300 samples from 21 reservoirs. Among these, 160 samples with Eunotia were selected, covering different habitats, seasons (summer/winter) and depths (shallow and deepest sites). Additional permanent slides will be prepared according to the sampling program until August 2014. Altogether, around 220 samples (slides) will be examined. Taxonomic study will be based on a detailed analysis of the populations from each environment and habitat by light and scanning electron microscopy (when necessary), as well as the taxonomic revision of the taxa citations within São Paulo State. Taxa delimitation will consider the circumscription of type-material available in literature. Ecological preferences of the species/varieties will be explored by the association between species quantitative distribution (relative abundance) and limnological variables (physical and chemical) available in the AcquaSed database. Quantitative analysis of populations will be conducted in slides transects at 1000x magnification and up to 500 valves in total for each sample. The association between species and environmental variables will be explored in the multivariate analyses. This proposal will advance the taxonomic and ecological characterization of Eunotia, and will provide a more consistent basis for a better understanding of tropical populations and their use as bioindicators. The association of taxonomy with ecological information about Eunotia is a pioneer for Brazil and very scarce worldwide. (AU)