Abundance of periphytic desmids in two Brazilian reservoirs with distinct environmental conditions
FELISBERTO1, S.A. & RODRIGUES1, L.
1 State University of Maringá, NUPÉLIA – G-90 -Av. Colombo, 5790 – Maringá – PR, Brazil, 87020-900
ABSTRACT: In order to evaluate and relate the abundance of periphytic desmids with abiotic and biotic factors of UHE Rosana and UHE Salto do Vau reservoirs, periphyton samples were carried out during 2002. Periphytic material was collected during two occasions, summer and winter, in the riverine, transition and lacustrine zones. Samples for determination of density were removed from substrata, stored in flasks, fixed and preserved with Transeau solution. Periphytic desmids community presented larger density during summer in both reservoirs. In the transition zone of Rosana Reservoir, it was registered greater densities values; while in Salto do Vau it occurred in the lacustrine zone. In riverine zone of both reservoirs, the abundance differed significantly from the other zones. A Principal Components Analysis using 15 environmental variables explained 76.7 % of the total variability of the data. A Detrended Correspondence Analysis applied on the density of desmids species identified a group of sampling sites, formed by some genera, especially Closterium, from the Salto do Vau Reservoir, whereas in the Rosana Reservoir, the other group was formed basically due to the higher density of Cosmarium. Pearson correlations suggest that nutrients, conductivity, water temperature, wind and aquatic macrophytes were the environmental variables that most explained the relation of sampling sites and desmids species.
Key-words: epiphytic desmids, littoral region, periphyton, reservoir.