Algas perifíticas em dois ambientes do baixo rio Doce (lagoa Juparanã e rio Pequeno – Linhares, Estado do Espírito Santo, Brasil): variação espacial e temporal

Abstract

This research aimed to evaluate the spatial and temporal variation of the periphytic algae community within two environments of the lower Doce River: Juparanã Lagoon and Pequeno River. Samplings were carried out every three months from August 2004 to May 2005 at both sites. Natural substrata of Eichhornia azurea (Sw.) Kunth petioles were collected from the sites. The community was analyzed according to species richness, frequency of occurrence, density of organisms, abundance and dominancy. Eighty-six taxa were recorded in the lagoon, and the density of organisms varied from 20,595 ind cm-2 (May/05) to 88,712 ind cm-2 (Nov/04). Eighty-three taxa were recorded in the river, and the density of organisms varied from 16,049 ind cm-2 (Feb/05) to 71,663 ind cm-2 (Aug/04). At both sites, the classes that predominated qualitatively were Cyanophyceae, Bacillariophyceae and Zygnemaphyceae, in which filamentous and unicellular forms dominated, followed by colonial forms. Quantitatively, the most representative classes were Cyanophyceae and Bacillariophyceae. A spatial variation was not observed. Precipitation, water temperature, electric conductivity and transparency were the variables that most oscillated according to seasonal variation (dry or rainy season). They also presented a greater number of significant correlations with the biological variables, showing evidence of temporal heterogeneity.