Influence of seasonal variation on the hydro-biogeochemical characteristics of two upland lakes in the Southeastern Amazon, Brazil oleh PRAFULLA K. SAHOO, JOSÉ T.F. GUIMARÃES, PEDRO W.M. SOUZA-FILHO, MARCIO S. DA SILVA, RENATO O. SILVA JÚNIOR, GUSTAVO PESSIM, BERGSON C. DE MORAES, PAULO F.P. PESSOA, TARCÍSIO M. RODRIGUES, MARLENE F. DA COSTA, ROBERTO DALL'AGNOL