The temporal and spatial variation of some limnologjcal variables in the limnetic zone of an Amazonian floodplain lake, Catalão Lake, was studied. The following parameters were measured weekly during the dry period of 2006 and the flood period of 2007: water temperature, euphoric zone, mixing zone, electrical conductivity, dissolved oxygen, water transparency and total phosphorus and nitrogen. Simple regressions were carried out to test the hypothesis of environmental homogeneity as a function of flooding. Also, diel temperature, dissolved oxygen and electric conductivity profiles were studied during the dry period and in the flood period. The results show the importance of the flood pulse in the variation of the physical and chemical variables in the lake. The PCA indicated that, during the dry period, the physical and chemical variables had a stronger spatial pattern of distribution, while during the flood period, the pattern was temporal. The regressions indicated the homogeneity of the environment as a function of flooding. The results of the diel cycles seem to indicate that Catalão lake has a polimictic and oligomictic behavior during the dry and flood periods, respectively.
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