AbstractLago Tupé, a Central Amazonian dystrophic black water “Ria lake” (blocked valley lake), lateral to the Rio Negro, was studied at all depths for a year. Physical and chemical results of that study are presented here as a prelude to the microbiological studies. The lake's origin and morphology are discussed. Results concerned with thermal properties, suspended matter and dissolved solids are presented, in addition to results on ionic composition, alkalinity, hardness, pH and dissolved oxygen. Nutrient studies include section of phosphate and nitrogen and conclude with silicate res