Biogeochemical Cycling of Metals in Freshwater Algae from Manaus and Carajás, Brazil

Abstract

Freshwater algae were analyzed in different riverine environments in Manaus and Carajás, Brazil. Filamentous algae from both locations were characterized by enhanced levels of a wide array of heavy metals. A comparison of the two main rivers in the Manaus area indicated that the algal samples from the solute-rich waters of the Rio Solimōes consistently contained higher metal concentrations than in the solute-deficient waters of the Rio Negro. A similar relationship also existed between algal samples collected from forested regions relative to adjacent deforested regions in the Carajás area

In the Rio Negro, diatoms were shown to be the most prolific eucaryotic micro-organisms found in the study area. These siliceous algae were found adhering to a variety of submerged solid substrates, including wood, rocks, and leaves. The abundance of these unicellular micro-organisms suggested that the dissolved silicon levels of the Rio Negro were influenced by biological activity.