The Fate of Cu, Zn and Mn in an Intensive Fish Aquaculture (Tilapia - Oreochromis niloticus) in an Artificial Reservoir in Northeastern Brazil

Emissions of Cu, Zn and Mn and their fate in a typical tilapia (Oreochromis niloticus) cage farm in an artificial reservoir in northeastern Brazil were estimated through the analysis of their concentrations in the various compartments of the farm. Major source of Cu and Zn, but not of Mn, to the farm is from aquafeeds, with annual inputs of 3.83, 57.50 and 10.95 kg.ha−1, respectively. Notwithstanding, only a small fraction of the added Mn and Zn (0.13%, 2.61%, respectively) is incorporated into fish biomass, resulting in a larger proportion of the introduced metals to be exported to reservoir environment. For Cu, a much larger fraction (47.4%) is exported within the fish biomass. Once released, metals are incorporated into bottom sediments within the farm area, resulting in higher metal contents compared to sediments far from the farm area. However, the analysis of sediment cores and the respective enrichment factors showed that a significant fraction of the net input of Zn (70%) and of Cu (30%) is exported out to the open reservoir.