Four sampling stations were selected in the Laranjo Bay along a transect defined by the distance from the mercury point source: station 1 (St 1) is considered to be at the mercury point source in the lagoon, and the others stations are progressively further from this one, respectively 600 m (station 2, St 2), 3000 m (station 3,St 3) and 5000 m (station 4, St 4) (Fig. 1).