Using a threshold of 20 percent effect value (Chial et al., 2003) the sediment samples St1 and St3 from the first and the third sediment traps and the sample P1-1 from the deep area of pond 1 were classified as toxic but the other samples were not toxic. For the chronic endpoint, growth inhibition, all sediment samples except those from ponds 8 and 10, and the well at the outlet were toxic (Table 1). For both the acute and the chronic responses there was a gradual decrease and loss of toxicity with treatment in the wetland system.