Oreochromis niloticus and Pistia stratiotes Sensibility to Copper and Chromium

Resumen

A few works about aquatic organisms sensibility to environmental contaminants are conducted using species common to Brazilian ecosystems. Oreochromis niloticus is a widespread species in reservoirs, as Pistia stratiotes, being the fish and macrophyte species, respectively, most abundant in Lobo reservoir. The aim of this work was to determine the sensibility range to Cr and Cu to this species. The LC₅₀ was calculated by the Trimmed Spearman-Karber method, after 96 h of exposition to fish, and the EC₅₀ after 168 h to macrophytes. The follow characteristics were measured in P. stratiotes individuals: height, diameter, number of leaves and number of roots. The LC₅₀ values range to Cr obtained with the individuals of O. niloticus was 107.2-164 mg/L, and the values to Cu ranged between 0.32 and 0.65 mg/L. The EC₅₀ values to Cr determined in the P. stratiotes tests ranged from 22.4 to 33.7 mg/L, as to the leaves number estimation as to the roots number estimation. In the tests with Cu, these values ranged between 0.2-0.3 mg/L, considering the roots number. Both the species tested were more sensible to Cu than to Cr, and the LC₅₀ values obtained to the fish and the EC₅₀ values obtained to the macrophytes were higher than the values determined by other works to different trophic level organisms, suggesting that the species studied in this work are not indicate to use as test organism, at least considering the effect parameters evaluated.