Water quality evaluation of the Ijuí River using the micronucleus test in fish

Abstract

The main sources of contamination of the Ijuí River are surface runoff from crops and domestic sewage. The micronucleus test (MN) in fish is a useful tool in the assessment of water quality, indicating the presence of toxic substances. This study aimed to evaluate the water quality of the Ijuí River using the MN test in a native fish species. Specimens of the Characidae family were collected in winter and summer at two points on the Ijuí River, approximately 170 km away, which have agriculture as the main economic activity, but differ in population density. The MN frequency showed no differences between the sites. However, at both points, the frequency of MN in summer (2.15‰ and 2.13‰, at points 1 and 2, respectively) was significantly higher than in winter (0.35‰ at point 1 and 0 .45‰ at point 2). There were no significant differences for the other nuclear abnormalities. The results indicate the occurrence of temporal variation in the mutagenic contamination of the Ijuí River water, which may be related to agricultural activities, since summer is the period when agricultural pests are more frequent in the region.