Micronucleus test in fish from a pampasic pond (Argentina): an estimation of the presence of genotoxic compounds

Abstract

The Los Padres pond is one of the commonly shallow, polymictic lakes from the so-called depressed Pampa (Argentina). Its watershed includes one affluent, named Los Padres creek, which flows through horticultural lands wherein great amounts of pesticides are applied. Opposite to this stream, the pond drains into La Tapera creek that is the effluent running toward the sea. Many studies have confirmed the capacity of various pesticides to induce genetic damage. The use of micronucleus (MN) tests in fish has enabled us to detect the presence of contaminants in the lake water and to evaluate their genotoxic effects. For this purpose, water samples were collected during April, August, and December 1999 from both creeks characterized by different environmental conditions. In the laboratory, specimens of tetras Cheirodon interruptus (Pisces, Characidae) were reared in water samples from the two creeks. Control fish were kept in drinking water. Fifteen individuals from each experimental group were sacrificed after 24-, 48-, and 72-hour exposure intervals. Micronucleus frequency in fish erythrocytes was determined, and the Kruskal–Wallis test for statistic analysis was used. We made the following observations: (1) Highly significant differences occurred in MN frequency between the control group and the samples from both creeks. (2) An increase in MN frequency was evident in specimens sampled from the affluent input during the month of December. These results allowed us to conclude that the increase in MN frequency observed in fish belonging to both sampling sites would indicate the existence of genotoxic compounds in the Los Padres pond. The high MN frequency in fish collected near Los Padres creek inlet might be related to the polluted load transported by the affluent and discharged into the lake’s surface waters. Future work would allow us to develop efficient methods for predicting the presence of genotoxic contaminants. It would be possible then to propose strategies for regulating and decreasing the sources of pollution that affect human health.