Water quality in agricultural watersheds of Córdoba: effect of pesticides on native microbiota

BACHETTI, ROMINA; INGARAMO, ROSA N; MORGANTE, VERÓNICA; PORPORATTO CARINA; MORGANTE CAROLINA

Tucuman

Congreso; VII Congreso Argentino de Microbiología General. SAMIGE del Bicentenario.; 2011

Modern agriculture depends on the use of pesticides to ensure the production of crops. Their continued and excessive use has led to the contamination of differents ecosystems. The persistence of pesticides in aquatic systems depends on biotic processes in which the microorganisms play an important role. Natural microbial degradation over a wide range of pesticides exposes catabolic capabilities for their use in bioremediation processes. In this work we monitored different organochlorinated and organophosphorous pesticides on environmental surface waters samples of the south-central region of Córdoba, Argentina. We also studied the effect of 2 pesticides on culturable heterotrophic microorganisms. Samples were taken from 6 stations located on Tercero River and Cuarto River watersheds during Febrary 2011 (summer), with high river-flow conditions. The analysis of 9 organophosphorus and 30 organochlorinated pesticides was performed using capillar gas chromatography with electron capture detector (GC-ECD). The effect of both Atrazine and 2,4D (Atanor, Argentina) on culturable heterotrophic bacteria was assayed from water samples of Pampayasta and Carcarañá River (López, 2005). Experiments were also conducted to isolate in minimal medium potential indigenous bacterial strains capable of utilizing either 2.4D or Atrazine (3000 ug/ml) as a sole N and C sources, respectively. Since high amounts of pesticides were added to cultures and soil, water quality was expected to be deteriorated. Preliminary results did not detect the presence of pesticide concentrations on the screneed water samples. In agreement with Cooman (2005) we considered that during high-flow conditions pesticides in running surface waters may be present at relatively high concentrations for only a short period of time after which a rapid decrease in concentrations takes place. Future studies will be encouraged in low river-flow conditions. The plate-count data indicated that total viable bacteria in the water samples from Pampayasta River amended with 2.4D or atrazine (10 ug/ml) were significantly higher by almost 0.83 log and 0.35  log, respectively, than unamended controls during the first 3 weeks of the experiments. In contrast, after the treatment with both pesticides in water samples of Carcarañá River bacterial microbiota did not increase the number of control. The results indicated that Pampayasta River harbor indigenous microorganisms with enhanced 2.4D and Atrazine catabolic potential. Three indigenous strains were isolated from water samples amended with 2.4D and 12 from Atrazine. In the present study no pesticide were detected in the aquatic environments at the time of sampling indicating no contamination derived from human activities. The indigenous bacteria isolated capable of utilize high concentrations of both 2.4D or Atrazine for growth are actually under study in our laboratory as potential biocatalysts for degradation of these compounds. Supported by MinCyT Cba; UNVM