Combined use of biomarkers and in situ bioassays in Daphnia magna to monitor environmental hazards of pesticides in the field

10 pages, 3 tables, 3 figures.-- PMID: 17713226 [PubMed].

The aim of this investigation was to evaluate toxicity effects of pesticides in aquatic invertebrates using in situ bioassays with the local species, Daphnia magna. Investigations were carried out in the Delta del Ebro (northeast Spain) during the main growing season of rice (May–August). Measures of energy consumption (i.e., algal grazing) and of specific biochemical responses (biomarkers) were conducted in individuals transplanted at four stations, including a clean site upstream of the affected area and the three main channels that collect and drain the water from the rice fields into the sea. Seventeen pesticides were analyzed in water by on-line solid-phase extraction–liquid chromatography–tandem mass spectrometry. The results obtained indicated high levels of pesticides in water, with peak values of 487 μg/L for bentazone, 8 μg/L for methyl-4-chlorophenoxyacetic acid, 5 μg/L for propanil, 0.8 μg/L for molinate, and 0.7 μg/L for fenitrothion. Measured biological responses denoted severe effects on grazing rates; a strong inhibition of cholinesterases and carboxylesterases, which are specific biomarkers of organophosphorous and carbamate pesticides; and altered patterns of the antioxidant enzyme catalase and the phase II metabolizing enzyme glutathione S-transferase. Correlation analysis with pesticide residue levels converted to toxic units relative to its acute 48-h median lethal concentration of D. magna indicated significant and negative coefficients between the dominant pesticide residues and the observed biological response, thus denoting a clear cause-and-effect relationship. The results emphasize the importance of considering specific (biomarkers) as well as more generalized and ecologically related (grazing) in situ responses to identify and evaluate biological effects of environmental contaminants in the field.

This work is supported by the European Union in "Integrated modeling of the river-sediments-soil-groundwater system; advanced tools for the management of catchment areas and river basins in the context of global change" [AQUATERRA, GOCE 505428] and the Spanish Ministry of Education and Science [CGL2004-03514/HD, CTM2005-25168-E] and reflects the authors' view. The European Union is not liable for any use that may be made of the information contained herein. Joana Damasio was supported by the Portuguese Fundacion de Ciencia y Tecnologia PhD grant (SFRH/BD/23269/2005) and Carlos Barata by a Spanish "Ramón y Cajal" contract.

Peer reviewed