2013/01/01 by Fabrice Martin‐Laurent, Martin-Laurent, Fabrice, Marion Devers‐Lamrani +2
Environmental Science · Agricultural and Biological Sciences · #Pesticide and Herbicide Environmental Studies #Environmental Toxicology and Ecotoxicology #Weed Control and Herbicide Applications
paper · doi:10.17180/xqwj-sq59
This study showed that the different compartments of the landscape within the Morcille watershed (vineyard soil, grass buffer strip soil, sediments), connected along the soil-water continuum, are able to mineralize the herbicide diuron. The purifying capability of these different compartments evolved according to the level of exposure to the contaminant. Indeed, the exposed grass buffer strip showed a better ability to mineralize diuron than the control one. The sediments of the Morcille river located nearby the buffer zone showed also a purifying capability following an upstream-downstream gradient in accordance with the one observed for the chemical quality of the water in Morcille river. The importance of the surface run-off from the vineyard to the sediments of the Morcille river for the adaptation of microbial communities to diuron-mineralization was showed. These original findings showed that although the microflora of the sediments was intrinsically able to adapt to diuron degradation, this process was favoured by soil run-off suggesting the transfer of purifying capabilities from soil to aquatic microbial communities, underlining the existence of chemical and microbiological connections of terrestrial and aquatic compartments of agro-systems. Monitoring of the evolution of the purifying capability of sediments in response to the ban of diuron uses evidenced the improvement of the chemical quality of the Morcille river. However, even four years after its ban, diuron was still detected in the river at the intermediary and downstream stations in spring and summer. Over this four-year period the purifying capability of the sediments significantly decreased. However an upstream-downstream gradient was still detectable, in accordance with the one observed for the chemical quality of the Morcielle water. The study of the diuron-degrading microbial community from the grass-buffer strip soil and from the sediments allowed isolating diuron-degrading microbial populations. Several Arthrobacter sp. isolates able to transform diuron to 3,4-dichloroaniline have been isolated from the soil and the sediments. Moreover, one additional bacterial isolate belonging to the Achromobacter genus and able to mineralize 3,4-dichloroaniline, has been isolated. A synthetic microbial consortium made of Arthrobacter sp. and Achromobacter sp. populations was shown to be able to fully mineralize diuron. These observations suggest that the microbial community able to mineralize the diuron in the soil of the buffer zone or in the sediments of the Morcille river was probably resulting from the metabolic cooperation of two bacterial populations, one transforming the diuron to 3,4-dichloroaniline while the other mineralized this intermediary metabolite. To conclude, this study shows that vineyard and grass buffer strip soils as well as the sediments of the Morcille River frequently exposed to diuron hosted a diuron-degrading microbial community able to degrade diuron. Degradation capabilities of these different compartments are variable and the level of exposure to the contaminant was shown as a major driver of the adaptation to diuron degradation. The purifying capability of vineyard and grass buffer strip soils sediments relied on the activity of microbial degrading populations developing cooperative metabolism.