Functional and structural responses of soil N-cycling microbial communities to the herbicide mesotrione: a dose-effect microcosm approach

Abstract

Microbial communities driving the nitrogen cycle contribute to ecosystem services such as crop production and air, soil, and water quality. The responses to herbicide stress of ammonia-oxidizing and ammonia-denitrifying microbial communities were investigated by an analysis of changes in structure-function relationships. Their potential activities, abundances (quantitative PCR), and genetic structure (denaturing gradient gel electrophoresis) were assessed in a microcosm experiment. The application rate (1 × FR, 0.45 μg g(-1) soil) of the mesotrione herbicide did not strongly affect soil N-nutrient dynamics or microbial community structure and abundances. Doses of the commercial product Callisto® (10 × FR and 100 × FR) or pure mesotrione (100 × FR) exceeding field rates induced short-term inhibition of nitrification and a lasting stimulation of denitrification. These effects could play a part in the increase in soil ammonium content and decrease in nitrate contents observed in treated soils. These functional impacts were mainly correlated with abundance shifts of ammonia-oxidizing Bacteria (AOB) and Archaea (AOA) or denitrifying bacteria. The sustained restoration of nitrification activity, from day 42 in the 100 × FR-treated soils, was likely promoted by changes in the community size and composition of AOB, which suggests a leading role, rather than AOA, for soil nitrification restoration after herbicide stress. This ecotoxicological community approach provides a nonesuch multiparameter assessment of responses of N-cycling microbial guilds to pesticide stress.

Toward Integrative Bacterial Monitoring of Metolachlor Toxicity in Groundwater

“…Nevertheless, more subtle changes, e.g., in rare OTUs, may reflect adaptation of bacterial communities to a specific factor such as presence of a micropollutant or its degradation. This type of response, however, may not have to be proportional to exposure dose, and will thus likely be difficult to evidence at environmental concentrations, as shown previously for soil ( Crouzet et al, 2010 ). Worthy of note in the perspective of future studies, temporal trajectories of community changes during incubation may additionally evidence transient responses of groundwater bacterial diversity during MET degradation.…”

Mesotrione Herbicide: Efficiency, Effects, and Fate in the Environment after 15 Years of Agricultural Use

“…After a microcosm study on a chernozem soil, no responses of the soil microbial communities (including N‐cycling and phototrophic communities) in terms of abundance, diversity, and activities were observed . These conclusions occurred for communities spread with both the environmental doses of pure and formulated (Callisto ® ) mesotrione.…”

Responses of Nitrogen-Cycling Microorganisms to Dazomet Fumigation

“…Fumigants in general kill not only target pathogens but also off-target microorganisms that can be important in the soil microbial community. Microorganisms, and in particular bacteria, are reported to significantly influence the soil quality and crop yield by regulating several important soil processes, such as organic matter decomposition, organic pollutant degradation and nutrient transformation ( Álvarez-Martín et al, 2016 ; Crouzet et al, 2016 ). Previous studies reported that the fumigants chloropicrin (CP), 1,3-dichloropropene and metam sodium (MS) significantly decreased soil bacterial diversity and significantly changed the predominance of bacterial phyla in microbial communities ( Liu et al, 2015 ; Li et al, 2017a , b ; Zhang et al, 2017 ).…”