The degradative characteristics of simazine （SIM）, microbial biomass carbon, plate counts of heterotrophic bacteria and most probably number （MPN） of SIM degraders in uninoculated non-rhizosphere soil, uninoculate...The degradative characteristics of simazine （SIM）, microbial biomass carbon, plate counts of heterotrophic bacteria and most probably number （MPN） of SIM degraders in uninoculated non-rhizosphere soil, uninoculated rhizosphere soil, inoculated non- rhizosphere soil, and inoculated rhizosphere soil were measured. At the initial concentration of 20 mg SIM/kg soil, the half-lives of SIM in the four treated soils were measured to be 73.0, 52.9, 16.9, and 7.8 d, respectively, and corresponding kinetic data fitted first-order kinetics. The experimental results indicated that higher degradation rates of SIM were observed in rhizosphere soils, especially in inoculated rhizosphere soil. The degradative characteristics of SIM were closely related to microbial process. Vegetation could enhance the magnitude of rhizosphere microbial communities, microbial biomass content, and heterotrophic bacterial community, but did little to influence those community components responsible for SIM degradation. This suggested that rhizosphere soil inoculated with microorganisms-degrading target herbicides was a useful pathway to achieve rapid degradation of the herbicides in soil.展开更多
Light intensity directly affects phytoplankton and can alter the toxicity of phytotoxic pollutants present in natural water bodies.Light fluctuation in aquatic ecosystems often occurs as a function of water turbidity,...Light intensity directly affects phytoplankton and can alter the toxicity of phytotoxic pollutants present in natural water bodies.Light fluctuation in aquatic ecosystems often occurs as a function of water turbidity,water movement,cloud cover,and seasonality.Atrazine and simazine are commonly used herbicides that inhibit photosynthesis,posing significant risks to aquatic primary producers,and may be found simultaneously in aquatic ecosystems.The interactions between light and herbicide mixtures on phytoplankton growth and physiological state are poorly understood.Therefore,we addressed the toxicity of the herbicides,atrazine and simazine(individually and mixed),on the growth and photosynthetic activity of three freshwater phytoplankton under three light intensities.We found that the toxic effects of single and mixed herbicides are species-specific and significantly modulated by light intensity,with synergistic effects observed for herbicide mixtures under high light conditions.Atrazine and simazine(individually and mixed)toxicities on photosynthesis were greater for the three species grown under low light than under very low light.However,high-light adapted strains of M.aeruginosa were less sensitive to single and mixed herbicides than those adapted to low-and very low-light conditions.Under low-and high-light conditions,the photoprotective ability was extremely sensitive to the inhibitory effects of atrazine and simazine,individually and when mixed.Understanding these interactions is important because microalgae form the base of aquatic food webs and their impairment can have cascading effects on ecosystems.These findings underscore the importance of considering multiple environmental stressors in assessing the ecological risks of herbicides,highlighting potential impacts on aquatic primary productivity.展开更多
基金This work was supported by the National Key Basic Research Program （973） of China （No. 2002CB410804）the National Natural Science Foundation of China （No. 40201026）.
文摘The degradative characteristics of simazine （SIM）, microbial biomass carbon, plate counts of heterotrophic bacteria and most probably number （MPN） of SIM degraders in uninoculated non-rhizosphere soil, uninoculated rhizosphere soil, inoculated non- rhizosphere soil, and inoculated rhizosphere soil were measured. At the initial concentration of 20 mg SIM/kg soil, the half-lives of SIM in the four treated soils were measured to be 73.0, 52.9, 16.9, and 7.8 d, respectively, and corresponding kinetic data fitted first-order kinetics. The experimental results indicated that higher degradation rates of SIM were observed in rhizosphere soils, especially in inoculated rhizosphere soil. The degradative characteristics of SIM were closely related to microbial process. Vegetation could enhance the magnitude of rhizosphere microbial communities, microbial biomass content, and heterotrophic bacterial community, but did little to influence those community components responsible for SIM degradation. This suggested that rhizosphere soil inoculated with microorganisms-degrading target herbicides was a useful pathway to achieve rapid degradation of the herbicides in soil.
基金supported by a Fisheries and Oceans Canada(DFO)grant(MECTS-#3789712)obtained by Philippe Juneau,Johann Lavaud and Beatrix Beisnerthe Natural Science and Engineering Research Council of Canada(NSERC)(RGPIN-2017-06210)awarded to Philippe Juneau。
文摘Light intensity directly affects phytoplankton and can alter the toxicity of phytotoxic pollutants present in natural water bodies.Light fluctuation in aquatic ecosystems often occurs as a function of water turbidity,water movement,cloud cover,and seasonality.Atrazine and simazine are commonly used herbicides that inhibit photosynthesis,posing significant risks to aquatic primary producers,and may be found simultaneously in aquatic ecosystems.The interactions between light and herbicide mixtures on phytoplankton growth and physiological state are poorly understood.Therefore,we addressed the toxicity of the herbicides,atrazine and simazine(individually and mixed),on the growth and photosynthetic activity of three freshwater phytoplankton under three light intensities.We found that the toxic effects of single and mixed herbicides are species-specific and significantly modulated by light intensity,with synergistic effects observed for herbicide mixtures under high light conditions.Atrazine and simazine(individually and mixed)toxicities on photosynthesis were greater for the three species grown under low light than under very low light.However,high-light adapted strains of M.aeruginosa were less sensitive to single and mixed herbicides than those adapted to low-and very low-light conditions.Under low-and high-light conditions,the photoprotective ability was extremely sensitive to the inhibitory effects of atrazine and simazine,individually and when mixed.Understanding these interactions is important because microalgae form the base of aquatic food webs and their impairment can have cascading effects on ecosystems.These findings underscore the importance of considering multiple environmental stressors in assessing the ecological risks of herbicides,highlighting potential impacts on aquatic primary productivity.
