Algae play a significant role in regulating the biogeochemical cycle of mercury(Hg),particularly its highly toxicform,methylmercury(MeHg),within wetlands and lakes.However,despite their widespread presence in paddyfield...Algae play a significant role in regulating the biogeochemical cycle of mercury(Hg),particularly its highly toxicform,methylmercury(MeHg),within wetlands and lakes.However,despite their widespread presence in paddyfields,their specific effects on MeHg dynamics are not yet fully understood.This study investigated the algae-mediated distribution and accumulation of MeHg in Hg-contaminated paddyfields,utilizingfield investigationand microcosm experiment.The results indicated that algae demonstrated a multi-source uptake pattern and hada high capacity to accumulate both total Hg(926±1.69 ng/g)and MeHg(83.6±1.12 ng/g).This accumulationwas predominantly characterized by inorganic Hg species,accounting for 88.4%.Algal capsular extracellularpolymeric substance(EPS)exhibited higher levels of labile organic fractions,such as cysteine(0.59±0.01μg/g),and increased MeHg concentration(84.2±4.51 ng/kg),which contrasted with the levels found in colloidal EPS(0.06±0.01 ng/g and 15.0±1.61 ng/kg).Meanwhile,a significant correlation(P<0.05)was observed betweenthiol-containing cysteine and MeHg concentrations in algal EPS.Algal incubation further revealed the formationof mineral-EPS-algae aggregates on algal surfaces,accompanied by the colonization of Hg-methylating bacteria.Therefore,the surface of algae may form a favorable matrix for microbial Hg methylation and the accumulationof MeHg.Thesefindings emphasize the crucial roles of algae in regulating MeHg dynamics within algae-watersystem in Hg-contaminated paddyfields.展开更多
Sediment cores（containing sediment and overlying water） from Baihua Reservoir（SW China）were cultured under different redox conditions with different microbial activities, to understand the effects of sulfate-reduc...Sediment cores（containing sediment and overlying water） from Baihua Reservoir（SW China）were cultured under different redox conditions with different microbial activities, to understand the effects of sulfate-reducing bacteria（SRB） on mercury（Hg） methylation at sediment–water interfaces. Concentrations of dissolved methyl mercury（DMe Hg） in the overlying water of the control cores with bioactivity maintained（BAC） and cores with only sulfate-reducing bacteria inhibited（SRBI） and bacteria fully inhibited（BACI） were measured at the anaerobic stage followed by the aerobic stage. For the BAC and SRBI cores, DMe Hg concentrations in waters were much higher at the anaerobic stage than those at the aerobic stage, and they were negatively correlated to the dissolved oxygen concentrations（r =- 0.5311 and r =- 0.4977 for BAC and SRBI, respectively）. The water DMe Hg concentrations of the SRBI cores were 50% lower than those of the BAC cores, indicating that the SRB is of great importance in Hg methylation in sediment–water systems, but there should be other microbes such as iron-reducing bacteria and those containing specific gene cluster（hgc AB）, besides SRB,causing Hg methylation in the sediment–water system.展开更多
基金supported by the Natural Science Foundation of China(Nos.22166009,42477268 and 42267032)the High-Level Talent Training Program in Guizhou Province(No.GCC[2023]045)the Post-funded Project of National Key Research and Development Program of China and the Natural Science Foundation of Chongqing(No.CSTB2022NSCQ-MSX0563).
文摘Algae play a significant role in regulating the biogeochemical cycle of mercury(Hg),particularly its highly toxicform,methylmercury(MeHg),within wetlands and lakes.However,despite their widespread presence in paddyfields,their specific effects on MeHg dynamics are not yet fully understood.This study investigated the algae-mediated distribution and accumulation of MeHg in Hg-contaminated paddyfields,utilizingfield investigationand microcosm experiment.The results indicated that algae demonstrated a multi-source uptake pattern and hada high capacity to accumulate both total Hg(926±1.69 ng/g)and MeHg(83.6±1.12 ng/g).This accumulationwas predominantly characterized by inorganic Hg species,accounting for 88.4%.Algal capsular extracellularpolymeric substance(EPS)exhibited higher levels of labile organic fractions,such as cysteine(0.59±0.01μg/g),and increased MeHg concentration(84.2±4.51 ng/kg),which contrasted with the levels found in colloidal EPS(0.06±0.01 ng/g and 15.0±1.61 ng/kg).Meanwhile,a significant correlation(P<0.05)was observed betweenthiol-containing cysteine and MeHg concentrations in algal EPS.Algal incubation further revealed the formationof mineral-EPS-algae aggregates on algal surfaces,accompanied by the colonization of Hg-methylating bacteria.Therefore,the surface of algae may form a favorable matrix for microbial Hg methylation and the accumulationof MeHg.Thesefindings emphasize the crucial roles of algae in regulating MeHg dynamics within algae-watersystem in Hg-contaminated paddyfields.
基金supported by the National Natural Science Foundation of China(nos.41063006,41363007,and 41273099)the Science and Technology Fund of Guizhou Province(no.[2013]2296)
文摘Sediment cores（containing sediment and overlying water） from Baihua Reservoir（SW China）were cultured under different redox conditions with different microbial activities, to understand the effects of sulfate-reducing bacteria（SRB） on mercury（Hg） methylation at sediment–water interfaces. Concentrations of dissolved methyl mercury（DMe Hg） in the overlying water of the control cores with bioactivity maintained（BAC） and cores with only sulfate-reducing bacteria inhibited（SRBI） and bacteria fully inhibited（BACI） were measured at the anaerobic stage followed by the aerobic stage. For the BAC and SRBI cores, DMe Hg concentrations in waters were much higher at the anaerobic stage than those at the aerobic stage, and they were negatively correlated to the dissolved oxygen concentrations（r =- 0.5311 and r =- 0.4977 for BAC and SRBI, respectively）. The water DMe Hg concentrations of the SRBI cores were 50% lower than those of the BAC cores, indicating that the SRB is of great importance in Hg methylation in sediment–water systems, but there should be other microbes such as iron-reducing bacteria and those containing specific gene cluster（hgc AB）, besides SRB,causing Hg methylation in the sediment–water system.
