Aquatic ecosystems have been identified as a globally significant source of nitrous oxide(N_2O) due to continuous active nitrogen involvement, but the processes and influencing factors that control N_2O production are...Aquatic ecosystems have been identified as a globally significant source of nitrous oxide(N_2O) due to continuous active nitrogen involvement, but the processes and influencing factors that control N_2O production are still poorly understood, especially in reservoirs. For that, monthly N_2O variations were monitored in Dongfeng reservoir(DFR)with a mesotrophic condition. The dissolved N_2O concentration in DFR displayed a distinct spatial–temporal pattern but lower than that in the eutrophic reservoirs. During the whole sampling year, N_2O saturation ranging from 144% to 640%, indicating that reservoir acted as source of atmospheric N_2O. N_2O production is induced by the introduction of nitrogen(NO_3^-, NH_4^+) in mesotrophic reservoirs, and is also affected by oxygen level and water temperature. Nitrification was the predominate process for N_2O production in DFR due to well-oxygenated longitudinal water layers.Mean values of estimated N_2O flux from the air–water interface averaged 0.19 μmol m^(-2)h^(-1) with a range of 0.01–0.61 μmol m^(-2)h^(-1). DFR exhibited less N_2O emission flux than that reported in a nearby eutrophic reservoir, but still acted as a moderate N_2O source compared with other reservoirs and lakes worldwide. Annual emissions from the water–air interface of DFR were estimated to be 0.32×10~5 mol N–N_2O, while N_2O degassing from releasing water behind the dam during power generation was nearly five times greater. Hence, N_2O degassing behind the dam should be taken into account for estimation of N_2O emissions from artificial reservoirs, an omission that historically has probably resulted in underestimates. IPCC methodology should consider more specifically N_2O emission estimation in aquatic ecosystems, especially in reservoirs, the default EF5 model will lead to an overestimation.展开更多
Spatial variations in phytoplankton community within a large mesotrophic reservoir （Miyun reservoir, North China） were investigated in relation to variations in physico-chemical properties, nutrient concentrations, ...Spatial variations in phytoplankton community within a large mesotrophic reservoir （Miyun reservoir, North China） were investigated in relation to variations in physico-chemical properties, nutrient concentrations, temperature and light conditions over a 5 month period in 2009. The dynamics of phytoplankton community was represented by the dominance of cyanobacteria through summer and fall, following with a short term dominance of chlorophyta in late fall, and a relatively high abundance of diatom in October; on the other hand, maximum phytoplankton biomass was recorded in the north shallow region of Miyun reservoir with a higher nutrients level. Particular attention was paid to the impacts of environmental conditions on the growth of two cyanobacteria genera, the toxin-producing Microcystis and the taste ＆ odor-producing Oscillatoria. Microcystis biomass was in general greatly affected by water temperature and mixing depth/local water depth ratio in this reservoir, while the Oscillatoria biomass in the surface and middle layers was greatly affected by total dissolved phosphorus, and that in the bottom layer was related with the Secchi depth/local water depth ratio. Abundant Oscillatoria biomass was observed only in late September when Microcystis biomass decreased and allowed sufficient light go through.展开更多
More than 500 lakes are found in Uzbekistan. Ayakagitma Lake is located on the border of the Northern Gijduvon and Shafirkon districts of Bukhara region. This lake was formed in 1985-1986 at the expense of the waters ...More than 500 lakes are found in Uzbekistan. Ayakagitma Lake is located on the border of the Northern Gijduvon and Shafirkon districts of Bukhara region. This lake was formed in 1985-1986 at the expense of the waters of the sewage dump collector. The area of the lake is 8200 hectares, the maximum depth is 35 m, on average 10 - 15 m, the minimum is 3 - 5 meters. The chemical composition of lake water is chloride-sulfate and has a calcareous character. 67 species of high plants belonging to 22 families were found in this area. 17 of these species are found in the water of the lake and 50 species are found around it. Of the most common species, Phragmites communis reach a height of 4.5 - 5.5 meters. Phragmites communis make up the total area of the lake 8 - 10 hectares.展开更多
Anammox and denitrification are key processes for nitrogen removal in lake sediments.However,how environmental changes mediate the community structure and functional genes of nitrogen removal bacteria in lakes remain ...Anammox and denitrification are key processes for nitrogen removal in lake sediments.However,how environmental changes mediate the community structure and functional genes of nitrogen removal bacteria in lakes remain unclear.Using metagenome and amplicon sequencing,we investigated the anammox and denitrifying bacteria and their nitrogen remov-ing potentials in lakes experiencing significant spatiotemporal and environmental variations.The community structure of anammox and denitrifying bacteria exhibited stronger lake-wide spatial variations than that of seasonality,while only the denitrification-related functional genes showed substantial variations in both lakes.Anammox genes(e.g.,hzsA/B/C and hdh)showed no significant spatial variations.However,the abundances of anammox and denitrifying genes were significantly higher in winter than in summer.The mesotrophic Lake Weishan demonstrated a greater capacity for complete denitrification in winter,while the eutrophic Lake Donghu exhibited a higher potential of anammox in summer.Differences in functional gene abundances between lakes were more pronounced than variations in phylogenetic diversity,indicating clear functional adaptations to local environments.The coupled nitrogen removal potentials also reflected ecological interactions among anammox and denitrifying genes.Importantly,anammox and denitrifying bacterial communities and their functional genes were primarily driven by dissolved organic carbon,total phosphorous and zinc(Zn).The dissimilarities of anammox and denitrifying bacterial communities increased with geographic distance,indicating a clear distance-decay effect.This study highlights the anammox and denitrifying bacteria and their nitrogen removal potentials in lake sediments that are mediated by both spatial and seasonal environmental changes.展开更多
基金financially supported by the National Key Research and Development Program of China through grant 2016YFA0601000the National Major Scientific Research Program Grant No.2013CB956401+1 种基金the National Natural Science Foundation of China through Grants Nos.41325010,41403082,and 41302285the Tianjin Research Program of Application Foundation and Advanced Technology Grant No.14JCQNJC08800
文摘Aquatic ecosystems have been identified as a globally significant source of nitrous oxide(N_2O) due to continuous active nitrogen involvement, but the processes and influencing factors that control N_2O production are still poorly understood, especially in reservoirs. For that, monthly N_2O variations were monitored in Dongfeng reservoir(DFR)with a mesotrophic condition. The dissolved N_2O concentration in DFR displayed a distinct spatial–temporal pattern but lower than that in the eutrophic reservoirs. During the whole sampling year, N_2O saturation ranging from 144% to 640%, indicating that reservoir acted as source of atmospheric N_2O. N_2O production is induced by the introduction of nitrogen(NO_3^-, NH_4^+) in mesotrophic reservoirs, and is also affected by oxygen level and water temperature. Nitrification was the predominate process for N_2O production in DFR due to well-oxygenated longitudinal water layers.Mean values of estimated N_2O flux from the air–water interface averaged 0.19 μmol m^(-2)h^(-1) with a range of 0.01–0.61 μmol m^(-2)h^(-1). DFR exhibited less N_2O emission flux than that reported in a nearby eutrophic reservoir, but still acted as a moderate N_2O source compared with other reservoirs and lakes worldwide. Annual emissions from the water–air interface of DFR were estimated to be 0.32×10~5 mol N–N_2O, while N_2O degassing from releasing water behind the dam during power generation was nearly five times greater. Hence, N_2O degassing behind the dam should be taken into account for estimation of N_2O emissions from artificial reservoirs, an omission that historically has probably resulted in underestimates. IPCC methodology should consider more specifically N_2O emission estimation in aquatic ecosystems, especially in reservoirs, the default EF5 model will lead to an overestimation.
基金supported by the National Natural Science Foundation of China (No. 50938007)
文摘Spatial variations in phytoplankton community within a large mesotrophic reservoir （Miyun reservoir, North China） were investigated in relation to variations in physico-chemical properties, nutrient concentrations, temperature and light conditions over a 5 month period in 2009. The dynamics of phytoplankton community was represented by the dominance of cyanobacteria through summer and fall, following with a short term dominance of chlorophyta in late fall, and a relatively high abundance of diatom in October; on the other hand, maximum phytoplankton biomass was recorded in the north shallow region of Miyun reservoir with a higher nutrients level. Particular attention was paid to the impacts of environmental conditions on the growth of two cyanobacteria genera, the toxin-producing Microcystis and the taste ＆ odor-producing Oscillatoria. Microcystis biomass was in general greatly affected by water temperature and mixing depth/local water depth ratio in this reservoir, while the Oscillatoria biomass in the surface and middle layers was greatly affected by total dissolved phosphorus, and that in the bottom layer was related with the Secchi depth/local water depth ratio. Abundant Oscillatoria biomass was observed only in late September when Microcystis biomass decreased and allowed sufficient light go through.
文摘More than 500 lakes are found in Uzbekistan. Ayakagitma Lake is located on the border of the Northern Gijduvon and Shafirkon districts of Bukhara region. This lake was formed in 1985-1986 at the expense of the waters of the sewage dump collector. The area of the lake is 8200 hectares, the maximum depth is 35 m, on average 10 - 15 m, the minimum is 3 - 5 meters. The chemical composition of lake water is chloride-sulfate and has a calcareous character. 67 species of high plants belonging to 22 families were found in this area. 17 of these species are found in the water of the lake and 50 species are found around it. Of the most common species, Phragmites communis reach a height of 4.5 - 5.5 meters. Phragmites communis make up the total area of the lake 8 - 10 hectares.
基金supported by the National Natural Sci-ence Foundation of China(32030015,W2433059,42377111)the Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(SML2024SP002,SML2024SP022).
文摘Anammox and denitrification are key processes for nitrogen removal in lake sediments.However,how environmental changes mediate the community structure and functional genes of nitrogen removal bacteria in lakes remain unclear.Using metagenome and amplicon sequencing,we investigated the anammox and denitrifying bacteria and their nitrogen remov-ing potentials in lakes experiencing significant spatiotemporal and environmental variations.The community structure of anammox and denitrifying bacteria exhibited stronger lake-wide spatial variations than that of seasonality,while only the denitrification-related functional genes showed substantial variations in both lakes.Anammox genes(e.g.,hzsA/B/C and hdh)showed no significant spatial variations.However,the abundances of anammox and denitrifying genes were significantly higher in winter than in summer.The mesotrophic Lake Weishan demonstrated a greater capacity for complete denitrification in winter,while the eutrophic Lake Donghu exhibited a higher potential of anammox in summer.Differences in functional gene abundances between lakes were more pronounced than variations in phylogenetic diversity,indicating clear functional adaptations to local environments.The coupled nitrogen removal potentials also reflected ecological interactions among anammox and denitrifying genes.Importantly,anammox and denitrifying bacterial communities and their functional genes were primarily driven by dissolved organic carbon,total phosphorous and zinc(Zn).The dissimilarities of anammox and denitrifying bacterial communities increased with geographic distance,indicating a clear distance-decay effect.This study highlights the anammox and denitrifying bacteria and their nitrogen removal potentials in lake sediments that are mediated by both spatial and seasonal environmental changes.
