Samples of sediments and the overlying water were collected in the Qi＇ao Island coastal zone,the Zhujiang（Pearl River） Estuary（ZE）.Denitrification rates,sediment oxygen demand（SOD）,and fluxes of inorganic nitro...Samples of sediments and the overlying water were collected in the Qi＇ao Island coastal zone,the Zhujiang（Pearl River） Estuary（ZE）.Denitrification rates,sediment oxygen demand（SOD）,and fluxes of inorganic nitrogen compounds were investigated with N2 flux method,using a self-designed continuous flow through and auto-sampling system.The results indicate that the denitrification rates varied between 222 and 908 μmol/（m2·h） with an average of 499 μmol /（m2·h）.During incubation,the sediments absorbed dissolved oxygen in the overlying water with SOD ranging from 300 to 2 363 μmol/（m2·h）.The denitrification rates were highly correlated with the SOD（r2=0.77） regardless of the NO-3＋NO-2 concentrations in the overlying water,organic carbon contents in sediments and water temperature,suggesting that the SOD was probably the main environmental factor controlling the denitrification in the Qi＇ao Island coastal zone.There was a net flux of NO-3＋NO-2 into the sediments from the overlying water.The NH＋4 flux from sediments into water as the result of mineralization was between 12.3 and 210.3 μmol/（m2·h）,which seems limited by both organic carbon content in sediment and dissolved oxygen concentration in the overlying water.展开更多
Subtropical sediment cores （QA09-1 and QA12-9） from the coastal zone of Qi’ao Island in the Zhujiang River Estuary were used to determine the rates of sulfate reduction and their response to experimental tempera-tu...Subtropical sediment cores （QA09-1 and QA12-9） from the coastal zone of Qi’ao Island in the Zhujiang River Estuary were used to determine the rates of sulfate reduction and their response to experimental tempera-ture changes. The depth distribution of the sulfate reduction rates was measured from whole-core incu-bations with radioactive tracer35SO42-, and peaks of 181.19 nmol/（cm3·d） and 107.49 nmol/（cm3·d） were exhibited at stations QA09-1 and QA12-9, respectively. The profiles of the pore water methane and sulfate concentrations demonstrated that anaerobic oxidation of methane occurred in the study area, which result-ed in an increase in the sulfate reduction rate at the base of the sulfate-reducing zone. Meanwhile, the sulfate concentration was not a major limiting factor for controlling the rates of sulfate reduction. In addition, the incubation of the sediment slurries in a block with a temperature gradient showed that the optimum tem-perature for the sulfate reduction reaction was 36°C. The Arrhenius plot was linear from the lowest tempera-ture to the optimum temperature, and the activation energy was at the lower end of the range of previously reported values. The results suggested that the ambient temperature regime of marine environments prob-ably selected for the microbial population with the best-suited physiology for the respective environment.展开更多
The controlling effects on Spartina alterniflora through planting various densities of Sonneratia apetala were studied conducted.The results showed that with the increasing forest density of S.apetala,S.alterniflora w...The controlling effects on Spartina alterniflora through planting various densities of Sonneratia apetala were studied conducted.The results showed that with the increasing forest density of S.apetala,S.alterniflora were more effectively controlled,especially in the planting density of 2 200 ind·hm-2.In the 2 200 ind·hm-2 forest,the light intensity was 50% of that on the non-forest meadow;the S.alterniflora coverage degree and density were less than 5%;the S.alterniflora height declined to 64%;and the above-ground biomass of S.alterniflora decreased to 9.1%,while the below-ground biomass to 27.2%.The net photosynthetic rate,stomatal conductance and transpiration rate of S.alterniflora leaves in the 2200 ind·hm-2 forest were only 26.8%,33.1% and 52.6% of those in the non-forest meadow,respectively.S.alterniflora almost subsided from the dense S.apetala forest.展开更多
基金The Key Program and General Program of the National Natural Science Foundation of China under contract Nos 40532011 and 40406010COMRA’s 11th Five Year Program under contract No. DYXM115-02-4-04the Natural Science Foundation of Guangdong Province under contract No.04300822
文摘Samples of sediments and the overlying water were collected in the Qi＇ao Island coastal zone,the Zhujiang（Pearl River） Estuary（ZE）.Denitrification rates,sediment oxygen demand（SOD）,and fluxes of inorganic nitrogen compounds were investigated with N2 flux method,using a self-designed continuous flow through and auto-sampling system.The results indicate that the denitrification rates varied between 222 and 908 μmol/（m2·h） with an average of 499 μmol /（m2·h）.During incubation,the sediments absorbed dissolved oxygen in the overlying water with SOD ranging from 300 to 2 363 μmol/（m2·h）.The denitrification rates were highly correlated with the SOD（r2=0.77） regardless of the NO-3＋NO-2 concentrations in the overlying water,organic carbon contents in sediments and water temperature,suggesting that the SOD was probably the main environmental factor controlling the denitrification in the Qi＇ao Island coastal zone.There was a net flux of NO-3＋NO-2 into the sediments from the overlying water.The NH＋4 flux from sediments into water as the result of mineralization was between 12.3 and 210.3 μmol/（m2·h）,which seems limited by both organic carbon content in sediment and dissolved oxygen concentration in the overlying water.
基金The National Natural Science Foundation of China under contract Nos 40803020 and 41176065
文摘Subtropical sediment cores （QA09-1 and QA12-9） from the coastal zone of Qi’ao Island in the Zhujiang River Estuary were used to determine the rates of sulfate reduction and their response to experimental tempera-ture changes. The depth distribution of the sulfate reduction rates was measured from whole-core incu-bations with radioactive tracer35SO42-, and peaks of 181.19 nmol/（cm3·d） and 107.49 nmol/（cm3·d） were exhibited at stations QA09-1 and QA12-9, respectively. The profiles of the pore water methane and sulfate concentrations demonstrated that anaerobic oxidation of methane occurred in the study area, which result-ed in an increase in the sulfate reduction rate at the base of the sulfate-reducing zone. Meanwhile, the sulfate concentration was not a major limiting factor for controlling the rates of sulfate reduction. In addition, the incubation of the sediment slurries in a block with a temperature gradient showed that the optimum tem-perature for the sulfate reduction reaction was 36°C. The Arrhenius plot was linear from the lowest tempera-ture to the optimum temperature, and the activation energy was at the lower end of the range of previously reported values. The results suggested that the ambient temperature regime of marine environments prob-ably selected for the microbial population with the best-suited physiology for the respective environment.
文摘The controlling effects on Spartina alterniflora through planting various densities of Sonneratia apetala were studied conducted.The results showed that with the increasing forest density of S.apetala,S.alterniflora were more effectively controlled,especially in the planting density of 2 200 ind·hm-2.In the 2 200 ind·hm-2 forest,the light intensity was 50% of that on the non-forest meadow;the S.alterniflora coverage degree and density were less than 5%;the S.alterniflora height declined to 64%;and the above-ground biomass of S.alterniflora decreased to 9.1%,while the below-ground biomass to 27.2%.The net photosynthetic rate,stomatal conductance and transpiration rate of S.alterniflora leaves in the 2200 ind·hm-2 forest were only 26.8%,33.1% and 52.6% of those in the non-forest meadow,respectively.S.alterniflora almost subsided from the dense S.apetala forest.
