Coastal wetlands play an important role in the global carbon cycle. Large quantities of sediment deposited in the Changjiang （Yangtze） estuary by the Changjiang River promote the propagation of coastal wetlands, the...Coastal wetlands play an important role in the global carbon cycle. Large quantities of sediment deposited in the Changjiang （Yangtze） estuary by the Changjiang River promote the propagation of coastal wetlands, the expansion of saltmarsh vegetation, and carbon sequestration. In this study, using the Chongming Dongtan Wetland in the Changjiang estuary as the study area, the spatial and temporal distribution of soil organic carbon （SOC） stocks and the influences of sedimentation and vegetation on the SOC stocks of the coastal wetland were examined in 2013. There was sediment accretion in the northern and middle areas of the wetland and in the Phragmites australis marsh in the southern area, and sediment erosion in the Scirpus mariqueter marsh and the bare mudflat in the southem area. More SOC accumulated in sediments of the vegetated marsh than in the bare mudflat. The total organic carbon （TOC） stocks increased in the above-ground biomass from spring to autumn and decreased in winter; in the below-ground biomass, they gradually increased from spring to winter. The TOC stocks were higher in the below-ground biomass than in the above-ground biomass in the P. australis and Spartina alterniflora marshes, but were lower in the below-ground biomass in S. mariqueter marsh. Stocks of SOC showed temporal variation and increased gradually in all transects from spring to winter. The SOC stocks tended to decrease from the high marsh down to the bare mudflat along the three transects in the order： P. australis marsh 〉 S. alterniflora marsh 〉 S. mariqueter marsh 〉 bare mudflat. The SOC stocks of the same vegetation type were higher in the northern and middle transects than in the southern transect. These results suggest that interactions between sedimentation and vegetation regulate the SOC stocks in the coastal wetland in the Changjiang estuary.展开更多
The changes in soil organic carbon(C) mineralization as affected by anthropogenic disturbance directly determine the role of soils as C source or sink in the global C budget. The objectives of this study were to inves...The changes in soil organic carbon(C) mineralization as affected by anthropogenic disturbance directly determine the role of soils as C source or sink in the global C budget. The objectives of this study were to investigate the effects of anthropogenic disturbance(aquaculture pond, pollutant discharge and agricultural activity) on soil organic C mineralization under different water conditions in the Minjiang River estuary wetland, Southeast China. The results showed that the organic C mineralization in the wetland soils was significantly affected by human disturbance and water conditions(P < 0.001), and the interaction between human disturbance activities and water conditions was also significant(P < 0.01). The C mineralization rate and the cumulative mineralized carbon dioxide-carbon(CO_2-C)(at the 49th day) ranked from highest to lowest as follows: Phragmites australis wetland soil > aquaculture pond sediment > soil near the discharge outlet > rice paddy soil. This indicated that human disturbance inhibited the mineralization of C in soils of the Minjiang River estuary wetland, and the inhibition increased with the intensity of human disturbance. The data for cumulative mineralized CO_2-C showed a good fit(R^2 > 0.91) to the first-order kinetic model C_t = C_0(1 – exp(–kt)). The kinetic parameters C_0, k and C_0 k were significantly affected by human disturbance and water conditions. In addition, the total amount of mineralized C(in 49 d) was positively related to C_0, C_0 k and electrical conductivity of soils. These findings indicated that anthropogenic disturbance suppressed the organic C mineralization potential in subtropical coastal wetland soils, and changes of water pattern as affected by human activities in the future would have a strong influence on C cycling in the subtropical estuarine wetlands.展开更多
The mangroves are specialized marine environments widely distributed along the coast lines, which support biologically diverse groups of organisms including microbes. The microorganisms present in this ecosystem contr...The mangroves are specialized marine environments widely distributed along the coast lines, which support biologically diverse groups of organisms including microbes. The microorganisms present in this ecosystem contribute significantly in the food web of the tropical marine ecosystem. In the present investigation, Actinomycete isolates obtained from mangrove sediments have been studied for diversity as well as for their bioactive potential. Seven different Actinomycete isolates （MS 1-MS7） were obtained from the sediments collected from the mangrove swamps. The phylogenetic analysis of these isolates showed that out or seven isolates, 3 isolates belong to Streptomyces sp., which has bioactive potential as several bioactive metabolites have been isolated from this group. One bacterium showed genetic similarity with Corynebacterium sp.. The microbes from this group are used for very important industrial applications. Three Actinomycete isolates showed very low similarity with the reported strains from the gene bank. In suggests that, these cultures could be novel and further research work is warranted to prove this speculation. In antagonistic studies, three Actinomycete isolates showed promising results. This investigation highlights the importance of mangrove ecosystem as a rich source of diverse Actinomycete strains for biotechnological applications.展开更多
This work represents sources of polycyclic aromatic hydrocarbons in the local environment of five major stations at marshland in southern Iraq from May 2013. Average concentration of PAHs （polycyclic aromatic hydroca...This work represents sources of polycyclic aromatic hydrocarbons in the local environment of five major stations at marshland in southern Iraq from May 2013. Average concentration of PAHs （polycyclic aromatic hydrocarbons） in the sampling sediments and three types of plants were lower than the guideline value. This study examined presence of PAHs may from reach aquatic environment in marshes, deposition of airborne particles. Having a relatively low water solubility to the suspended particulate matter, most of the PAHs introduced to the aquatic environment tend to accumulate in bottom sediments. Sedimentary PAHs may thus provide a record of the input and history of these pollutants, and the distribution of PAH／＇s in aquatic sediments has received considerable attention. Owing to the concentration of PAHs in the study area, its concentration level still meets the sediment quality guideline value （ERL： 4,022 ng/g dry weight）; however, according to the PELq （probable effects level） factor, slightly adverse biological effects are associated with the exposure to PAHs levels in the study area （0.1 〈 PELq = 0.24 〈 0.5）.展开更多
基金Supported by the Marine Science Project of Shanghai Committee of Science and Technology,China(No.14DZ1206004)the National Natural Science Foundation of China(No.41571083)the autonomous research fund of the State Key Laboratory of Estuarine and Coastal Research,China(No.2015KYYW03)
文摘Coastal wetlands play an important role in the global carbon cycle. Large quantities of sediment deposited in the Changjiang （Yangtze） estuary by the Changjiang River promote the propagation of coastal wetlands, the expansion of saltmarsh vegetation, and carbon sequestration. In this study, using the Chongming Dongtan Wetland in the Changjiang estuary as the study area, the spatial and temporal distribution of soil organic carbon （SOC） stocks and the influences of sedimentation and vegetation on the SOC stocks of the coastal wetland were examined in 2013. There was sediment accretion in the northern and middle areas of the wetland and in the Phragmites australis marsh in the southern area, and sediment erosion in the Scirpus mariqueter marsh and the bare mudflat in the southem area. More SOC accumulated in sediments of the vegetated marsh than in the bare mudflat. The total organic carbon （TOC） stocks increased in the above-ground biomass from spring to autumn and decreased in winter; in the below-ground biomass, they gradually increased from spring to winter. The TOC stocks were higher in the below-ground biomass than in the above-ground biomass in the P. australis and Spartina alterniflora marshes, but were lower in the below-ground biomass in S. mariqueter marsh. Stocks of SOC showed temporal variation and increased gradually in all transects from spring to winter. The SOC stocks tended to decrease from the high marsh down to the bare mudflat along the three transects in the order： P. australis marsh 〉 S. alterniflora marsh 〉 S. mariqueter marsh 〉 bare mudflat. The SOC stocks of the same vegetation type were higher in the northern and middle transects than in the southern transect. These results suggest that interactions between sedimentation and vegetation regulate the SOC stocks in the coastal wetland in the Changjiang estuary.
基金Under the auspices of National Basic Research Program of China(No.2012CB956100)National Natural Science Foundation of China(No.41301085)the Key Foundation of Science and Technology Department of Fujian Province(No.2016R1032-1)
文摘The changes in soil organic carbon(C) mineralization as affected by anthropogenic disturbance directly determine the role of soils as C source or sink in the global C budget. The objectives of this study were to investigate the effects of anthropogenic disturbance(aquaculture pond, pollutant discharge and agricultural activity) on soil organic C mineralization under different water conditions in the Minjiang River estuary wetland, Southeast China. The results showed that the organic C mineralization in the wetland soils was significantly affected by human disturbance and water conditions(P < 0.001), and the interaction between human disturbance activities and water conditions was also significant(P < 0.01). The C mineralization rate and the cumulative mineralized carbon dioxide-carbon(CO_2-C)(at the 49th day) ranked from highest to lowest as follows: Phragmites australis wetland soil > aquaculture pond sediment > soil near the discharge outlet > rice paddy soil. This indicated that human disturbance inhibited the mineralization of C in soils of the Minjiang River estuary wetland, and the inhibition increased with the intensity of human disturbance. The data for cumulative mineralized CO_2-C showed a good fit(R^2 > 0.91) to the first-order kinetic model C_t = C_0(1 – exp(–kt)). The kinetic parameters C_0, k and C_0 k were significantly affected by human disturbance and water conditions. In addition, the total amount of mineralized C(in 49 d) was positively related to C_0, C_0 k and electrical conductivity of soils. These findings indicated that anthropogenic disturbance suppressed the organic C mineralization potential in subtropical coastal wetland soils, and changes of water pattern as affected by human activities in the future would have a strong influence on C cycling in the subtropical estuarine wetlands.
文摘The mangroves are specialized marine environments widely distributed along the coast lines, which support biologically diverse groups of organisms including microbes. The microorganisms present in this ecosystem contribute significantly in the food web of the tropical marine ecosystem. In the present investigation, Actinomycete isolates obtained from mangrove sediments have been studied for diversity as well as for their bioactive potential. Seven different Actinomycete isolates （MS 1-MS7） were obtained from the sediments collected from the mangrove swamps. The phylogenetic analysis of these isolates showed that out or seven isolates, 3 isolates belong to Streptomyces sp., which has bioactive potential as several bioactive metabolites have been isolated from this group. One bacterium showed genetic similarity with Corynebacterium sp.. The microbes from this group are used for very important industrial applications. Three Actinomycete isolates showed very low similarity with the reported strains from the gene bank. In suggests that, these cultures could be novel and further research work is warranted to prove this speculation. In antagonistic studies, three Actinomycete isolates showed promising results. This investigation highlights the importance of mangrove ecosystem as a rich source of diverse Actinomycete strains for biotechnological applications.
文摘This work represents sources of polycyclic aromatic hydrocarbons in the local environment of five major stations at marshland in southern Iraq from May 2013. Average concentration of PAHs （polycyclic aromatic hydrocarbons） in the sampling sediments and three types of plants were lower than the guideline value. This study examined presence of PAHs may from reach aquatic environment in marshes, deposition of airborne particles. Having a relatively low water solubility to the suspended particulate matter, most of the PAHs introduced to the aquatic environment tend to accumulate in bottom sediments. Sedimentary PAHs may thus provide a record of the input and history of these pollutants, and the distribution of PAH／＇s in aquatic sediments has received considerable attention. Owing to the concentration of PAHs in the study area, its concentration level still meets the sediment quality guideline value （ERL： 4,022 ng/g dry weight）; however, according to the PELq （probable effects level） factor, slightly adverse biological effects are associated with the exposure to PAHs levels in the study area （0.1 〈 PELq = 0.24 〈 0.5）.
