The methane concentration of water samples at five stations collected by the CTD rosette water sampler in the areas of southwest Dongsha Islands and the Xisha Trough was analyzed by the gas-stripping method on aboard ...The methane concentration of water samples at five stations collected by the CTD rosette water sampler in the areas of southwest Dongsha Islands and the Xisha Trough was analyzed by the gas-stripping method on aboard ship. It shows abnormal high methane concentrations in near bottom water samples at three stations. In the southwest Dongsha Islands area, the methane concentration of 4.25 and 10.64 nmol/dm3 occurs in near bottom water samples at Stas E105A and E106, respectively. In the Xisha Trough area, the high methane concentrations of 5.17, 8.48 and 8.70 nmol/dm3 in water depths of 1 750, 1 900 and 2 050 m, respectively, have been observed at Sta. E413. It is believed that the abnormal high methane concentrations are generated from the leakage of methane from sediments. Combining with previous geophysical and geochemical data from these two areas, this was probably related to the submarine gas hydrates decomposition and cold seep system. In May 2007, gas hydrate samples were successfully obtained by the drilling in the Shenhu Sea area located in the southwest Dongsha Islands area. It is called for further drilling surveys to confirm the existence of gas hydrate and cold seep system in the Xisha Trough as early as possible.展开更多
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...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
In this study, we investigated the distributions of sea-surface suspended particulate organic carbon(POC) and its stable isotope(δ13CPOC) in Prydz Bay, Antarctica, and examined the factors infl uencing their distribu...In this study, we investigated the distributions of sea-surface suspended particulate organic carbon(POC) and its stable isotope(δ13CPOC) in Prydz Bay, Antarctica, and examined the factors infl uencing their distribution, sources, and transport. We used measurements collected from 61 stations in Prydz Bay during the 29 th Chinese National Antarctic Research Expedition, in combination with remote sensing data on sea surface temperature(SST), chlorophyll a concentration, and sea ice coverage. The POC concentration in the surface waters of Prydz Bay was 0.28–0.84 mg·L-1, with an average concentration of 0.48 mg·L-1. The δ13CPOC value ranged from-29.68‰ to-26.30‰, with an average of-28.01‰. The concentration of suspended POC was highest in near-shore areas and in western Prydz Bay. The POC concentration was correlated with chlorophyll a concentration and sea ice coverage, suggesting that POC was associated with phytoplankton production in local water columns, while the growth of phytoplankton was obviously affected by sea ice coverage. The δ13CPOC value in suspended particles decreased gradually towards the outer waters of Prydz Bay, while in eastern Prydz Bay the δ13CPOC value become gradually more negative from nearshore to deep-water areas, suggesting that δ13CPOC was mainly infl uenced by CO2 fixation by phytoplankton. The δ13CPOC value in suspended particles near Zhongshan Station was significantly negative, possibly as a result of the input of terrigenous organic matter and changes in the phytoplankton species composition in the nearshore area.展开更多
Recent studies have highlighted the valuable role played by mangrove forests in carbon sequestration and storage.Although Indonesia accounts for a large proportion of global mangrove area, knowledge on the carbon stoc...Recent studies have highlighted the valuable role played by mangrove forests in carbon sequestration and storage.Although Indonesia accounts for a large proportion of global mangrove area, knowledge on the carbon stock and sources in the Indonesian mangrove is still limited. In this study, we quantified the ecosystem organic carbon(OC) stock and its spatial variation at an oceanic mangrove in Wori, North Sulawesi, Indonesia. The sources of soil OC were also investigated. The results showed that the mangrove soil had a substantial OC stock containing15.4 kg/m^2(calculated by carbon) in the top 50 cm soil, and represented the majority of the ecosystem OC stock at the Wori mangrove. The mangrove biomass and ecosystem OC stock were 8.3 kg/m^2 and 23.7 kg/m^2, respectively.There was no significantly difference in the soil OC stock among the stations with difference distances offshore,while the highest mangrove biomass OC stock was found at the seaward station. Isotope mixing calculations showed that the rich OC in mangrove soils was attributed to the accumulated autochthonous mangrove source while the suspended organic matter in tidal water and the mangrove-adjacent seagrass contributed less than 20%to the soil OC. The results further demonstrated the importances of the oceanic mangrove in carbon storage and the mangrove plants in contributing OC to their soils.展开更多
The CDE hydrothermal field was first discovered during a Chinese cruise to the East Lau Basin Spreading Centre in 2007.Apart from significant amounts of loose Fe-Si-Mn(oxyhydr) oxide(referred to as oxide below) precip...The CDE hydrothermal field was first discovered during a Chinese cruise to the East Lau Basin Spreading Centre in 2007.Apart from significant amounts of loose Fe-Si-Mn(oxyhydr) oxide(referred to as oxide below) precipitates,a small Si-rich oxide chimney was also recovered on this cruise.In this study,we report on the mineralogical and geochemical analyses of this chimney and a model for its growth that has been developed.Based on the mineralogy and O isotope results,the chimney walls can be divided into four growth generations(layers) from the inner to the outer layers:amorphous opal and barite layer(precipitation temperature 68.5°C based on oxygen isotope determinations),a rod-like amorphous layer(precipitation temperature 39.6°C),a filamentous Fe-Si oxide layer,and an outer Fe-Mn oxide layer.Investigations based on SEM and EDS showed that neutrophilic Fe-oxidizing bacteria play an important role in the formation of this chimney,particularly in the outer two generations.In the first stage,the metabolic activity of the microbes results in the pervasive precipitation of the filamentous Fe-rich oxides inside a ring formed by some amorphous opal and barite;therefore,a loose porous layer forms.In the second stage,amorphous opal then precipitates inside this wall as a result of conductive cooling and gradually controls the mixing between the hydrothermal fluids and ambient seawaters.In the third stage,barite and some amorphous opal form from the higher temperature fluids at the summit of the chimney growth history.In the last stage,the chimney wall becomes thicker and denser and the exchange of hydrothermal fluids and seawater ceases.As a result,a Fe-Mn oxide layer precipitates onto the outer surface of the chimney wall as neutrophilic Fe-oxidizing bacteria reoccupy the surface of the chimney.This mineral sequence and the resultant growth generations are confirmed by the chemical characteristics of the chimney wall.Sr isotopes extracted from the Fe oxides of the four-generation wall generally show a decreasing trend of the 87 Sr/86 Sr ratios from the second layer to the inner layer(from 0.707008 to 0.705877) except for the outer layer(0.706502).The Sr isotope and chondrite normalized REE patterns of the corresponding bulk samples from the chimney wall also display a similar trend.Our study shows that the biogenic filament network plays a key role in the formation of the chimney in contrast to previous growth models of higher temperature chimneys,which often ignore the influence of biogenic factors.展开更多
基金The National "863" High Technology Research Foundation of China under contract No.2006AA09Z222the Fujian Province Natural Science Foundation of China under contract No.2005YZ1013
文摘The methane concentration of water samples at five stations collected by the CTD rosette water sampler in the areas of southwest Dongsha Islands and the Xisha Trough was analyzed by the gas-stripping method on aboard ship. It shows abnormal high methane concentrations in near bottom water samples at three stations. In the southwest Dongsha Islands area, the methane concentration of 4.25 and 10.64 nmol/dm3 occurs in near bottom water samples at Stas E105A and E106, respectively. In the Xisha Trough area, the high methane concentrations of 5.17, 8.48 and 8.70 nmol/dm3 in water depths of 1 750, 1 900 and 2 050 m, respectively, have been observed at Sta. E413. It is believed that the abnormal high methane concentrations are generated from the leakage of methane from sediments. Combining with previous geophysical and geochemical data from these two areas, this was probably related to the submarine gas hydrates decomposition and cold seep system. In May 2007, gas hydrate samples were successfully obtained by the drilling in the Shenhu Sea area located in the southwest Dongsha Islands area. It is called for further drilling surveys to confirm the existence of gas hydrate and cold seep system in the Xisha Trough as early as possible.
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supported by the Chinese Polar Environment Comprehensive Investigation and Assessment Program (Grant nos. CHINARE2012-01-02, CHINARE2013-01-02, CHINARE201301-07, CHINARE2013-04-01)
文摘In this study, we investigated the distributions of sea-surface suspended particulate organic carbon(POC) and its stable isotope(δ13CPOC) in Prydz Bay, Antarctica, and examined the factors infl uencing their distribution, sources, and transport. We used measurements collected from 61 stations in Prydz Bay during the 29 th Chinese National Antarctic Research Expedition, in combination with remote sensing data on sea surface temperature(SST), chlorophyll a concentration, and sea ice coverage. The POC concentration in the surface waters of Prydz Bay was 0.28–0.84 mg·L-1, with an average concentration of 0.48 mg·L-1. The δ13CPOC value ranged from-29.68‰ to-26.30‰, with an average of-28.01‰. The concentration of suspended POC was highest in near-shore areas and in western Prydz Bay. The POC concentration was correlated with chlorophyll a concentration and sea ice coverage, suggesting that POC was associated with phytoplankton production in local water columns, while the growth of phytoplankton was obviously affected by sea ice coverage. The δ13CPOC value in suspended particles decreased gradually towards the outer waters of Prydz Bay, while in eastern Prydz Bay the δ13CPOC value become gradually more negative from nearshore to deep-water areas, suggesting that δ13CPOC was mainly infl uenced by CO2 fixation by phytoplankton. The δ13CPOC value in suspended particles near Zhongshan Station was significantly negative, possibly as a result of the input of terrigenous organic matter and changes in the phytoplankton species composition in the nearshore area.
基金The China-Indonesia Ecological Station Establishment and Marine Biodiversity Investigation in North Sulawesi Seathe Development and Implement Ocean Strategic Planning and Policy supported by Ministry of Natural Resources,PRCthe National Natural Science Foundation of China under contract Nos 41606105 and 41776102
文摘Recent studies have highlighted the valuable role played by mangrove forests in carbon sequestration and storage.Although Indonesia accounts for a large proportion of global mangrove area, knowledge on the carbon stock and sources in the Indonesian mangrove is still limited. In this study, we quantified the ecosystem organic carbon(OC) stock and its spatial variation at an oceanic mangrove in Wori, North Sulawesi, Indonesia. The sources of soil OC were also investigated. The results showed that the mangrove soil had a substantial OC stock containing15.4 kg/m^2(calculated by carbon) in the top 50 cm soil, and represented the majority of the ecosystem OC stock at the Wori mangrove. The mangrove biomass and ecosystem OC stock were 8.3 kg/m^2 and 23.7 kg/m^2, respectively.There was no significantly difference in the soil OC stock among the stations with difference distances offshore,while the highest mangrove biomass OC stock was found at the seaward station. Isotope mixing calculations showed that the rich OC in mangrove soils was attributed to the accumulated autochthonous mangrove source while the suspended organic matter in tidal water and the mangrove-adjacent seagrass contributed less than 20%to the soil OC. The results further demonstrated the importances of the oceanic mangrove in carbon storage and the mangrove plants in contributing OC to their soils.
基金supported by National Natural Science Foundation of China(Grant Nos.40976045,40976025 and 41006072)
文摘The CDE hydrothermal field was first discovered during a Chinese cruise to the East Lau Basin Spreading Centre in 2007.Apart from significant amounts of loose Fe-Si-Mn(oxyhydr) oxide(referred to as oxide below) precipitates,a small Si-rich oxide chimney was also recovered on this cruise.In this study,we report on the mineralogical and geochemical analyses of this chimney and a model for its growth that has been developed.Based on the mineralogy and O isotope results,the chimney walls can be divided into four growth generations(layers) from the inner to the outer layers:amorphous opal and barite layer(precipitation temperature 68.5°C based on oxygen isotope determinations),a rod-like amorphous layer(precipitation temperature 39.6°C),a filamentous Fe-Si oxide layer,and an outer Fe-Mn oxide layer.Investigations based on SEM and EDS showed that neutrophilic Fe-oxidizing bacteria play an important role in the formation of this chimney,particularly in the outer two generations.In the first stage,the metabolic activity of the microbes results in the pervasive precipitation of the filamentous Fe-rich oxides inside a ring formed by some amorphous opal and barite;therefore,a loose porous layer forms.In the second stage,amorphous opal then precipitates inside this wall as a result of conductive cooling and gradually controls the mixing between the hydrothermal fluids and ambient seawaters.In the third stage,barite and some amorphous opal form from the higher temperature fluids at the summit of the chimney growth history.In the last stage,the chimney wall becomes thicker and denser and the exchange of hydrothermal fluids and seawater ceases.As a result,a Fe-Mn oxide layer precipitates onto the outer surface of the chimney wall as neutrophilic Fe-oxidizing bacteria reoccupy the surface of the chimney.This mineral sequence and the resultant growth generations are confirmed by the chemical characteristics of the chimney wall.Sr isotopes extracted from the Fe oxides of the four-generation wall generally show a decreasing trend of the 87 Sr/86 Sr ratios from the second layer to the inner layer(from 0.707008 to 0.705877) except for the outer layer(0.706502).The Sr isotope and chondrite normalized REE patterns of the corresponding bulk samples from the chimney wall also display a similar trend.Our study shows that the biogenic filament network plays a key role in the formation of the chimney in contrast to previous growth models of higher temperature chimneys,which often ignore the influence of biogenic factors.
