Salt marshes are important carbon and nutrient sinks that are threatened by climate changes and human activities.In this study,the accumulation rates of sedimentary total organic carbon(TOC),total nitrogen(TN),and tot...Salt marshes are important carbon and nutrient sinks that are threatened by climate changes and human activities.In this study,the accumulation rates of sedimentary total organic carbon(TOC),total nitrogen(TN),and total phosphorus(TP)from two cores in the Andong salt marsh,Hangzhou Bay,were investigated to determine whether TOC,TN,and TP show increasing or decreasing trends toward the present.The TOC accumulation rates at the relatively lower marsh were lower during 1990-1996(1.63-2.37 g/(cm^(2)·a))than 1997-2014(1.15-4.30 g/(cm^(2)·a)).The TN accumulation rates increased from 1990(0.14 g/(cm^(2)·a))toward 2012(0.40 g/(cm^(2)·a)),then decreased toward 2014(0.16 g/(cm^(2)·a)).The TP accumulation rates were lower during 1990-1999(0.10-0.21 mg/(cm^(2)·a)),and decreased from 2000(0.32 mg/(cm^(2)·a))toward 2014(0.15 mg/(cm^(2)·a)).The TOC accumulation rates along the relatively upper marsh during 1982-1992(1.18-3.25 g/(cm^(2)·a))were lower than during 1998-2010(2.30-4.20 g/(cm^(2)·a)),and then decreased toward 2015(2.15 g/(cm^(2)·a)).TN increased from 1982(0.18 g/(cm^(2)·a))to 2005(0.41 g/(cm^(2)·a)),then decreased toward 2015(0.22 g/(cm^(2)·a)).TP accumulation rates fluctuated within a narrow range during 1982-1997(0.21-0.41 mg/(cm^(2)·a)),increased from 1998(0.50 mg/(cm^(2)·a))to 2004(0.87 mg/(cm^(2)·a)),then decreased to 2015(0.38 mg/(cm^(2)·a)).Thus,increases in accumulation rates of TOC,TN,and TP from the 1980s to 1990s indicates that the marsh likely served as carbon and nutrient sinks,then the rates decreased during 2000-2015 due probably to the reduced sediment inputs from rivers and intensified sea level rise.展开更多
Distinctive white laminations appear in the generally black sediments of the anoxic, subalpine Great Ghost Lake in southern Taiwan. These white laminations have lower porosity, organic matter content and C/N ratio, bu...Distinctive white laminations appear in the generally black sediments of the anoxic, subalpine Great Ghost Lake in southern Taiwan. These white laminations have lower porosity, organic matter content and C/N ratio, but higher C/S, N/S ratios and magnetic susceptibility, and contain organic matter most probably derived from phytoplankton. This and the collision marks on the quartz particles suggest that they have an aeolian component and have been deposited in cooler and drier periods. The organic matter of the black sediments is mainly from land plants and the quartz particles bear no collision marks, suggesting local deposition under warmer and wetter climates. These high resolution data, the first not only in Taiwan but also for Southeast Asia, are in good agreement with the local climatological records deduced from documentary sources since 1681 and direct instrumental rainfall measurements at stations nearby since 1900. Rainfall over the past 2600 years has been reconstructed. Major droughts appear in 240 BC, 80 BC, 90 AD, 420-520 AD, 620-700 AD, 850-930 AD, 1350-1430 AD, 1570 AD, 1730-1800 AD and 1960 AD, and correspond to not only the periods of cold/dry and frequent dust storms but also major population declines based on the historical and natural records of China. These seem to reflect large scale climatic changes.展开更多
Siliceous diatoms are one of the most prominent actors in the oceans,and they account for approximately 40%of the primary production and particulate organic carbon export flux.It is believed that changes in carbon flu...Siliceous diatoms are one of the most prominent actors in the oceans,and they account for approximately 40%of the primary production and particulate organic carbon export flux.It is believed that changes in carbon flux caused by variations in diatom distribution can lead to significant climate shifts.Although the fundamental pathways of diatom-driven carbon sequestration have long been established,there are no reports of CaCO_(3) precipitation induced by marine diatom species.This manuscript introduces novel details regarding the enhancement of aragonite precipitation during photosynthesis in Skeletonema costatum in both artificial and natural seawater.Through direct measurements of cell surfaces via a pH microelectrode and zeta potential analyzer,it was determined that the diatom-mediated promotion of CaCO_(3) precipitation is achieved through the creation of specific microenvironments with concentrated[CO_(3)^(2-)]and[Ca^(2+)]and/or the dehydrating effect of adsorbed Ca^(2+).Based on this mechanism,it is highly plausible that diatom-mediated calcification could occur in the oceans,an assertion that was supported by the significant deviation of total alkalinity(TA)from the conservative TA-salinity mixing line during a Skeletonema costatum bloom in the East China Sea and other similar occurrences.The newly discovered calcification pathway establishes a link between particulate inorganic and organic carbon flux and thus helps in the reassessment of marine carbon export fluxes and CO_(2) sequestration efficiency.This discovery may have important ramifications for assessing marine carbon cycling and predicting the potential effects of future ocean acidification.展开更多
基金Supported by the Zhejiang University Self Program Fund for the Research of Heavy Metal Geochemical Characteristics in Sediments of Hangzhou Baythe Zhejiang University Fundamental Research Funds for the Central Universities(No.2013QNA4037)+1 种基金the National Key Research and Development Plan of China(No.2016YFC1401603)the National Natural Science Foundation of China(No.41876031)。
文摘Salt marshes are important carbon and nutrient sinks that are threatened by climate changes and human activities.In this study,the accumulation rates of sedimentary total organic carbon(TOC),total nitrogen(TN),and total phosphorus(TP)from two cores in the Andong salt marsh,Hangzhou Bay,were investigated to determine whether TOC,TN,and TP show increasing or decreasing trends toward the present.The TOC accumulation rates at the relatively lower marsh were lower during 1990-1996(1.63-2.37 g/(cm^(2)·a))than 1997-2014(1.15-4.30 g/(cm^(2)·a)).The TN accumulation rates increased from 1990(0.14 g/(cm^(2)·a))toward 2012(0.40 g/(cm^(2)·a)),then decreased toward 2014(0.16 g/(cm^(2)·a)).The TP accumulation rates were lower during 1990-1999(0.10-0.21 mg/(cm^(2)·a)),and decreased from 2000(0.32 mg/(cm^(2)·a))toward 2014(0.15 mg/(cm^(2)·a)).The TOC accumulation rates along the relatively upper marsh during 1982-1992(1.18-3.25 g/(cm^(2)·a))were lower than during 1998-2010(2.30-4.20 g/(cm^(2)·a)),and then decreased toward 2015(2.15 g/(cm^(2)·a)).TN increased from 1982(0.18 g/(cm^(2)·a))to 2005(0.41 g/(cm^(2)·a)),then decreased toward 2015(0.22 g/(cm^(2)·a)).TP accumulation rates fluctuated within a narrow range during 1982-1997(0.21-0.41 mg/(cm^(2)·a)),increased from 1998(0.50 mg/(cm^(2)·a))to 2004(0.87 mg/(cm^(2)·a)),then decreased to 2015(0.38 mg/(cm^(2)·a)).Thus,increases in accumulation rates of TOC,TN,and TP from the 1980s to 1990s indicates that the marsh likely served as carbon and nutrient sinks,then the rates decreased during 2000-2015 due probably to the reduced sediment inputs from rivers and intensified sea level rise.
文摘Distinctive white laminations appear in the generally black sediments of the anoxic, subalpine Great Ghost Lake in southern Taiwan. These white laminations have lower porosity, organic matter content and C/N ratio, but higher C/S, N/S ratios and magnetic susceptibility, and contain organic matter most probably derived from phytoplankton. This and the collision marks on the quartz particles suggest that they have an aeolian component and have been deposited in cooler and drier periods. The organic matter of the black sediments is mainly from land plants and the quartz particles bear no collision marks, suggesting local deposition under warmer and wetter climates. These high resolution data, the first not only in Taiwan but also for Southeast Asia, are in good agreement with the local climatological records deduced from documentary sources since 1681 and direct instrumental rainfall measurements at stations nearby since 1900. Rainfall over the past 2600 years has been reconstructed. Major droughts appear in 240 BC, 80 BC, 90 AD, 420-520 AD, 620-700 AD, 850-930 AD, 1350-1430 AD, 1570 AD, 1730-1800 AD and 1960 AD, and correspond to not only the periods of cold/dry and frequent dust storms but also major population declines based on the historical and natural records of China. These seem to reflect large scale climatic changes.
基金supported by the National Natural Science Foundation of China(Grant Nos.42188102&42176036)the Zhejiang Provincial Natural Science Foundation of China(Grant No.LD24D060002)+1 种基金the Science and Technology Program of Zhoushan City(Grant No.2022C81002)the Fundamental Research Funds for the Central Universities,and the Ocean Negative Carbon Emission(ONCE)。
文摘Siliceous diatoms are one of the most prominent actors in the oceans,and they account for approximately 40%of the primary production and particulate organic carbon export flux.It is believed that changes in carbon flux caused by variations in diatom distribution can lead to significant climate shifts.Although the fundamental pathways of diatom-driven carbon sequestration have long been established,there are no reports of CaCO_(3) precipitation induced by marine diatom species.This manuscript introduces novel details regarding the enhancement of aragonite precipitation during photosynthesis in Skeletonema costatum in both artificial and natural seawater.Through direct measurements of cell surfaces via a pH microelectrode and zeta potential analyzer,it was determined that the diatom-mediated promotion of CaCO_(3) precipitation is achieved through the creation of specific microenvironments with concentrated[CO_(3)^(2-)]and[Ca^(2+)]and/or the dehydrating effect of adsorbed Ca^(2+).Based on this mechanism,it is highly plausible that diatom-mediated calcification could occur in the oceans,an assertion that was supported by the significant deviation of total alkalinity(TA)from the conservative TA-salinity mixing line during a Skeletonema costatum bloom in the East China Sea and other similar occurrences.The newly discovered calcification pathway establishes a link between particulate inorganic and organic carbon flux and thus helps in the reassessment of marine carbon export fluxes and CO_(2) sequestration efficiency.This discovery may have important ramifications for assessing marine carbon cycling and predicting the potential effects of future ocean acidification.
基金supported by the National Natural Science Foundation of China(42188102,42176036,and 51120195001)the Science and Technology Program of Zhoushan City(2022C81002)the Fundamental Research Funds for the Central Universities,and the Ocean Negative Carbon Emission(ONCE)Program。
