Diglycerol(DAG)is a structural lipid with the functions to lower body fat accumulation and decrease serum triglyceride level.However,the enzymatic synthesis of DAG is limited by the high-efficient and economic lipases...Diglycerol(DAG)is a structural lipid with the functions to lower body fat accumulation and decrease serum triglyceride level.However,the enzymatic synthesis of DAG is limited by the high-efficient and economic lipases.In this paper,the immobilized lipase PS@LXTE-1000 was self-made by immobilizing the Pseudomomas cepacian lipase on to the hydrophobic microporous resin LXTE-1000.The results indicate that LXTE-1000 was a uniform mesoporous sphere with the mean diameter of 400μm,pore size of 14.6 nm,pore volume of 0.5 cm3/g and surface area of 126.0 m^(2)/g,showing superior structural properties for lipase immobilization.Under the optimal reaction conditions with the molar ratio of rapeseed oil to glycerol being 1:1,adding amount of immobilized lipase being 4%,reaction at 50℃,the highest DAG content of 46.7%was achieved in 3 h via enzymatic glycerolysis catalyzed by LXTE-1000.After 7 cycles of reuse,the self-made LXTE-1000 could still retain 78.3%of its initial catalytic ability.Besides,LXTE-1000 was observed to facilitate the DAG production via glycerolysis reaction between glycerol with other seven edible oils including corn oil,sesame oil,peony seed oil,rice bran oil,peanut oil,soybean oil and flaxseed oil.Specifically,the glycerolysis reaction with sesame oil,peony seed oil and rice bran oil even led to the DAG content of 52.1%,53.3%and 51.2%,respectively,Hence,this paper provide a novel strategy to produce high-efficient and economic immobilized lipases,which shows great potential in the green synthesis of functional lipids such as DAG.展开更多
Activin A, which was first described in 1986, has been shown to maintain hippocampal neuronal survival. Activin A increases intracellular free Ca2＋ via L-type Ca2＋ channels. Our previous study showed that activin A ...Activin A, which was first described in 1986, has been shown to maintain hippocampal neuronal survival. Activin A increases intracellular free Ca2＋ via L-type Ca2＋ channels. Our previous study showed that activin A promotes neurite growth of dorsal root ganglia in embryonic chickens and inhibits nitric oxide secretion. The present study demonstrated for the first time that activin A could maintain cerebral cortex neuronal survival in vitro for a long period, and that activin A was shown to increase voltage-gated Na＋ current （/Na） in Neuro-2a cells, which was recorded by patch clamp technique. The present study revealed a novel mechanism for activin A, as well as the influence of activin A on neurons by regulating expressions of vasoactive intestine peptide and inducible nitric oxide synthase.展开更多
Qinghai Lake, China, is located near the northern limit of the East Asian summer monsoon （EASM） and thus is an ideal region for studies of past monsoonal changes. However, isotope records from this region reflect th...Qinghai Lake, China, is located near the northern limit of the East Asian summer monsoon （EASM） and thus is an ideal region for studies of past monsoonal changes. However, isotope records from this region reflect the combined effects of multiple climatic factors, and make climatic interpretations difficult. The authors use multi-proxy records, generated from the same sediment core from Qinghai Lake, to disentangle these multiple effects in isotope records and to infer EASM variability during the late Holocene. Records of leaf wax （C2s） δD, lake carbonate 5180 and the Dunde ice core δ18O all indicate a millennial-scale depletion of mean isotopic values at -1500-1250 years before present. Compared with independent lake temperature and salinity records, the authors suggest that this depletion of long-term mean isotopic values must have resulted from changes in moisture sources in this region. In contrast, the authors attribute high-frequency （centennial timescale） C2s δD and ice core δ18O variability dominantly to a temperature effect. The multiproxy records provide a coherent picture in that many aspects of this regional climate （temperature, dryness, and moisture source） are strongly linked to the EASM variability.展开更多
The Indo-Pacific warm pool(IPWP) is crucial for regional and global climates. However, the development of the IPWP and its effect on the regional climate during the Cenozoic remain unclear. Here, using a compilation o...The Indo-Pacific warm pool(IPWP) is crucial for regional and global climates. However, the development of the IPWP and its effect on the regional climate during the Cenozoic remain unclear. Here, using a compilation of sea surface temperature(SST) records(mainly since the middle Miocene) and multimodel paleoclimate simulations, our results indicated that the extent, intensity and warmest temperature position of the IPWP changed markedly during the Cenozoic. Specifically, its extent decreased, its intensity weakened, and its warmest temperature position shifted from the Indian to western Pacific Ocean over time. The atmospheric CO_(2) dominated its extent and intensity, while paleogeography, by restricting the distribution of the Indian Ocean and the width of the tropical seaways, controlled the shift in its warmest temperature position. In particular, the eastward shift to the western Pacific Ocean from the middle to late Miocene inferred from compiled SST records likely resulted from the constriction of tropical seaways. Furthermore, by changing the atmospheric thermal structure and atmospheric circulation,the reduced extent and intensity of the IPWP decreased the annual precipitation in the western Indian Ocean, eastern Asia and Australia, while the shift in the warmest temperature position from the Indian to western Pacific Ocean promoted aridification in Australia. Qualitative model-data agreements are obtained for both the IPWP SST and regional climate. From the perspective of past warm climates with high concentrations of atmospheric CO_(2), the expansion and strengthening of the IPWP will occur in a warmer future and favor excessive precipitation in eastern Asia and Australia.展开更多
Orbital-scale global climatic changes during the late Quaternary are dominated by high-latitude influenced~100,000-year global ice-age cycles and monsoon influenced~23,000-year low-latitude hydroclimate variations.How...Orbital-scale global climatic changes during the late Quaternary are dominated by high-latitude influenced~100,000-year global ice-age cycles and monsoon influenced~23,000-year low-latitude hydroclimate variations.However,the shortage of highly-resolved land temperature records remains a limiting factor for achieving a comprehensive understanding of long-term low-latitude terrestrial climatic changes.Here,we report paired mean annual air temperature(MAAT)and monsoon intensity proxy records over the past 88,000 years from Lake Tengchongqinghai in southwestern China.While summer monsoon intensity follows the~23,000-year precession beat found also in previous studies,we identify previously unrecognized warm periods at 88,000-71,000 and 45,000-22,000 years ago,with 2-3℃amplitudes that are close to our recorded full glacial-interglacial range.Using advanced transient climate simulations and comparing with forcing factors,we find that these warm periods in our MAAT record probably depends on local annual mean insolation,which is controlled by Earth’s~41,000-year obliquity cycles and is anti-phased to annual mean insolation at high latitudes.The coincidence of our identified warm periods and intervals of high-frequent dated archaeological evidence highlights the importance of temperature on anatomically modern humans in Asia during the last glacial stage.展开更多
Macrophages play critical roles in innate immune and acquired immune v/a secreting pro-inflammatory mediators, phagocytosing microorganisms and presenting antigens. Activin A, a member of transforming growth factor （...Macrophages play critical roles in innate immune and acquired immune v/a secreting pro-inflammatory mediators, phagocytosing microorganisms and presenting antigens. Activin A, a member of transforming growth factor （TGF-β） superfamily, is produced by macrophages and microglia cells. In this study, we reported a direct effect of activin A as a pro-inflammatory factor on mouse macrophage cell line RAW264.7 cells. Our data revealed that activin A could not only increase IL-1β and IL-6 production from RAW264.7 cells, but also promote pinocytic and phagocytic activities of RAW264.7 cells. In addition, activin A obviously up-regulated MHC Ⅱ expression on the surface of RAW264.7 cells, whereas did not influence MHC I expression. Activin A also enhanced CD80 expression, which is a marker of activated macrophages, but did not influence RAW264.7 cell proliferation. These data suggest that activin A may regulate primary macrophage-mediated innate and acquired immune response via promoting the activation of rest macrophages.展开更多
Activin A, a multifunctional factor of the transforming growth factor-beta （TGF-β） superfamily, is mainly produced by microglia and macrophages, and its anti-inflammatory and pro-inflammatory activities are both re...Activin A, a multifunctional factor of the transforming growth factor-beta （TGF-β） superfamily, is mainly produced by microglia and macrophages, and its anti-inflammatory and pro-inflammatory activities are both related to macrophage functions. However the direct effect of activin A on the rest macrophages in vivo remains unclear. In the present study, the results showed that activin A not only increased NO and IL-1β release, but also promoted phagocytic abilities of mouse peritoneal macrophages in vitro and in vivo, whereas it did not influence MHC Ⅰ and MHC Ⅱ expression. Moreover, we found that activin A significantly upregulated the expressions of CD14 and CD68, markers of mature macrophages, on the surface of macrophages in vitro and in vivo. These data suggest that activin A can induce primary macrophage maturation in vitro and in vivo, but may not trigger the acquired immune response via regulating expression of MHC molecules involved in presentation of antigen.展开更多
One of the Holocene abrupt events around 4200 years ago,lasting for~200 years,is thought to have caused cultural disruptions,yet terrestrial climatic status right after the cold/dry event remains poorly defined and is...One of the Holocene abrupt events around 4200 years ago,lasting for~200 years,is thought to have caused cultural disruptions,yet terrestrial climatic status right after the cold/dry event remains poorly defined and is often presumed that a generally cool condition prevailed during the Bronze Age(~4000-2200 years ago).Here we report an alkenone-based summer temperature record over the past~12,000 years,in addition to two updated alkenone records,from Northwest China,providing new insights into the climatic status right after the event.Our results indicate that exceptional terrestrial warmth,up to~6°C,occurred around 4200-2800 years ago during the Bronze Age,superimposed on the long-term Holocene cooling trend.The exceptional warmth in Northwest China,together with other climate anomalies elsewhere,suggests an unusual large-scale climatic reorganization at 4200-2800 years ago when solar activity remained high,with important implications to the climate background for cultural developments during the Bronze Age.展开更多
Aquatic plants are major input sources of autochthonous organic matter in lake sediments, but investigations on fatty acid(FA) and n-alkane distributions in aquatic plants are currently limited, greatly hindering the ...Aquatic plants are major input sources of autochthonous organic matter in lake sediments, but investigations on fatty acid(FA) and n-alkane distributions in aquatic plants are currently limited, greatly hindering the applications of their isotope geochemistry in lacustrine environments. Here, the reported n-alkyl lipid distributions of aquatic plants in globally studied lakes,together with newly obtained aquatic plant n-alkyl lipid data in Chinese lakes(Yunnan and Inner Mongolia), are used to understand their distribution characteristics. The results show that aquatic plants have predominantly mid-chain lipids(C23–C25 n-alkanes and C22–C24 FAs), differing from that of terrestrial plants(dominant by long-chain lipids), but the long-chain n-alkanes(e.g., C27 and C29) and long-chain FAs(e.g., C26 and C28) also show high abundances in most samples. Submerged plants have high concentrations of long-chain n-alkanes(avg. 47 μg g-1) and long-chain FAs(avg. 170 μg g-1), close to those in terrestrial plants, indicating that submerged plants may make large contributions of long-chain n-alkyl lipids to lake sediments, while the contributions of long-chain n-alkyl lipids derived from algae to lake sediments may be small because of their low concentrations(avg. 2 μg g-1 for n-alkanes and 9 μg g-1 for FAs). We find that lipid molecular proxies(including ACL14-32 and ATR14-18) can be reliably used to distinguish the FAs sourced from algae and other plants, and Paq′ values can be utilized to distinguish the nalkane sources between submerged plants and terrestrial plants. Aquatic plants do not have significant δD differences among different chain-length n-alkanes and FAs for each sample, suggesting that the offset between δD values of different chain-length n-alkyl lipids in lake sediments can help determine sedimentary lipid input sources and infer paleohydrological changes.展开更多
To investigate the relationship between the alkenone unsaturation index(U^(K′)_(37)) and sea surface temperature(SST) in coastal and continental shelf waters, 58 surface sediment samples were collected from the South...To investigate the relationship between the alkenone unsaturation index(U^(K′)_(37)) and sea surface temperature(SST) in coastal and continental shelf waters, 58 surface sediment samples were collected from the South China Sea(SCS), Taiwan Strait,and East China Sea(ECS). We combined the new results with the previously published 71 data points from the SCS, the shallow water areas of the Yellow Sea(YS) and northern ECS, to form a dataset with sample sites spanning across 6°N and 37°N(including annual SST calibration between 14.3℃ and 28.6℃). With this dataset, we examined the U^(K′)_(37)-SST relationship based on 129 samples from the Western North Pacific(WNP) margin as well as using 85 samples from specific WNP shallow water.The U^(K′)_(37)index from the low-mid latitudinal WNP margin demonstrated a good correlation with the surface annual mean SST(0–50 m water depth;R^(2)=0.89). The slope of linear regression(U^(K′)_(37)-SST) based on the coastal-continental shelf samples with water depth less than 200 m is similar to that of the published global open ocean regression equation. These results confirm that U^(K′)_(37)can be used as a shallow sea water SST proxy in mid-low latitudes of the WNP marginal seas. In addition, our reintegrated U^(K′)_(37)-SST results based on 172 global shallow water samples are similar(similar slopes and intercepts) to the shallow ocean results in the WNP marginal seas. However, the similarity of the regression formula to the open ocean does not imply that the formula is applicable. For example, of the 85 data in the shallow waters from the marginal sea in this study, the majority of data points lie above the regression line, showing positive residuals for U^(K′)_(37). This regression bias appears to be caused by specific marine environments, such as warm ocean currents and/or high nutrient conditions that result in positive U^(K′)_(37)residuals. Taken together,considering the specific temperature and environmental factors in the shallow waters of the low-mid-latitude WNP margin, we propose a nonlinear U^(K′)_(37)-SST regression formula: U^(K′)_(37)=-1.2488+0.1740×SST-0.0035×(SST)2, R2=0.93, N=85, specifically for the environments with SST below 24℃.展开更多
基金supported by the National Key Research and Development Project of China(2021YFD2100303)the National Natural Science Foundation of China(32272271,32302021)+2 种基金the Hubei Province Natural Science Foundation of China(2021CFB209,2023AFB324)the Major Project of Hubei Hongshan Laboratory(2022hszd002)Central Public-interest Scientific Institution Basal Research Fund(No.1610172024002).
文摘Diglycerol(DAG)is a structural lipid with the functions to lower body fat accumulation and decrease serum triglyceride level.However,the enzymatic synthesis of DAG is limited by the high-efficient and economic lipases.In this paper,the immobilized lipase PS@LXTE-1000 was self-made by immobilizing the Pseudomomas cepacian lipase on to the hydrophobic microporous resin LXTE-1000.The results indicate that LXTE-1000 was a uniform mesoporous sphere with the mean diameter of 400μm,pore size of 14.6 nm,pore volume of 0.5 cm3/g and surface area of 126.0 m^(2)/g,showing superior structural properties for lipase immobilization.Under the optimal reaction conditions with the molar ratio of rapeseed oil to glycerol being 1:1,adding amount of immobilized lipase being 4%,reaction at 50℃,the highest DAG content of 46.7%was achieved in 3 h via enzymatic glycerolysis catalyzed by LXTE-1000.After 7 cycles of reuse,the self-made LXTE-1000 could still retain 78.3%of its initial catalytic ability.Besides,LXTE-1000 was observed to facilitate the DAG production via glycerolysis reaction between glycerol with other seven edible oils including corn oil,sesame oil,peony seed oil,rice bran oil,peanut oil,soybean oil and flaxseed oil.Specifically,the glycerolysis reaction with sesame oil,peony seed oil and rice bran oil even led to the DAG content of 52.1%,53.3%and 51.2%,respectively,Hence,this paper provide a novel strategy to produce high-efficient and economic immobilized lipases,which shows great potential in the green synthesis of functional lipids such as DAG.
基金the National Natural Science Foundation of China, No.30903123, 30901329the Project of Science and Technology of Jilin Province, No.20090741, 20090185
文摘Activin A, which was first described in 1986, has been shown to maintain hippocampal neuronal survival. Activin A increases intracellular free Ca2＋ via L-type Ca2＋ channels. Our previous study showed that activin A promotes neurite growth of dorsal root ganglia in embryonic chickens and inhibits nitric oxide secretion. The present study demonstrated for the first time that activin A could maintain cerebral cortex neuronal survival in vitro for a long period, and that activin A was shown to increase voltage-gated Na＋ current （/Na） in Neuro-2a cells, which was recorded by patch clamp technique. The present study revealed a novel mechanism for activin A, as well as the influence of activin A on neurons by regulating expressions of vasoactive intestine peptide and inducible nitric oxide synthase.
基金US NSF grants to Yong- song Huang (ESH-0318050, 0318123, 0402383 and OPP- 0520718)
文摘Qinghai Lake, China, is located near the northern limit of the East Asian summer monsoon （EASM） and thus is an ideal region for studies of past monsoonal changes. However, isotope records from this region reflect the combined effects of multiple climatic factors, and make climatic interpretations difficult. The authors use multi-proxy records, generated from the same sediment core from Qinghai Lake, to disentangle these multiple effects in isotope records and to infer EASM variability during the late Holocene. Records of leaf wax （C2s） δD, lake carbonate 5180 and the Dunde ice core δ18O all indicate a millennial-scale depletion of mean isotopic values at -1500-1250 years before present. Compared with independent lake temperature and salinity records, the authors suggest that this depletion of long-term mean isotopic values must have resulted from changes in moisture sources in this region. In contrast, the authors attribute high-frequency （centennial timescale） C2s δD and ice core δ18O variability dominantly to a temperature effect. The multiproxy records provide a coherent picture in that many aspects of this regional climate （temperature, dryness, and moisture source） are strongly linked to the EASM variability.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB42000000)the Second Tibetan Plateau Scientific Expedition and Research Program (2019QZKK0101)the National Natural Science Foundation of China (42071113 and 42371166)。
文摘The Indo-Pacific warm pool(IPWP) is crucial for regional and global climates. However, the development of the IPWP and its effect on the regional climate during the Cenozoic remain unclear. Here, using a compilation of sea surface temperature(SST) records(mainly since the middle Miocene) and multimodel paleoclimate simulations, our results indicated that the extent, intensity and warmest temperature position of the IPWP changed markedly during the Cenozoic. Specifically, its extent decreased, its intensity weakened, and its warmest temperature position shifted from the Indian to western Pacific Ocean over time. The atmospheric CO_(2) dominated its extent and intensity, while paleogeography, by restricting the distribution of the Indian Ocean and the width of the tropical seaways, controlled the shift in its warmest temperature position. In particular, the eastward shift to the western Pacific Ocean from the middle to late Miocene inferred from compiled SST records likely resulted from the constriction of tropical seaways. Furthermore, by changing the atmospheric thermal structure and atmospheric circulation,the reduced extent and intensity of the IPWP decreased the annual precipitation in the western Indian Ocean, eastern Asia and Australia, while the shift in the warmest temperature position from the Indian to western Pacific Ocean promoted aridification in Australia. Qualitative model-data agreements are obtained for both the IPWP SST and regional climate. From the perspective of past warm climates with high concentrations of atmospheric CO_(2), the expansion and strengthening of the IPWP will occur in a warmer future and favor excessive precipitation in eastern Asia and Australia.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(XDB40010200 and XDA2009000004)the Program of Global Change and Mitigation+1 种基金Ministry of Science and Technology of China(2016YFA0600502)the National Natural Science Foundation of China(41877293,41672162,41977381,and 41472315)。
文摘Orbital-scale global climatic changes during the late Quaternary are dominated by high-latitude influenced~100,000-year global ice-age cycles and monsoon influenced~23,000-year low-latitude hydroclimate variations.However,the shortage of highly-resolved land temperature records remains a limiting factor for achieving a comprehensive understanding of long-term low-latitude terrestrial climatic changes.Here,we report paired mean annual air temperature(MAAT)and monsoon intensity proxy records over the past 88,000 years from Lake Tengchongqinghai in southwestern China.While summer monsoon intensity follows the~23,000-year precession beat found also in previous studies,we identify previously unrecognized warm periods at 88,000-71,000 and 45,000-22,000 years ago,with 2-3℃amplitudes that are close to our recorded full glacial-interglacial range.Using advanced transient climate simulations and comparing with forcing factors,we find that these warm periods in our MAAT record probably depends on local annual mean insolation,which is controlled by Earth’s~41,000-year obliquity cycles and is anti-phased to annual mean insolation at high latitudes.The coincidence of our identified warm periods and intervals of high-frequent dated archaeological evidence highlights the importance of temperature on anatomically modern humans in Asia during the last glacial stage.
基金supported by grants from the Natural Science Foundation of China (30671953 and 30801005)Ministry of Education of China (No. 20070183013)
文摘Macrophages play critical roles in innate immune and acquired immune v/a secreting pro-inflammatory mediators, phagocytosing microorganisms and presenting antigens. Activin A, a member of transforming growth factor （TGF-β） superfamily, is produced by macrophages and microglia cells. In this study, we reported a direct effect of activin A as a pro-inflammatory factor on mouse macrophage cell line RAW264.7 cells. Our data revealed that activin A could not only increase IL-1β and IL-6 production from RAW264.7 cells, but also promote pinocytic and phagocytic activities of RAW264.7 cells. In addition, activin A obviously up-regulated MHC Ⅱ expression on the surface of RAW264.7 cells, whereas did not influence MHC I expression. Activin A also enhanced CD80 expression, which is a marker of activated macrophages, but did not influence RAW264.7 cell proliferation. These data suggest that activin A may regulate primary macrophage-mediated innate and acquired immune response via promoting the activation of rest macrophages.
基金Acknowledgments This research was supported by grants provided by the Natural Science Foundation of China （Grant No. 30671953, 30801005 and 30901329）, Ministry of Education of China （Grant No 20070183013） and the Project of Science and Technology of Jilin Province （Grant No 20080160）.
文摘Activin A, a multifunctional factor of the transforming growth factor-beta （TGF-β） superfamily, is mainly produced by microglia and macrophages, and its anti-inflammatory and pro-inflammatory activities are both related to macrophage functions. However the direct effect of activin A on the rest macrophages in vivo remains unclear. In the present study, the results showed that activin A not only increased NO and IL-1β release, but also promoted phagocytic abilities of mouse peritoneal macrophages in vitro and in vivo, whereas it did not influence MHC Ⅰ and MHC Ⅱ expression. Moreover, we found that activin A significantly upregulated the expressions of CD14 and CD68, markers of mature macrophages, on the surface of macrophages in vitro and in vivo. These data suggest that activin A can induce primary macrophage maturation in vitro and in vivo, but may not trigger the acquired immune response via regulating expression of MHC molecules involved in presentation of antigen.
基金financially supported by the Strategic Priority Research Program of Chinese Academy of Sciences(XDB40000000)the National Natural Science Foundation of China(41672349,40802084)Hong Kong Research Grants Council(17325516)。
文摘One of the Holocene abrupt events around 4200 years ago,lasting for~200 years,is thought to have caused cultural disruptions,yet terrestrial climatic status right after the cold/dry event remains poorly defined and is often presumed that a generally cool condition prevailed during the Bronze Age(~4000-2200 years ago).Here we report an alkenone-based summer temperature record over the past~12,000 years,in addition to two updated alkenone records,from Northwest China,providing new insights into the climatic status right after the event.Our results indicate that exceptional terrestrial warmth,up to~6°C,occurred around 4200-2800 years ago during the Bronze Age,superimposed on the long-term Holocene cooling trend.The exceptional warmth in Northwest China,together with other climate anomalies elsewhere,suggests an unusual large-scale climatic reorganization at 4200-2800 years ago when solar activity remained high,with important implications to the climate background for cultural developments during the Bronze Age.
基金supported by the National Natural Science Foundation of China (Grant No. 41573005)the National Basic Research Programme of China (Grant No. 2013CB955901)+1 种基金the Key Program of the Chinese Academy of Sciences (Grant No. QYZDY-SSWDQC001)the State Key Laboratory of Loess and Quaternary Geology (Grant No. SKLLQG1632)
文摘Aquatic plants are major input sources of autochthonous organic matter in lake sediments, but investigations on fatty acid(FA) and n-alkane distributions in aquatic plants are currently limited, greatly hindering the applications of their isotope geochemistry in lacustrine environments. Here, the reported n-alkyl lipid distributions of aquatic plants in globally studied lakes,together with newly obtained aquatic plant n-alkyl lipid data in Chinese lakes(Yunnan and Inner Mongolia), are used to understand their distribution characteristics. The results show that aquatic plants have predominantly mid-chain lipids(C23–C25 n-alkanes and C22–C24 FAs), differing from that of terrestrial plants(dominant by long-chain lipids), but the long-chain n-alkanes(e.g., C27 and C29) and long-chain FAs(e.g., C26 and C28) also show high abundances in most samples. Submerged plants have high concentrations of long-chain n-alkanes(avg. 47 μg g-1) and long-chain FAs(avg. 170 μg g-1), close to those in terrestrial plants, indicating that submerged plants may make large contributions of long-chain n-alkyl lipids to lake sediments, while the contributions of long-chain n-alkyl lipids derived from algae to lake sediments may be small because of their low concentrations(avg. 2 μg g-1 for n-alkanes and 9 μg g-1 for FAs). We find that lipid molecular proxies(including ACL14-32 and ATR14-18) can be reliably used to distinguish the FAs sourced from algae and other plants, and Paq′ values can be utilized to distinguish the nalkane sources between submerged plants and terrestrial plants. Aquatic plants do not have significant δD differences among different chain-length n-alkanes and FAs for each sample, suggesting that the offset between δD values of different chain-length n-alkyl lipids in lake sediments can help determine sedimentary lipid input sources and infer paleohydrological changes.
基金supported by the Guangzhou Science and Technology Plan Project(Grant No.202102080366)the Guangdong Academy of Sciences(Grant No.2016GDASRC-0209)+1 种基金the Research Grant Council of Hong Kong(Grant No.HKU17311816)the National Natural Science Foundation of China(Grant Nos.42106062,41706039&41606070)。
文摘To investigate the relationship between the alkenone unsaturation index(U^(K′)_(37)) and sea surface temperature(SST) in coastal and continental shelf waters, 58 surface sediment samples were collected from the South China Sea(SCS), Taiwan Strait,and East China Sea(ECS). We combined the new results with the previously published 71 data points from the SCS, the shallow water areas of the Yellow Sea(YS) and northern ECS, to form a dataset with sample sites spanning across 6°N and 37°N(including annual SST calibration between 14.3℃ and 28.6℃). With this dataset, we examined the U^(K′)_(37)-SST relationship based on 129 samples from the Western North Pacific(WNP) margin as well as using 85 samples from specific WNP shallow water.The U^(K′)_(37)index from the low-mid latitudinal WNP margin demonstrated a good correlation with the surface annual mean SST(0–50 m water depth;R^(2)=0.89). The slope of linear regression(U^(K′)_(37)-SST) based on the coastal-continental shelf samples with water depth less than 200 m is similar to that of the published global open ocean regression equation. These results confirm that U^(K′)_(37)can be used as a shallow sea water SST proxy in mid-low latitudes of the WNP marginal seas. In addition, our reintegrated U^(K′)_(37)-SST results based on 172 global shallow water samples are similar(similar slopes and intercepts) to the shallow ocean results in the WNP marginal seas. However, the similarity of the regression formula to the open ocean does not imply that the formula is applicable. For example, of the 85 data in the shallow waters from the marginal sea in this study, the majority of data points lie above the regression line, showing positive residuals for U^(K′)_(37). This regression bias appears to be caused by specific marine environments, such as warm ocean currents and/or high nutrient conditions that result in positive U^(K′)_(37)residuals. Taken together,considering the specific temperature and environmental factors in the shallow waters of the low-mid-latitude WNP margin, we propose a nonlinear U^(K′)_(37)-SST regression formula: U^(K′)_(37)=-1.2488+0.1740×SST-0.0035×(SST)2, R2=0.93, N=85, specifically for the environments with SST below 24℃.
