长链烯酮及Uk37值在北极海洋古温度的应用研究

在北极楚科奇海和白令海表层沉积物中检出长链烯酮化合物,研究结果表明楚科奇海和白令海沉积物中长链烯酮以G37:3甲基酮占优势,C37～C39不饱和烯酮丰度变化顺序为C37＞C38＞C39.根据∑C37/∑C38比值,所检出的长链烯酮母质生物主要是颗石藻(Emiliania huxleyi).应用Uk37和Uk37标准校正关系式估算了表层海水古温度,其中Uk37估算值为4.147～5.706℃(平均为5.092℃).     

长链烯酮及U_(37)~k值在北极海洋古温度的应用研究

在北极楚科奇海和白令海表层沉积物中检出长链烯酮化合物 ,研究结果表明楚科奇海和白令海沉积物中长链烯酮以C37∶3甲基酮占优势 ,C37～C39不饱和烯酮丰度变化顺序为C37>C38>C39.根据∑C37/∑C38比值 ,所检出的长链烯酮母质生物主要是颗石藻 (Emilianiahuxleyi) .应用Uk37和Uk′37标准校正关系式估算了表层海水古温度 ,其中Uk′37估算值为 4.1 47～ 5.70 6℃ (平均为 5.0 92℃ ) .     

楚科奇海、白令海表层沉积物210 Pb和137 Cs分布

通过分析第十次北极考察楚科奇海、白令海考察区表层沉积物样品中放射性核素~(210)Pb和~(137)Cs,获得表层沉积物(0～8 cm)中~(210)Pb和~(137)Cs在不同断面和不同层的比活度范围和分布。楚科奇海陆架区R断面表层沉积物(0～2 cm层)~(210)Pb比活度范围为44.80～117.45 Bq·kg~(-1);~(137)Cs检出主要分布在表层沉积物(2～4 cm和4～6 cm层),比活度范围为未检出～2.23 Bq·kg~(-1)。白令海BL和BR断面表层沉积物(0～2 cm层)~(210)Pb比活度范围分别为29.93～141.35 Bq·kg~(-1)和40.78～620.43 Bq·kg~(-1);BL和BR断面~(137)Cs比活度范围分别为未检出～2.48 Bq·kg~(-1)和未检出～2.08 Bq·kg~(-1)。其中在白令海考察区南端陆坡区深海站位出现~(210)Pb比活度高值;结合表层沉积物垂向分层数据揭示水体中~(210)Pb随颗粒物移除沉降到海底,随海底深度增加而显著升高;各站位的表层沉积物年沉积率随海底深度增加而降低。深海区域站位表层沉积物~(210)Pb比活度随海底深度增加而增加现象说明,颗粒物沉降过程的吸附作用是主要原因。也表明表层沉积物~(210)Pb比活度与海水深度的比值作为~(210)Pb均化因子(HF),可指征颗粒物中~(210)Pb比活度从水体上层至海洋底层随沉降过程的平均变化。研究结果表明楚科奇海陆架区部分站位表层沉积物~(210)Pb存在明显的扰动情况,楚科奇海陆架区、白令海陆架区表层沉积物中~(137)Cs在沉积物各层深分布不均匀。     

北冰洋西部沉积物有机碳、氮同位素特征及其环境指示意义

通过对楚科奇海及邻近的北冰洋深水区表层沉积物中有机碳同位素含量(δ13C)、氮同位素含量(δ15N)及生物成因SiO₂(BSiO₂)含量分析,结果表明海源和陆源有机质的分布受海区环流结构和营养盐结构所制约.楚科奇海中西部和楚科奇海台受太平洋富营养盐海水的影响,海洋生产力高,沉积物中海源有机质和BSiO₂含量高;靠阿拉斯加一侧海域海水的营养盐含量和生产力都偏低,沉积物中陆源有机质比重增加;在研究区北部和东北部的楚科奇高地和加拿大海盆,冰封时间较长,营养盐供应少,海洋生产力低,但来自马更些河和阿拉斯加北部的陆源有机质增多,沉积物中BSiO₂含量小于5%,海源有机质百分含量小于40%.由于亚北极太平洋水通过楚科奇海向北冰洋海盆输送,研究区营养盐池表现为开放系统,营养盐的利用率与它的供应成反比,与海洋生产力成反比.     

北极沉积物中正构烷烃的组合特征及古沉积环境的研究

报道了北极楚科奇海和白令海沉积物中正构烷烃的含量和分布类型,并通过因子分析方法对正构烷烃的来源和古沉积环境加以初步探讨.研究结果表明,正构烷烃碳数分布范围多数在nC₁₅～nC₃₃之间,分布类型有两种,第1种高分子碳范围,MH为nC₂₅～nC₂₇,CPI大于1,奇偶优势显著.第2种低分子碳范围,MH为nC₁₇～nC₂₀,奇偶优势不明显.以上特征指示了正构烷烃来源于陆源高等植物和海洋内生两个部分,并且以陆源贡献最大.楚科奇海和白令海大部分测站的Pr/Ph小于1,指示了缺氧还原沉积环境.因子分析结果与样品中正构烷烃不同分子组成特征相互对应.     

冲绳海槽二万年以来沉积物中烯酮化合物与古温度的研究

应用烯酮化合物的不饱和比值U₃₇k计算得出冲绳海槽海水古温度波动幅度在15.9～26.2℃之间,平均为22.9℃,和冬季实测表层水温22.0℃相接近,探讨了U₃₇k值在冲绳海槽指示的古海水温度和季节有关,主要反映在冬季。     

冲绳海槽2万年以来沉积物中生物标志化合物与古温度,古环境的研究

应用生物标志化合物长链烯酮不饱和比值 Uk37估算冲绳海槽 2万年以来古海水表层温度 ,其波动范围在 1 5.9～ 2 6.2℃之间 ,平均为 2 2 .9℃。并与常用的浮游有孔虫转换函数测算的表层海水温度进行对照 ,结果与冬季表层水温 ( 2 2 .0℃ )相近 ,Uk37值指示的古海水温度与季节有关 ,主要反映在冬季。在沉积物中还检出了另一类生物标志化合物甾、萜类等 ,对它们的组成进行了地球化学研究 ,结果表明 :冲绳海槽沉积物中有机质具有多源性特点 ,由陆源碎屑、生物碎屑和火山碎屑共同组成 ;该海域沉积有机质的成熟度不高 ,沉积环境具有强的还原性。     

白令海和西北冰洋表层沉积物磁化率特征初步研究

为了准确解释环境磁学参数记录的极地古气候环境变化信息,本研究对白令海和西北冰洋61个站位的表层沉积物进行了高、低频质量磁化率(χ)、非磁滞磁化率(χARM)和磁化率-温度(k-T)分析,以探明该区沉积物中磁性矿物的种类、来源与搬运路径。结果显示,样品的χ具有明显的地域分布特征。白令海的χ值整体高于楚科奇海,并在育空河口外侧和圣劳伦斯岛南侧较高,向北和向西南方向逐渐减小。楚科奇海中东部陆架上表层沉积χ值高于阿拉斯加沿岸,而西北冰洋深海平原和洋脊区的χ值最低。χARM的变化趋势与质量磁化率相似,但频率磁化率的变化趋势与质量磁化率正好相反。k-T分析结果显示阿留申海盆沉积物中的铁磁性矿物以磁赤铁矿占主导,白令海陆架育空河口外侧和圣劳伦斯岛南北两侧为磁铁矿,白令海陆架西部和楚科奇海陆架中东部为磁赤铁矿和磁铁矿,楚科奇海阿拉斯加沿岸为黄铁矿,而西北冰洋陆坡、深海平原和洋脊区为胶黄铁矿和黄铁矿,但高纬度区沉积物中的胶黄铁矿含量更高。沉积物中磁性矿物的区域性分布受沉积物来源、洋流和底质环境等因素的控制。白令海和楚科奇海陆架磁赤铁矿来源于亚洲大陆,白令海陆架东部的磁铁矿来自育空河流域,阿拉斯加沿岸沉积物中的黄铁矿,应为阿拉斯加西北部陆源侵蚀来源的或早期成岩作用形成的,西北冰洋深海盆区的胶黄铁矿,为自生成因的。     

正构烷烃组成的古环境指示：以中全新世以来珠江口沉积物研究为例

该文分析了珠江口沉积物柱状样HKUV16中正构烷烃的长链奇碳烷烃含量(∑oddC_25～33)、碳优势指数(CPI)、平均链长(ACL)、C₃₁/C₂₇和海洋水生植物比重(P_mar-aq),探讨了中全新世以来正构烷烃来源变化及对珠江流域环境变迁的指示。HKUV16的长链正构烷烃特征指示其主要来自陆源高等植物。在8.0～7.0 ka BP期间,∑oddC_25～33、CPI值和P_mar-aq值增加,ACL和C₃₁/C₂₇为低值,指示该时期陆源有机质输入增加,木本植物占比大,珠江流域气候湿润。在7.0～3.2 ka BP期间,∑oddC_25～33降低,表明陆源有机质输入减少,而ACL和C₃₁/C₂₇呈增—减—增的变化趋势,指示珠江流域可能经历了干旱—湿润—干旱的气候变化。3.2～2.2 ka BP,ACL、C₃₁/C₂₇     

楚科奇海附近表层沉积物中类脂生物标志物的分布特征和意义

多参数生物标记物法已被广泛用于重建浮游植物生产力和种群结构,研究了2003年夏季我国二次北极考察时采集的楚科奇海表层沉积物样品中浮游植物生物标志物的比例变化及其作为浮游植物种群结构替代指标的潜力。观测海区表层沉积物中菜子甾醇、甲藻甾醇、长链烯酮的总含量为20~3149 ng/g,平均值为1 010 ng/g,生物标志物总量分布表明南部的楚科奇陆架海域生产力明显高于北部海台区,不同站位的菜子甾醇和甲藻甾醇相对比例有明显变化,但都显示菜子甾醇占优势,楚科奇海陆架的站位中都是硅藻为主,菜子甾醇占生物标志物总量的比例为42%~74%,甲藻甾醇占生物标志物总量的比例为17%~37%,在海台区仍然是硅藻占优势,但是甲藻和颗石藻的比例有了很大的提高,加拿大海盆的4个站位中以甲藻和颗石藻为主,硅藻并非加拿大海盆的优势种群。这与用显微镜下鉴定得到的硅藻和甲藻分布趋势相似。研究结果为生物标志物作为浮游植物种群结果替代指标并为利用柱状样中的生物标志物研究古生态提供现代依据。     

Application of long-chain alkenones and U37k values for paleotemperature estimation in the Arctic Chukchi Sea-Bering Sea area

-Long-chain alkenones were detected in samples of sea surface sediments from the Chukchi Sea and the Bering Sea areas, the Arctic Pole. The analysis result indicates that C37:3 methylketone is pre dominate in the long-chain alkenones from the Chukchi and Bering Sea sediments. The abundance of C37to C39 unsaturated alkenones changes in an order of C37 ＞C38 ＞C39. Based on ∑37/∑38 ratio, the de tected organism precursors of the long-chain alkenones are mainly coccolithophrid (Emiliania huxleyi).By the calibration relationship between U3k7 and U37k indices, the sea surface paleotemperature in these seas is estimated. The estimated values of U37k vary from 4.147℃ to 5. 706℃, with a mean value of 5.092℃.     

Time-series sediment trap record of alkenones from the western Sea of Okhotsk

C₃₇–C₃₉ alkenones were measured in time-series sediment trap samples collected from August 1998 to June 2000 at two depths in the seasonal sea ice region of the western Sea of Okhotsk, off Sakhalin, in order to investigate alkenone production and water-column processes in the region. Measurable export fluxes of alkenones are ranged from < 0.1 to 5.8 μg/m²/day and clearly showed that the alkenone production was restricted to autumn. In 1998, maximum export flux of alkenones occurred in September when surface water column was well stratified with low nutrients in the surface mixing layer. In the next year, the maximum flux is observed in October. Comparison between alkenone temperature and satellite based sea surface temperature (SST) shows that the estimated alkenone temperatures in August 1998 were found to be  10 °C lower than the temporal satellite SST, suggesting that alkenones are produced in surface to subsurface thermocline layers during the period. Annual mean flux of alkenones is lower in the lower traps than that of the upper traps, suggesting rapid degradation of alkenones in water column, but the U^K₃₇′ value is not significantly altered. This study indicates that U^K₃₇′ values preserved in the surface sediments off Sakhalin reflect the seasonal temperature signal of near surface water, rather than annual mean surface temperature.     

Distributions and air-sea fluxes of CO2 in the summer Bering Sea

The 3rd Chinese National Arctic Research Expedition(CHINARE–Arctic III) was carried out from July to September in 2008. The partial pressure of CO2(pCO2) in the atmosphere and in surface seawater were determined in the Bering Sea during July 11–27, 2008, and a large number of seawater samples were taken for total alkalinity(TA) and total dissolved inorganic carbon(DIC) analysis. The distributions of CO2 parameters in the Bering Sea and their controlling factors were discussed. The pCO2 values in surface seawater presented a drastic variation from 148 to 563 μatm(1 μatm = 1.013 25×10-1 Pa). The lowest pCO2 values were observed near the Bering Sea shelf break while the highest pCO2 existed at the western Bering Strait. The Bering Sea generally acts as a net sink for atmospheric CO2 in summer. The air-sea CO2 fluxes in the Bering Sea shelf, slope, and basin were estimated at-9.4,-16.3, and-5.1 mmol/(m2·d), respectively. The annual uptake of CO2 was about 34 Tg C in the Bering Sea.     

Seasonal variations of alkenones and U37 in the Chesapeake Bay water column

Alkenone unsaturation indices (U^K₃₇ and U^K′₃₇) have long been used as proxies for surface water temperature in the open ocean. Recent studies have suggested that in other marine environments, variables other than temperature may affect both the production of alkenones and the values of the indices. Here, we present the results of a reconnaissance field study in which alkenones were extracted from particulate matter filtered from the water column in Chesapeake Bay during 2000 and 2001. A multivariate analysis shows a strong positive correlation between U^K₃₇ (and U^K′₃₇) values and temperature, and a significant negative correlation between U^K₃₇ (and U^K′₃₇) values and nitrate concentrations. However, temperature and nitrate concentrations also co-vary significantly. The temperature vs. U^K₃₇ relationships (U^K₃₇=0.018 (T)−0.162, R²=0.84, U^K′₃₇=0.013 (T)−0.04, R²=0.80) have lower slopes than the open-ocean equations of Prahl et al. [1988. Further evaluation of long-chain alkenones as indicators of paleoceanographic conditions. Geochimica et Cosmochimica Acta 52, 2303–2310] and Müller et al. [1998. Calibration of the alkenone paleotemperature index U^K′₃₇ based on core-tops from the eastern South Atlantic and the global ocean (60°N–60°S). Geochimica et Cosmochimica Acta 62, 1757–1772], but are similar to the relationships found in controlled studies with elevated nutrient levels and higher nitrate:phosphate (N:P) ratios. This implies that high nutrient levels in Chesapeake Bay have either lowered the U^K₃₇ vs. temperature slope, or nutrient levels are the main controller of the U^K₃₇ index. In addition, particularly high abundances (>5% of total C₃₇ alkenones) of the tetra-unsaturated ketone, C_37:4, were found when water temperatures reached 25 °C or higher, thus posing further questions about the controls on alkenone production as well as the biochemical roles of alkenones.     

长链烯酮化合物与生物化石

本文研究了南海北部３１孔岩芯样的长链烯酮化合物的分布与微体古生物（钙质超微化石和浮游有孔虫）的关系。烯酮化合物主要来自定鞭金藻的赫胥黎艾氏石Ｅｍｉｌｉａｎｉｓａｈｕｘｌｅｙｉ，其中Ｃ３７∶２Ｍｅ含量在３１％～７０％。应用Ｃ３７的不饱和比值（Ｕ３７ｋ）计算了南海３１孔柱状样的海水古温度，波动幅度在２３．２～２８．３℃之间，平均为２５．３℃，低于该海域海水实测年平均温度（２８．１℃）。Ｕ３７ｋ值的变化与浮游有孔虫壳体的氧同位素值分期有着对应的关系，亦可相应分成５期。     

南黄海北部表层沉积物中生物标志物的组成特征及其地球化学意义

通过对南黄海北部14个站位的19个表层沉积物样品进行了粒度、有机碳、GC-FID和GC-MS-MS测定,探讨沉积物有机质中生物标志物组成特征及地球化学意义。研究区表明,沉积物有机碳含量较高,正构烷烃呈双峰分布,具有明显奇偶优势、平均L/H为0.36,说明沉积物中陆源高等植物贡献占优,分析对比表明其沉积物可能主要来自古黄河输入。类异戊二烯烃Pr/Ph均值0.46,表明有机质沉积于强还原环境;Pr/C₁₇和Ph/C₁₈值均小于1,并且随深度有减小的趋势,反映了研究区微生物的降解作用。甾类化合物C₂₉豆甾烷>C_（?）胆甾烷>C₂₈麦角甾烷,说明萜类化合物和甾类化合物主要为陆相输入。较高OEP值、高丰度的藿烯和莫烷及甾烷S构型含量均反映了现代沉积物中有机质未熟-低熟特征,但由于原始母质影响和微生物发育,Ts/Tm和C₃₁αβS/（S+R）、C₃₂αβS/（S+R）、C₃₃αβS/（S+R）和C₂₉αββ/（ααα+αββ）值较高。     

Seasonal and depth variations in molecular and isotopic alkenone composition of sinking particles from the western North Pacific

Seasonal and depth variations in alkenone flux and molecular and isotopic composition of sinking particles were examined using a 21-month time-series sediment trap experiment at a mooring station WCT-2 (39°N, 147°E) in the mid-latitude NW Pacific to assess the influences of seasonality, production depth, and degradation in the water column on the alkenone unsaturation index U^K′₃₇. Analysis of the underlying sediments was also conducted to evaluate the effects of alkenone degradation at the water–sediment interface on U^K′₃₇. Alkenone sinking flux and U^K′₃₇-based temperature showed strong seasonal variability. Alkenone fluxes were higher from spring to fall than they were from fall to spring. During periods of high alkenone flux, the U^K′₃₇-based temperatures were lower than the contemporary sea-surface temperatures (SSTs), suggesting alkenone production in a well-developed thermocline (shallower than 30 m). During low alkenone flux periods, the U^K′₃₇-based temperatures were nearly constant and were higher than the contemporary SSTs. The nearly constant carbon isotopic ratios of C_37:2 and C_38:2 alkenones suggest that alkenones produced in early fall were suspended in the surface water until sinking. The alkenone sinking flux decreased exponentially with increasing depth. The decreasing trend was enhanced during the periods of high alkenone flux, suggesting that fresh and labile particles sank from spring to fall, while old and stable particles sank from fall to spring. The U^K′₃₇-based temperature usually increased with increasing depth. The preservation efficiency of alkenones was ∼2.7–5.2% at the water–sediment interface. Despite the significant degradation of the alkenones, there was little difference in U^K′₃₇ levels between sinking particles and the surface sediment.     

光和温度对两种绿潮藻光合途径及抗氧化功能的影响

绿潮是潮间带绿藻大量增殖形成的高生物量生态灾害，其暴发不仅受到温度、营养盐等环境因素的驱动，而且与自身光合能力的强弱密切相关。本研究以绿潮物种—肠浒苔(Ulva intestinalis)和Ulva expansa为研究对象，通过室外培养实验，检测了它们在夏季高温、高光强条件下的光合途径与抗氧化生理特征，并分析了与光合产物的对应关系。研究结果表明，肠浒苔与U. expansa的光合途径与抗氧化能力存在显著差异。前者的C₄光合途径关键酶活性在光合作用过程中出现高表达特征，与光、温度存在显著相关性，C₃光合途径关键酶活性在中午受到强光抑制；组织δ13C的变化范围为?17.1‰～?15.7‰，表明其光合作用可能由C₃和C₄途径共同参与。后者的C₄光合途径关键酶活性表达较弱，且与光、温度不存在显著相关性，C₃光合途径关键酶活性没有出现明显的光抑制现象；组织δ13C的范围为?23.5‰～?21.9‰，表明其光合作用主要依靠C₃途径进行。此外，肠浒苔在培养过程中表现出了较强的抗氧化能力，可能与其在高温、高光强条件下启动C₄光合途径密切相关。肠浒苔与U. expansa的比较研究说明，藻类C₄光合途径存在显著种间差异性。