1993~1996年南海中部海洋沉降颗粒通量的季节和年际变化

通过对南海中部1993~1996年获得的浅层和深层时间系列沉积物捕获器的样品分析,发现了稳定同位素值、颗粒总通量、碳酸盐、生物蛋白石、有机碳、表层初级生产力、浮游有孔虫总通量和属种的分布存在明显的季节性变化,其通量都是在东北季风和西南季风盛行期出现高值,在季风转向期出现低值.浮游有孔虫Globigerinoides sacculifer,G.ruber,Globigerinita glutinata,Neo-globoquadrina dutertrei等种的通量和相对百分含量也是在东北季风和西南季风盛行期都出现高值,但Globigerina bulloides,Globorotalia menardii和Pulleniatina obliquiloculata等种则在东北季风盛行期出现高值.分析还发现Globigerinoides sacculifer和Globorotalia menardii等种的通量和百分含量以及有孔虫总通量和碳酸盐通量等从1993到1996年存在下降趋势,而Globigerina.bulloides和Globigerinita glutinata的通量和百分含量以及生物蛋白石通量等在该期间显示为上升趋势.浅层捕获器样品中的碳酸盐和有机碳的通量比深层的高.研究表明海洋沉降通量和浮游有孔虫属种的季节和年际变化主要受与东亚季风相关的表层初级生产力和海洋水文条件变化所控制,深层捕获器样品中的碳酸盐和有机碳的通量低应与碳酸盐溶解作用有关.     

Regional variations in the fluxes of foraminifera carbonate,coccolithophorid carbonate and biogenic opal in the northern Indian Ocean

Mass fluxes of diatom opal, planktonic foraminifera carbonate and coccolithophorid carbonate were measured with time-series sediment traps at six sites in the Arabian Sea, Bay of Bengal and Equatorial Indian Ocean (EIOT). The above fluxes were related to regional variations in salinity, temperature and nutrient distribution. Annual fluxes of diatom opal range between 3 and 28 g m⁻² yr⁻¹, while planktonic foraminifera carbonate fluxes range between 6 and 23 g m⁻² yr⁻¹ and coccolithophorid carbonate fluxes range between 4 and 24 g m⁻² yr⁻¹. Annual planktonic foraminifera carbonate to coccolithophorid carbonate ratios range between 0.8 and 2.2 and coccolithophorid carbonate to diatom opal ratios range between 0.5 and 3.3.In the western Arabian Sea, coccolithophorids are the major contributors to biogenic flux during periods of low nutrient concentrations. Coccolithophorid carbonate fluxes decrease and planktonic foraminiferal carbonate and diatom opal fluxes increase when nutrient-rich upwelled waters are advected over the trap site. In the oligotropic eastern Arabian Sea, coccolithophorid carbonate fluxes are high throughout the year. Planktonic foraminiferal carbonate fluxes are the major contributors to biogenic flux in the EIOT. In the northern and central Bay of Bengal, when surface salinity values drop sharply during the SW monsoon, there is a drastic reduction in planktonic foraminiferal carbonate fluxes, but coccolithophorid carbonate and diatom opal fluxes remain steady or continue to increase. Distinctly higher annual molar Si_bio/C_inorg (>1) and C_org/C_inorg (>1.5) ratios are observed in the northern and central Bay of Bengal mainly due to lower foraminiferal carbonate production as a result of sharp salinity variations. We can thus infer that the enhanced freshwater supply from rivers should increase oceanic CO₂ uptake. Its silicate supply favours the production of diatoms while the salinity drop produces conditions unfavourable for most planktonic foraminifera species.     

Seasonal variation of pteropods from the Western Arabian Sea sediment trap

Sediment trap samples collected from the Western Arabian Sea yielded a rich assemblage of intact and non-living (opaque white) pteropod tests from a water depth of 919 m during January to September 1993. Nine species of pteropods were recorded, all (except one) displaying distinct seasonality in abundance, suggesting their response to changing hydrographical conditions influenced by the summer/winter monsoon cycle. Pteropod fluxes increased during the April–May peak of the intermonsoon, and reached maximum levels in the late phase of the southwest summer monsoon, probably due to the shallowing of the mixed layer depth. This shallowing, coupled with enhanced nutrient availability, provides ideal conditions for pteropod growth, also reflected in corresponding fluctuations in the flux of the foraminifer Globigerina bulloides. Pteropod/planktic foraminifer ratios displayed marked seasonal variations, the values increasing during the warmer months of April and May when planktic foraminiferal fluxes declined. The variation in fluxes of calcium carbonate, organic carbon and biogenic opal show positive correlations with fluxes of pteropods and planktic foraminifers. Calcium carbonate was the main contributor to the total particulate flux, especially during the SW monsoon. In the study area, pteropod flux variations are similar to the other flux patterns, indicating that they, too could be used as a potential tool for palaeoclimatic reconstruction of the recent past.     

A 9-year time-series of planktonic foraminifer fluxes and environmental change in the Bering sea and the central subarctic Pacific Ocean, 1990–1999

A 9-year study of planktonic foraminifer fluxes was conducted in the Bering Sea (Station AB) and in the central subarctic Pacific (Station SA). Results clearly reflected variations of the water mass characteristics in the upper layers. The 9-year means of total foraminifer fluxes were the same (1400 shells m⁻² d⁻¹) at both stations. However, total foraminifer flux at Station AB tended to show its primary maximum during fall (October–December) and its secondary maximum in spring (April–June), whereas the primary maximum appeared in spring and the secondary maximum in fall at Station SA. Seasonal variation was more apparent at hemipelagic Station AB than at pelagic Station SA. Planktonic foraminifers found at both stations were of six species: Neogloboquadrina pachyderma, Globigerina umbilicata, Globigerinita glutinata, Globigerina quinqueloba, Globorotalia wilesi, and Orbulina universa. The foraminifer assemblages at the two stations reflected the temperature difference in the surface waters. The variable %G. umbilicata tended to be high in the warm surface waters during the summers. The temporal and geographical variation of %G. quinqueloba indicated that this taxon prefers regions with relatively low diatom fluxes. A notable appearance of O. universa occurred in 1997 at Station SA. During this period, other measured biogenic particle fluxes, such as those of diatoms, were low. This unusual 1997 event may be a reflection of global climatic change that happened to be observed in the central subarctic Pacific Ocean.     

Seasonal export and sediment preservation of diatomaceous, foraminiferal and organic matter mass fluxes in a trophic gradient across the SE Atlantic

Seasonal deposition fluxes of sinking phytoplankton, zooplankton and major mass compounds (i.e. calcium carbonate, biogenic opal and organic matter), intercepted by deep-moored sediment traps, are contrasted with their sediment accumulation rates over the 2700 m deep central Walvis Ridge in the oligotrophic SE Atlantic. These data provide the first seasonally resolved record of biogenic particle fluxes in the South Atlantic Central Gyre and serve as the oligotrophic end member of a gradient across the Benguela system to the highly productive coastal upwelling off Namibia. Maximum fluxes at the central Walvis Ridge were deposited in early austral spring, following winter deepening of the surface mixed layer and associated nutrient entrainment. Nearly 25% of the annual mass flux arrived in October, when sea surface temperature rose, deep vertical mixing halted and surface production collapsed. The annual flux of diatoms was dominated by small specimens of Nitzschia bicapitata (60%) whereas Globorotalia inflata dominated the foraminiferal fluxes (25%). Diatom diversity dropped significantly during the bloom periods, when up to 80% was composed of small N. bicapitata, but foraminiferal diversity remained about constant. The diatom flux maximum, together with those of biogenic silica and organic matter, preceded those of the foraminifera, pteropods, carbonate and total mass by 1 week. Fluxes of the left- and right-coiled shells of the deep-dwelling foraminifer Globorotalia truncatulinoides peaked in different seasons, a distinctive ecological behaviour which merits their taxonomic recognition as separate species. These findings testify to recent evidence for the existence of several genetic species within G. truncatulinoides and now suggest that such species may also have different seasonal responses.The Benguela trophic gradient showed a shoreward increase in particle fluxes, but differences were surprisingly small, testifying to only moderately enhanced export productivity and deposition at the Namibian margin relative to the oligotrophic central gyre. From the open ocean toward coastal upwelling, small and weakly silicified diatoms were substituted by other, larger and more heavily silicified species, possibly in response to decreased silica limitation. Foraminiferal deposition fluxes were increasingly dominated by G. inflata, accompanied by a change-over from many warm- to few cold-water minor species. The late winter maximum at the Namibian margin and the early spring maximum at the central Walvis Ridge were generated by the same process of collapsing surface productivity in response to the shut down of nutrient entrainment at the winter to summer transition, although delayed by up to 2 months in the Central Gyre. At the sediment-water interface, intense degradation of organic matter and biogenic silica resulted in poor preservation accompanied by pronounced changes in the species composition of siliceous phytoplankton. Of all particle groups at the central Walvis Ridge, only the export of foraminiferal shells appeared to be fully transferred into the sediment, and through their species assemblage to provide a sedimentary record of past seasonal productivity conditions of the upper ocean.     

Calcareous nannofossil and planktonic foraminiferal distributional patterns during deposition of sapropels S6, S5 and S1 in the Libyan Sea (Eastern Mediterranean)

In core ADE3-23 collected in the Libyan Sea, the nannofossil species Coccolithus pelagicus, Coronosphaera spp., Helicosphaera spp., Syracosphaera spp., Calcidiscus spp., small Gephyrocapsa spp., and the planktonic foraminifers Globigerina bulloides, Neogloboquadrina pachyderma, Globorotalia scitula, Turborotalita quinqueloba and Neogloboquadrina dutertrei prevail in sapropel S6 (midpoint at 172 ka b.p.), indicative of cold and highly productive surface conditions. Warm and highly stratified water-column conditions are recorded by the characteristic assemblage of Globigerinoides ruber, Globoturborotalita rubescens, Florisphaera profunda, Rhabdosphaera spp. during the sapropel S5 depositional interval (midpoint at 124 ka b.p.). Compared with S5, Globigerinita glutinata, Globorotalia inflata, Globigerinella siphonifera, Globorotalia truncatulinoides and the calcareous nannofossil Emiliania huxleyi characterise less stratified conditions within sapropel S1 (midpoint at 8.5 ka b.p.). Multivariate statistical analyses of calcareous nannofossil and planktonic foraminifers in core ADE3-23 identify planktonic assemblages which typify sapropels S6, S5 and S1 in the Libyan Sea. A warmer interval is recognised in the middle part of the cold S6, and can be associated with an influx of less saline waters and the occurrence of a faint, temporary deep chlorophyll maximum. Evidence for enhanced surface productivity and breakdown of stratification is observed in the middle–upper part of the warm S5, associated with climatic deterioration. Moreover, an increase in surface productivity in the upper S1 implies weak stratification. Our combined calcareous nannofossil and planktonic foraminiferal data add to the evidence that climate variability was more pronounced than commonly considered to date for all the three studied Eastern Mediterranean sapropel depositional intervals.     

越南岸外上升流区48万年来高分辨率的生源组分记录及其古海洋学意义

南海西部越南岸外MD05-2901孔沉积物分析显示,该孔覆盖氧同位素1-12期,底界年龄约为48万年。生源组分记录显示表层古生产力冰期高、间冰期低,体现间冰期海平面下降、陆源物质输入增强的影响。生产力在末次冰期达到最高,体现末次盛冰期海陆差异增强,东北风发育对生产力提高的促进作用。碳酸钙含量变化呈现冰期早期含量低、冰消期和间冰期含量高的趋势。其冰消期的高值在MIS1/2、MIS3/4和MIS5/6分界处,与浮游有孔虫碳同位素低值对应,揭示该地区的碳酸钙沉积旋回是“稀释旋回”。同时碳酸钙含量变化领先于同一地区浮游有孔虫氧同位素的变化,证明低纬海区碳酸钙泵作用对大气二氧化碳浓度和温度有影响。滤波分析结果显示碳同位素存在23 ka的岁差周期和偏心率长周期,生源组分的含量变化显示出典型的岁差周期,体现南海季风环流的轨道响应,证明低纬热带过程是调节气候变化的重要因素。     

安达曼海浮游有孔虫群落对全新世海洋环境变化的响应

通过对安达曼海重力柱ADM-C1的浮游有孔虫群落分析, 探讨了该区全新世以来的海洋环境演化。研究发现, 该区浮游有孔虫群落总体以热带暖水种Globigerinoides ruber、Globigerinoides sacculifer、Neogloboquadrina dutertrei和Pulleniatina obliquiloculata等为主。其中G. ruber的相对丰度从早全新世至今呈逐渐降低的趋势, G. sacculifer则呈大致相反的变化趋势。N. dutertrei的相对丰度从11—7.9ka BP较高, 到7.9—3.8ka BP偏低, 3.8ka BP以来又逐渐升高。而P. obliquiloculata的变化趋势则与N. dutertrei大致相反。研究认为, 安达曼海不存在与冲绳海槽类似的晚全新世普林虫低值事件。浮游有孔虫群落Q型因子显示全新世海洋环境呈现三个明显的阶段变化: 早全新世 11—7.9ka BP期间, 浮游有孔虫群落以G. ruber、N. dutertrei与G. bulloides为主, 反映了该阶段较强的夏季风降水会导致表层水体盐度较低, 同时冬季风的影响相对较强; 7.9—3.8ka BP期间, 以G. ruber、P. obliquiloculata和Globigerinella aequilateralis为主, 指示水体盐度仍然较低, 同时次表层属种显著增多, 对应了该阶段强盛的印度夏季风, 上层海水混合强烈; 3.8—0ka BP期间, 以G. sacculifer、N. dutertrei和P. obliquiloculata为主要特征属种, 而G. ruber相对丰度明显下降, 表明该时期表层海水的盐度有显著上升, 对应了印度夏季风降水的明显减弱。安达曼海浮游有孔虫群落所呈现的全新世海洋环境阶段性变化和陆地夏季风记录有很好的一致性, 也与该孔敏感粒级组分所反映的印度季风的强度变化一致, 表明热带边缘海区的有孔虫群落组合可以很好地响应区域海洋环境变化。     

Paleoecological Relations of Foraminifera in a Desert-Enclosed Sea -The Gulf of Aqaba (Elat), Red Sea

Abstract. Planktonic and benthonic foraminifera live in the desert-enclosed, hypersaline and oligotrophic Gulf of Aqaba and northernmost Red Sea near the edge of their ecological tolerance. Marked changes in foraminiferal abundance patterns in the past, resulting from hydrological shifts related to global climatic fluctuations, facilitate a high-resolution ecostratigraphic subdivision of deep-sea records covering the last 150,000 years. Of particular significance are the foraminiferal plankton/benthos ratios, the presence/absence pattern of such species as Globigerinoides sacculifer , as well as the frequency variation of Globigerina bulloules-falconensis, Buliminacea, Miiiolacea and various "rotaliform" species. Paleoceanographic interpretation of the shifts in assemblage composition and of stable oxygen isotope data obtained on planktonic foraminifera and pteropods indicates that during glacial intervals - because of global cooling, lowered sea-level and reduced water exchange at the straits of Bab-el-Mandeb - the temperature of the upper waters fell by about 4–6 ^oC (to 15–17 ^oC), salinity rose by about 10%o to more than 50%₀ while residence time of the water became longer and the input/output ratio of nutrients became higher. As a consequence, fertility of the photic zone was higher, the organic content of the sediments increased and oxygen levels in the deep basin became reduced. Thus, sea level-oscillations and strait-dynamics played a major role in the foraminiferal paleoecology of the Red Sea.     

黄、东海陆架2011年秋季活体浮游有孔虫生态分布

现代活体浮游有孔虫的生态研究是其古环境重建应用的重要基础。根据黄、东海陆架2011年秋季采集的20个垂直浮游拖网样品,分析了该海域浮游有孔虫的秋季生态分布特征。结果表明,黄海秋季基本上没有浮游有孔虫的出现。东海共发现13种活体浮游有孔虫,主要优势属种依次为Globigerinoides sacculifer、Pulleniatina obliquiloculata、Globigerina bulloides、Neogloboquadrina dutertrei和Globigerinoides ruber。浮游有孔虫丰度整体上呈现东南高,西北低的分布格局,这种分布格局反映了浮游有孔虫在黄、东海陆架区的分布主要受外海水影响强弱控制。浮游有孔虫主要属种在东海陆架呈现明显的区域分布差异:暖水种G. sacculifer是秋季陆架海区的主要优势种,其分布格局与总丰度基本一致,相对含量从南至北、从东至西逐渐降低,主要受区域表层海水温度变化的控制。G. bulloides与G. sacculifer呈相反的含量分布变化,其高含量主要出现在东海中陆架,从北往南逐渐降低,此外,在闽浙沿岸也有较高含量,表明了温度和生产力是影响G. bulloides在黄、东海陆架分布的主要因素。秋季P. obliquiloculata和N. dutertrei的高含量主要出现在东海南部中陆架区和济州岛西南黄海暖流影响区,可能受暖水与生产力的共同制约。     

Seasonal and annual variability in particle fluxes in the Gulf of California: A response to climate forcing

A six-year time series of sediment trap samples is used to document seasonal and interannual changes in particle fluxes in Guaymas Basin, Gulf of California. Sedimentation in this region of the Gulf of California is dominated by two seasonally varying components: biogenic silica during the late fall–spring and lithogenic material during the summer. This variability in sediment fluxes is a direct response to the seasonally reversing monsoon climate in this region. In addition, this seasonal variability in particle flux to the seafloor combined with the lack of bioturbation results in the formation of sediment laminae or varves in Guaymas Basin. Observed interannual differences in the magnitude of sediment fluxes appear to be related to ENSO. These findings indicate that biogenic sediment fluxes, and hence primary productivity, are higher during non-ENSO years in the central Gulf of California. A decrease in the carbonate: opal flux ratio from 1991 to 1996 indicates that diatoms became an increasingly important component of the plankton during this period and further supports our findings that productivity in Guaymas Basin is higher during non-ENSO years.     

台湾海峡中、北部上升流区浮游有孔虫的生态研究

分析１９８７—１９８８年在台湾海峡中、北部用浮游生物网采集的水层中的浮游有孔虫标本，研究调查海区浮游有孔虫的生态分布特征及其与海水温度和盐度的关系。结果表明：该海区浮游有孔虫计有１６种，以泡抱球虫Ｇｌｏｂｉｇｅｒｉｎａｂｕｌｌｏｉｄｅｓ为主要优势种类，其次是袋拟抱球虫Ｇｌｏｂｉｇｅｒｉｎｏｉｄｅｓｓａｃｃｕｌｉｆｅｒ和红拟抱球虫Ｇ．ｒｕｂｅｒ。在夏季的７月和８月（特别是７月），浮游有孔虫密集在福建中部沿岸的南日岛至闽江口外海海域一带沿岸水域，其中９０％以上的个体由泡抱球虫组成。此现象推测与夏季出现在福建沿岸的上升流活动有关。     

Holocene and Pleistocene dissolution cycles in deep-sea cores of Baffin Bay and Davis Strait: Palaeoceano-graphic implications

Calcium-carbonate dissolution has been studied in several grab samples and piston cores from Baffin Bay and Davis Strait ranging in water depth from 200 to 2300 m. The intensity of dissolution was determined from examining: (1) the ratio of arenaceous to calcareous benthonic foraminifera; (2) the ratio of benthonic to planktonic foraminifera; (3) the relationships between the dissolution-susceptible and dissolution-resistant foraminifera; (4) the degree of foraminiferal test fragmentation; and (5) the relationships between plankton tows and the fauna in the surface sediments. All core tops and grab samples from Baffin Bay surface sediments below 600–900 m water depth demonstrated intense dissolution of calcium carbonate. Sediments below 900 m were biogenic carbonate free, indicating 100% foraminiferal loss due to dissolution. Possible causes of substantial undersaturation in calcium carbonate of Baffin Bay Bottom Water are very low temperatures, and higher concentrations of carbon dioxide. All cores also demonstrated intense dissolution during interglacial or interstadial isotope stages 1, 3, 5, 7 and 9. Similarities in planktonic foraminiferal assemblages suggested the presence of similar bottom-water masses during these periods. The preservation state of biogenic carbonate debris in glacial isotope stages 2, 4, 6, 8 and 10 is similar to the assemblage found in the water at present.     

冲绳海槽表层沉积物中浮游有孔虫壳体的氧同位素分布特征及其影响因素

选择冲绳海槽的3个剖面A、B、C上的现代表层沉积物样品，对浮游有孔虫Globigerinoides ruber、Glo-bigerinoides sacculifer和Neogloboquadrina dutertrei进行了氧同位素分析，结果表明，几乎所有样品从G.ruber到G.sacculifer到N.dutertrei其氧同位素值均由轻变重，表明3种有孔虫其生活水层依次由浅到深，进一步证实了这3个种的生态生活习性在冲绳海槽区域与开放大洋同样一致，在槽穿海槽的A、C两个剖面上，G.ruber和N.dutertrei的氧同位素有相似的变化，从西向东氧内闰素值依次由轻变重，然后又变轻，表明剖面西侧站位有孔虫壳体氧同位素因受冲淡水影响较强而变轻，而在东侧站位受高温黑潮的影响氧同位素同样有变轻的趋势，沿海槽轴向展布的剖面B上的氧同位素变化主要受冲淡水的影响，表层水体在剖面中部和南端冲淡水影响相对较大，而次表层水只在剖面南端受冲淡水影响相对较强，剖面A、C上的N.dutertrei和G.ruber的氧同位素差值有着相反的变化趋势，在剖面A上，氧同位素差值从近陆端向近岛弧端逐渐由小变大，而在剖面C上，则逐渐由大变小，上述变化可能表明了磁部区域黑潮支流对表层水体的影响要大于次表层水体，而在南部海槽区域，黑潮暖流对次表层水体有相对较强的影响。     

Seasonal and interannual variability of the planktic foraminiferal flux in the vicinity of the Azores Current

Planktic foraminiferal (PF) flux and faunal composition from three sediment trap time series of 2002–2004 in the northeastern Atlantic show pronounced year-to-year variations despite similar sea surface temperature (SST). The averaged fauna of the in 2002/2003 is dominated by the species Globigerinita glutinata, whereas in 2003/2004 the averaged fauna is dominated by Globigerinoides ruber. We show that PF species respond primarily to productivity, triggered by the seasonal dynamics of vertical stratification of the upper water column. Multivariate statistical analysis reveals three distinct species groups, linked to bulk particle flux, to chlorophyll concentrations and to summer/fall oligotrophy with high SST and stratification. We speculate that the distinct nutrition strategies of strictly asymbiontic, facultatively symbiontic, and symbiontic species may play a key role in explaining their abundances and temporal succession. Advection of water masses within the Azores Current and species expatriation result in a highly diverse PF assemblage. The Azores Frontal Zone may have influenced the trap site in 2002, indicated by subsurface water cooling, by highest PF flux and high flux of the deep-dwelling species Globorotalia scitula. Similarity analyses with core top samples from the global ocean including 746 sites from the Atlantic suggest that the trap faunas have only poor analogs in the surface sediments. These differences have to be taken into account when estimating past oceanic properties from sediment PF data in the eastern subtropical North Atlantic.     

东北太平洋胡安·德富卡隆起西翼晚第四纪以来的碳酸盐记录

通过对东北太平洋胡安·德富卡隆起西翼沉积柱样中的碳酸盐含量和浮游有孔虫氧同位素测试以及浮游有孔虫丰度、溶解指数和粗组分的统计,发现在晚第四纪约65 ka以来碳酸盐含量变化幅度大(0 4%~77 2%),相差非常悬殊,但其变化未呈现出冰期时溶解作用减弱、间冰期时溶解作用强烈这样明显的旋回性。粗组分分析结果显示,地层中有明显的浊流沉积发育。另外,碳酸盐含量和浮游有孔虫丰度分析结果揭露了研究区的 CCD在3 500 m左右。研究认为,在约65 ka来水深浅于3 500 m的区域碳酸盐含量的无规律性变化应与浊流沉积影响有直接的关系,而水深深于3 500 m的区域碳酸盐含量主要受控于深海碳酸盐的溶解作用。     

南海东北部表层沉答中微体化石与碳酸盐溶跃面和补偿深度

通过对南海东北部(12°～22°N,116°～122°E)表层沉积中的浮游有孔虫、底栖有孔虫、钙质超微化石、硅质与钙质生物丰度和比值的定量分析以及碳酸盐含量的测定,发现碳酸盐含量、浮游有孔虫、钙质超微化石丰度以及钙质生物比值随水深的增大迅速减小,而底栖有孔虫占有孔虫全群的比值和硅质生物比值以及底栖有孔虫胶结质壳类的百分含量却随水深的增大迅速增加.研究表明,调查区内微体化石丰度和比值以及碳酸钙含量的高低,与碳酸盐溶跃面(lysocline)和碳酸盐补偿深度密切相关,碳酸盐溶跃面和碳酸盐补偿深度南、北还存在一定差异,碳酸盐溶跃面南部较北部深,南部在2600m上下,北部则在2200m上下;碳酸盐补偿深度也是南部的较深,南部为3 600 m上下,而北部在3 400 m上下。     

Microfossils, carbonate lysocline and compensation depth in surface sediments of the northeastern South China Sea

INTRODUCTIONTwoimportantinterfacespunctuatingtheabyssalverticaltrans sectionarecarbonatelyso clineandcarbonatecompensationdepth (CCD) .Thecarbonatelysoclineislabeledbyabruptincrementofcarbonatedissolutiononcalcitemicrofossilssuchasplanktonicforaminifertests(Berger,1 96 8) ,ordecreasingapparentlyinpercentageofthecarbonateproportion (Panetal ,1 988) .ThoughtherearemanyachievementsonthecarbonatecycleandCCDresearches(Wangetal ,1 995;Rottman ,1 979;Thunelletal ,1 992 ;Zhengetal ,1 993;Mia…     

Particle fluxes to the interior of the Southern Ocean in the Western Pacific sector along 170°W

An array of five bottom-tethered moorings with 19 PARFLUX time-series sediment trap at three depths (1 and 2 km below the surface, and 0.7 km above the sea-floor) was deployed in the western Pacific sector of the Southern Ocean, along 170°W. The five stations were selected to sample settling particles in the main hydrological zones of the Southern Ocean. The sampling period spanned 425 days (November 28, 1996–January 23, 1998) and was divided into 13 or 21 synchronized time intervals. A total of 174 sequential samples were recovered and analyzed to estimate fluxes of total mass (TMF), organic carbon, carbonate, biogenic silica, and lithogenic particles. The fluxes of biogenic material were higher than anticipated, challenging the notion that the Southern Ocean is a low-productivity region. Organic carbon fluxes at 1 km depth within the Polar Frontal Zone and the Antarctic Zone were relatively uniform (1.7–2.3 g m⁻² yr⁻¹), and about twice the estimated ocean-wide average (ca. 1 g m⁻² yr⁻¹). Carbonate fluxes were also high and uniform between the Subantarctic Front and ca. 64°S (11–13 g m⁻² yr⁻¹). A large fraction of the carbonate flux in the Antarctic Zone was due to the presence of pteropod shells. Coccoliths were found only to the north of the Polar Front, and calcium carbonate became the dominant phase in the Subantarctic Zone. In contrast, carbonate particles were nearly absent near 64°S. Latitudinal variations in biogenic silica fluxes were substantial. The large opal flux (57 g m⁻² yr⁻¹) measured in the Antarctic Zone suggests that opal productivity in this region has been previously underestimated and helps to explain the high sedimentary opal accumulation often found south of the Polar Front. Unlike biogenic material, fluxes of lithogenic particles were among the lowest measured in the open-ocean (0.12–0.05 g m⁻² yr⁻¹), reflecting a very low dust input.     

Seasonal and vertical variations of sinking particle fluxes in the West Caroline Basin

A sediment trap experiment was carried out in the West Caroline Basin, located in the equatorial western Pacific between influences of the Asian monsoon and the open ocean. Annual mass flux at the shallow trap at Site 1 was 57.10 g m^-2 yr^-1. Generally, the higher flux of organic matter was associated with higher activities of biogenic opal-producing and carbonate-producing plankton communities. In addition, as the organic matter content increases, the organic carbon/carbonate carbon ratio shows a tendency to increase. Carbonate-producing plankton was predominant during periods 1 and 3 (May to July and November to the beginning of December), which could be due to limited silica supply to the euphotic zone. On the other hand, surface sea water was more nutrient-rich during periods 2 and 4 (August to October and the end of December to April) at Site 1. These high total mass fluxes could be stimulated by wind.The amount of biogenic components collected in the sediment traps and the accumulation in surface sediments at Site 1 could be compared with primary productivity values. Carbonate and biogenic opal fluxes were 99% and 90% less, respectively, in the surface sediments compared to those in the shallow sediment trap. This could be due to the reaction of sinking particles with undersaturated deep sea water just above the sea floor, rather than with the water column during sinking. About 20% of the organic matter was decomposed between the shallow and deep sediment traps and more than 98% between the deep sediment trap and final burial in the surface sediments. The relative amount of organic carbon preserved in surface sediments was about 0.10% of annual primary productivity.