Latitudinal Differences in the Planktonic Biomass and Community Structure Down to the Greater Depths in the Western North Pacific     

Atsushi Yamaguchi  Yuji Watanabe  Hiroshi Ishida  Takashi Harimoto  Kazushi Furusawa  Shinya Suzuki  Joji Ishizaka  Tsutomu Ikeda  Masayuki Mac Takahashi 《Journal of Oceanography》2004,60(4):773-787

As part of the research program WEST-COSMIC Phase I (1997–2001), vertical profiles down to the greater depths (0–2000 m or 5800 m) of the plankton community structure composed of heterotrophic bacteria, phytoplankton, protozooplankton and metazooplankton were studied at one station in each subarctic (44°N) and in transitional region (39°N), and two stations in subtropical region (30°N and 25°N); all in 137–155°E in the western North Pacific Ocean. The biomass of all four taxonomic groups decreased rapidly with increasing depths at all stations, although the magnitude of depth-related decrease differed among the groups. As plankton community structure, metazooplankton biomass and bacterial biomass occupied >50% of the total in 0–2000 and 2000–4000 or 5000 m strata, respectively, at subarctic and transitional stations, while bacterial biomass contributed to >50% of the total consistently from 0 through 4800 or 5800 m at subtropical stations. Metazooplankton biomass integrated over the greater depths exhibited a clear latitudinal pattern (high north and low south), but this was not the case for those of the other taxonomic groups. As a component of metazooplankton, an appreciable contribution of diapausing copepods to the metazooplankton was noted at subarctic and transitional stations, but they were few or nil at subtropical stations. As protozooplankton assemblages, heterotrophic microflagellates (HMF) and dinoflagellates were two major components at subarctic and transitional stations, but were only HMF predominated at subtropical stations. From biomass ratios between heterotrophic bacteria, HMF and dinoflagellates, “sinking POC-DOC-heterotrophic bacteria-HMF-heterotrophic dinoflagellates” link was proposed as a microbial food chain operative in the deep layer of the western North Pacific. All results are discussed in the light of latitudinal differences in the structure and functioning of plankton community contributing to the ‘biological pump’ in the western North Pacific Ocean. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Experimental study on strong interaction between regular waves and wind waves—I     

Mitsuhiko Hatori  Masayuki Tokuda  Yoshiaki Toba 《Journal of Oceanography》1981,37(3):111-119

The interaction between mechanically generated regular waves and wind waves is experimentally investigated in a wind-wave tunnel. It is shown that the growth process of regular waves is divided into the four distinct stages as follows: (1) almost independent coexistence of wind waves and regular waves, (2) attenuation of wind waves with simultaneous growth of regular waves, (3) rapid growth of regular waves after disappearance of wind waves, and (4) transition of regular waves to wind waves after the wave breaking. At the second stage there is an apparent relation between the attenuation of wind waves and the growth of regular waves. This fact suggests that there is some strong nonlinear interactions which transfers energy effectively from wind waves to regular waves.  相似文献   

Netplankton Chlorophyll Biomass along 175°E in the Pacific Ocean     

Dong-Hoon Han  Tohru Ikeya  Masayuki Mac Takahashi 《Journal of Oceanography》2004,60(3):543-551

An analysis is presented of data on chlorophyll a concentrations of the total and the netplankton (>10 μm), determined either in April to June or in August to September from 48°N to 15°S along 175°E in the Pacific Ocean during 6 years by the NOPACCS (Northwest Pacific Carbon Cycle Study). Particular attention was given to the variability of absolute concentrations of the netplankton chlorophyll a and their percentage shares of the total chlorophyll a concentration. Below 0.2 μg l⁻¹ of surface total chlorophyll a, the netplankton chlorophyll a showed low percentage shares (such as 12.7% on average) with a large variation, but above 0.2 μg l⁻¹ it was 35.9% on average with less variation, showing an accelerated increase at high total chlorophyll a concentrations. High netplankton chlorophyll a concentrations in surface waters were observed at high latitudes, in waters having high chlorophyll a concentrations at sub-surface depth, and in equatorial upwelling. The percentage shares of netplankton in the total chlorophyll a in the euphotic zone were 8.5% and 25.9% above and below 0.2 μg l⁻¹, respectively, although the data points scattered over a wide range (from 7.2% to 53.8%) depending on differences in water masses, depths and seasons. High chlorophyll a concentrations and high percentage shares of netplankton corresponded to high ambient nitrate plus nitrite concentrations. Integrated netplankton chlorophyll a concentrations in the euphotic zone varied from 0.7 to 19.5 mg m⁻² in waters below 0.2 μg l⁻¹ of surface total chlorophyll a, and from 2.0 to 29.5 mg m⁻² above 0.2 μg l⁻¹, and the percentage shares of netplankton for the former were 7.4% on average and 23.7% for the latter. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Simplified technique for the rapid determination of phytoplankton pigments by reverse-phase high-performance liquid chromatography   总被引：1，自引：0，他引：1  

Reiko Suzuki  Masayuki Takahashi  Ken Furuya  Takashi Ishimaru 《Journal of Oceanography》1993,49(5):571-580

A simplified technique for the rapid analysis of photosynthetic pigments in marine phytoplankton is described. The pigments extracted in N,N-dimethylformamide (DMF) are injected directly into the reverse-phase high-performance liquid chromatograph fitted with a photodiode array detector. We developed a new stepwise program; that is methanol-water (7525 v/v), methanol, methanol-acetone (8020) and methanol-acetone (6535). This program gives a good separation of at least 13 carotenoids, and 10 chlorophylls and their derivatives, completed within 20 min. The quantitative precision is high; the maximum standard error was less than 6%. The stability of pigments in DMF were also considered for application of this technique to the lab work on board the ship.  相似文献   

Chlorophyll distribution and photosynthetic activity in the north and equatorial Pacific Ocean along 155°W     

Masayuki Takahashi  Ken-ichi Satake  Nobutada Nakamoto 《Journal of Oceanography》1972,28(1):27-36

The distribution of chlorophylla and photosynthetic characterestics of phytoplankters were investigated along 155°W between 50°N and 15°S during the KH-69-4 cruise of the R. V. Hakuh Maru (Aug. 12–Nov. 13, 1969). High concentrations of chlorophylla (more than 0.2 mg Chla/m³) were observed above the depths of 150 m at all stations except in 17°N, 5°S and 15°S. North of 20°N, the depths of chlorophyll accumulation shifted from near the surface to 50–100 m with southwards. In the equatorial region, chlorophyll accumulation centered at a depth of about 70 m and ranged vertically between 10 and 150 m. In all cases in the present study area, chlorophyll accumulation occurred within the euphotic zone (above the depth corresponding to 1% of the surface illumination), and except in the subarctic and some equatorial waters, this was usually prevalent in the lower half of the euphotic zone.The photosynthetic activities (initial slope of P vs I curve) of samples from the depths of chlorophyll accumulation were similar to, or lower than, those of shallow samples from the depths of upper half of the euphotic zone. At the depths of chlorophyll accumulation, calculatedin situ photosynthesis was high in the central Pacific and equatorial waters but low in the subarctic waters.  相似文献   

Temporal changes in the geographic distribution of two clam species <Emphasis Type="Italic">Meretrix lusoria</Emphasis> and <Emphasis Type="Italic">M. petechialis</Emphasis> along the coast of Japan and South Korea     

Shin’ichi Sato  Yoshitaka Kaneko  Hiroshi Torii  Jae-Sang Hong 《Ocean Science Journal》2016,51(3):455-463

The objectives of this study were to distinguish fossil specimens of Meretrix (Bivalvia, Veneridae) using discriminant score and multivariate analysis, and to examine temporal changes in the geographical distributions of M. lusoria and M. petechialis in Japan and South Korea. Fossil shells of Meretrix were collected from Miyagi, Fukui, Aichi and Kumamoto in Japan, and Gimhae, Seosan, Siheung and Ganghwa-do in South Korea. The outside of the right valve was photographed with a digital camera, and ten characteristics of the shell morphology, such as shell height and shell length, were measured using image analysis software and a digital slide caliper. The discriminant score and multivariate analysis of the shell morphology identified all of the examined fossils as M. lusoria, while living individuals collected from the western coast of South Korea were identified as M. petechialis. These results suggest that the fossil shells excavated from the western coast of South Korea are a different species from the living individuals collected from the same areas. Radioactive carbon isotopic results revealed that the ages of the four fossil shells collected from tidal flats in Ganghwa-do ranged between 3,270 ± 30 and 1,830 ± 30 Cal BP. These results suggest that M. lusoria inhabited the western coast of South Korea until at least 2,000 years ago, but was replaced by M. petechialis during the last 2,000 years. Therefore, we propose that either M. petechialis spats were introduced artificially, or planktonic larvae migrated naturally from China to the western coast of South Korea during the last 2,000 years.  相似文献   

黄土-古土壤磁化率述评   总被引：30，自引：4，他引：26  

鸟居雅之  福间浩司  苏黎  杜克玲  方小敏 《海洋地质与第四纪地质》1999,19(3):83-96

黄土－古土壤是研究亚洲大陆内部过去２．６０Ｍａ间古环境变化的最好记录,特别是研究其与季风气候形成的密切关系,以及黄土扩展到日本甚至广泛的太平洋区域（北半球）等重大气候环境现象。其研究对第四纪古环境恢复具有极大的意义。最近基于黄土－古土壤而进行的古环境研究取得了很大的进展,一是因为黄土－古土壤磁化率的变化与深海沉积物的氧同位素比的变化非常一致,指示陆相沉积物亦可作为古气候的良好代用指标。另一方面,为什么黄土－古土壤中的磁化率存在差别,特别是古土壤磁化率为什么增大等问题,已成为这１０ａ间岩石磁学研究的中心课题。磁化率不单单只与强磁性矿物的含量成比例,同时也与不同种类的强磁性矿物的粒径分布有很大关系。发现在土壤化过程中形成的０．１μｍ以下的单畴－超顺磁性颗粒是造成古土壤磁化率增强的主要原因,它是否与生物作用有关目前仍不确定,但不论哪种情况,都可以肯定暖湿气候是古土壤磁化率增加的共同原因。磁化率增强的系统理论明确建立以来,使得从磁化率的变化来推算降水量,以及建立古气候复元的定量模型等都已成为可行。  相似文献   

差分主成分分析法在辽河三角洲景观变化中的应用   总被引：7，自引：0，他引：7  

杨翠芬  田村正行 《地理学报》2004,59(4):592-598

差分主成分分析法是应用遥感数据检测景观变化的一种新方法。为了提高检测精度,我们利用TM卫星遥感数据,改进了主成分分析法和图像差值法,提出了差分主成分分析法。并以辽河三角洲地区为例,对该方法进行了验证。研究结果表明：(1) 与传统的检测法-分类后比较法相比,差分主成分分析法具有较高的检测精度,总检测精度为0.89,Kappa指数为0.82;(2) 在1984~2000年的16年间,辽河三角洲地区有近22%的景观发生了变化,主要包括芦苇湿地的减少、水稻田的增加以及城镇用地的增加。  相似文献   

Distribution,age, and origin of a submarine landslide deposit in the Pleistocene Kiwada Formation,forearc basin fill on the Boso Peninsula,east‐central Japan: Constraints from tephro‐ and biostratigraphy          下载免费PDF全文

Masayuki Utsunomiya 《Island Arc》2018,27(4)

A mass‐transport deposit named MTD1 (up to 100 m in thickness) is intercalated in the upper Kiwada Formation, a Pleistocene forearc basin fill on the Boso Peninsula, east‐central Japan. The present study aims to examine the origin, age, and distribution of MTD1. MTD1 consists mainly of mudstone blocks containing thin very fine‐ to medium‐grained sandstones, and ranges from tens of centimeters to more than tens of meters in length and thickness. Correlation of marker tuff beds and application of the biostratigraphy of calcareous nannofossils suggest that the blocks in MTD1 were derived from the underlying strata. The total thickness of the stratified blocks from the different stratigraphic horizons exceeds 60 m, implying that MTD1 originated from deeply‐excavated slope failure. The slope failure occurred in a short time interval at ca 1.3 Ma. MTD1 provides an estimate of the height of the escarpment on the basis of the stratigraphic origin of the blocks.  相似文献   

Magnetism and mineralogy of Almahata Sitta polymict ureilite (= asteroid 2008 TC3): Implications for the ureilite parent body magnetic field     

Viktor H. HOFFMANN  Rupert HOCHLEITNER  Masayuki TORII  Minoru FUNAKI  Takashi MIKOUCHI  Melanie KALIWODA  Peter JENNISKENS  Muawia H. SHADDAD 《Meteoritics & planetary science》2011,46(10):1551-1564

Abstract– The Almahata Sitta meteorite is the first case of recovered extraterrestrial material originating from an asteroid that was detected in near Earth space shortly before entering and exploding in the high atmosphere. The aims of our project within the 2008 TC₃ consortium were investigating Almahata Sitta’s (AS) magnetic signature, phase composition and mineralogy, focussing on the opaque minerals, and gaining new insights into the magnetism of the ureilite parent body (UPB). We report on the general magnetic properties and behavior of Almahata Sitta and try to place the results in context with the existing data set on ureilites and ureilite parent body models. The magnetic signature of AS is dominated by a set of low‐Ni kamacites with large grain sizes. Additional contributions come from micron‐sized kamacites, suessite, (Cr) troilite, and daubreelite, mainly found in the olivine grains adjacent to carbon‐rich veins. Our results show that the paleomagnetic signal is of extraterrestrial origin as can be seen by comparing with laboratory produced magnetic records (IRM). Four types of kamacite (I–IV) have been recognized in the sample. The elemental composition of the ureilite vein metal Kamacite I (particularly Co) clearly differs from the other kamacites (II‐IV), which are considered to be indigenous. Element ratios of kamacite I indicate that it was introduced into the UPB by an impactor, supporting the conclusions of Gabriel and Pack (2009) .  相似文献