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71.
Abundance and size composition of the summer phytoplankton communities in the western North Pacific Ocean,the Bering Sea,and the Gulf of Alaska 总被引:2,自引:0,他引:2
Tsuneo Odate 《Journal of Oceanography》1996,52(3):335-351
Chlorophylla concentrations (Chla) of size-fractionated phytoplankton samples were measured in the western North Pacific Ocean, the Bering Sea, and the Gulf of Alaska during the summer of 1986. Among samples collected in the upper 100 m (total of 210 samples), 207 samples were dominated by micro- (>10 m) or picoplankton (<2 m) and only three samples were represented by nanoplankton (2–10 m). These 207 samples were classified based on the total Chla content into three types: Type H (>1.0 g l–1), Type M (0.5–1.0 g l–1), and Type L (<0.5 g l–1). These types further divided into two subtypes (-p and-m), depending upon dominancy of pico (-p) and microplankton (-m). The phytoplankton community was represented by Type L-p in the Gulf of Alaska, where 80% of the samples fell into this type. It was represented by Type M-p in the western North Pacific and the Oceanic Domain in the Bering Sea, where 53 and 41% of samples were identified as this type, respectively. In the Middle Domain of the Bering Sea, 68% of samples collected below the nitracline was Type H-m, which indicates blooms of microplanton. This type was also observed in the neritic waters near the Aleutian Islands. These types described above are consistent with a general trend that an increase in phytoplankton abundance is attributed to the growth of microplankton. An unusual type occurred above the nitracline of the Middle Domain, where microplankton prevailed, although the total Chla was less (Type L-m). This type represents a feature of late phase of an ice edge bloom. Another unusual type was found mainly in the Outer Domain of the Bering Sea, where the total Chla was high and picoplankton prevailed (Type H-p). The predominance of picoplankton seems to result from the heavy grazing intensity of large calanoid copepods upon microplankton but not upon picoplankton 相似文献
72.
To verify the actual usefulness of time-dependent tracer dating techniques in the ocean, we simultaneously obtained two cross
sections of sulfur hexafluoride (SF6) and chlrofluoromethanes (CFC-11, trichlorofluoromethane; CFC-12, dichloro-difluromethane; CFC-113, trichlorotrifluoroethane)
in the western North Pacific in 1998. The vertical distribution patterns of SF6 and CFC-113 were similar in shape to those of CFC-11 and CFC-12. Maximum penetration depths of SF6 and CFC-113 remained around 800 m in the subpolar region and 400 m in the tropical region, while the maximum penetration
depths of CFC-11 and CFC-12 were still found below 1000 m depth. We also found all maximum contents of these tracers around
26.6−26.8σθ with a gradual decrease southward. This suggested that a new subsurface water mass in the subpolar region spread out over
the entire North Pacific, which agrees closely with previous studies based on the salinity minimum. Moreover, we compared
the tracer ages (the elapsed period of a water mass from when the water mass left from the ocean surface) using ten time-dependent
tracer dating techniques, CFC-11, CFC-12, CFC-113, SF6, CFC-11/CFC-12, CFC-113/CFC-11, CFC-113/CFC-12, SF6/CFC-11, SF6/CFC-12 and SF6/CFC-113. This quantitative evaluation of multiple tracer dating techniques in the ocean was the first confirmation of its
usefulness based on the observational data on the ocean basin-wide scale. We conclude that SF6/CFC-11, SF6/CFC-12, SF6/CFC-113 and SF6 dating techniques would be the most promising tools for determining the age of water mass not only just for the past several
decades but for the future, too.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
73.
Tsuneo Odate Mitsuru Yanada Lourdes V. Castillo Yoshiaki Maita 《Journal of Oceanography》1990,46(4):184-189
Cell densities of phycoerythrin-fluorescing cyanobacteria and other chlorophyll-fluorescing picophytoplankton in the 0.2–2.0 µm size fraction were investigated, using an epifluorescence microscope, in the western North Pacific Ocean (36.5–44.0 °N, 155.0°E) in the summer of 1989. Cyanobacteria were most abundant in the surface of the subtropical water (36.5–38.0°N) and less in the northern sea area (39.5–44.0°N). The cell density of other picophytoplankton was, however, high in the northern part and low in the subtropical water. Results showed that algae other than cyanobacteria may significantly contribute to the picophytoplankton community under the low water temperature conditions of open waters. Chlorophylla concentration represented well the abundance of picophytoplankton other than cyanobacteria, but had no significant correlation with the cyanobacteria cell density. Chlorophylla-based data must be interpreted with caution, since the abundances of cyanobacteria were often considerably different even though the chlorophylla concentrations were the same level. 相似文献
74.
Tsuneo?OnoEmail author Hiromi?Kasai Takashi?Midorikawa Yusuke?Takatani Kazuhiro?Saito Masao?Ishii Yutaka?W.?Watanabe Katsuyuki?Sasaki 《Journal of Oceanography》2005,61(6):1075-1087
Eight-year observation results of DIC from 1996 to 2003 in the Oyashio region have been analyzed to obtain a climatological
view of its seasonal variation and interannual variation. Data of DIC obtained by several institutes are synthesized to give
a dataset with an uncertainty lower than 5 μmol/kg. The obtained climatology of NDIC seasonal variation in the Oyashio mixed layer shows a seasonal amplitude of 176 μmol/kg, with a maximum in January and a minimum in September. These features closely resemble those observed in the southern
half of the western subarctic North Pacific (WSNP) including Station KNOT, although the timing of the NDIC maximum is slightly
advanced in the case of the Oyashio. Analysis using a quasi-conservative tracer Cp0 (NDIC - 106NP) shows that among 176 μmol/kg of NDIC seasonal variation, only 16 μmol/kg is attributed to hydrographic processes while the remaining 160 μmol/kg is attributed to biological processes. The Cp0 value in the Oyashio mixed layer also resembles that of the WSNP mixed
layer during the months May to November, suggesting further resemblance of the Oyashio water mass to that of WSNP in terms
of carbon dynamics. The present results also suggest that a single data obtained in Oyashio mixed layer contains 30 μmol/kg of potential uncertainty for the representativity of this region, which leads to a note about a need to treat with
caution results obtained by a single observation in this region. 相似文献
75.
Size-fractionated primary productivity and chlorophylla concentration were studied at two stations in the temperate neritic water of Funka Bay, Japan, from April 1984 to May 1985. Size distributions of phytoplankton were discussed in relation to nutrient availability. In the central part of the bay, 66% of the annual primary production occurred during the spring phytoplankton bloom with 95% of the spring production being accounted for by the greater than 10µm size fraction, which was dominated by diatoms. The increase in this large fraction was enhanced at both stations when nutrient concentrations increased in the bay's upper layer. Under low nutrient concentrations during summer, small phytoplankters (<2µm) accounted for 40 to 75% (average 60%) of the total14C uptake at the central station, and from 25 to 59% (average, 45%) at the coastal station. However, a sudden nutrient enrichment at the coastal station during the summer triggered the growth of the large size fraction. These seasonal and regional changes in total14C uptake were attributed to the large size fraction, composed mainly of diatoms. From the decreases in various nutrients during diatom blooms, it was further suggested that the predominance of diatoms was determined, not only by nutrient concentrations, but also by their relative availability.Contribution No. 205 from the Research Institute of North Pacific Fisheries, Faculty of Fisheries, Hokkaido University. 相似文献
76.
Zooplankton biomass consisting of large and small-size copepods, copepod nauplii and tintinnids were investigated over a period of one year at two stations in Funka Bay, Japan. The food requirement of zooplankton was also estimated using the method of Ikeda and Motoda. Estimated total carbon requirement of zooplankton in the coastal and central parts of the bay was equivalent to 52 and 38% of the annual primary production, respectively. These corresponded to zooplankton production of 12–13 gC·m–2·yr–1.The total carbon requirement at each station increased to 63 and 74% of the primary production during summer compared with 26 and 3% in spring or 19 and 17% in winter. The microzooplankton (copepod nauplii and tintinnids) accounted for about half of the carbon requirement from April to November.Food requirements reached 161% at the coastal station and 194% at the central station of the daily organic carbon production during September. Zooplankton may also feed on carbon sources other than living phytoplankton. This could account for the observed decrease in particulate organic carbon in a water column.Contribution No. 202 from the Research Institute of North Pacific Fisheries, Faculty of Fisheries, Hokkaido University. 相似文献
77.
We have used density functional theory to investigate the stability of MgAl2O4 polymorphs under pressure. Our results can reasonably explain the transition sequence of MgAl2O4 polymorphs observed in previous experiments. The spinel phase (stable at ambient conditions) dissociates into periclase and
corundum at 14 GPa. With increasing pressure, a phase change from the two oxides to a calcium-ferrite phase occurs, and finally
transforms to a calcium-titanate phase at 68 GPa. The calcium-titanate phase is stable up to at least 150 GPa, and we did
not observe a stability field for a hexagonal phase or periclase + Rh2O3(II)-type Al2O3. The bulk moduli of the phases calculated in this study are in good agreement with those measured in high-pressure experiments.
Our results differ from those of a previous study using similar methods. We attribute this inconsistency to an incomplete
optimization of a cell shape and ionic positions at high pressures in the previous calculations. 相似文献
78.
Christopher J. Norton Youichi Kondo Akira Ono Yingqi Zhang Mark C. Diab 《Quaternary International》2010,211(1-2):113-122
The nature of late Quaternary megafaunal extinctions has been the subject of intense debate since the 1960s. Traditionally, scientists cite either climatic changes or human predation as the primary reason for worldwide megafaunal extinctions. In many island cases (e.g., Madagascar, New Zealand), scientists have had a tendency to lean toward humans as being the direct or indirect dominant cause for the relatively quick extirpation of indigenous megafaunas. This study evaluates the record for megafaunal (e.g., Palaeoloxodon, Mammuthus, Sinomegaceros) extinctions in the Japanese islands and draw the tentative conclusion that: (1) humans directly and/or indirectly influenced the extinction of some large herbivores; and (2) the megafaunal extinctions likely began earlier than originally proposed; during the marine isotope stage (“MIS”) 3–2 transition (~30–20 ka) rather than during the MIS 2–1 (~15–10 ka) shift that roughly coincides with the advent of the Jomon period in Japan. However, we temper our findings due to the current paucity of sites in Japan that have associated archaeology and vertebrate paleontological materials that date to the MIS 3–2 transition. 相似文献
79.
Yasuhiro Yamasaki Yanan Zou Jyoji Go Tomoyuki Shikata Yukihiko Matsuyama Kiyohito Nagai Yohei Shimasaki Kenichi Yamaguchi Yuji Oshima Tatsuya Oda Tsuneo Honjo 《Journal of Sea Research》2011,65(1):76-83
We used bi-algal culture experiments to investigate and verify the roles of growth interaction between Heterocapsa circularisquama and Prorocentrum dentatum in monospecific bloom formation. Growth of H. circularisquama was slightly inhibited when inoculated at 102 cells mL–1 along with P. dentatum at 104 cells mL–1. In other combinations of inoculation densities, P. dentatum density rapidly decreased to extremely low levels in the presence of H. circularisquama. We used a mathematical model to simulate growth and interactions of H. circularisquama and P. dentatum in bi-algal cultures. The model indicates that one species will always inhibit the growth of the other and that the relative initial cell densities of the species are critical in determining the outcome. When cultured together under conditions without cell contact, growth of H. circularisquama and P. dentatum was not inhibited. As with P. dentatum, the growth of Heterosigma akashiwo and Skeletonema costatum was inhibited in intact cell suspensions with H. circularisquama, but a nontoxic species, Heterocapsa triquetra, did not affect the growth of P. dentatum or the other species. Similarly, cell suspensions of H. circularisquama showed hemolytic activity toward rabbit erythrocytes, but those of H. triquetra did not. In addition, the cell-free supernatant of H. circularisquama cultures showed no significant hemolytic activity. These results suggest that H. circularisquama causes lethality in P. dentatum by direct cell contact in which live-cell-mediated hemolytic activity might be a contributing factor. 相似文献
80.
Satoru Yamamoto Ryosuke Nakamura Tsuneo Matsunaga Yoshiko Ogawa Yoshiaki Ishihara Tomokatsu Morota Naru Hirata Makiko Ohtake Takahiro Hiroi Yasuhiro Yokota Junichi Haruyama 《Icarus》2012,218(1):331-344
The distribution and the geological context of the olivine-rich exposures in the South Pole-Aitken (SPA) Basin on the Moon were investigated based on the spectral data obtained from the Spectral Profiler (SP) and Multiband Imager (MI) onboard the Japanese lunar explorer Kaguya/SELENE. The olivine-rich exposures are found only in the peak rings or central peaks of the Schrödinger basin and Zeeman crater, which are located in the outer region of the SPA Basin and not in the center region. On a localized scale, the olivine-rich materials are exposed on landslide features on the crater walls or sloped wall of the central peaks or the peak rings. Another observational finding is the co-existence of olivine-rich and plagioclase-rich materials on a kilometer scale spanning most of the olivine-rich sites in the Schrödinger basin. Pyroxene-rich materials are found in fresh craters outside the peak rings or the central peaks with olivine-rich materials. Based on these results, the following scenario are proposed: (1) the impact to form the SPA Basin melted a large amount of the lunar upper mantle and crust, and distributed the melted materials to the outer region; (2) local differentiation of melted materials hid the olivine-rich materials in the center region of the SPA Basin; (3) later impacts that formed the Schrödinger and Zeeman craters excavated and exposed the olivine-rich materials to the surface again; and (4) space weathering and regolith gardening obscured the olivine-rich spectra at the exposure sites, but recent, small scale impacts or landslides on the sloped wall exposed fresh olivine-rich materials, allowing the identification of the olivine-rich exposures by spectral remote-sensing. This suggests that several, different scale events play an important role in forming the surface distributions of originally deep-seated materials on the Moon, as well as on other planetary bodies. 相似文献