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1.
2.
Tetsuo Yanagi Koji Ishikawa Koh-ichi Inoue Satoshi Susami 《Journal of Oceanography》1995,51(2):225-238
The detailed flow structure around a tical front in Hiuchi-Nada, Japan was observed with the use of ADCP (Acoustic Doppler Current Profiler). The surface convergence region is observed at the transition zone between vertically well mixed area and the stratified area. The surface divergence regions exist next to the surface convergence region. The strong downward current is estimated in the middle layer just below the surface convergence region. The maximum surface convergence and the maximum downward velocity in the middle layer are 1.0×10–4 s–1 and 0.12 cm s–1, respectively. 相似文献
3.
Koji Suzuki Akira Hinuma Hiroaki Saito Hiroshi Kiyosawa Hongbin Liu Toshiro Saino Atsushi Tsuda 《Progress in Oceanography》2005,64(2-4):167
To verify the hypothesis that the growth of phytoplankton in the Western Subarctic Gyre (WSG), which is located in the northwest subarctic Pacific, is suppressed by low iron (Fe) availability, an in situ Fe fertilization experiment was carried out in the summer of 2001. Changes over time in the abundance and community structure of phytoplankton were examined inside and outside an Fe patch using phytoplankton pigment markers analyzed by high-performance liquid chromatography (HPLC) and flow cytometry (FCM). In addition, the abundance of heterotrophic bacteria was also investigated by FCM. The chlorophyll a concentration was initially ca. 0.9 μg l−1 in the surface mixed layer where diatoms and chlorophyll b-containing green algae (prasinophytes and chlorophytes) were predominant in the chlorophyll biomass. After the iron enrichment, the chlorophyll a concentration increased up to 9.1 μg l−1 in the upper 10 m inside the Fe patch on Day 13. At the same time, the concentration of fucoxanthin (a diatom marker) increased 45-fold in the Fe patch, and diatoms accounted for a maximum 69% of the chlorophyll biomass. This result was consistent with a microscopic observation showing that the diatom Chaetoceros debilis had bloomed inside the Fe patch. However, chlorophyllide a concentrations also increased in the Fe patch with time, and reached a maximum of 2.2 μg l−1 at 5 m depth on Day 13, suggesting that a marked abundance of senescent algal cells existed at the end of the experiment. The concentration of peridinin (a dinoflagellate marker) also reached a maximum 24-fold, and dinoflagellates had contributed significantly (>15%) to the chlorophyll biomass inside the Fe patch by the end of the experiment. Concentrations of 19′-hexanoyloxyfucoxanthin (a prymnesiophyte marker), 19′-butanoyloxyfucoxanthin (a pelagophyte marker), and alloxanthin (a cryptophyte marker) were only incremented a few-fold increment inside the Fe patch. On the contrary, chlorophyll b concentration reduced to almost half of the initial level in the upper 10 m water column inside the Fe patch at the end of the experiment. A decrease with time in the abundance of eukaryotic ultraphytoplankton (<ca. 5 μm in size), in which chlorophyll b-containing green algae were possibly included was also observed by FCM. Overall, our results indicate that Fe supply can dramatically alter the abundance and community structure of phytoplankton in the WSG. On the other hand, cell density of heterotrophic bacteria inside the Fe patch was maximum at only ca. 1.5-fold higher than that outside the Fe patch. This indicates that heterotrophic bacteria abundance was little respondent to the Fe enrichment. 相似文献
4.
Sohiko Kameyama Satoshi Yoshida Hiroshi Tanimoto Satoshi Inomata Koji Suzuki Hisayuki Yoshikawa-Inoue 《Journal of Oceanography》2014,70(3):225-239
We measured dissolved isoprene (2-methyl-1,3-butadiene; C5H8) concentrations in a broad area of the southern Indian Ocean and in the Indian sector of the Southern Ocean from 35°S to 64°S and from 37°E to 111°E during austral summer 2010–2011. Isoprene concentrations were continuously measured by use of a proton-transfer-reaction mass spectrometer combined with a bubbling-type equilibrator. Concentrations of isoprene and its emission flux throughout the study period ranged from 0.2 to 395 pmol L?1 and from 181 to 313 nmol m?2 day?1, respectively, the averages being generally higher than those of previous studies. Although we found a significant linear positive relationship between isoprene and chlorophyll-a concentrations (r 2 = 0.37, n = 36, P < 0.001), the correlation coefficient was lower than previously reported. In contrast, in the high-latitude area (>53°S) we identified a significant negative correlation (r 2 = 0.59, n = 1263, P < 0.001) between isoprene and the temperature-normalized partial pressure of carbon dioxide (n-pCO2), used as an indicator of net community production in this study. This suggests that residence times and factors controlling variations in isoprene and n-pCO2 are similar within a physically stable water column. 相似文献
5.
A shipborne wave-recording system which consists of a sonic wave gauge, accelerometers, gyroscopes and a computer system is described. Signals from the measuring apparatus are fed directly into a shipborne digital computer system at a prescribed sampling rate. The time series of wave heights and the acceleration are transformed into Fourier series using an algorithm of Fast Fourier Transform. Errors contained in the observed wave heights due to ship motion are corrected in the Fourier series by using the Fourier coefficients for the vertical acceleration. Power spectra and waveforms can also be calculated in a short time with this system from Fourier coefficients. Examples of the observational results obtained in the central part of the East China Sea in 1969 are presented. 相似文献
6.
7.
Koji Sugie Kenshi Kuma Satoshi Fujita Satomi Ushizaka Koji Suzuki Tsutomu Ikeda 《Journal of Oceanography》2011,67(2):183-196
We report on the ability for luxury Fe uptake and the potential for growth utilizing intracellular Fe pools for 4 coastal
centric diatom isolates and in situ phytoplankton assemblages, mainly composed of diatoms. Iron uptake of the diatom isolates
and natural phytoplankton assemblages in the Oyashio region during spring blooms were prevented by adding hydroxamate siderophore
desferrioxamine B (DFB). After the addition of DFB, intracellular Fe in the diatom isolates supported 2.4–4.2 cell divisions
with 1.2–2.6 Chl a doublings. The intracellular Fe was primarily used for cell generation rather than Chl a production, leading to a reduction in the Chl a cell quota in the Fe-starved cells with time. The metabolic properties of the Fe-starved cells with their cell morphologies
were different among species or genera. An on-deck incubation experiment also exhibited 1.9 cell divisions and 0.81 Chl a doublings of phytoplankton after the addition of DFB, also indicating the preference of cell generation over Chl a production. A decrease in the level of cellular Chl a, a main light-harvesting pigment in Fe-starved diatoms, may become a superior survival strategy to protect the cells from
high irradiance that can cause photo-oxidative damages through photosynthesis. Such relatively low-Fe with high-light conditions
could often occur in surface waters of the Oyashio region from spring to summer. 相似文献
8.
Robert S. Pickart Michael A. Spall G.W.K. Moore Thomas J. Weingartner Rebecca A. Woodgate Knut Aagaard Koji Shimada 《Progress in Oceanography》2011,88(1-4):78-100
The spin up and relaxation of an autumn upwelling event on the Beaufort slope is investigated using a combination of oceanic and atmospheric data and numerical models. The event occurred in November 2002 and was driven by an Aleutian low storm. The wind field was strongly influenced by the pack-ice distribution, resulting in enhanced winds over the open water of the Chukchi Sea. Flow distortion due to the Brooks mountain range was also evident. Mooring observations east of Barrow Canyon show that the Beaufort shelfbreak jet reversed to the west under strong easterly winds, followed by upwelling of Atlantic Water onto the shelf. After the winds subsided a deep eastward jet of Atlantic Water developed, centered at 250 m depth. An idealized numerical model reproduces these results and suggests that the oceanic response to the local winds is modulated by a propagating signal from the western edge of the storm. The disparity in wave speeds between the sea surface height signal—traveling at the fast barotropic shelf wave speed—versus the interior density signal—traveling at the slow baroclinic wave speed—leads to the deep eastward jet. The broad-scale response to the storm over the Chukchi Sea is investigated using a regional numerical model. The strong gradient in windspeed at the ice edge results in convergence of the offshore Ekman transport, leading to the establishment of an anti-cyclonic gyre in the northern Chukchi Sea. Accordingly, the Chukchi shelfbreak jet accelerates to the east into the wind during the storm, and no upwelling occurs west of Barrow Canyon. Hence the storm response is fundamentally different on the Beaufort slope (upwelling) versus the Chukchi slope (no upwelling). The regional numerical model results are supported by additional mooring data in the Chukchi Sea. 相似文献
9.
Genki I. Matsumoto Yukinori Tani Koji Seto Tomoko Tazawa Masumi Yamamuro Takahiro Watanabe Toshio Nakamura Tetsuo Takemura Satoshi Imura Hiroshi Kanda 《Journal of Paleolimnology》2010,44(2):677-693
Antarctic climate changes influence environmental changes at both regional and local scales. Here we report Holocene paleolimnological
changes in lake sediment core Sk4C-02 (length 378.0 cm) from Lake Skallen Oike in the Soya Kaigan region of East Antarctica
inferred from analyses of sedimentary facies, a range of organic components, isotope ratios of organic carbon and nitrogen,
and carbon-14 dating by Tandetron accelerator mass spectrometry. The sediment core was composed of clayish mud (378.0–152.5 cm)
overlain by organic sediments (152.5 cm-surface). The age of the surface and the core bottom were 150 (AD1950-1640) and ca.
7,030 ± 73 calibrated years before present (cal BP), respectively, and the mean sedimentation rate was estimated to be 0.55 mm/year.
Multi-proxy analyses revealed that the principal environmental change in the core is a transition from marine to lacustrine
environments which occurred at a depth of 152.5 cm (ca. 3,590 cal BP). This was caused by relative sea level change brought
about by ongoing retreat of glaciers during the mid-Holocene warming of Antarctica, and ongoing isostatic uplift which outpaced
changes in global (eustatic) sea level. The mean isostatic uplift rate was calculated to be 2.8 mm/year. The coastal marine
period (378.0–152.5 cm, ca. 7,030–3,590 cal BP) was characterized by low biological production with the predominance of diatoms.
During the transition period from marine to freshwater conditions (152.5-approximately 135 cm, ca. 3,590–3,290 cal BP) the
lake was stratified with marine water overlain by freshwater, with a chemocline and an anoxic (sulfidic) layer in the bottom
of the photic zone. Green sulfur bacteria and Cryptophyta were the major photosynthetic organisms. The Cryptophyta appeared
to be tolerant of the moderate salinity and stratified water conditions. The lacustrine period (approximately 135 cm-surface,
ca. 3,290 cal BP-present) was characterized by high biological production by green algae (e.g. Comarium clepsydra and Oedegonium spp.) with some contributions from cyanobacteria and diatoms. Biological production during this period was 8.7 times higher
than during the coastal marine period. 相似文献
10.
Koji Hamasaki 《Journal of Oceanography》2006,62(6):793-799
Recently, bromodeoxyuridine (BrdU) has been successfully applied to the measurement of bacterial productivity as an alternative
to tritiated thymidine (3H-TdR), which is widely used but often restricted by regulations, particularly in field settings. Here, I report improvements
to existing BrdU methods to simplify procedures and increase sensitivity. The feasibility of the method was tested measuring
bacterial production in low-productive waters. The method provided radioisotope-free measurements of bacterial production
rates at shorter (∼1 h) on-board processing time of samples than previously reported procedures. It was applicable to the
detection of rates ranging from 0.021 to 2.7 pmol BrdU l−1h−1. BrdU incorporation rates measured by immunoassay showed a statistically significant correlation with 3H-TdR incorporation rates measured by radioassay (r = 0.74, n = 24, p < 0.001). The linear regression obtained (BrdU = 0.80[3H-TdR] − 0.016) showed a similar relationship to previously reported regressions (BrdU = 0.65[3H-TdR] + 0.12, [3H-BrdU] = 0.69[3H-TdR] − 0.81). There were no statistically significant differences among these regression lines. These results suggest that
the method described here provides a non-radioisotopic productivity measurement of bacteria in oceanic epipelagic waters,
while retaining continuity of the data with other existing 3H-TdR and BrdU methods. 相似文献