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111.
T.?KobariEmail author R.?Nakamura K.?Unno M.?Kitamura K.?Tanabe H.?Nagafuku A.?Niibo H.?Kawakami K.?Matsumoto M.?C.?Honda 《Journal of Oceanography》2016,72(3):403-418
We investigated seasonal changes in carbon demand and flux by mesozooplankton communities at subtropical (S1) and subarctic sites (K2) in the western North Pacific Ocean to compare the impact of mesozooplankton communities on the carbon budget in surface and mesopelagic layers. Fecal pellet fluxes were one order higher at K2 than at S1, and seemed to be enhanced by copepod and euphausiid egestion under high chlorophyll a concentrations. The decrease in pellet volume and the lack of any substantial change in shape composition during sink suggest a decline in fecal pellet flux due to coprorhexy and coprophagy. While respiratory and excretory carbon by diel migrants at depth (i.e., active carbon flux) was similar between the two sites, the actively transported carbon exceeded sinking fecal pellets at S1. Mesozooplankton carbon demand in surface and mesopelagic layers was higher at K2 than S1, and an excess of demand to primary production and sinking POC flux was found during some seasons at K2. We propose that this demand was met by supplementary carbon sources such as feeding on protozoans and fecal pellets at the surface and carnivory of migrants at mesopelagic depths. 相似文献
112.
Kazuhiro?AokiEmail author Manabu?Shimizu Hiroshi?Kuroda Toshifumi?Yamatogi Naoya?Ishida Shigeru?Kitahara Keiji?Hirano 《Journal of Oceanography》2016,72(5):811-816
In both 2009 and 2010, massive Chattonella blooms occurred in Tachibana Bay. Observation results show that high cell densities of Chattonella were distributed in the central area of Tachibana Bay with low salinity water. Model results indicate that the low salinity water originated from the Ariake Sea and intruded into Tachibana Bay during the northerly or weak winds. It is suggested that low salinity water was mainly discharged from the northern area of the Ariake Sea. Northerly wind enhanced the horizontal advection of the low salinity water intruding into Tachibana Bay originating from the northern area of the Ariake Sea. 相似文献
113.
Minoru Kitamura Toru Kobari Makio C. Honda Kazuhiko Matsumoto Kosei Sasaoka Rie Nakamura Kazuyuki Tanabe 《Journal of Oceanography》2016,72(3):387-402
Seasonal changes in mesozooplankton biomass and their community structures were observed at time-series stations K2 (subarctic) and S1 (subtropical) in the western North Pacific Ocean. At K2, the maximum biomass was observed during the spring when primary productivity was still low. The annual mean biomasses in the euphotic and 200- to 1000-m layers were 1.39 (day) and 2.49 (night) g C m?2 and 4.00 (day) and 3.63 (night) g C m?2, respectively. Mesozooplankton vertical distribution was bimodal and mesopelagic peak was observed in a 200- to 300-m layer; it mainly comprised dormant copepods. Copepods predominated in most sampling layers, but euphausiids were dominant at the surface during the night. At S1, the maximum biomass was observed during the spring and the peak timing of biomass followed those of chlorophyll a and primary productivity. The annual mean biomasses in the euphotic and 200- to 1000-m layers were 0.10 (day) and 0.21 (night) g C m?2 and 0.47 (day) and 0.26 (night) g C m?2, respectively. Copepods were dominant in most sampling layers, but their mean proportion was lower than that in K2. Mesozooplankton community characteristics at both sites were compared with those at other time-series stations in the North Pacific and with each other. The annual mean primary productivities and sinking POC fluxes were equivalent at both sites; however, mesozooplankton biomasses were higher at K2 than at S1. The difference of biomasses was probably caused by differences of individual carbon losses, population turnover rates, and trophic structures of communities between the two sites. 相似文献
114.
115.
The development and evolution of the persistent counterclockwise circulation in Suo-Nada have been studied in detail using
a three-dimensional numerical model. The realistic circulation has been reproduced from the monthly climatological fields
of salinity, temperature along the open boundary, wind, heat flux and buoyancy input from twenty-two major rivers surrounding
the basin. The seasonal variation of fresh-water discharge from the rivers proved to be the most important forcing mechanism
driving the circulation. The expansion and contraction of coastal low salinity water well corresponded with the development
of counterclockwise circulation from spring to summer and dissipation from autumn to winter. The circulation was found to
be vertically homogenous and quasi-barotropic. However, confined along the coastal zone is an estuarine flow (i.e., oppositely
directed currents in the upper and lower layers) whose horizontal dimension conforms to the period of maximum buoyancy flux
from the rivers. This indicates that the flow pattern in Suo-Nada can be separated into two distinct regions where the relative
dominance of estuarine circulation plays a significant role. Furthermore, the monthly water exchange capacity for autonomous
purification of the basin has been evaluated from the average residence time of conservative material based on the calculated
current field. It is demonstrated that the kinetic energy of the basin is directly responsible in promoting water exchange
in Suo-Nada.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
116.
Hiroshi Kuroda Manabu Shimizu Yuuichi Hirota Hideki Akiyama 《Journal of Oceanography》2007,63(5):849-862
Through analysis of monthly in situ hydrographic, tide gauge, altimetry and Kuroshio axis data for the years 1993–2001, the intraannual variability of sea level
around Tosa Bay, Japan, with periods of 2–12 months is examined together with the intraannual variability of the Kuroshio
south of the bay. It is shown that the intraannual variation of steric height on the slope in Tosa Bay can account for that
of sea level at the coast around the bay as well as on this slope. It is found that the steric height (or sea level) variation
on the slope in this bay is mainly controlled by the subsurface thermal variation correlated with the Kuroshio variation off
Cape Ashizuri, the western edge of Tosa Bay. That is, when the nearshore Kuroshio velocity south of the cape is intensified
[weakened] concurrently with the northward [southward] displacement of the current axis, temperature in an entire water column
decreases [increases] simultaneously, mainly due to the upward [downward] displacement of isotherms, coincident with that
of the main thermocline. It follows that the steric height (or sea level) decreases [increases]. 相似文献
117.
Chattonella antiqua (Raphidophyceae), which causes heavy red tides in the Seto Inland Sea, Japan, was placed in axenic clonal culture by micropipette washing. The effects of temperature, salinity, light intensity and pH on growth were monitored. Maximum growth occurred at 25°C, at salinities between 25 and 41‰, under light intensities above 0.04 ly min?1. The pH effect was not significant in the pH range from 7.6 to 8.3. Comparisons of our results with those from field observations suggest that the development of theC. antiqua red tide is strongly temperature dependent. 相似文献
118.
Strontium concentrations and strontium-chlorinity ratios in sea water of the North Pacific and the adjacent seas of Japan 总被引:1,自引:0,他引:1
Strontium contents of 232 sea water samples collected at various stations in the North Pacific and adjacent seas of Japan were measured by the atomic absorption spectrophotometry and strontium-chlorinity ratios were determined. Mean Sr concentration is 8.08 mg/kg and mean Sr/Cl ratio is 0.425 mg/kg/Contrary to some recent reports, regional and vertical variations of Sr/Cl ratios were statistically insignificant, and presence of particulate strontium was not confirmed. 相似文献
119.
Rolando S. Balotro Atsuhiko Isobe Manabu Shimizu Atsushi Kaneda Takatoshi Takeuchi Hidetaka Takeoka 《Journal of Oceanography》2002,58(6):759-773
An attempt was made to reproduce the circulation pattern in Suo-Nada, Japan during spring and summer season in order to elucidate
the water exchange mechanism in the basin. Two hydrographic surveys at the end of each season were conducted covering the
entire Suo-Nada area. A three-dimensional hydrodynamic Princeton Ocean Model (POM) was used to compute the current resulting
from the observed density and wind field. During spring, a very pronounced counter clockwise gyre is situated near the opening
of the basin. This is replaced by a clockwise circulation which seemed to occupy the whole domain during summer. Within each
season, however, the vertical distribution of current does not show any remarkable differences, indicating the dominance of
horizontal current and a very weak estuarine flow. These observational and numerical results were used to estimate the remnant
function and the corresponding average residence time of permanently dissolved matter (PDM) and transformable matter (TM).
The results revealed a small difference in the average residence times of materials within each season but a large seasonal
variability between spring and summer. Furthermore, calculations based on climatological density fields have indicated a similar
trend of variation between the seasonal values of average residence times.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
120.
Tomohiro Nakamura Takahiro Toyoda Yoichi Ishikawa Toshiyuki Awaji 《Journal of Oceanography》2004,60(2):411-423
A numerical study using a 3-D nonhydrostatic model has been applied to baroclinic processes generated by the K
1 tidal flow in and around the Kuril Straits. The result shows that large-amplitude unsteady lee waves are generated and cause
intense diapycnal mixing all along the Kuril Island Chain to levels of a maximum diapycnal diffusivity exceeding 103 cm2s−1. Significant water transformation by the vigorous mixing in shallow regions produces the distinct density and potential vorticity
(PV) fronts along the Island Chain. The pinched-off eddies that arise and move away from the fronts have the ability to transport
a large amount of mixed water (∼14 Sv) to the offshore regions, roughly half being directed to the North Pacific. These features
are consistent with recent satellite imagery and in-situ observations, suggesting that diapycnal mixing within the vicinity
of the Kuril Islands has a greater impact than was previously supposed on the Okhotsk Sea and the North Pacific. To examine
this influence of tidal processes at the Kurils on circulations in the neighboring two basins, another numerical experiment
was conducted using an ocean general circulation model with inclusion of tidal mixing along the islands, which gives a better
representation of the Okhotsk Sea Mode Water than in the case without the tidal mixing. This is mainly attributed to the added
effect of a significant upward salt flux into the surface layer due to tidal mixing in the Kuril Straits, which is subsequently
transported to the interior region of the Okhotsk Sea. With a saline flux into the surface layer, cooling in winter in the
northern part of the Okhotsk Sea can produce heavier water and thus enhance subduction, which is capable of reproducing a
realistic Okhotsk Sea Mode Water. The associated low PV flux from the Kuril Straits to the open North Pacific excites the
2nd baroclinic-mode Kelvin and Rossby waves in addition to the 1st mode. Interestingly, the meridional overturning in the
North Pacific is strengthened as a result of the dynamical adjustment caused by these waves, leading to a more realistic reproduction
of the North Pacific Intermediate Water (NPIW) than in the case without tidal mixing. Accordingly, the joint effect of tidally-induced
transport and transformation dominating in the Kuril Straits and subsequent eddy-transport is considered to play an important
role in the ventilation of both the Okhotsk Sea and the North Pacific Ocean.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献