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391.
Seasonal fluctuations of cell density of cyanobacteria and other picophytoplankton in Iwanai Bay,Hokkaido, Japan 总被引:1,自引:0,他引:1
In Iwanai Bay, which is located on the Japan Sea coast in Hokkaido, seasonal fluctuations in cell densities of phycoerythrin-dominant cyanobacteria and chlorophyll-dominant, other picophytoplankton were examined. Cell densities of cyanobacteria and other picophytoplankton ranged from 1.4×105 to 1.9×108 and from 4.0×104 to 4.3×106 cells 1–1, respectively. The cell densities of both groups tended to increase after spring diatom bloom with remarkable fluctuations from June to August. This tendency was caused by the vertical distributions of both groups. The maximum density layer shifted from 0–20 m depth in April–June to 20–50 m depth in August–October. Cyanobacteria were dominant in picophytoplankton community which accounted for 73–99% of the total cell density during the whole year. Present results show that the picophytoplankton community in Iwanai Bay was influenced by a single water mass system (Tsushima Warm Current) during the whole year.This is contribution No. 254 from the Research Institute of North Pacific Fisheries, Faculty of Fisheries, Hokkaido University. 相似文献
392.
In the Suo-Nada area of the Seto Inland Sea, Japan, sedimentation rates and the sedimentary record of anthropogenic metal loads were determined by combining the Pb-210 dating technique with heavy metal analysis of the sediments. The sedimentation rates vary from 0.11 to 0.27 g cm–2 yr–1. Lower sedimentation rates were observed in the eastern part of the basin which is characterized by a bottom with sand and gravel, and fast tidal currents.Anthropogenic and natural loads of copper and zinc into the sediments are 34 and 326, and 65 and 375 ton yr–1, respectively. The anthropogenic loads are fairly low compared with those of the other main areas of sediment accumulation in the Seto Inland Sea. The highest level of zinc and copper pollution was observed in the western part of the basin because of waste discharge from an old and big ironworks outside basin since the early 1900's. 相似文献
393.
Akira Masuda 《Journal of Oceanography》1988,44(1):40-45
In previous studies of the completeness of Rossby normal modes in a closed basin, proofs have been obtained by rather technical methods based on the Green's function for the Laplacian operator or based on the theory of compact self-adjoint operators. This short note (1) gives a much simpler proof by the use of only the norm relations between the sine functions and the Rossby normal modes and (2) clarifies the relations between the two different sets of eigenfunctions and between the ordinary norm and the Dirichlet norm, though the validity of the present method is restricted to a special one-dimensional case. The expansion theorem is also derived from the completeness theorem with the aid of transformation laws, where the assumption about the smoothness of the expanded function is weaker than in the elementary proof of Masuda (1987a). Both the set of Rossby normal modes and that of sine functions are shown to be complete for the Dirichlet norm as well. 相似文献
394.
The metal load into sediments and the change in the sedimentary environment of Osaka Bay in the Seto Inland Sea have been studied through geochemical analysis of core sediments, using both Pb-210 dating and a selective chemical leaching technique. Analytical results from a 6-m core of sediment show that copper and zinc pollution started in the late 1800's and the present enrichment ratios of copper and zinc, relative to background levels (20 mg kg–1 for Cu and 94 mg kg–1 for Zn), are 2.8 and 4.1, respectively. The present anthropogenic copper and zinc loads into Osaka Bay sediments, are 47 and 368 ton yr–1, while natural copper and zinc loads are 40 and 186 ton yr–1, respectively. Osaka Bay sediment at the present day is considered to be seriously polluted by zinc, now. The vertical profiles of copper and zinc in four successively separated fractions (10% acetic acid soluble fraction: F-HAC, 0.1M hydrochloric acid-soluble fraction: F-HCl, hydrogen peroxide-soluble fraction: F-H2O2 and hydrofluoric acid-soluble fraction: F-HF) from the core sediments indicate that enrichments of copper and zinc in the upper layer of the sediment are dependent on increases in the metal contents of the F-HAC, F-HCl and F-H2O2 fractions. Copper in F-HAC, and zinc in F-HAC and F-HCl, seem to be of anthropogenic origin.Results of sequential studies of the whole Seto Inland Sea can be summarized as follows: At the present time, the sedimentary loads of copper and zinc over the whole Seto Inland Sea area are 630 and 3,500 ton yr–1, respectively, while the natural and anthropogenic loads are 320 and 310 ton yr–1 for copper and 1,800 and 1,700 ton yr–1 for zinc, respectively. 相似文献
395.
Deep convection seesaw controlled by freshwater transport through the Denmark Strait 总被引:1,自引:0,他引:1
Akira Oka Hiroyasu Hasumi Naosuke Okada Takashi T. Sakamoto Tatsuo Suzuki 《Ocean Modelling》2006,15(3-4):157
Observations of deep ocean temperature and salinity in the Labrador and Greenland Seas indicate that there is negative correlation between the activities of deep convection in these two sites. A previous study suggests that this negative correlation is controlled by the North Atlantic Oscillation (NAO). In this study, we discuss this deep convection seesaw by using a coupled atmosphere and ocean general circulation model. In this simulation, the deep convection is realistically simulated in both the Labrador and Greenland Seas and their negative correlation is also recognized. Regression of sea level pressure to wintertime mixed layer depth in the Labrador Sea reveals strong correlation between the convection and the NAO as previous studies suggest, but a significant portion of their variability is not correlated. On the other hand, the convection in the Greenland Sea is not directly related to the NAO, and its variability is in phase with changes in the freshwater budget in the GIN Seas. The deep convection seesaw found in the model is controlled by freshwater transport through the Denmark Strait. When this transport is larger, more freshwater flows to the Labrador Sea and less to the Greenland Sea. This leads to lower upper-ocean surface salinity in the Labrador Sea and higher salinity in the Greenland Sea, which produces negative correlation between these two deep convective activities. The deep convection seesaw observed in the recent decades could be interpreted as induced by the changes in the freshwater transport through the Denmark Strait, whose role has not been discussed so far. 相似文献
396.
Akira Shibata 《Journal of Oceanography》2006,62(3):321-330
Ocean microwave emissions changed by the ocean wind at 6 GHz were investigated by combining data of the Advanced Microwave
Scanning Radiometer (AMSR) and SeaWinds, both aboard the Advanced Earth Observation Satellite-II (ADEOS-II). This study was
undertaken to improve the accuracy of the sea surface temperature (SST) retrieved from the AMSR 6 GHz data. Two quantities,
6V*(H*), were defined by the brightness temperature of the AMSR at 6 GHz with two polarizations (V-pol and H-pol), adjusted
for atmospheric effects and with a calm ocean surface emission removed. These quantities represent a microwave emission change
due to the ocean wind at 6 GHz. 6V* does not change in a region where 6H* is less than around 4 K (referred to as z0). Both
6V* and 6H* increase above z0. The 6V* to 6H* ratio, sp, varies with the relative wind directions. Furthermore, the sp values
vary with the SST, between the northern and southern hemisphere, and seasonally. By specifying appropriate values for z0 and
sp, the SST error between AMSR and buoy measurement became flat against 6H*, which is related to the ocean wind. Two extreme
cases were observed: the Arabian Sea in summer and the Northwestern Atlantic Ocean in winter. The air-sea temperature difference
in the former case was largely positive, while it was largely negative in the latter. The 6V* and 6H* relations differed from
global conditions in both cases, which resulted in incorrect SSTs in both areas when global coefficients were applied. 相似文献
397.
A study of planktonic foraminiferal shells collected in the northern Pacific and the Bering and Chukchi Seas revealed that the number of chambers was large in layers above and in the thermocline but small in the underlying layer. The mean number in both strata was 6.2±0.65 and 4.1±0.36, respectively. This observation indicates that the recruitment of foraminifera occurs at depth and juveniles grow in the productive surface layers. 相似文献
398.
Atsushi Tsuda Hiroshi Kiyosawa Akira Kuwata Mamiko Mochizuki Naonobu Shiga Hiroaki Saito Sanae Chiba Keiri Imai Jun Nishioka Tsuneo Ono 《Progress in Oceanography》2005,64(2-4):189
Phytoplankton species composition was analyzed inside and outside of the iron-enriched patch during the SEEDS experiment. Before the iron-enrichment, the phytoplankton community consisted of similar proportions of pico-, nano- and micro-sized phytoplankton, and the micro-phytoplankton was dominated by the pennate diatom Pseudo-nitzschia turgidula. Although all the diatoms, except the nano-sized Fragilariopsis sp., increased during the two weeks of the observation period, the flora in the patch dramatically changed with the increase of phytoplankton biomass to a centric diatom-dominated community. Neritic diatoms, especially Chaetoceros debilis, showed higher growth rates than other diatoms, without any delay in the initiation of growth after the enrichment, and accounted for 90% of the micro-phytoplankton after day 9. In contrast, the oceanic diatoms showed distinct delays in the initiation of growth. We conclude that the responses of the diatoms to the manipulation of iron concentration were different by species, and the fast and intensive response of the phytoplankton to iron-enrichment resulted from the presence of a small amount of neritic diatoms at the study site. The important factors that determine the dominant species in the bloom are the potential growth rates under an iron-replete condition and the growth lag. Abundant species in the patch are widely distributed in the North Pacific and their relative contributions in the Oyashio area and at Stn KNOT are high from spring to summer. However, a characteristic difference of species composition between the SEEDS bloom and natural blooms was the lack of Thalassiosira and Coscinodiscus species in the patch, which usually account for a major part of the phytoplankton community under blooming conditions in the western North Pacific. 相似文献
399.
Akira Yoshimori 《Journal of Oceanography》1993,49(5):521-533
Semi-geostrophic dynamics of jets are studied using a potential vorticity front in an equivalent barotropic model. Meandering processes of the front are examined in the thin-jet limit on a -plane by a curvilinear coordinate system. For calculated along-front velocity fields, asymmetrical profiles are caused by meandering. This asymmetry of the velocity profile is enhanced as the Rossby number becomes large. Using the along-front velocity fields, the normal velocity of front is expressed so that the Rossby number is explicitly included. This expression can be rewritten in the form of the mKdV equation. 相似文献
400.
Sedimentation rates in ten sediment cores from Hiroshima Bay in the Seto Inland Sea of Japan were determined with the |2210|0Pb
technique, and heavy metals were analyzed. The sedimentation rates vary from 0.18 to 0.33 g cm|2-2|0 yr|2-1|0. The highest
sedimentation rates were observed in the northern part of the bay at the mouth of Ota River, while lower sedimentation rates
not more than 0.20 g cm−2 yr−1 were observed at stations close to narrow water-ways, or where water depth was shallow. The contents of copper and zinc in
the sediment cores began to increase around 1930 as a result of increased human activity, and have remained almost unchanged
since 1970 possibly because of regulation of pollutant discharge. The natural background values of copper and zinc in the
sediment of this bay range from 16 to 27 mgkg−1 and 70 to 105 mg kg−1, respectively. The total amounts of anthropogenic copper and zinc deposited in the sediments since about 1930 are estimated
to be 0.5–2.7 ton km−2 and 2.2–14.5 ton km−2, respectively. At the present-day, the anthropogenic loads of copper and zinc to the sediments of the whole bay are 26 ton
yr−1 and 183 ton yr−1, and these values constitute 39% and 48% of the total sedimentary loads at the present-day, respectively. 相似文献