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101.
Takehiko Fukushima Je-chul Park Akio Imai Kazuo Matsushige 《Aquatic Sciences - Research Across Boundaries》1996,58(2):139-157
The seasonal and spatial changes in dissolved organic carbon (DOC) in Lake Kasumigaura, a shallow, eutrophic lake, were analyzed and the lability of DOC was tested by long-term incubations. There was a nearly 1 mgCl–1 downstream increase in refractory DOC in the lake; at the center it fluctuated little seasonally. The characteristic UV-absorbance: DOC ratios were determined for samples from the influent rivers (pedogenic: used interchangeably with allochthonous) and outdoor experimental ponds (autochthonous) during incubations. These ratios were then used to calculate the proportion of total measured lake water DOC in each of four components: pedogenic-refractory (PR), pedogenic-labile (PL), autochthonous-refractory (AR) and autochthonous-labile (AL). PR was uniform (around 1.5 mgCl–1) or diminished very slightly over time. AR increased from nearly zero at the station closest to an influent river to 1 mgCl–1 at the lake center. PL declined downstream from 0.3 mgCl–1 to zero. AL was virtually constant at 0.8 mgCl–1 except at the station closest to the influent river. The constancy of the UV-absorbance: DOC ratio during the biodegradation process was confirmed for Lake Kasumigaura; hence a two-component model (pedogenic-autochthonous) could be applied here without consideration of DOC lability. However, this assumption is not always met for other water bodies, and therefore it should be checked before applying a two-component model elsewhere. 相似文献
102.
Akio Maeda 《Journal of Oceanography》1971,27(3):109-115
Temperature field in the vicinal area of station T (29N, 135E) before and after Typhoon 6411 in summer 1964 is analysed from measurements with BT. At a location 68 km distant from the path of the typhoon, temperature at each depth became lower in the upper layer from surface to 50 m deep and became higher in the lower layer from 50 m to 130 m deep in connection with passage of the typhoon than temperature at each depth in these layers before the typhoon, respectively. Heat loss in the upper layer and heat gain in the lower layer are estimated to be almost comparable in amount. Equivalence in the heat gain and loss suggests that temperature changes were caused by vertical mixing due to strong wind of the typhoon. At a location 164 km distant from the path of the typhoon, however, heat gain of the lower layer from 35 m to 250 m deep exceeded heat loss of the upper layer from surface to 35 m deep. In addition to vertical mixing, horizontal advection or some other processes should be taken into account in order to explain the temperature changes in the area a little distant from the typhoon path. For recovery of the temperature changes at these locations 8 days were needed. This recovery time is almost equal to those in the case of some other typhoons, about which the discussion was made in the previous paper (Maeda, 1965). 相似文献
103.
Time series of velocity and water temperature were measured at three stations on the continental shelf, on the shelf margin and on the slope off the northwest Tokunoshima in December 1980 to study influences of the slope on tides.Tidal currents with semidiurnal periods were dominant at the stations on the shelf and shelf margin. However, semidiurnal components in temperature fluctuations were dominant at the stations on the shelf margin and the slope. We estimated horizontal currents due to semidiurnal internal tides from the vertical distribution of water density and temperature, assuming that the temperature fluctuations were caused by the vertical displacement of water particles due to semidiurnal internal tides. The tidal ellipses at the station on the shelf and the phase relation of the tidal currents between the two stations on the shelf and shelf margin indicated that the M2 surface tide on the shelf was a Sverdrup wave propagating to the northwest.Semidiurnal tidal currents on the slope were also caused by tides of surface and internal modes. Furthermore, the axis of the tidal ellipse was not perpendicular to the co-tidal line estimated by Ogura (1934) but rather parallel to the isobaths on the slope, which shows a striking effect of the bottom topography on the tidal currents. 相似文献
104.
Abstract. In the callianassid shrimp Nihonotrypaea harmandi (Bouvier 1901), the trichomycete fungus Enteromyces callianassae Lichtwardt 1961 occurs exclusively on the foregut lining. The enzymes from both the shrimp and the fungus apparently hydrolyze certain nitrogen and carbon compounds in detritus. The activities of various proteases and carbohydrases contained in the foregut juice were compared between fungus-infected shrimps collected from a sandflat in Kyushu, Japan (51 % infection rate) and uninfected shrimps from a nearby sandflat. The concentration of enzymatically hydrolyzable amino acids (EHAA) in sediment liberated by the foregut juice with fungi was slightly lower than that by 0.1 mg·ml-1 proteinase-K and significantly higher than that by the foregut juice without fungi. In both foregut juices, substantial enzyme activities were recorded for proteinase(s), peptidases, amylase, cellulase and β-1,3-glucanase, and minimal ones for maltase and cellobiase. Of the commercial substrates examined, only in the case of the mixture of 16 kinds of dipeptides was a significantly higher enzyme activity in the foregut juice with fungi observed. In the process of EHAA liberation from sediment, peptidases secreted by the fungus most probably act as a supplement to the endogenous secretion by the shrimp. This may explain the higher shrimp growth rate recorded for the population with fungi. However, the significantly higher sediment EHAA concentration of the sandflat inhabited by this population versus the population without fungi could be another crucial factor explaining the site difference in shrimp growth rate. 相似文献
105.
Akio Maeda 《Journal of Oceanography》1971,27(4):163-174
Phase velocity of semi-diurnal internal waves is determined from differences between phases at three stations which were situated to form a triangle in the vicinity of sta. T (29N, 135E). The wave phases are estimated from temporal variations in depths of isotherms obtained from serial measurements of vertical temperature profiles at these stations. The measurements were carried out in cooperative operation of two vessels, the R. V.Tansei-maru and theNojima, during the period from 30 July to 1 August 1965. Wave propagation with the speed of about 2 m/s in the direction from east to west is obtained as an average over several isotherms of temperature from 19C to 23C. The area of measurement is to the west of Izu-Mariana ridge and the distance from the ridge to the station is about 500 km, which would be about 5 times as large as the wave length of the internal waves under consideration, and so it is possible to suppose that the internal waves observed generated at the ridge and propagated to the area without being subjected to serious refraction, scattering, reflection and decay. 相似文献
106.
Sahadev Sharma Md. Kamruzzaman A. T. M. Rafiqul Hoque Akio Hagihara 《Journal of Oceanography》2012,68(6):831-840
Data on leaf phenological traits and longevity of mangroves are important for improved understanding of the adaptation strategies, growth, and productivity of these trees. We studied leaf phenological traits and longevity of Rhizophora stylosa, Bruguiera gymnorrhiza, and Kandelia obovata monthly from April 2008 to March 2009. Both tree sampling (direct observation) and litterfall (indirect observation) were used. All leaves and branches of each sample tree were numbered and marked with tags at the beginning of the experiment. Peaks of leaf recruitment and death occurred in July and June, respectively, for B. gymnorrhiza and K. obovata but both occurred in July for R. stylosa. Leaf recruitment for all the species was lowest in January; leaf death was minimum in December for R. stylosa and B. gymnorrhiza, and in January for K. obovata. Leaf recruitment for the three species was significantly correlated with monthly mean air temperature and monthly hours of sunshine. K. obovata and R. stylosa leaf death was correlated with monthly mean air temperature, monthly hours of sunshine, monthly mean air vapor pressure deficit, and monthly rainfall; B. gymnorrhiza leaf death was not correlated with any environmental factors. Specific leaf area for R. stylosa (45.4?±?1.0?cm2?g?1) and K. obovata (48.6?±?0.8?cm2?g?1) was not significantly different, but means for these two species were significantly different from that for B. gymnorrhiza (71.0?±?2.8?cm2?g?1). Mean leaf longevity was 13.9?months for R. stylosa, 17.2?months for B. gymnorrhiza, and 12.1?months for K. obovata. Different measured variables between B. gymnorrhiza and the other two species may have been because of the growth strategy and shade tolerance of B. gymnorrhiza. Mean leaf longevity increased with increasing mean annual air temperature. 相似文献
107.
Effects of mesoscale eddies on the marine ecosystem in the Kuroshio Extension (KE) region are investigated using an eddy-resolving
coupled physical-biological model. The model captures the seasonal and intra-seasonal variability of chlorophyll distribution
associated with the mesoscale eddies, front variability, Kuroshio meanders, and upwelling. The model also reproduces the observed
interannual variability of sea surface height anomaly (SSHA) in the KE region along a zonal band of 32–34°N from 2002 to 2006.
The distribution of high surface chlorophyll corresponds to low SSHA. Cyclonic eddies are found to detach from the KE jet
near 150°E and 158°E and propagate westward. The westward propagating cyclonic eddies lift the nutrient-rich thermocline into
the euphotic zone and maintain high levels of chlorophyll in summer. In the subsurface layer, the pattern in chlorophyll is
influenced by both lateral and vertical advection. In winter, convection inside the eddy entrains high levels of nutrients
into the mixed layer, increasing production, and resulting in high chlorophyll concentration throughout the surface mixed
layer. There is significant interannual variability in both the cyclonic eddy activity and the surface phytoplankton bloom
south of the KE jet, although whether or not there is a causal link is unclear. 相似文献
108.
We evaluated the quantitative effects of artificial barriers, water-cooling and guiding channels on lava flow using the lava
simulation program LavaSIM. Lava flow is basically subject to the topography around the path, effusive rate and viscosity.
To prevent damage due to lava flow, we conducted experiments in controlling the flow direction, velocity and temperature.
The simulation demonstrated that artificial barriers can successfully change the direction of a lava flow and is more effective
when placed nearly parallel to the flow direction at a point where the topography is not very steep, while a barrier placed
perpendicular to the flow direction can only stop the flux temporarily, ultimately allowing the solidified crust to accumulate
and causing the following mass to go over the barrier. The water-cooling trial was also effective in controlling the direction
and temperature, although the amount of water was as much order as 105 m3. The guiding channels successfully control the direction and inundated area but only in local areas. 相似文献
109.
Sato Minoru Oba Takashi Hosokawa Takao Yamaguchi Toshiyasu Nakano Toshiki Saito Tadao Muramoto Koji Kahara Takashi Funayama Katsura Kobayashi Akio Nakano Takahisa 《中国海洋大学学报(英文版)》2005,4(3)
1 IntroductionIncreased blood pressure appears to be one of theprimary risk factors of circulatory organ diseases suchas encepharo-apoplexy, encepharo-infarction and cardi-ac infraction. Angiotensin-I-converting enzyme (ACE)plays an important role in the rennin-angiotensin sys-tem by regulating blood pressure. Antihypertensivedrugs such as captopril and enalapril are potent ACEinhibitors (Ondetti et al., 1977). Recently, severalinhibitory peptides derived from food proteins havebeen isolat… 相似文献
110.
Akio Makishima Hiroshi Kitagawa Eizo Nakamura 《Geostandards and Geoanalytical Research》2011,35(1):57-67
A method for the simultaneous determination of Cd with In, Tl and Bi by isotope dilution‐internal standardisation (ID‐IS) ICP‐QMS using the same aliquot for rare earth element and other trace element determinations was developed. Samples mixed with an enriched 149Sm spike were decomposed using a HF‐HClO4 mixture, which was evaporated and then diluted with HNO3. After determination of Sm by ID‐ICP‐QMS and Cd, In, Tl and Bi concentrations were determined using the 149Sm intensity as an internal standard. The interference of MoO+ on Cd+ was corrected using the MoO+/Mo+ ratio separately measured using a Mo standard solution, and the validity of the externally determined oxide‐forming ratio correction was evaluated. The MoO+/Mo+ ratios measured using the standard solution and samples were ~ 0.0002 and < 0.002, respectively. Detection limits for Cd, In, Tl and Bi in silicate samples were at levels of < 1 ng g?1 with a total uncertainty of < 7%. Cadmium in the carbonaceous chondrites, Orgueil (CI1), Murchison (CM2) and Allende (CV3) as well as Cd, In, Tl and Bi in the reference materials, JB‐2, JB‐3, JA‐1, JA‐2, JA‐3, JP‐1 (GSJ), BHVO‐1, AGV‐1, PCC‐1 and DTS‐1 (USGS) and NIST SRM 610, 612, 614 and 616 were determined to show the applicability of this method. 相似文献