Abundance and biomass of scyphomedusae, Aurelia aurita and Chrysaora melanaster, and Ctenophora, Bolinopsis mikado, with estimates of their feeding impact on zooplankton in Tokyo Bay, Japan     

Junji Kinoshita  Juro Hiromi  Yoshiaki Yamada 《Journal of Oceanography》2006,62(5):607-615

The abundance of a scyphomedusae, Aurelia aurita and Chrysaora melanaster, and a ctenophore, Bolinopsis mikado, in Tokyo Bay was investigated from 1995 to 1997. Aurelia aurita appeared throughout the year with a peak in abundance occurring from spring to summer. The average abundance and biomass during this period for the three successive years was 4.8, 43.8 and 3.2 ind. m⁻², and 1.02, 10.0 and 0.42 gC m⁻², respectively. The values in 1995 and 1997 were comparable with those previously reported for A. aurita abundance from 1990 to 1992. Values were very high in 1996, but the size composition of the bell diameter did not differ from other years, which suggested the absence of food limitation for A. aurita in 1996. C. melanaster was scarce over the survey period (<1.0 ind. m⁻²) while Bolinopsis mikado was more abundant during September to December, with maximum values of 172 ind. m⁻² and 0.33 gC m⁻² observed in December 1997. The weight-specific clearance rate for A. aurita on zooplankton (mainly copepods and their nauplii) was 0.16 ± 0.05 lgWW⁻¹ h⁻¹ (n = 13). Population clearance rate peaked from spring to summer, with average levels of 14.2%, 162% and 5.0% day⁻¹ obtained from spring to summer for respective years. Population clearance rates for B. mikado, calculated based on minimum carbon requirements, was 7.1% day⁻¹ in December 1997. Consequently, the trophic role of gelatinous zooplankton as predators in Tokyo Bay is important all the year round, considering the high impact of A. aurita from spring to summer and B. mikado from autumn to winter.  相似文献   

Contractual solution to the tragedy of property right in coastal fisheries     

Arif Satria  Yoshiaki Matsuda  Masaaki Sano 《Marine Policy》2006

This article aims to analyze how private property regimes can co-exist with common property regimes in a coastal area. The case study shows how the dynamics of private property and common property right holders is in creating commitment to make symbiosis in resource use. This is based on a case study in two villages in West Lombok, Indonesia, where pearl-culture as a private property resource exists in a common property regime. This is a successful story in dealing with the tragedy of property rights in the country wherein established institutional arrangement is still absent. Nevertheless, this may be site specific, and fragile if there is no institutional arrangement combining formal and informal rules and involving both formal and informal authorities. To make a robust solution, multilevel solution must be considered: national, local, and community level, with reference to Japan case.  相似文献   

Statistical study on the local equilibrium between wind and wind waves by using data from ocean data buoy stations   总被引：6，自引：0，他引：6  

Naoto Ebuchi  Yoshiaki Toba  Hiroshi Kawamura 《Journal of Oceanography》1992,48(1):77-92

The local equilibrium between the wind and wind waves, which is defined by a range of the coefficient of the 3/2-power law between the non-dimensional significant wave height and period, is statistically investigated by using wind and wave data obtained at four ocean data buoy stations in the seas near Japan. The friction velocity is calculated from the wind speed measured at one height together with the significant wave period by using formulas of the wave dependent drag coefficient proposed by Tobaet al. (1990). The data for small waves or for weak winds indicate that the waves do not satisfy the criterion for the local equilibrium, because they may be affected by changing winds or remotely generated swells. In the seas near Japan, the data which satisfy the local equilibrium are about 6% through a year. Otherwise swells are dominant in most situations. Changing winds also cause deviations from the local equilibrium. The degree of satisfaction of the local equilibrium can be classified by ranges of the significant wave height. As the significant wave height exceeds 4 m, the local equilibrium is more frequently satisfied.  相似文献   

Heat balance of the surface layer of the sea at ocean weather station T     

Yoshikazu Kurasawa  Kimio Hanawa  Yoshiaki Toba 《Journal of Oceanography》1983,39(4):192-202

Heat balance of the upper 200 m of the sea south of Japan is studied, by the use of marine meteorological and oceanographic data at Ocean Weather Station T (29°N, 135°E), intensively obtained from June 1950 to November 1953. Local time change of the heat content in the surface layer and the net heat flux through the air-sea interface are calculated directly from these data, and the heat convergence in the sea is estimated from their residuals. Regarding the relative importance of one- and three-dimensional processes, it is found that, on a time scale of a few days to one month, the variation of heat content depends on heat convergence in the sea, while on a seasonal time scale, the heat content is determined primarily by the heat flux through the sea surface in December through February, by heat convergence within the sea from March to May, and by both processes from June to November. It is inferred that the heat convergence in the sea is caused by advection of water masses which are bounded by sharp fronts. Spectral analysis of sea surface temperature indicates that they typically take 2 to 3 days to pass the station, and their typical size is estimated as around 20 km by assuming the typical advection velocity of water masses to be 10 cm s^?1.  相似文献   

Interannual variability of the Kuroshio Extension and its relation to the Southern Oscillation/El Niño     

Toshio Yamagata  Yoshiaki Shibao  Shin-ichiro Umatanit 《Journal of Oceanography》1985,41(4):274-281

The interannual variability of the temperature structure of the Kuroshio Extension is studied by establishing time series for the period 1950 to 1970 and then comparing it with the time series of sea level differences across the North Equatorial Current obtained by Wyrtki (1975). First, the present analysis shows a significant correlation between the interannual fluctuation of the Kuroshio Extension and the eddy activity south of the Kuroshio axis, suggesting the importance of the eddy-driven mechanism. Secondly, spectral analysis shows close connections between the Kuroshio Extension and the North Equatorial Current with a reasonable time lag of about 1.5 years. This time lag of the mid-latitude variability is also supported by other independent data. In particular, the present preliminary study strongly suggests that the bimodal behavior of the Kuroshio path south of Japan and the intensity of the Kuroshio Countercurrent are closely connected with the Southern Oscillation/El Niño.  相似文献   

Local balance in the air-sea boundary processes     

Yoshiaki Toba 《Journal of Oceanography》1972,28(3):109-120

A new growth equation for wind waves of simple spectrum is presented upon three basic concepts. The period and the wave height of significant waves in dimensionless forms, which are considered to correspond to the peak frequency and the energy level, respectively, are used as representative quantities of wind waves. One of the three basic concepts is the concept of local balance, and the other two concern the acquisition of wave energy and the dissipation of wave energy, respectively. It is shown from some actual data that the equation, together with two universal constants concerning the acquisition and the dissipation of wave energy (B=6.2×10^?2 andK=2.16×10^?5, respectively), is applied universally to wide ranges of wind waves from those in a wind-wave tunnel to fully developed sea in the open ocean. “The three-second power law for wind waves of simple spectrum”, and a few relations as the lemmas, are derived, such that the mean surface transport due to the orbital motion of wind waves is always proportional to the friction velocity in wind, and that the steepness is inversely proportional to the root of the wave age. It is also derived that the portion of wind stress which directly enters the wind waves decreases exponentially with increasing wave age and is 7.5 % of the total wind stress for very young waves. Also, equations are presented as to the increase of momentum of drift current, and as to the supply of turbulent energy by wind waves into the upper ocean.  相似文献   

Rates of net assimilation and respiration of amino acids by marine bacteria     

Yoshiaki Maita  Mitsuru Yanada  Akira Rikuta 《Journal of Oceanography》1974,30(1):1-9

The selectivity of amino acid assimilation by marine bacteria was examined using seven kinds of¹⁴C-amino acids and the acid hydrolysate of¹⁴C-labelled proteins. It was found that the net assimilation and respiration by marine bacteria followed MICHAELIS-MENTEN kinetics for all of amino acids used in our experiments. Maximum velocities of amino acids were 0.01 to 0.19g carbon/hour per 2×10⁷ cells for net assimilation and less than 0.18g carbon/hour per 2×10⁷ cells for respiration at 20C. The velocity of gross assimilation was found with the following order: phenylalanine>valine, glutamic acid>serine, arginine>tryptophan>glycine. The assimilation velocities of amino acids in these laboratory works showed almost the same order as those in field experiments. The assimilation velocity of an amino acid was influenced by coexisting another amino acids or glucose. The assimilation velocity in lower substrate range of amino acids was directly proportional to the number of bacterial cells in the range from 6×10² to 3×10⁴ cells per ml. No linear relation between the assimilation velocity of amino acids and reciprocal of absolute temperature was found, but a marked bending was observed at 15 to 20C. The velocity at the optimum temperature was three to six times of that at 5C.  相似文献   

Studies on physical processes at the sea surface     

Yoshiaki Toba 《Journal of Oceanography》1989,45(5):350-359

I feel greatly honoured to be awarded the Oceanographical Society of Japan Prize for 1989, and to be given this opportunity to look back at my past activities in research and education, and to present them as an example for younger members of our Society. Taking this opportunity, I acknowledge with sincere thanks many persons who guided me or who have collaborated with me since I was a young student up to the present.My past academic history may be divided into three periods. In the first period (1955–71) at Kyoto University which included and eighteen month visit to the University of Chicago, I studied the production of air bubbles and droplets at the sea surface by wind-wave breaking, and the supply and distribution of the sea-salt particles from the sea to the atmosphere. The first nondimensional formulation of the form of single air bubbles floating at liquid surfaces was also presented. In the second period (1971–1981) I pursued, at the new Physical Oceanography Laboratory of Tohoku University, the concept of wind waves which are coupled with the wind. I proposed the 3/2-power law of wind waves and the high frequency part of the wind-wave spectral form which is proportional to the friction velocity of air and to the –4th power of frequency. Detailed investigations of wind-wave phenomena were also performed in wind-wave tunnels by introducing quantitative flow visualization techniques and together with my students, we elucidated ordered motions in the flows below and above wind waves. The Tohoku Wave Model was also developed in which the similarity laws of wind waves, which are strongly coupled with the air flow, were explicitly used. In the third period (1982-present), my area of interest has become broader and, togerther with my students and my overseas collaboratos, we are studying the connection of local physical processes at the air-sea boundary with studies of larger scale ocean-atmosphere interactions. One aspect of this has led to the organization of the Ocean Mixed Layer Experiment (OMLET, 1987–91), as part of the Japanese national programmes of the World Climate Research Programme. Another interest is the ongoing fundamental study of the use of satellite data for the estimation of air-sea fluxes over a broad area. Pursuit of the roots of the similarity laws of the windsea remains one of my present tasks.  相似文献   

Wind-wave coupled downward-bursting boundary layer (DBBL) beneath the sea surface     

Yoshiaki Toba  Hiroshi Kawamura 《Journal of Oceanography》1996,52(4):409-419

By synthesizing data of the turbulent structure beneath wind waves in laboratory tanks, with some re-analyses, we propose the existence of a particular turbulent boundary layer which is directly coupled with wind waves, a downward-bursting boundary layer (DBBL) in water beneath wind waves. The data set indicates that the depth of this layer is from 3 to 7, or about 5 times the significant wave height of wind waves. The data observed in laboratory tanks agree with data of acoustic observations of bubble clouds under breaking wind waves in the sea made by Thorpe (1986, 1992). It is inferred that DBBL is formed in equilibrium with the local wind waves, as a common feature from initially generated wind waves, young laboratory wind waves to mature wind waves in the sea.  相似文献   

A Spectral Approach for Determining Altimeter Wind Speed Model Functions   总被引：9，自引：0，他引：9  

Dongliang Zhao  Yoshiaki Toba 《Journal of Oceanography》2003,59(2):235-244

We propose a new analytical algorithm for the estimation of wind speeds from altimeter data using the mean square slope of the ocean surface, which is obtained by integration of a widely accepted wind-wave spectrum including the gravity-capillary wave range. It indicates that the normalized radar cross section depends not only on the wind speed but also on the wave age. The wave state effect on the altimeter radar return becomes remarkable with increasing wind speed and cannot be neglected at high wind speeds. A relationship between wave age and nondimensional wave height based on buoy observational data is applied to compute the wave age using the significant wave height of ocean waves, which could be simultaneously obtained from altimeter data. Comparison with actual data shows that this new algorithm produces more reliable wind speeds than do empirical algorithms. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献