Chemical environment for red tides due toChattonella antiqua in the seto inland sea,Japan     

Yasuo Nakamura  Jun Takashima  Masataka Watanabe 《Journal of Oceanography》1988,44(3):113-124

Severe red tides due toChattonella antiqua occur sporadically during summer in the Seto Inland Sea, Japan, and cause significant damage to the fishing industry. In order to assess the chemical environment with respect to the outbreak ofC. antiqua, environmental factors that affect the growth ofC. antiqua were monitored around the Ie-shima Islands, the Seto Inland Sea, in the summer of 1986. In addition, a growth bioassay of the seawater usingC. antiqua was conducted under a semicontinuous culture system. Although temperature, salinity and light intensity were optimum for the growth ofC. antiqua, red tides by this species did not occur. Concentrations of NH ₄ ⁺ , NO ₃ ^? and PO ₄ ^3? were low (<0.4, <0.2, <0.06 µM, respectively) above the thermocline (8–12 m) and high below it (0.6–2, 4–8, 0.4–0.8 µM, respectively). Vitamin B₁₂ concentrations did not change significantly between the surface (0 m) and below the thermocline (25 m) in the level of 2–4 ng·l^?1. The growth bioassay revealed that in the surface waters, concentrations of N- as well as P- nutrients were too low to support a rapid growth ofC. antiqua. At the depth of 25 m, neither N, P nor B₁₂ limited the growth rate. In order to obtain more quantitative information on the growth rate as a function of the concentrations of N- and P- nutrients,C. antiqua was grown in a semicontinuous culture system by changing nutrient concentrations systematically. The observed growth rate (μ) can be approximated as follows: $$\mu = \mu _{\max } .\frac{{S_N }}{{K_g ^N + S_N }}.\frac{{S_{PO4} }}{{K_g ^P + S_{PO4} }},$$ whereS _N is the concentration of NO ₃ ^? plus NH ₄ ⁺ (0–6 µM),S _PO, the concentration of PO ₄ ^3? (0–0.6 µM), μ_max (0.97 d^?1) the maximal growth rate,K ₀ ^N (1.0 µM) andK ₀ ^P (0.11 µM) the half saturation constants for NO ₃ ^? and PO ₄ ^3? , respectively. Using the above equation with nutrient concentrations measured, the rate at which seawater supports the growth ofC. antiqua can be estimated and this can be used for the assessment of chemical environments with respect to the outbreak ofC. antiqua.  相似文献   

Ecological aspects of hydrothermal vent animals in captivity at atmospheric pressure     

Hiroshi Miyake  Mitsugu Kitada  Shinji Tsuchida  Yoko Okuyama  & Ko-ichi Nakamura 《Marine Ecology》2007,28(1):86-92

Hydrothermal vent animals were kept and displayed at atmospheric pressure with an artificial hydrothermal vent system in Enoshima Aquarium, Fujisawa, Kanagawa, Japan. The artificial hydrothermal vent system was composed of a main rearing tank, a heating tank, a hot water outlet with added Na₂S as the source of H₂S, and added CO₂ for chemosynthetic bacteria and pH regulation. When the need arises, a dissolved oxygen control unit and submersible heaters can be attached. We are now rearing hydrothermal vent crabs (Austinograea yunohana), hydrothermal vent galatheid crabs (Shinkaia crosnieri), vestimentiferan tubeworms (Lamellibrachia satsuma), hydrothermal vent shrimp (Opaepele spp.), hydrothermal vent barnacles (Ashinkailepas seepiophilia and Neoverruca sp.), and tonguefish (Symphurus sp.). In the artificial hydrothermal vent tank, shrimp and crabs have been observed to cluster close to the artificial hydrothermal vent. In particular, large (adult) crabs needed a heat source to live in the aquarium over a long term. Additionally, some species (A. yunohana, S. crosnieri, Opaepele sp. and Symphurus sp.) have spawned and hatched in captivity. It is likely higher water temperatures are needed for egg and larval development compared with temperatures for adult requirements.  相似文献   

Possible subsurface source of an acoustic tsunami precursor     

Shigehisa Nakamura 《Journal of Oceanography》1987,43(4):228-236

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Variability of Northeastward Current Southeast of Northern Ryukyu Islands   总被引：8，自引：4，他引：8  

Hiroshi Ichikawa  Hirohiko Nakamura  Ayako Nishina  Masataka Higashi 《Journal of Oceanography》2004,60(2):351-363

To better understand the mechanism underlying the variation of the Kuroshio south of central Japan, we have examined the variability of current structure in its upstream region, southeast of Amami-Ohshima Island in the northern Ryukyu Islands. By combined use of ship-mounted Acoustic Doppler Current Profiler (ADCP) and the TOPEX/POSEIDON satellite altimeter data on Path 214, the sea surface absolute geostrophic currents were estimated every ten days from January 1998 to July 2002. The 4.5-year mean surface current was found to flow northeastward north of 26.8°N with a maximum speed of 14 cm s⁻¹ over the shelf slope at 3000 m depth. The moored current-meter observations at three or four mooring stations from Dec. 1998 to Oct. 2002 suggested the existence of a northeastward undercurrent with a maximum core velocity of 23 cm s⁻¹ at 600 m depth over the shelf slope at 1600 m depth. The mean volume transport in the top 1500 m between 27.9°N and 26.7°N is estimated to be 16 × 10⁶ m³s⁻¹ northeastward, including the subsurface core current related component of 4 × 10⁶ m³s⁻¹. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Chemical environment for red tides due toChattonella antiqua     

Yasuo Nakamura  Tatsushi Umemori  Masataka Watanabe 《Journal of Oceanography》1989,45(2):116-128

Environmental parameters that affect the growth ofChattonella antiqua were monitored throughout the outbreak period of this species around the Ie-shima Islands, the Seto Inland Sea, in the summer of 1987 (20 July–13 August). Averaged cell concentration ofC. antiqua over the water column (21 m) was below 10 cells· ml^–1 on 20 July, gradually increased to reach the maximum of 250 cells·ml^–1 on 7 August, and then rapidly decreased to the value of 30 cells·ml^–1 on 13 August.Thermal stratifications were prominent from 20 July to 3 August and were destroyed after 4 August. Temperature and salinity were optimum for the growth ofC. antiqua throughout the survey period.At the bloom initiation period (20–21 July), concentrations of N- and P-nutrients (S _N andS _P ) were high throughout the water column. From 22 July to 3 August, whenC. antiqua increased its populations,S _N andS _P at the depth of 0–5m were low but those at the depth of 10–20m kept a high value. After 4 August,S _n andS _P at the depth of 10–20m decreased rapidly due to wind mixing coupled with the nutrient uptake byC. antiqua. When the populations ofC. antiqua reached the maximum (7–9 August), N-nutrients were depleted throughout the water column but P-nutrients were not. Concentrations of vitamin B₁₂ were almost in the same range as those of the previous years and were optimum for the growth ofC. antiqua.GP- value (growth potential of the seawater with respect to nitrogen and phos-phorus) was higher than 0.6 even at the surface layer (0–5 m) at the bloom-initiation period. During the bloom development period (22 July–3 August), GP at the surface layer (0–5m) was low (<0.2), but GP at the depth of 10–20m kept a rather high value (>0.4).In situ growth rates ofC. antiqua at the depth of 0 and 5m estimated from bottle experiments coincided well with the values expected from GP. A high value of GP at the surface layer in the initiation period and a shallow GP-cline in the development period, combined with the ability of diurnal vertical migration seemed to be at least one reason that natural populations ofC. antiqua grew at a rather high rate and formed red tides in the summer of 1987.  相似文献   

Encystment ofChattonella antiqua in laboratory cultures     

Yasuo Nakamura  Tatsushi Umemori  Masataka Watanabe  David M. Kulis  Donald M. Anderson 《Journal of Oceanography》1990,46(2):35-43

Cysts ofChattonella antiqua (Raphidophyceae) were obtained in laboratory cultures for the first time. They were formed on the surface of glass coverslips added to both P- and N- depleted mediums. The yield was 50–250 cysts cm^–2. Crossing experiments showed the highest cyst production in mixed cultures, although cysts were observed in clonal cultures as well. Cysts had approximately double the DNA content of synchronously growing vegetative cells (G₁ phase). The encystment process was also monitored: Under P-depleted conditions, small cells were formed that fused to become a triangle-shaped cell which in turn changed into a cyst.These results strongly suggest that cysts are the products of fusion and are diploid. Small cells, triangle-shaped cells, and cysts are considered to be gametes, planozygotes, and hypnozygotes, respectively. Significant mortality was observed in laboratory cysts stored in the cold and dark for five months, although those remaining were capable of germination to reestablish a motile, vegetative population.  相似文献   

90Sr and137Cs contents in the surface waters of the adjacent seas of Japan and the North Pacific during 1969 to 1973     

Yutaka Nagaya  Kiyoshi Nakamura 《Journal of Oceanography》1976,32(5):228-234

The concentrations of⁹⁰Sr and¹³⁷Cs, derived from the radioactive fallout, in the surface layers of the adjacent seas of Japan and the North Pacific were determined radiochemically during 1969 to 1973. The⁹⁰Sr and¹³⁷Cs concentrations in sea water decreased markedly with increase of the depth and below the depth of 1,000 m, the concentrations were approximately uniform. The distribution of⁹⁰Sr in the surface water of the North Pacific in spring of 1970 was approximately uniform, except two regions; rather large low-concentration region between 160°E and 170°W and relatively higher contamination area around 32°N and 146°W.  相似文献   

Continental shelf waves off the fukushima coast Part I: Observations     

Masahisa Kubota  Kisaburo Nakata  Yoshiharu Nakamura 《Journal of Oceanography》1981,37(5):267-278

Current records obtained in the inshore region along the Fukushima coast are analyzed. The existence of periodical current fluctuations whose period is about 100 hours and whose amplitude is as large as 15–25cm s^–1 is recognized. Auto-spectral analyses are made also for sea level, atmospheric pressure and wind records. Each spectrum has significant peaks at the similar period to the current spectrum. The wind spectrum has a broad peak compared with the current. The periodical current fluctuations propagate southward with speed of 3–5 km h^–1. These propagation speeds seem to correspond to those of the second-and third-mode shelf waves.  相似文献   

Kuroshio warm filament and the source of the warm water of the Tsushima Current   总被引：3，自引：2，他引：3  

Guo Binghuo  Xiu Shumeng  Haruo Ishii  Yasuaki Nakamura 《海洋学报(英文版)》1991,10(3):325-340

Characteristics and evolution of the Kuroshio frontal eddies and warm filaments are analyzed according to two series of satellite images (March 5 to 7, 1986 and April 14 to 16, 1988). The results show that the frontal eddies in the East China Sea are generated at the shelf break and move along the continental slope at a speed of 15 cm/s with the Kuroshio. The frontal eddies occur about every 10 d and evolve to be warm filaments a few hundred km in length and 30-40 km in width in the area west of the Yaku-shima. Meanwhile, the existence of the warm filament was also found in the area by analysing the hydrographic data in the area west of Kyushu during May 24-June 5, 1988.The Kuroshio warm filaments move westward opposite to the Kuroshio and then turn northward at the shelf break and become the main source of the warm water of the Tsushima Warm Current. A simple dynamic explanation for the process is presented in this paper.  相似文献   

Tourmaline breakdown in a pelitic system: implications for boron cycling through subduction zones     

Tsutomu Ota  Katsura Kobayashi  Tomoo Katsura  Eizo Nakamura 《Contributions to Mineralogy and Petrology》2008,155(1):19-32

Pressure–temperature conditions of tourmaline breakdown in a metapelite were determined by high-pressure experiments at 700–900°C and 4–6 GPa. These experiments produced an eclogite–facies assemblage of garnet, clinopyroxene, phengite, coesite, kyanite and rare rutile. The modal proportions of tourmaline clearly decreased between 4.5 and 5 GPa at 700°C, between 4 and 4.5 GPa at 800°C, and between 800 and 850°C at 4 GPa, with tourmaline that survived the higher temperature conditions appearing corroded and thus metastable. Decreases in the modal abundance of tourmaline are accompanied by decreasing modal abundance of coesite, and increasing that of clinopyroxene, garnet and kyanite; the boron content of phengite increases significantly. These changes suggest that, with increasing pressure and temperature, tourmaline reacts with coesite to produce clinopyroxene, garnet, kyanite, and boron-bearing phengite and fluid. Our results suggest that: (1) tourmaline breakdown occurs at lower pressures and temperatures in SiO₂-saturated systems than in SiO₂-undersaturated systems. (2) In even cold subduction zones, subducting sediments should release boron-rich fluids by tourmaline breakdown before reaching depths of 150 km, and (3) even after tourmaline breakdown, a significant amount of boron partitioned into phengite could be stored in deeply subducted sediments.  相似文献