Gokasho Bay Research Articles

Morphology and infraciliature of a marine scuticociliate with a polymorphic life cycle: Urocryptum tortum n. gen., n. comb.

A new genus and species combination are proposed for Urocryptum tortum n. gen., n. comb., a scuticociliate with a polymorphic life cycle. This marine ciliate was isolated from a sample taken at Gokasho Bay in Mie Prefecture (Japan). Specimens from different phases of the growth cycle were examined in vivo and with two silver staining techniques. Three life-history stages were observed: an exponential growth phase stage (trophont), a stationary phase stage (tomite), and finally a resting stage (cyst). The exponential growth form is laterally flattened and ovoid; it has 20-24 somatic kineties (SK) and a typical complement of scuticociliate oral structures. Polykinetid 1 (Pk1) has two longitudinal files of 6 kinetosomes (Ks); sometimes one or two additional kinetosomes are located anteriorly. Polykinetid 2 (Pk2) has two files of 6 or 7 Ks; a third file of three widely spaced kinetosomes is located on its right side, as well as a small curved row of 5 Ks positioned on the right hand side of the posterior end of Pk2. Polykinetid 3 (Pk3) has 3 rows of 4, 5, and 7 Ks's perpendicular to the haplokinety (Hk) or paroral membrane. The stationary growth phase cell is spindle-shaped and has a similar number of SK that are much more closely spaced than in exponentially growing specimens. Oral infraciliary structures are reduced in size, having fewer kinetosomes and being positioned more anteriorly in the cell. Pk1 is composed of two files of 5-Ks, Pk2 has only two files of 6-7 Ks, and Pk3 has two to three rows of 3-4 Ks. The Hk is displaced anteriorly and becomes straight, losing the shape typical of exponential growth phase cells. Cysts are pyriform with a wide cyst wall; no infraciliary structures were visible.

Seasonal Fluctuations in the Occurrence of Abnormal Enlargement of the Ovary of Pacific Oyster Crassostrea gigas at Gokasho Bay, Mie, Japan.

Seasonal occurrences of the abnormally enlarged ovary of Pacific oystersCrassostrea gigascaused by an unidentified intracellular protozoan parasite was investigated in Gokasho Bay, Mie Prefecture, Japan. Cultured and wild oysters were collected bimonthly for one year from July 1996, and seasonal fluctuations in the prevalence of infection, parasite development and histological changes of the infected tissue were examined. Parasites, very similar toMarteilioides chungmuensisinfecting Pacific oysters in Korea, had 8 forms, 4 of which were frequently observed, while the other 4 forms, which were not described inM. chungmuensis, were rare. The total prevalence of infection (percentage of infected oysters positive for at least one of the two examinations : gross and smear inspections of the ovary) was usually higher than the gross prevalence of infection, indicating that infected oysters included ones without visible legions. In cultured oysters, the prevalence of infection increased in summer, suggesting that active multiplication of the parasite takes place in warm water months. From autumn through spring, no substantial change in the total prevalence of infection was observed in cultured oysters (18-20%), while it continued to decline in wild oysters during that period. These differences between cultured and wild oysters could be attributed to the oyster size and environmental factors such as salinity. Histologically, the number of infected oocytes increased in summer, but decreased in winter. From the variations in the parasite morphology and maturation of oocytes, the life cycle of the parasite and the mechanism of the legion formation are postulated.

Hydraulic Model Experiments of Diffusion Induced by Density Current in a Rotating Tank

Recently, new type of equipments using density current are applied to improve water quality in enclosed bays such as Gokasho Bay and Ohmura Bay. In order to obtain a knowledge on diffusion by density current in the topography of real sea, hydraulic model experiments were carried out by using the distorted models installed in the rotating tank which could simulate the effect of the earth's rotation. In the experiments, density current was produced which is intruded between the stratified two water layers with different density, for the purpose of examine the effects of the equipments of improving water quality. A new similarity law was proposed to reproduce density current under the distorted model. In the analysis procedure, a technique was established which measured the distribution of dyestuffs concentration by means of the luminance method. Then, effects of tide, density current, the earth's rotation on the material diffusion under the topography of real sea was examined.

A Study on Characteristics of Generated Output of the Offshore Floating Type Wave Power Device “Mighty Whale”

“Mighty Whale” is an offshore floating type wave power device based on the oscillating water column (OWC) principle. It converts wave energy into electric energy, and produces a relatively calm sea area behind it. These electric energy and calm sea area will be able to utilize for varied applications such as to improve a deteriorated ocean environment and fish farming. JAMSTEC constructed the prototype of Mighty Whale for open sea tests by May 1998, and the open sea tests were started on September 1998 at the mouth of Gokasho Bay in Mie prefecture. This paper describes the characteristics of wave energy absorption of the prototype by the open sea tests data. Particularly the results of the prediction method of electrical output and water tank experiments were compared with open sea tests data on the output of air chamber, turbine output and generated output. The outline of the discussion about these results, the validity of prediction method of generated output was confirmed. And we recognized characteristics of wave energy absorption and wave energy efficiency of floating type wave power device. Based these results, the validity of the design for the prototype was confirmed.

A Study on Environmental Conditions at the Test Site of the Offshore Floating Wave Power Devise “Mighty Whale”

“Mighty Whale” is an offshore floating type wave power device based on the oscillating water column (OWC) principle. The prototype of Mighty Whale was installed at the test location, the mouth of Gokasho bay in Mie Prefecture, on July 1998. The open sea tests were started on Sep. 1998, and we are keeping on measuring many data to show the safety and economic features of the device.Generally, it is important to decide environmental design conditions, wind speed, wave height and so on, when we design offshore structures. Therefore, these design methods are showed by many papers and rules. However, there are few cases to verify whether design methods for actual installed offshore structures are right.In this paper, we verify design methods by using measurement data on Mighty Whale, and have some concluded points as follows. 1) It is necessary to consider long return year (over 50 years) even if actual year is short (4 or 5 years). 2) In case of using adjacent site conditions data, it is important to consider geographical features. 3) It is practical to cut off extreme data if we decide return years by short-term data. 4) It is better to consider swell conditions by typhoon on the coasts of the Pacific.

Research and Development of Density Current Generator

A research and development on “Density Current Generator” which is a new concept machine to agitate and upwell the stratified water area widely and calmly by using a density current is carried out. The machine draws water from top and bottom layer of the water area, and the vertical pipes of the machine lead both top and bottom waters to the pump casing located on middle layer of the water area. Two different waters are mixed up and blown off horizontally via the ring-nozzle by the motor-driven impeller installed in the pump casing. The mixed water is diffused toward every direction on the horizontal plane as a density current which is driven by gravity.A model test and study using the law of similarity was carried out to predict the performance of the full scale prototype machine, which is working in Gokasho Bay, Mie Prefecture Japan since June 1997. The result of performance measurement is that the density current of 120, 000 m3/day is generated by electric power of only 12 kw, and the water area measurement is that the significant changes of sea water qualities are observed. Although further study should be needed to verify that these changes are caused by the machine, it is clear that the machine widely influences on the environment of the water area. These results lead us to believe that the Density Current Generator has excellent potential in terms of agitating and purifying stratified water of very large area.

Stratified Flow Characteristics and Intemal Tide in Gokasho Bay

Stratified Flow Characteristics and Intemal Tide in Gokasho Bay

A Relationship between Winter Water Temperature and the Timing of Summer Gymnodinium nagasakiense Red Tides in Gokasho Bay.

A Relationship between Winter Water Temperature and the Timing of Summer Gymnodinium nagasakiense Red Tides in Gokasho Bay.

Photo synthetic products and nutrient availability in phytoplankton population from Gokasho Bay, Japan

Weekly changes in the photosynthetic products of natural phytoplankton population in Gokasho Bay, Japan, were determined by the combined 13C and gas chromatography-mass spectrometry ( 13C-GC-MS) method. Total organic carbon production rate determined by the daytime incubation (8.5 h) ranged from 7.5 to 47 μg C ̇ 1 −1 C ̇ h −1 , and from 2.3 to 17 μg C ̇ 1 −1 C ̇ h −1 in the day-nighttime incubation (21.5 h). Carbohydrate carbon production rate accounted for 15–81% of total organic carbon production rate in the daytime, and high values were obtained in the low inorganic nitrogen condition. In the low inorganic nitrogen period, glucose accounted for > 90% of carbohydrate production in the daytime. On the other hand, protein carbon formed 7.7–25 and 14–47% of total organic carbon production in the daytime and the day-nighttime, respectively. A high protein contribution was observed under the high nutrient concentration. These results strongly suggested that the distribution pattern of incorporated carbon was affected by nutrient availability.

赤潮鞭毛藻に関する研究-II

To find the reason for outbreak of red tide, physiological characteristics of causative planktons have been studied. Present paper deals with Heterosigma inlandica n. sp. which caused red tide in Gokasho bay, Shima peninsula, 1966. Heterosigma inlandica was obtained in axenic culture by micropipette washings. The organism is wide range euryhaline. The optimal pH range was 8.5 to 9.0, the growth decreased with changing of pH. In the axenic culture, H. inlandica needs vitamin B12 for growth. The addition of other vitamins does not increase growth further. The pattern of specificity is similar to that of Ochromonas malhamensis. All the analogues containing henzimidazole can replace B12•H. inlandica prefers NO3 as nitrogen source. Urea and NH4 in low concentration, glutamine are good N sources. Uric acid, asparagine and arginine are also utilized but growth is less abundant. Inorganic and organic phosphates are utilized. Three purines (xanthine, hypoxanthine and guanine), and three pyrimidines (uracil, cytosine and thymine) increase growth in the presence of vitamin B12. From these results, the primary cause of the great increase of H. inlandica was discussed.