Shiba, Japan
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Arakawa H.,Tokyo University of Marine Science and Technology | Ohi Y.,Tokyo University of Marine Science and Technology | Ohi Y.,Tokyo kyuei Co. | Matsumoto A.,Tokyo University of Marine Science and Technology | Kawabe K.,Tokyo Metropolitan Ogasawara Fisheries Research Center
Fisheries Science | Year: 2012

The populations of red alga Gelidium elegans along the coast of Miyakejima Island were severely damaged by a volcanic eruption in 2000. The effect of this volcanic eruption has been long lasting, and populations of this red alga still have not recovered. We investigated the effect of seabed sediment particles derived from volcanic ash on the substrate adhesion of G. elegans spores. The analysis provides evidence that increasing amounts of sediment particles result in lower adhesion rates of G. elegans spores, and that smaller sediment particles have a greater influence on adhesion. The amount of seabed sediment particles around Miyakejima Island was 9. 3-1815. 4 mg/cm 2. This amount has changed greatly from year to year. The adhesion rate of G. elegans spores in water around Miyakejima Island was 0 % at all points in 2008 and 2010, but it was estimated as 6. 3-38. 6 % in 2009. These results suggest that there is significant inhibition of algal spore adhesion by seabed sediment particles derived from volcanic ash around Miyakejima Island. © 2012 The Japanese Society of Fisheries Science.


Kono H.,University of Hyogo | Watanabe S.,University of Hyogo | Iwai Y.,Sonic Corporation | Ito Y.,Sonic Corporation | And 3 more authors.
International Journal of Environment and Pollution | Year: 2011

We observed the turbulence and vertical profile of temperature in and above the roughness sublayer (RS) using a tower, a tethered balloon and a Doppler sodar in Himeji City. A 3-D ultrasonic anemometer-thermometer was sited at a height of 54 m on the tower. The present results showed that in the RS, the ratio of friction velocity to wind speed, u*/u, observed under unstable conditions of - 4.2 < z′/L < -0.5 were close to those under neutral conditions, where z′ = z - d; the displacement height d = 2 m; L is the Monin-Obkhov stability length. In addition, σ w/u* were lower than the universal function presented by Panofsky et al. (1977). The cross correlation coefficients for u′w′ and T′w′ under neutral and unstable conditions were also studied. Copyright © 2011 Inderscience Enterprises Ltd.


Sato C.,Tokyo Kyuei Co. | Nakayama K.,Kitami Institute of Technology | Furukawa K.,Japan National Institute for Land and Infrastructure Management
Estuarine, Coastal and Shelf Science | Year: 2012

This paper proposes a method of evaluating the occurrence of hypoxia or anoxia in bottom water of Tokyo Bay, which is typical of enclosed bays in Japan. In Tokyo Bay, the exchange of seawater with the ocean has previously been found to be dominantly controlled by estuarine circulation. Thus, one would expect the concentrations of dissolved oxygen (DO) in the bay head to be influenced mainly by estuarine circulation, which changes according to wind strength and river discharges. We investigated the effects of wind and river discharge on DO concentration around the bay head using a three-dimensional ecological model. To evaluate the occurrence of hypoxic or anoxic water, we developed a conceptual DO model, which was verified through the good agreement with the results from a three-dimensional ecological model. We conclude that the conceptual DO model has good potential for evaluating the factors leading to hypoxic or anoxic water around the bay head. Modeling suggested that, on average, wind effects were the dominant factor in the variation of bottom DO concentrations. However, we found that the contribution of extreme events, such as floods and strong winds exceeding 10 m s -1, was 50% or more. This suggests that extreme events play an important role in controlling the variation in DO concentration at the bottom of Tokyo Bay. © 2012 Elsevier Ltd.


Asano T.,Kagoshima University | Yamashiro T.,Kagoshima University | Nishimura N.,Tokyo Kyuei Co.
Natural Hazards | Year: 2012

A seasonal scale field observation extending over a period of 82 days was conducted in Urauchi Bay on Kami-Koshiki Island, to record meteotsunami events, disastrous secondary oscillations locally known as "abiki." The bay has an elongated T-shape topography with a narrow mouth opening westward to the East China Sea. The area has suffered the effects of meteotsunami causing flooding in residential area and damage to fishing fleets and facilities. A comprehensive observation system for sea level, ocean currents and barometric pressure was deployed to cover the regions within and offshore from Urauchi Bay and the open sea near the island of Mejima in the East China Sea. Vigorous meteotsunami events, where the total height exceeded 150 cm, were observed over five-day periods during the observation period. One or two hours prior to the arrival of meteotsunami events at Kami-Koshiki Island, abrupt 1-2 hPa pressure changes were observed at the Mejima observation site. Pressure disturbances were found to travel eastward or northeastward. The propagation speed was found to nearly coincide with that of ocean long waves over the East China Sea, and as a result, resonant coupling should be anticipated. The incoming long waves were also amplified by geometric resonance with eigen oscillations inherent in the T-shape topography of Urauchi Bay. © 2012 Springer Science+Business Media B.V.


Sakurai I.,Tokai University | Nakayama T.,Hokkaido Government Kushiro General subprefectural Bureau | Hada Y.,Hokkaido Research Organization Central Fisheries Institute | Maekawa K.,Lake Saroma Fisheries and Aquaculture Co operation Organization | And 3 more authors.
Nippon Suisan Gakkaishi (Japanese Edition) | Year: 2014

We examined a suitable site for the growth and survival of juvenile Japanese littleneck clam Ruditapes philippinarum. The survey was conducted in three artificial clam nurseries constructed along the intertidal coastline of Lake Saroma, Hokkaido. Cages accommodating the juveniles were embedded in the offshore side of nurseries 1, 2, and 4 in April; then, juvenile growth was investigated after 6 months. The proportion of the juveniles that would be dislodged from the sand by bottom disturbance due to wave action was calculated using a simulation model. Caging experiments revealed that the offshore side of nursery 1 was suitable for achieving high shell growth. The simulation suggested that the survival rate of the juveniles was higher towards the offshore side of the nurseries. On the basis of the results, we hypothesized that the offshore side of nursery 1 would be suitable for the growth and survival of the juveniles. Around 18,000 juveniles were released in the offshore and land sides of nurseries 1 and 4. Mean shell length and survival rate of the juveniles in nursery 1 was 1.7 and 4.4 times as high as that in nursery 4 after 12 months of releasing; this result supported our hypothesis.


Li Z.,Hanyang University | Li Z.,Korea Advanced Institute of Science and Technology | Matsuoka K.,Nagasaki University | Shin H.H.,Korea Advanced Institute of Science and Technology | And 4 more authors.
Phycologia | Year: 2015

Two morphologically distinct species, Brigantedinium majusculum and Trinovantedinium applanatum, have been suggested as a cyst stage of Protoperidinium pentagonum; however, the cyst-theca relationships are still virtually undefined. In this study, we re-examined the motile stage of B. majusculum via thecal plate analysis together with a molecular phylogenetic analysis based on partial large-subunit ribosomal DNA gene sequences. The morphological features of motile cells germinated from B. majusculum were identical to those of Pr. sinuosum, and the molecular phylogenetic analysis showed that the germinated cells and B. majusculum are closely related to Pr. pentagonum and Pr. latissimum as a sister group. Additionally, high sequence divergences were observed between the germinated cells and B. majusculum as well as Pr. pentagonum and Pr. latissimum (18.0-19.5% according to P-values and 20.7-22.9% according to Kimura two-parameter values). On the basis of these results, our study indicates that B. majusculum should be accepted as the cyst of Pr. sinuosum. Copyright © 2015 International Phycological Society.


Nambu R.,Japan National Research Institute of Fisheries Engineering | Saito H.,Japan National Research Institute of Fisheries Engineering | Tanaka Y.,Tokyo Kyuei Co. | Higano J.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Kuwahara H.,Japan National Research Institute of Fisheries Engineering
Estuarine, Coastal and Shelf Science | Year: 2012

There are many studies on spatial distributions of Asari clam Ruditapes philippinarum adults on tidal flats but few have dealt with spatial distributions of newly settled Asari clam (<0.3 mm shell length, indicative of settlement patterns) in relation to physical/topographical conditions on tidal flats. We examined small-scale spatial distributions of newly settled individuals on the Matsunase tidal flat, central Japan, during the low spring tides on two days 29th-30th June 2007, together with the shear stress from waves and currents on the flat. The characteristics of spatial distribution of newly settled Asari clam markedly varied depending on both of hydrodynamic and topographical conditions on the tidal flat. Using generalized linear models (GLMs), factors responsible for affecting newly settled Asari clam density and its spatial distribution were distinguished between sampling days, with " crest" sites always having a negative influence each on the density and the distribution on both sampling days. The continuously recorded data for the wave-current flows at the " crest" site on the tidal flat showed that newly settled Asari clam, as well as bottom sediment particles, at the " crest" site to be easily displaced. Small-scale spatial distributions of newly settled Asari clam changed with more advanced benthic stages in relation to the wave shear stress. © 2011 Elsevier Ltd.


Akiyama Y.B.,Japan National Research Institute of Fisheries Engineering | Akiyama Y.B.,Nagoya University | Saito H.,Japan National Research Institute of Fisheries Engineering | Nanbu R.,Japan National Research Institute of Fisheries Engineering | And 4 more authors.
Ecology and Civil Engineering | Year: 2011

Spatial statistics was applied to the dataset collected in the Matsunase tidal flat in Mie Prefecture, Japan, in order to elucidate the effect of physico-biological factors that restrict spatial pattern of Manila clam, Ruditapes philippinarum, with spatial autocorrelation considered. Among 12 independent variables, the clam abundance was positively correlated with abundance of cyanobacterium (P <0.05; partial Mantel test) and negatively correlated with ground elevation (P <0.05), while diversity of macrofauna was marginally significant (P <0.1). Faunal diversity was strongly correlated with ground elevation rather than the clam abundance. Manila clam was dominant in the study site and mainly lived in the offshore half of the intertidal zone. The upper margin of the clam habitat was close to the lower end of the swash bar. These results suggested that environmental factors relevant to ground elevation, i. e. extreme temperature and food insufficiency, could restrict vertical range of the clam habitat, inspiring what factor should be focused in future studies.

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