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Aoki K.,Japan National Research Institute of Fisheries Science | Onitsuka G.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Shimizu M.,Japan National Research Institute of Fisheries Science | Kuroda H.,Hokkaido National Fisheries Research Institute | And 7 more authors.
Estuarine, Coastal and Shelf Science | Year: 2012

A harmful bloom due to the raphidophycean flagellate, Chattonella antiqua, was found in the Yatsushiro Sea, western Kyushu, Japan, from the end of July to the beginning of August 2009. The bloom resulted in enormous economic damage to cultured finfish production in aquaculture farms concentrated in the southwestern area. To investigate the factors controlling the spatio-temporal distribution of the bloom, data analysis and numerical simulations were conducted using field monitoring data and a three-dimensional hydrodynamic model coupled to a Lagrangian particle-tracking model. Results of the monitoring data analysis showed that the initial development of the C. antiqua bloom occurred in Kusuura Bay and the northeastern area near the mouth of the Kuma River, and subsequently the bloom expanded rapidly to the whole area. The simulation results indicated that the source region of the widespread bloom was not Kusuura Bay but the northeastern area. The southwestward evolution of the bloom was primarily controlled by the passive transport due to the surface residual current driven by fresh water discharge from the Kuma River and northeasterly winds. On the favorable conditions of river discharge and wind, the massive bloom of C. antiqua that formed in the northeastern area was quickly transported southwestward within a few days. © 2012 Elsevier Ltd. Source


Ohshimo S.,Seikai National Fisheries Research Institute | Gotoh T.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Otsuka T.,Kumamoto Prefectural Fisheries Research Center | Gejima K.,Kagoshima Prefectural Fisheries Technology and Development Center
Nippon Suisan Gakkaishi (Japanese Edition) | Year: 2011

We analyzed the biological characteristics such as growth and maturation of round herring Etrumeus teres in the East China Sea. Von Bertalanffy's growth curve was calculated based on monthly size frequency distributions from 1997 to 2009, and the estimated growth formula was BL m=244.8[1-exp {-0.10(m-0.55)}](r 2=0.92, p <0.01), where BL m is body length at age m (months). Additionally, the estimated formula was supported by the results of scale reading in the adult stage and number of otolith increments in the juvenile stage. Based on histological observations of the gonads, the main spawning period in the East China Sea was from December to June. Combining the results from the growth model and relationships between body length and maturation rate, the first maturation age was estimated to be one year old for both sexes. Source


Shikata T.,Prefectural University of Kumamoto | Shikata T.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Sakurada K.,Kumamoto Prefectural Fisheries Research Center | Jomoto Y.,Prefectural University of Kumamoto | And 6 more authors.
Nippon Suisan Gakkaishi (Japanese Edition) | Year: 2011

In the Yatsushiro Sea, from June to October 2008, growth dynamics of Chattonella antiqua were investigated by weekly and monthly samplings in relation to nutrients. To test how well the water in the samples supported the growth of C. antiqua, bioassays of growth of a cultured strain of C. antiqua were also conducted. In closed-off sections of the sea, DIN and DIP concentrations increased and then C. antiqua bloomed at the end of August. In the bioassays, C. antiqua growth decreased with the lack of N-, P- or Fe-sources in comparison with the growth in the complete media. However, the addition of N-source promoted the growth although the addition of P- or Fe-sources had almost no effect, in comparison with basic seawater. The present study indicates that C. antiqua growth is limited primarily by N-source, and secondarily by P- and Fe-sources in the Yatsushiro Sea. Source


Aoki K.,Japan National Research Institute of Fisheries Science | Onitsuka G.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Shimizu M.,Japan National Research Institute of Fisheries Science | Kuroda H.,Hokkaido National Fisheries Research Institute | And 6 more authors.
Marine Pollution Bulletin | Year: 2014

The dynamics of river plume in relation to harmful blooms of the raphidophycean flagellate, Chattonella antiqua in summer 2008-2010 in the Yatsushiro Sea, Japan were studied using a hydrodynamic model and monitoring data. In the southern area, the bloom formed in the waters stratified by a halocline caused by the southward expansion of riverine water from the Kuma River after the bloom initially forming in the northern area. The timing of the southward riverine water advection can be explained by the balance between the wind stress term and the pressure gradient term calculated from the horizontal density difference between the northern and southern areas. The wind stress and pressure gradient terms were evaluated using the sea surface temperature, salinity, wind speed and direction at two stations. Real time monitoring or continuous observations in these areas will enable nowcasts of bloom expansion when a bloom develops in the northern area. © 2014 Elsevier Ltd. Source


Nishitani G.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Nishitani G.,Tohoku University | Nagai S.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Hayakawa S.,National Institute of Genetics | And 4 more authors.
Applied and Environmental Microbiology | Year: 2012

Kleptoplastidy is the retention of plastids obtained from ingested algal prey, which may remain temporarily functional and be used for photosynthesis by the predator. We showed that the marine dinoflagellate Dinophysis mitra has great kleptoplastid diversity. We obtained 308 plastid rbcL sequences by gene cloning from 14 D. mitra cells and 102 operational taxonomic units (OTUs). Most sequences were new in the genetic database and positioned within Haptophyceae (227 sequences [73.7%], 80 OTUs [78.4%]), particularly within the genus Chrysochromulina. Others were closely related to Prasinophyceae (16 sequences [5.2%], 5 OTUs [4.9%]), Dictyochophyceae (14 sequences [4.5%], 5 OTUs [4.9%]), Pelagophyceae (14 sequences [4.5%], 1 OTU [1.0%]), Bolidophyceae (3 sequences [1.0%], 1 OTU [1.0%]), and Bacillariophyceae (1 sequence [0.3%], 1 OTU [1.0%]); however, 33 sequences (10.8%) as 9 OTUs (8.8%) were not closely clustered with any particular group. Only six sequences were identical to those of Chrysochromulina simplex, Chrysochromulina hirta, Chrysochromulina sp. TKB8936, Micromonas pusilla NEPCC29, Micromonas pusilla CCMP491, and an unidentified diatom. Thus, we detected >100 different plastid sequences from 14 D. mitra cells, strongly suggesting kleptoplastidy and the need for mixotrophic prey such as Laboea, Tontonia, and Strombidium-like ciliates, which retain numerous symbiotic plastids from different origins, for propagation and plastid sequestration. © 2012, American Society for Microbiology. Source

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