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Senjyu T.,Kyushu University | Matsui S.,Fukuoka Fisheries and Marine Technology Research Center | Han I.-S.,South Korean National Fisheries Research and Development Institute
Journal of Oceanography | Year: 2010

Spatiotemporal characteristics of interannual temperature variations in the Tsushima Strait are investigated on the basis of historical hydrographic data applying the same procedures as Senjyu et al. (2006). Empirical orthogonal function (EOF) analysis revealed that the most energetic mode of variation (the EOF first mode), which accounts for about 31. 5% of the total variance, is the in-phase temperature change for the entire strait. The wintertime temperature variation described by the first mode is associated with the wintertime heat flux in the northern East China Sea, while they are poorly correlated in other seasons. The large standard deviation in the time coefficient of the first mode in August suggests a relationship with the horizontal heat advection in summer in the northern East China Sea. On the other hand, the EOF second mode, which explains about 12. 6% of the total variance, is associated with the stratification and baroclinicity in the strait. The time coefficient of the EOF second mode negatively correlates with the baroclinic volume transport through the strait in summer. Comparison of temporal variations among the leading EOF modes for temperature and salinity shows no significant correlations. This indicates that the principal modes of variation in temperature and salinity vary independently within an interannual timescale. © 2010 Springer Science+Business Media B.V. Source


Umino T.,Hiroshima University | Ueno K.,Hiroshima University | Mihara T.,Hiroshima University | Koike M.,Chugoku Branch | And 3 more authors.
Conservation Genetics Resources | Year: 2013

Small-scale sillago, (Sillago parvisquamis) form the basis of a traditional recreational fishery in Japan. Historically distributed across a wide range, this species is now limited to a single population in the southwest region of the Suonada Sound in the Seto Inland Sea, Japan. Eleven candidate microsatellite loci were isolated from a small insert genomic DNA library of S. parvisquamis. In a screen of 40 individuals from Buzen Sea, we identified polymorphisms at all loci with levels of variability ranging from 2 to 20 alleles with no evidence of linkage disequilibrium. Observed heterozygosities ranged from 0.45 to 0.95, with no locus exhibiting significant departure from Hardy-Weinberg equilibrium. A test for cross-amplification with Sillago japonica revealed a subset of seven polymorphic loci that were successfully amplified. The polymorphic microsatellite loci developed in the current study will facilitate conservation genetic studies in both species, particularly the endangered S. parvisquamis. © 2013 Springer Science+Business Media Dordrecht. Source


Qiu X.,Kyushu University | Yamasaki Y.,National Fisheries University | Shimasaki Y.,Kyushu University | Gunjikake H.,Kyushu University | And 8 more authors.
Marine Ecology Progress Series | Year: 2012

Growth interactions between the raphidophyte Heterosigma akashiwo and the dinoflagellate Akashiwo sanguinea were examined by using bi-algal culture experiments under axenic conditions. There was a lethal effect of H. akashiwo (initial cell density: 1 × 10 2 or 1 × 10 4 cells ml -1) on A. sanguinea at an initial cell density of 1 × 10 2 cells ml -1. Growth of both species was suppressed concurrently when initial cell densities of H. akashiwo and A. sanguinea were 1 × 10 2 and 2 × 10 3 cells ml -1, respectively. A mathematical model was used to simulate growth and interactions in bi-algal cultures. The model predicted that H. akashiwo would outcompete A. sanguinea over time. A cell-free enriched filtrate prepared from dense culture of H. akashiwo reduced both maximum growth rate and maximum yield of A. sanguinea. A filtrate of A. sanguinea prepared in the same manner only reduced maximum yield of H. akashiwo but did not affect its maximum growth rate. Growth of A. sanguinea in bi-algal cultures under contact conditions was significantly lower than that in mono-algal culture and in bi-algal cultures under noncontact conditions. Morphologically abnormal A. sanguinea cells occurred at high frequency only when A. sanguinea was cultured together with H. akashiwo under direct cell contact condition. Moreover, growth inhibition and formation of morphologically abnormal cells of A. sanguinea were induced in a concentration-dependent manner by allelochemicals (including allelochemical polysaccharide-protein complexes) produced by H. akashiwo. These results suggest that growth inhibition effects, via allelochemicals and direct cell contact by Heterosigma akashiwo, influence bloom formation of Akashiwo sanguinea in the field. © 2012 Inter-Research. Source


Qiu X.,Kyushu University | Yamasaki Y.,National Fisheries University | Shimasaki Y.,Kyushu University | Gunjikake H.,Kyushu University | And 7 more authors.
Thalassas | Year: 2011

We investigated growth interactions between the raphidophytes Chattonella antiqua (Hada) Ono and Heterosigma akashiwo (Hada) Hada ex Hara et Chihara using bi-algal cultures under axenic conditions. The growth of C. antiqua and H. akashiwo each tended to be strongly suppressed when the other species reached early stationary phase. A mathematical model was used to simulate the growth interactions of C. antiqua and H. akashiwo in bi-algal cultures. The model showed that C. antiqua outcompetes H. akashiwo over time in bi-algal cultures under all experimental conditions. Furthermore, despite re-enrichment with nutrients, the filtrate from dense cultures of C. antiqua reduced the maximum growth rate of H. akashiwo and filtrate from dense cultures of H. akashiwo reduced both the maximum growth rate and maximum yield of C. antiqua. Source


Qiu X.,Kyushu University | Yamasaki Y.,National Fisheries University | Shimasaki Y.,Kyushu University | Gunjikake H.,Kyushu University | And 6 more authors.
Harmful Algae | Year: 2011

We investigated the growth interactions between the raphidophyte Chattonella antiqua and the dinoflagellate Akashiwo sanguinea by using bi-algal cultures under axenic conditions. When initial cell densities of C. antiqua and A. sanguinea both were 1×102 cells ml-1, C. antiqua grew faster and its growth inhibitory effect on A. sanguinea was stronger than that of A. sanguinea on C. antiqua. In other combinations of inoculation densities, the species that was inoculated at lower cell density (1×102 cells ml-1) stopped growing soon after the start of the experiments, and cell density of this species gradually decreased after the other species reached early stationary phase. The mathematical model used to simulate the growth and interactions between the two species predicts that C. antiqua and A. sanguinea will approach an unstable equilibrium point of about 2.16×104 cells ml-1 (C. antiqua) and 1.46×104 cells ml-1 (A. sanguinea). Thus, one of the species always inhibits the growth of the other and their initial cell densities are critical in determining the successful species in growth competition. When one of these two species was inoculated at the cell density of 2×103 cells ml-1 in bi-algal culture experiments under noncontact and contact conditions, its growth inhibitory effect toward the other species was greater under contact conditions than under noncontact conditions. Furthermore, enriched filtrate from dense culture of C. antiqua resulted in both reduced maximum yield and maximum growth rate of A. sanguinea, whereas that of A. sanguinea resulted only in reduced maximum yield of C. antiqua but did not affect its growth rate. © 2011 Elsevier B.V. Source

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