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Ichiro Imai - One of the best experts on this subject based on the ideXlab platform.

  • Long-term (36-year) observations on the dynamics of the fish-killing raphidophyte Chattonella in Harima-Nada, eastern Seto Inland Sea, Japan
    Journal of Oceanography, 2014
    Co-Authors: Tetsuya Nishikawa, Satoshi Nagai, Yutaka Hori, Kazutaka Miyahara, Yukinobu Nakamura, Kazuhiro Harada, Kuninao Tada, Ichiro Imai
    Abstract:

    Long-term changes of the fish-killing raphidophyte Chattonella spp. ( Chattonella antiqua , Chattonella marina and Chattonella ovata ) were examined in relation to environmental factors at 19 sampling stations in Harima-Nada, eastern Seto Inland Sea, Japan, for 36 years from 1973 to 2008. Long-term trends in the dynamics of Chattonella populations were considered to relate to environmental factors such as nutrient concentrations and water temperature. High nutrient levels during the period from the 1970s to the early 1980s have contributed to the high cell density and large-scale red tides of Chattonella spp. in Harima-Nada. However, nutrient levels exhibited a decreasing trend thereafter, and it is thought that Chattonella spp. cannot form large-scale blooms under the present conditions. After the mid-1990s, the occurrence period of vegetative cells of Chattonella spp. has been several weeks or 1 month earlier than that of the 1970s and early 1980s, and the appearance frequency of Chattonella spp. has increased in the northern coastal area, although the cell density and the spatial scale of the distribution have become lower and smaller than those in the previous decades. It is suggested that the timing of germination of Chattonella cysts has become earlier as a result of the increase in water temperature, and the chances of vegetative growth have also increased, especially at the northern coast where most of large rivers discharge into the Harima-Nada. In addition, the present results revealed that fewer diatoms were also one of the significant factors for the high abundance of Chattonella spp. in Harima-Nada.

  • Life cycle, physiology, ecology and red tide occurrences of the fish-killing raphidophyte Chattonella
    Harmful Algae, 2012
    Co-Authors: Ichiro Imai, Mineo Yamaguchi
    Abstract:

    Abstract The marine fish-killing raphidophytes of the genus Chattonella currently consist of five species, i.e. C. antiqua , C. marina , C. minima , C. ovata and C. subsalasa . The distribution of Chattonella species was confirmed in tropical, subtropical and temperate regions in the world accompanying mass mortalities of fishes in nature and in aquaculture. The fish-killing mechanisms are still unclear, but suffocation is the ultimate cause of fish death. Increasing evidence is pointing towards the generation of reactive oxygen species (ROS, e.g. superoxide), which are responsible for the gill tissue injury and mucus production that leads to death of fishes. A taxonomic revision was proposed based on morphology and genetic diversity that Chattonella antiqua and Chattonella ovata should be varieties of Chattonella marina possessing nomenclatural priority. Optimum temperatures for growth are 25 °C for C. antiqua and C. marina , 25–30 °C for C. ovata and 20–30 °C for Chattonella subsalsa . Adequate ranges of salinity for growth were about 20–30 for Chattonella species. Chattonella cells generally divide once a day. Laboratory culture experiments with artificial synthetic medium demonstrated that C. antiqua , C. marina and C. ovata used only Fe chelated with EDTA for growth, although tested diatoms and dinoflagellates used rather many kinds of chelated Fe. A suitable concentration of humic acid supplied with iron also had enhancing effects on the growth of C. antiqua . Diel vertical migration was observed in Chattonella , and the cells reached 7.5 m deep at night in the case of C. antiqua demonstrated by a mesocosm experiment in the Seto Inland Sea. Chattonella species have diplontic life history and have haploid cyst stage in their life cycle. Encystment was observed through formation of pre-encystment small cells after the depletion of nitrogen, and the small cells sink to the sea bottom to complete cyst formation by attachment to the solid surface such as diatom frustules and sand grains. Newly formed cysts are in the state of spontaneous dormancy and they need cold temperature period of four months or longer for maturation (acquisition of germination ability). Cysts germinate in early summer and resultant vegetative cells play an important role as seed populations in blooming in the summer season. However, relatively small part of cyst populations actually germinate from bottom sediments, and success of red tide formation is dependent on the growth in water columns. Since red tides of Chattonella were observed when diatoms were scarce in seawater, diatoms appear to have a key for the predominance of Chattonella in water columns. Diatom resting stages in sediments need light for germination/rejuvenation, whereas Chattonella cysts can germinate even in the dark, implying the selective germination of Chattonella cysts at the sea bottom under calm oceanographic conditions which contribute to bloom formation of Chattonella . As a mechanism of red tide occurrences of Chattonella in coastal sea, “diatom resting hypothesis” was presented. Biological control using diatoms is proposed through the germination/rejuvenation of resting stages suspending from bottom sediments to euphotic layer by sediment perturbation with submarine tractors or fishing trawling gears. Since diatoms have much higher growth rates, and newly joined diatom vegetative cells grow faster and prevent occurrence of Chattonella red tides as a result. As another prevention strategy for Chattonella red tides, algicidal bacteria inhabiting in seaweed beds and seagrass beds are presented. Co-culture of fish and seaweeds in aquaculture areas, and the developments of seaweed- and seagrass-beds would be practical and ultimately environment-friendly strategies for the prevention of harmful red tides of Chattonella by virtue of natural algicidal bacteria supplied from seaweeds and leaves of seagrass.

  • algicidal bacteria in particle associated form and in free living form during a diatom bloom in the seto inland sea japan
    Aquatic Microbial Ecology, 2010
    Co-Authors: Junghwan Park, Tetsuya Nishikawa, Ikuo Yoshinaga, Ichiro Imai
    Abstract:

    To analyze the interrelated dynamics of microalgae and algicidal bacteria (i.e. bacteria that kill and utilize microalgal cells) in a seawater environment, we investigated particle-associated and free-living algicidal bacteria during a diatom bloom in the Seto Inland Sea (Japan) in the sum- mer of 2005. A conventional most probable number (MPN) protocol revealed that bacteria that are algicidal against the harmful microalga Chattonella antiqua (Raphidophyceae) increased in number towards the end of the diatom bloom, during which only a few cells of Chattonella species were observed. Relatively abundant heterotrophic bacteria were present during the bloom period, indicat- ing that the bloom promoted the growth and activity of the ambient bacterial population, including algicidal bacteria. The algicidal abilities of 487 strains isolated from the particle-associated bacteria (PAB) fraction and 249 strains isolated from the free-living bacteria (FLB) fraction were tested against axenic cultures of 3 dinoflagellates and 3 raphidophycean flagellates. About half of the PAB isolates (231/487 strains) showed algicidal activity against 1 or more tested microalgae, while only 22% of the FLB isolates (55/249 strains) were algicidal. Eighty percent of algicidal bacteria from the PAB fraction could kill multiple species of tested microalgae, whereas most of the algicidal bacteria from the FLB fraction killed only a single species. These observations suggest that diatom blooms provide a habi- tat for algicidal bacteria with a wide prey range that potentially limit harmful algal blooms caused by dinoflagellates and raphidophycean flagellates.

  • Occurrence of the polyamines caldopentamine and homocaldopentamine in axenic cultures of the red tide flagellates Chattonella antiqua and Heterosigma akashiwo (Raphidophyceae).
    FEMS microbiology letters, 2009
    Co-Authors: Naoyoshi Nishibori, Masaru Niitsu, Shinsuke Fujihara, Takefumi Sagara, Sachio Nishio, Ichiro Imai
    Abstract:

    The polyamines caldopentamine and homocaldopentamine were detected in axenic strains of Chattonella antiqua and Heterosigma akashiwo (Raphidophyceae), respectively, as well as spermidine, the most abundant polyamine in both phytoplankton species. Trace amounts of putrescine, diaminopropane and norspermine were also detected in both species. Spermine was detected only from C. antiqua. These long linear polyamines are characteristic components of thermophilic bacteria. The detection from two species of Raphidophyceae indicates that the occurrence of long linear polyamines is not restricted to thermophilic microorganisms.

  • High toxicity of the novel bloom-forming species Chattonella ovata (Raphidophyceae) to cultured fish
    Harmful Algae, 2005
    Co-Authors: Shingo Hiroishi, Ichiro Imai, Hideaki Okada, Takashi Yoshida
    Abstract:

    Abstract A toxicological study of an axenic cell line of novel species Chattonella ovata Y. Hara et Chihara (Raphidophyceae) revealed that cultured species of sea bream ( Pagrus major ), horse mackerel ( Trachurus japonicus ), and yellowtail ( Seriola quinqueradiata ) were killed by 4.1–6.8 × 10 3 , 5.4 × 10 3 , and 2.8 × 10 3  cells/mL, respectively. The sensitivity of the gill lamellae to C. ovata differed among the fish species tested. This finding revealed that C. ovata was highly toxic to the cultured fish. Histological examination showed that edema and hyperplasia of the secondary gill lamellae of red sea bream and horse mackerel occurred when exposed to, or killed by C. ovata , whereas severe damage in the gill lamellae was not observed in yellowtail. Chattonella produced high amounts of superoxide anion radicals and hydrogen peroxide, possibly responsible for the fish death observed. Based on the results of this study and occurrence of a red tide by this organism in China in 2001, we consider this organism to be one of the harmful algae in coastal waters. This is the first report demonstrating that C. ovata is highly toxic to fish, and that it produces superoxide and hydrogen peroxide.

Mineo Yamaguchi - One of the best experts on this subject based on the ideXlab platform.

  • Life cycle, physiology, ecology and red tide occurrences of the fish-killing raphidophyte Chattonella
    Harmful Algae, 2012
    Co-Authors: Ichiro Imai, Mineo Yamaguchi
    Abstract:

    Abstract The marine fish-killing raphidophytes of the genus Chattonella currently consist of five species, i.e. C. antiqua , C. marina , C. minima , C. ovata and C. subsalasa . The distribution of Chattonella species was confirmed in tropical, subtropical and temperate regions in the world accompanying mass mortalities of fishes in nature and in aquaculture. The fish-killing mechanisms are still unclear, but suffocation is the ultimate cause of fish death. Increasing evidence is pointing towards the generation of reactive oxygen species (ROS, e.g. superoxide), which are responsible for the gill tissue injury and mucus production that leads to death of fishes. A taxonomic revision was proposed based on morphology and genetic diversity that Chattonella antiqua and Chattonella ovata should be varieties of Chattonella marina possessing nomenclatural priority. Optimum temperatures for growth are 25 °C for C. antiqua and C. marina , 25–30 °C for C. ovata and 20–30 °C for Chattonella subsalsa . Adequate ranges of salinity for growth were about 20–30 for Chattonella species. Chattonella cells generally divide once a day. Laboratory culture experiments with artificial synthetic medium demonstrated that C. antiqua , C. marina and C. ovata used only Fe chelated with EDTA for growth, although tested diatoms and dinoflagellates used rather many kinds of chelated Fe. A suitable concentration of humic acid supplied with iron also had enhancing effects on the growth of C. antiqua . Diel vertical migration was observed in Chattonella , and the cells reached 7.5 m deep at night in the case of C. antiqua demonstrated by a mesocosm experiment in the Seto Inland Sea. Chattonella species have diplontic life history and have haploid cyst stage in their life cycle. Encystment was observed through formation of pre-encystment small cells after the depletion of nitrogen, and the small cells sink to the sea bottom to complete cyst formation by attachment to the solid surface such as diatom frustules and sand grains. Newly formed cysts are in the state of spontaneous dormancy and they need cold temperature period of four months or longer for maturation (acquisition of germination ability). Cysts germinate in early summer and resultant vegetative cells play an important role as seed populations in blooming in the summer season. However, relatively small part of cyst populations actually germinate from bottom sediments, and success of red tide formation is dependent on the growth in water columns. Since red tides of Chattonella were observed when diatoms were scarce in seawater, diatoms appear to have a key for the predominance of Chattonella in water columns. Diatom resting stages in sediments need light for germination/rejuvenation, whereas Chattonella cysts can germinate even in the dark, implying the selective germination of Chattonella cysts at the sea bottom under calm oceanographic conditions which contribute to bloom formation of Chattonella . As a mechanism of red tide occurrences of Chattonella in coastal sea, “diatom resting hypothesis” was presented. Biological control using diatoms is proposed through the germination/rejuvenation of resting stages suspending from bottom sediments to euphotic layer by sediment perturbation with submarine tractors or fishing trawling gears. Since diatoms have much higher growth rates, and newly joined diatom vegetative cells grow faster and prevent occurrence of Chattonella red tides as a result. As another prevention strategy for Chattonella red tides, algicidal bacteria inhabiting in seaweed beds and seagrass beds are presented. Co-culture of fish and seaweeds in aquaculture areas, and the developments of seaweed- and seagrass-beds would be practical and ultimately environment-friendly strategies for the prevention of harmful red tides of Chattonella by virtue of natural algicidal bacteria supplied from seaweeds and leaves of seagrass.

  • Effects of temperature, salinity and irradiance on growth of the novel red tide flagellate Chattonella ovata (Raphidophyceae)
    Harmful Algae, 2010
    Co-Authors: Haruo Yamaguchi, Setsuko Sakamoto, Koichiro Mizushima, Mineo Yamaguchi
    Abstract:

    Abstract To elucidate the mechanism of bloom outbreaks of the ‘novel’ noxious flagellate Chattonella ovata (Raphidophyceae), we examined the growth responses of the organism with 42 different combinations of temperature (10–35 °C) and salinity (10–35), and under various light intensities (0–381 μmol photons m −2  s −1 ). The three strains, CO2, CO3, and CO8 of C. ovata isolated from Hiroshima Bay, tolerated a wide range of temperature (15–32.5 °C) and salinity (10–35). The organism could grow rapidly at over 20 °C and salinity of 20, and the maximal growth rates of 1.11–1.47 divisions day −1 were found in the combination 25–30 °C and salinity of 25–30. These maximum growth rates and optimal temperatures and salinities of the C. ovata strains were clearly higher than those of Chattonella antiqua and Chattonella marina . A statistical analysis showed that growth rates of C. ovata were significantly influenced by temperature–salinity interaction. Furthermore, growth of the strain CO2 and CO8 was observed at the irradiance 15–45 μmol photons m −2  s −1 or more and was saturated at over 300 μmol photons m −2  s −1 . The half-saturation constants of irradiance for the growth of C. ovata were much higher than those of C. antiqua and C. marina . These results showed that C. ovata is better adapted to higher temperature, salinity and light environments than C. antiqua and C. marina . These physiological features of C. ovata would be an ecological advantage to development of the bloom during summer seasons.

  • Morphology and germination characteristics of the cysts of Chattonella ovata (Raphidophyceae), a novel red tide flagellate in the Seto Inland Sea, Japan
    Harmful Algae, 2008
    Co-Authors: Mineo Yamaguchi, Haruo Yamaguchi, Setsuko Sakamoto, Goh Nishitani, Shigeru Itakura
    Abstract:

    To elucidate the mechanism of bloom outbreaks of Chattonella ovata (Raphidophyceae), we investigated the cysts of C. ovata and succeeded in finding them from the bottom sediments of Hiroshima Bay. The morphology of the cysts was mostly hemispherical in shape, with a diameter of ca. 30 μm and height of ca. 20 μm. The cysts were usually adhering to solid materials, such as diatom frustules, yellow-greenish in color and had several dark brown grains. The cyst wall was smooth and had no ornamentation. Because the morphological characteristic of the cysts was in general agreement with those of Chattonella antiqua and Chattonella marina, it was difficult to differentiate the cysts of these three species. Germination of the cysts of C. ovata was observed at temperatures from 17.5 to 30 °C, but not at 15 °C or below. The number of the germinated cysts increased with increasing temperature and the optimum temperature for germination was 30 °C. Although cysts of C. antiqua and C. marina germinated at temperatures from 15 to 30 °C, optimum temperature of germination was 22.5 °C. The lower limit and optimum temperatures for germination of C. ovata cysts was higher than for C. antiqua and C. marina. The role of cysts in the population dynamics of C. ovata is discussed.

Haruo Yamaguchi - One of the best experts on this subject based on the ideXlab platform.

  • Effects of temperature, salinity and irradiance on growth of the novel red tide flagellate Chattonella ovata (Raphidophyceae)
    Harmful Algae, 2010
    Co-Authors: Haruo Yamaguchi, Setsuko Sakamoto, Koichiro Mizushima, Mineo Yamaguchi
    Abstract:

    Abstract To elucidate the mechanism of bloom outbreaks of the ‘novel’ noxious flagellate Chattonella ovata (Raphidophyceae), we examined the growth responses of the organism with 42 different combinations of temperature (10–35 °C) and salinity (10–35), and under various light intensities (0–381 μmol photons m −2  s −1 ). The three strains, CO2, CO3, and CO8 of C. ovata isolated from Hiroshima Bay, tolerated a wide range of temperature (15–32.5 °C) and salinity (10–35). The organism could grow rapidly at over 20 °C and salinity of 20, and the maximal growth rates of 1.11–1.47 divisions day −1 were found in the combination 25–30 °C and salinity of 25–30. These maximum growth rates and optimal temperatures and salinities of the C. ovata strains were clearly higher than those of Chattonella antiqua and Chattonella marina . A statistical analysis showed that growth rates of C. ovata were significantly influenced by temperature–salinity interaction. Furthermore, growth of the strain CO2 and CO8 was observed at the irradiance 15–45 μmol photons m −2  s −1 or more and was saturated at over 300 μmol photons m −2  s −1 . The half-saturation constants of irradiance for the growth of C. ovata were much higher than those of C. antiqua and C. marina . These results showed that C. ovata is better adapted to higher temperature, salinity and light environments than C. antiqua and C. marina . These physiological features of C. ovata would be an ecological advantage to development of the bloom during summer seasons.

  • Morphology and germination characteristics of the cysts of Chattonella ovata (Raphidophyceae), a novel red tide flagellate in the Seto Inland Sea, Japan
    Harmful Algae, 2008
    Co-Authors: Mineo Yamaguchi, Haruo Yamaguchi, Setsuko Sakamoto, Goh Nishitani, Shigeru Itakura
    Abstract:

    To elucidate the mechanism of bloom outbreaks of Chattonella ovata (Raphidophyceae), we investigated the cysts of C. ovata and succeeded in finding them from the bottom sediments of Hiroshima Bay. The morphology of the cysts was mostly hemispherical in shape, with a diameter of ca. 30 μm and height of ca. 20 μm. The cysts were usually adhering to solid materials, such as diatom frustules, yellow-greenish in color and had several dark brown grains. The cyst wall was smooth and had no ornamentation. Because the morphological characteristic of the cysts was in general agreement with those of Chattonella antiqua and Chattonella marina, it was difficult to differentiate the cysts of these three species. Germination of the cysts of C. ovata was observed at temperatures from 17.5 to 30 °C, but not at 15 °C or below. The number of the germinated cysts increased with increasing temperature and the optimum temperature for germination was 30 °C. Although cysts of C. antiqua and C. marina germinated at temperatures from 15 to 30 °C, optimum temperature of germination was 22.5 °C. The lower limit and optimum temperatures for germination of C. ovata cysts was higher than for C. antiqua and C. marina. The role of cysts in the population dynamics of C. ovata is discussed.

  • Development of compound microsatellite markers in the harmful red tide species Chattonella ovata (Raphidophyceae)
    Molecular Ecology Notes, 2007
    Co-Authors: Goh Nishitani, Shigeru Itakura, Satoshi Nagai, Haruo Yamaguchi, Chunlan Lian, S. Sakamoto, S. Yoshimatsu, K. Oyama, M. Yamaguchi
    Abstract:

    We isolated 12 polymorphic microsatellites from the noxious red-tide-causing alga Chattonella ovata. These loci provide a class of highly variable genetic markers, as the number of alleles ranged from four to 12, and the observed and expected heterozygosities ranged from 0.238 to 0.850 and from 0.310 to 0.889, respectively. These loci are useful for revealing the genetic structure of and gene flow among C. ovata populations.

Núñez-vázquez, Erick Julian - One of the best experts on this subject based on the ideXlab platform.

  • Co-ocurrencia de Chattonella marina y Gymnodinium catenatum en laBahía de LaPaz, Golfo de California (primavera2009)
    'Universidad Autonoma Metropolitana', 2017
    Co-Authors: López-cortés, David Javier, Band Schmidt, Christine Johanna, Gárate-lizárraga Ismael, Bustillos-guzmán, José Jesús, Hernández-sandoval, Francisco Eduardo, Núñez-vázquez, Erick Julian
    Abstract:

    During the period of 24 March to 14 May 2009, water and net samples were obtained for phytoplankton analyses; one aliquot was fixed in Lugol´s solution for species quantification and identification. Net samples were used for the identification of live phytoplankton species. Additionally, temperature in situ, chlorophyll a and inorganic nutrients were measured weekly in three stations. Two species were identified: Chattonella marina (Subrahmanyan) Y. Hara et Chihara and Gymnodinium catenatum Graham. Chattonella marina was the most abundant species with a density at subsurface level of 14 × 103 to 36 × 103 cell L-1 . Gymnodinium catenatum had densities were of 1 × 103 to 19 × 103 cell L-1 . Water column temperature was quasi homogeneous from surface to 20 m in depth, with an interval of 19.5 to 22.0 °C and 20.0 to 21.5 °C from March to April respectively. In the middle of May stratification of the water column initiated with a slight temperature difference of 5.0 °C recorded from surface to 20 m in depth. Nitrates varied from 0.5 to 11.0 µM and orthophosphates from 0.4 to 2.6 µM. Chlorophyll a showed a value at surface level of 7.5 mg m-3 and 3.5 mg m-3 at 20 m in March; in May chlorophyll a values ranged between 2.0 to 7.0 mg m-3 . We conclude that the presence of these two species during this study period was associated to the relaxation of the mixing processes in the zoneDurante el período del 24 de marzo al 14 de mayo de 2009 en la Bahía de La Paz, se obtuvieron muestras de agua y de red para análisis de fitoplancton. Una alícuota se fijó con una solución de Lugol para la identificación y cuantificación, la de red se utilizó para la identificación in vivo. Semanalmente se midió la temperatura in situ, se determinaron nutrientes inorgánicos y clorofila a en tres estaciones. Se identificaron dos especies: Chattonella marina (Subrahmanyan) Y. Hara et Chihara y Gymnodinium catenatum Graham. Chattonella marina fue la especie más abundante con densidades de 14 × 103 a 36 × 103 cél. L-1 a nivel sub-superficial. Gymnodinium catenatum se registró con densidades de 1 × 103 a 19 × 103 cél. L-1 . La temperatura del agua fue homogénea desde la superficie hasta los 20 m de profundidad, con un intervalo de 19.5 a 22.0 °C y de 20.0 a 21.5 °C a finales de marzo y abril respectivamente. En la primera mitad de mayo se inició la estratificación, con una diferencia térmica de 5.0 °C entre la superficie y los 20 m. Los nitratos variaron de 0.5 a 11.0 µM y los ortofosfatos de 0.4 a 2.6 µM. La clorofila a en marzo presentó un valor en superficie de 7.5 mg m-3 y a 20 m de 3.5 mg m-3 , en mayo varió de 2.0 a 7.0 mg m-3 . Se concluye que la aparición de las dos especies observadas en este estudio se asocia a la disminución de los procesos de mezcla en esta bahía

  • Co-ocurrencia de Chattonella marina y Gymnodinium catenatum en la Bahía de La Paz, Golfo de California (primavera 2009)
    Hidrobiológica, 2011
    Co-Authors: López-cortés, David Javier, Band Schmidt, Christine Johanna, Gárate-lizárraga Ismael, Bustillos-guzmán, José Jesús, Hernández-sandoval, Francisco Eduardo, Núñez-vázquez, Erick Julian
    Abstract:

    Durante el período del 24 de marzo al 14 de mayo de 2009 en la Bahía de La Paz, se obtuvieron muestras de agua y de red para análisis de fitoplancton. Una alícuota se fijó con una solución de Lugol para la identificación y cuantificación, la de red se utilizó para la identificación in vivo. Semanalmente se midió la temperatura in situ, se determinaron nutrientes inorgánicos y clorofila a en tres estaciones. Se identificaron dos especies: Chattonella marina (Subrahmanyan) Y.Hara et Chihara y Gymnodinium catenatum Graham. Chattonella marina fue la especie más abundante con densidades de 14 × 103 a 36 × 103 cél. L-1 a nivel sub-superficial. Gymnodinium catenatum se registró con densidades de 1 × 103 a 19 × 103 cél. L-1. La temperatura del agua fue homogénea desde la superficie hasta los 20 m de profundidad, con un intervalo de 19.5 a 22.0 °C y de 20.0 a 21.5 °C a finales de marzo y abril respectivamente. En la primera mitad de mayo se inició la estratificación, con una diferencia térmica de 5.0 °C entre la superficie y los 20 m. Los nitratos variaron de 0.5 a 11.0 μM y los ortofosfatos de 0.4 a 2.6 μM. La clorofila a en marzo presentó un valor en superficie de 7.5 mg m-3 y a 20 m de 3.5 mg m-3, en mayo varió de 2.0 a 7.0 mg m-3. Se concluye que la aparición de las dos especies observadas en este estudio se asocia a la disminución de los procesos de mezcla en esta bahía

Shigeru Itakura - One of the best experts on this subject based on the ideXlab platform.

  • Morphology and germination characteristics of the cysts of Chattonella ovata (Raphidophyceae), a novel red tide flagellate in the Seto Inland Sea, Japan
    Harmful Algae, 2008
    Co-Authors: Mineo Yamaguchi, Haruo Yamaguchi, Setsuko Sakamoto, Goh Nishitani, Shigeru Itakura
    Abstract:

    To elucidate the mechanism of bloom outbreaks of Chattonella ovata (Raphidophyceae), we investigated the cysts of C. ovata and succeeded in finding them from the bottom sediments of Hiroshima Bay. The morphology of the cysts was mostly hemispherical in shape, with a diameter of ca. 30 μm and height of ca. 20 μm. The cysts were usually adhering to solid materials, such as diatom frustules, yellow-greenish in color and had several dark brown grains. The cyst wall was smooth and had no ornamentation. Because the morphological characteristic of the cysts was in general agreement with those of Chattonella antiqua and Chattonella marina, it was difficult to differentiate the cysts of these three species. Germination of the cysts of C. ovata was observed at temperatures from 17.5 to 30 °C, but not at 15 °C or below. The number of the germinated cysts increased with increasing temperature and the optimum temperature for germination was 30 °C. Although cysts of C. antiqua and C. marina germinated at temperatures from 15 to 30 °C, optimum temperature of germination was 22.5 °C. The lower limit and optimum temperatures for germination of C. ovata cysts was higher than for C. antiqua and C. marina. The role of cysts in the population dynamics of C. ovata is discussed.

  • Development of compound microsatellite markers in the harmful red tide species Chattonella ovata (Raphidophyceae)
    Molecular Ecology Notes, 2007
    Co-Authors: Goh Nishitani, Shigeru Itakura, Satoshi Nagai, Haruo Yamaguchi, Chunlan Lian, S. Sakamoto, S. Yoshimatsu, K. Oyama, M. Yamaguchi
    Abstract:

    We isolated 12 polymorphic microsatellites from the noxious red-tide-causing alga Chattonella ovata. These loci provide a class of highly variable genetic markers, as the number of alleles ranged from four to 12, and the observed and expected heterozygosities ranged from 0.238 to 0.850 and from 0.310 to 0.889, respectively. These loci are useful for revealing the genetic structure of and gene flow among C. ovata populations.