The population of Sargassum autumnale in Maizuru Bay was investigated using methods of permanent quadrat and mapping over 52 months. The density of thalli varied from 10 to 30 individuals per ㎡. The monthly mortality rate increased to 26% from disturbance by a typhoon, and it was less than 15% in other periods. Loss of thalli was recorded throughout the year, not for a particular season. Juvenile thalli occurred in autumn and winter, and their density ranged from 0 to 50.3 individuals per ㎡. The density of adult thalli increased following the mass occurrence of juveniles. More than half of thalli less than 1 year old become larger than the minimum reproductive size（20 ㎝ of total length）.

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Carposporelings of Gracilaria blodgettii Harvey were exposed to different temperature (20℃, 25℃, 30℃ and 35℃), salinity (20‰, 25‰, 30‰ and 35‰) and irradiance (60 µmol photons m^-2s^-1 and 100µmol photons m^-2s^-1) levels to determine effects on growth and photosynthetic performance using a series of factorial experiments. Growth was significantly affected by variations in temperature and irradiance levels with highest growth rates obtained at 25℃ (13.1% d^-1) and 100µmol photons m^-2s^-1 (12.7% d^-1). No significant difference was found at all salinity levels tested. Photosynthesis-irradiance (P-I) parameters were directly proportional with increasing temperature. Significantly higher net photosynthesis (Pmax) was obtained at 30℃ and 35℃ than at 25℃ and 20℃ but were complemented with higher respiration rates (1.19 for 30℃ and 1.32 for 35℃) ( p < 0.05). The high photosynthetic efficiency (α) which suggests its ability to maximize low-light conditions was also significantly higher at 25℃ to 35℃ (0.04 to 0.05) than at 20℃ ( p < 0.05). This is further shown by the low compensation point photon fluxes (Ic) (19-27µmol photons m^-2s^-1) and saturation photon fluxes (110-159µmol photons m^-2s^-1). Salinity did not produce significant differences on the photosynthetic responses of the seaweed. This study concludes good culture conditions for Gracilaria blodgettii at 25℃ and 100µmol photons m^-2s^-1 based on high growth rates and high photosynthetic rates with low respiration.

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Morphological studies of the Porphyra akasakae Miura (Rhodophyta, Bangiales) collected on December 14, 2005 were reported from Iwaizaki, Miyagi Prefecture, northern Pacific coasts of Honshu, Japan. It has been considered that P. angusta sensu Kurogi and P. angusta f. sanrikuensis Kurogi were synonyms of Porphyra akasakae Miura. Zygotospores and conchospores were cultured at 10-30 ℃ and 60μmol m^-2s^-1 under 14L: 10D and 10L:14D. Conchospores germinated and grew to normal shape blades at 10-20℃. However, the germlings did not grow to normal size at 25℃. The maturation of male and female blades occurred at 20℃, and the spermatia in the male blade and zygotospores in the female blades were produced after 10 - 12 weeks in culture, and mother cells divided into 128 (a/4, b/4, c/8) sprematia and 8 (a/2, b/2, c/2) zygotospores, respectively. The conchocelis grew rapidly at 25℃ and 14L:10D, and the conchospores were released 3 weeks after zygotospore germination. This species has been known to have dioecious or monoecious blade, however, in this culture, blades were mostly dioecious, and about 7 % of blades in cultures were monoecious, and spermatangia or zygotospores produced and divided at the upper or lower portion of the blade. The life cycle of this species was different from the previous reports and revealed to be P. dentata-type.

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