Four morphologically-different populations based on the blade shape of Ecklonia stolonifera Okamura were found from the small island of Nakanoshima, Dozen, Oki Islands, Shimane Prefecture, Japan. There are a very similar in shape to Ecklonia kurome Okamura but the shoot has a short and oblong central blade with well developed lateral pinnate bladelets, a slender central blade with slender lateral pinnate bladelets, a round central blade with short lateral pinnate bladelets and a long stipe and bigger blade with a dentate margin and lack of lateral bladelets. Evaluation and principal component analysis of the four different blade shape population was made based on the size and characteristics of various parts of the blade. However, these four morphologically-different populations were not distinguished by the results of the molecular analysis of the ITS-1. We concluded that the each population is a different four blade types strain.

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The effects of temperature, irradiance and salinity on the growth and survivorship of gametophyte and young sporophyte in Ecklonia kurome collected from the coast of Fukui Prefecture, were examined in laboratory culture. The upper critical temperature of gametophyte was 28℃ and that of young sporophyte was 26℃ . The optimal growth conditions at different temperature/irradiance levels were 22-24℃/50-100μmol/m²/s in female gametophyte, 20-22℃/100μmol/m²/s in male gametophyte, and 15℃/100μmol/m²/s in young sporophyte, respectively. The upper critical temperature for maturation of gametophyte was 22-24℃. The optimal growth conditions of gametophyte and young sporophyte at different temperature/salinity levels were 20-24℃/28-36 psu and 15℃/32 psu, respectively. The high maturation rates of female gametophyte were observed under the combination of 15-20℃ /24-32 psu. The significant decline of survivorship under high temperature and low salinity was observed at 24-28℃ in gametophyte and 22-28℃ in young sporophyte, respectively.

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In order to increase the solubility of alkali-treated agar biopolymers extracted from Gracilariopsis lemaneiformis, sixteen hydrolysis methods with four kinds of acids (sulfuric acid, acetic acid, oxalic acid, and citric acid) were evaluated to determine a suitable procedure. The agar solubility against DMSO and water were tested at 25 ℃ and 95 ℃. Among the procedures tested, partial hydrolysis with 0.001 N acetic acid for 2 ～3 h was more effective for increasing agar solubility (against DMSO at 25 ℃) while maintaining its gelling ability. The results indicated that partial hydrolysis of agar under effective conditions improves agar solubility and produces high grade agar from the Japanese agarophyte, especially Gracilaria (Gracilariopsis). The resulting high solubility agar may facilitate the spread of industrial applications of Gracilaria agars.

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Seasonal changes in thallus length were investigated in populations of two dominant temperate Sargassum species, S. okamurae and S. micracanthum, on a rocky shore off Kutsuu in Tosa Bay, southern Japan from February 2006 to March 2007. Maximum thallus length in S. okamurae appeared in August 2006, at which time, seawater temperature was the highest of the year. Maximum thallus length in S. micracanthum occurred in December 2006. Receptacles were produced after termination of vegetative growth in both species. Apical segments were taken from wild thalli of S. okamurae and S. micracanthum in October 2005 and March 2006, and they were cultured under various temperature conditions. The optimal temperatures for growth of S. okamurae segments in October were 15-30℃, though that in March was at 25 ℃. The relative growth rate in the October segment under the optimal temperatures was 1.5-2.2-times greater than that in the March segment. The optimal temperatures for growth of S. micracanthum segments in October and March were 20 and 25℃, respectively. The relative growth rate in the October segments was 3-times higher than that in the March segments. Seasonal growth patterns in S. okamurae and S. micracanthum are discussed, based on results from the present culture studies and previous field studies.

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