SEASONAL-VARIATION IN THE PHYSICAL-PROPERTIES OF AGAR AND BIOMASS OF GRACILARIA SP (CHORDA TYPE) FROM TOSA BAY, SOUTHERN JAPAN

Plants of Gracilaria sp.(chorda type), which grow along the coast of U ranouchi Inlet in Tosa Bay, southern Japan, showed the highest biomass in the summer (26-degrees-C to 31-degrees-C) and spring season (15.1- degrees-C to 24.9-degrees-C). Maximum biomass was 6952 g M-2 in July, but gradually decreased in the autumn (30.5-degrees-C in September to 20-degrees-C in November) and winter (19.5-degrees-C in December to 14 .9-degrees-C in February). Variation in yields and gel strength of the agars, were shown to depend on the time in the season. After alkali t reatment (5 % NaOH, 2 h) at three different temperatures (70, 80, and 90-degrees-C), the agars showed gel strengths essentially that of comm ercial grade agars, with the best gel obtained at 80-degrees-C. Maximu m gel strength (1455 g CM-2 of 1.5 % agar gel) occurred in winter when the biomass and agar yield were low. Minimum gel strength was in spri ng. Gel strength was inversely correlated with agar yield, but was pos itively correlated with apparent viscosity. Maximum viscosity was 40 c P. in December. Gelling temperatures, pH of 1.5 % agar gel, and moistu re content in agars showed little variation.