Sargassum glaucescens is distributed in the tropical and subtropical regions in the western Pacific including Japan and Southeast Asian countries. In Japan, this species was first reported in 1993, inhabiting the coastal zone of Shimaura Island, Miyazaki Prefecture. However, the morphological description of this species, in addition to its distribution in Japan, has remained unclear, due to limited subsequent reports. Between 2004 and 2013, we collected specimens of a species resembling S. glaucescens from southern Japan, to clarify the status of this species in Japan using both morphological and molecular diagnostic techniques. The specimens examined in this study exhibited the following morphological characteristics of S. glaucescens : (1) terete or slightly compressed main branches with a smooth surface, which extend from a short stem with a holdfast ; (2) linear oblong to lanceolate shaped leaves ; (3) spherical-shaped vesicles with a round apex ; (4) slightly compressed dioecious receptacles with zygocarpic characters. Moreover, we determined the nucleotide sequences of specimens collected from several sites around Japan, and compared them with morphologically closely related species. The results of both the morphological and molecular analyses indicated that the specimens examined in this study were S. glaucescens, and that at present, it is one of the dominant species in southern Japan.
In this study, the efficiency of ultra-structural observations was shown to enable estimation of the nutritive value and activity of Pavlova sp. as a food organism, in addition to the nutritive analysis of cells. Batch style culture of the alga using 10-L carboys was carried out for 30 days, and cells were collected at day 10, day 20 and day 30 after inoculation. These collections corresponded to the exponentially growth phase, stationary phase and death phase, respectively. Nutritive Pavlova cells containing high levels of EPA and DHA have a large developed chloroplast and few small oil droplets. Following change from the exponentially growth phase to death phase, the fatty acid content decreased conspicuously. In parallel with the nutritive change, the chloroplast shrank and many oil droplets accumulated in cells. Thus, a large quantity of these fatty acids seems to be contained in chloroplast membranes. Active swimming Pavlova sp. in the exponentially growth phase had two flagella. Moreover, the results of the feeding experiment to pearl oyster spats showed that the nutritive value of the exponentially growth phase Pavlova sp. was higher than those of other phases. From the results of this study, Pavlova sp. collected during the exponentially growth phase is recommended to be used as food.
Seedling production of Undaria pinnatifida using free-living gametophytes has remained at an experimental scale despite the ease of stock preservation and cultivar improvement, due to methodological difficulties during the attachment process of gametophytes to so-called seed strings. The present study tested the feasibility of U. pinnatifida seedling production on a commercial-scale using free-living male/female gametophytes that respectively originated from single zoospores. A new practical method of “gametophyte application”was developed, in which free-living gametophytes are applied to seed strings using a brush. Commercial-scale seedling production and cultivation experiments showed that the new method with free-living gametophytes successfully produced seedlings both in indoor bottles and in outdoor tank culture and these seedlings grew normally. Results indicate that the method has potential for both environmentally stable indoor facilities and also outdoor facilities with low initial cost and labor requirements. These findings show that the new method using free-living gametophytes can be used as an alternative source for seedling production of U. pinnatifida for commercial-scale production..
A mechanism that seaweeds collecting activities based on the collection calendar making a contribution to sustainable utilization of algal resources, was elucidated. The collection calendars were described through one year during 1995 to 2013 for analyzing the relationship between seaweeds collecting activities and sustainable utilization of algal resources at Choshi (35°73′N, 140°83′E) and Tateyama (34°98′N, 139°86′E) areas where the oceanographic conditions are different in Boso Peninsula, Japan. As a result, seaweeds collecting activities are minor subsistence as small occupation for the domestic and/or local consumption, though the collecting forms of seaweeds are different at two areas. Seaweeds have been collected without overfishing at seasons having high productive capacity all year round on the basis of knowledge of ecology of seaweeds, folk taxonomy and shallow water environment in many years of fisherman's experience. The fisherman's community takes a calendar of fisherman's daily life and the regional sociocultural events into the collection calendar of seaweeds. In fact, both the beginning and the end of seaweeds collecting activities depend on regional ceremony and festival as a signal. Sustainable utilization of algal resources as part of ecosystem services has been maintained on regional seaweeds collection as minor subsistence.
The Ecklonia kurome population off Gounoura, Iki Island, northern Kyushu was heavily grazed by herbivorous fish in autumn 2013 and the frond of E. kurome had been removed partially or completely. From December 2013 to March 2014, we monitored frond regeneration of tagged E. kurome. Most of E. kurome with blade primordia formed secondary laminae along both sides of the primary lamina, becoming the same morphology as that before they were grazed. More than half the number of E. kurome stipes, for which the entire frond including blade primordia had been removed, also regenerated a frond.
Diving surveys were conducted in the Avacha Bay, Kamchatka State, Far East Russia in 2012 and 2014, to research available macroalgal resources in this area. It was suggested that the major algal resource was the digit type kelp Saccharina bongardiana, which covered at least 50% of the rocky substrata within the depth range of 1-9 m. The standing crop of S. bongardiana was 11 kg m -2 and the mean blade length was 90.7 cm. Its length and wet weight reached their maximum in June, while sorus occurrence on the kelp surface was recorded in August and September. These results were compared with previous studies of kelp fisheries carried out in Hokkaido (Japan) and Sakhalin (Russia).