Annual life cycle and productivity of Sargassum confusum population off the coast of western Shakotan Peninsula in southwestern Hokkaido, Japan
2001
Tsuda, F. (Hokkaido Nuclear Environmental Observation Center, Kyowa (Japan)) | Akaike, S.
The present studies were carried out from May 1997 to August 1998. Its annual life cycle was divided into four periods: slow growing, rapid growing, mature, and withering. Small plants under 10 cm in length were constantly present all the year round, comprising 35.4 to 98.8 percent of the population. Population density increased in December due to the inclusion of newly developed young plants and decreased gradually to the following April. However, density fluctuation was minimal from May to November, this indicating the number of plants older than 1-year was stable. Plants with receptacles were first observed in early June when water temperature reached 13 deg C and were continued to be observed until mid August Female plants released eggs from late June to early August m water temperature ranging from 18 to 23 deg C. Annual net production of the species was estimated at 950.2g, dry/square m which was about 1.1 times as great as the maximum standing crop in July 1998.
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