Growth and Maturation of <i>Sargassum macrocarpum</i> C. Agardh in Fukawa Bay, the Sea of Japan

Abstract

Growth and maturation of Sargassum macrocarpum C. Agardh were studied in Fukawa Bay fac ing to the Sea of Japan, Yamaguchi Prefecture, at the depth of 8 m, from June 1993 to July 1994. New main branches on perennial stem had been apparently observed in June, and grew increasingly through July to March in the next year, then reached the maximum length and dry weight of the branches in March and May, respectively. Thalli with three or more growth rings in holdfast matured and formed receptacles through March to June. The release of oospores and embryos was observed only in June. The number of main branches was almost the same among adult thalli and did not show variation throughout the year. The minimum and maximum standing crops were 257.6 g m-2 in August 1993 and 1155.7 g m-2 in May 1994, respectively.

Relationships between critical photon irradiance for growth and daily compensation point of juvenile Sargassum macrocarpum

“…It took 4–5 h for a series of measurements starting from 10:00. Photosynthesis and respiration were measured at 20°C which was nearly the same as the in situ seawater temperature of the sampling area 5 . Thereafter, the leaf surface area was measured with an image analysis system (GT‐6500; Seiko Epson, Nagano, Japan and PC‐9801DX; NEC, Tokyo, Japan).…”

“…The perennial brown alga Sargassum macrocarpum C. Agardh is widely distributed from Chiba Prefecture to Kyushu Island in the Pacific Ocean, and from Aomori Prefecture to Kyushu Island in the Sea of Japan 1,2 . This species usually grows at depths of 0–20 m, 2 and forms dense beds at depths of 4–10 m 3–5 . The information on the vegetative structure, growth, maturation, standing crop and production from both an ecological and fisheries perspective has been accumulated for this species 3–6 …”

“…This species usually grows at depths of 0–20 m, 2 and forms dense beds at depths of 4–10 m 3–5 . The information on the vegetative structure, growth, maturation, standing crop and production from both an ecological and fisheries perspective has been accumulated for this species 3–6 …”

“…macrocarpum population in Fukawa Bay of Yamaguchi Prefecture is a multiple age assemblage 5 . The adult thalli‐forming canopy accounts for a large part of the biomass and production of the population 5 . The adult thalli exhibit deciduous main branches which develop from the perennial stem.…”

“…The adult thalli exhibit deciduous main branches which develop from the perennial stem. These main branches deteriorate over winter and spring, approximately 1 year after development 4,5 . In contrast, juvenile thalli on the floor of the population play an important role as major constituents of the coming generation.…”