The productive structures and productivity of a Sargassum alternato-pinnatum population at a depth of 5 to 6 m were studied from February to July 2011 on the coast of Misaki, Nagasaki City, Nagasaki Prefecture. Thalli grew increasingly through April to May. The maximum standing crop was 232.0 g d.wt. m^{-2} in May. Net production of the population in February to July was 248.4 g d.wt. m^{-2} by the summation method, which was calculated from the monthly changes in the productive structure. The maximum daily net production of 5.5 g d.wt. m^{-2} day^{-1} occurred from April to May. The release of oospores and embryos was observed in July.
Sargassum alternato-pinnatum
Growth
Net production
Productivity
Productive structure