Abstract
Seasonal changes in the biomass and occurrence of wild Saccharina
japonica (J.E. Areschoug) C.E. Lane, C. Mayes, Druehl & G.W.
Saunders sporophytes were investigated at the coast of Cape Ohma,
northernmost point of Honshu island, Japan. The blade sizes of marked 25 -
30 sporophytes were monitored at a depth of 14 m each month from November
1991 to December 1994. Their blade elongation was monitored by recording the
position of punched holes on the blades to calculate growth rates. The data
of algal standing crop, water temperature and NO3-N concentration
were also obtained at each time of sampling. The sporophytes of S. japonica
occurred every year except 1992. First- and second-year-old sporophytes grew
to the maximum length of ca. 0.8 m and 2 m in spring, respectively. Both of
them formed zoosporangial sori from October to February. Regeneration of the
blade was observed from October to March for the first-year-old sporophytes.
Deterioration of the second-year-old sporophytes occurred from November to
December. Annual elongation of the blades of first- and second-year-old
sporophytes at the meristematic part was calculated as 1.6 m and
1.8 m, respectively. The blade growth had a significant negative correlation
with water temperature, but positive correlation with NO3-N
concentration. First- and second-year- old sporophytes grew at the water
temperature lower than 20 °C and 14 °C, respectively. The growth rates
decreased at rates of 1.7 mm day-1 for former and 2.8 mm day-1
for latter per 1 °C increase.
