Seasonal variation in morphology, growth and reproduction of Zostera caespitosa on the southern coast of Korea

Seasonal dynamics of Zostera caespitosa Miki were monthly monitored in Jangmok Bay of Geoje Island, Korea by examining morphometrics, reproductive phenology, leaf productivity and environmental factors from July 2001 to July 2002. Shoot size and weight reached to maximum values during summer, but the number of leaves per shoot did not exhibit a clear seasonal pattern. The leaf area was approximately 2-fold greater in summer in during winter, which was mainly due to the increase in shoot length. Flowering shoot appeared in early March, and developed into fruits in early May. By the end of May, all reproductive shoots bore mature fruits. Leaf growth exhibited a seasonal pattern, ranging from 1.5 mg DW shoot−1 d−1 in November to 16.3 mg DW shoot−1 d−1 in June. The leaf plastochrone intervals varied from 12.5 days in May to 37.5 days in November. The mean lifetime of leaves was 99.1 days and the annual leaf turnover was estimated to be 3.7 times per year. This study indicated that the growth and flowering phenology of Z. caespitosa was strongly coupled to seasonal light conditions.