Growth and maturation of Saccharina cichorioides Miyabe on the coast of Soya, northern Hokkaido, Japan

Abstract

Seasonal changes in growth and maturation of 2 year old sporophytes of Saccharina cichorioides were surveyed on the coast of Soya, northern Hokkaido, Japan, from 2008 to 2010. Sporophytes were collected and observed every 20-90 days by SCUBA. Collected samples were measured for the blade length and width, and the sorus formation rate was calculated. On the other hand, tagged samples were observed the growth and erosion (tissue loss) rate of each individuals. Sporophytes formed a new blade in early December and the blade length and width remarkably increased between December and May. Then blade length was shortened by erosion of the tip from June, and the dry weight, dry/wet weight ratio and blade substantiality (thickness) value increased until October. Sporophytes began to form sori on the blade from the middle of September. Maximum daily growth rate was 0.7 cm day^-1 between April and May, and erosion rate was 0.5 cm day^-1 between May and July. The seasonal changes of growth and maturation of S. cichorioides can be distinguished into three phases, growth phase (end of November to May), blade thickening phase (June to October), and maturation phase (from middle of September).