2013 Volume 61 Issue 1 Pages 073-080
To clarify the seasonal change of the brown alga Eckloniopsis radicosa, the growth of leaf length and weight, individual density, standing crop, leaf area index (LAI) and sorus formation rate were measured by monthly quadrat samplings at depths of 11 m in Izu-Oshima Island, almost the northern limit of the Pacific distribution, central Japan, from February 2005 to December 2007. The annual life cycle was characterized into four phases: germination phase from January to April, growth phase of leaf length from April to June, growth phase of leaf thickness from June to August, maturation and wither phase from August to November. Biomass of E. radicosa at Izu-Oshima Island changed greatly during the three years investigation. The individual density of germination phase of sporophyte was one of the major factors affecting yearly biomass changes, and the individual density was affected by the seawater temperature of growth phase of gametophyte of the previous year. The date of 50% sorus formation was found to be correlated with seawater temperature anomalies calculated for the three months prior to the date; colder seawater resulted in later sorus formation.
