Abstract
Seaweed forests composed of Eisenia bicyclis Setchell and Eclonia cava Kjellman are widely distributed along the coast of central Honshu Island, Japan, facing the Pacific Ocean. This study aimed to clarify a zonation of these plants and their causes. We measured their stipe arid maximal blade lengths for one year and attaching force of their hold fast to a substratum in a field and a fluid force on them in a laboratory. They grew rapidly from winter to summer, and maturated from summer to fall. We observed intraspecies and inter-species zonation. Attaching force of their hold fast depended on a condition of substratum surface. Under an oscillatory current, the dominant fluid force exerted on the plants was a drag force in a blade part but an inertial force in a stipe part.
