A trial of marine afforestation of the brown alga Eckloniopsis radicosa by using the spore bag method on the coast of Izu-Oshima Island, central Japan

A trial of marine afforestation of the brown alga Eckloniopsis radicosa by using the spore bag method was tried at three ISOYAKE (barren ground) areas around Izu-Oshima Island, central Japan. Several net bags, in which mature E. radicosa sporophytes and each with a float, were set in summer 2002, 2003 and 2004 in different areas of 5 to 9 m depth. In each area, many young sporophytes appeared around the spore bags in the following spring to summer. In two areas, Senzugyokou and Goishihama, some sporophytes formed zoosporangial sori in the next August, and E. radicosa formed a small community for three years at Senzugyokou after the initiation of the trial. But in two areas, Goishihama and Nomashimaehama, all of the sporophytes were reduced in size due to herbivore grazing. At Goishihama almost all sporophytes were observed within a 5 m radius from the setting site of the spore bags.