1Department of Aquatic Biosciences, Tokyo University of Fisheries, Tokyo 108-8477, 2Tyugoku Marine Paints, LTD., Hiroshima 739-0652, 3Faculty of Bioresources, Mie University, Mie 514-8507, 4Shizugawa Nature Center, Miyagi 986-0781, Japan
This study was designed to examine the relationships between the seasonal fluctuations in nitrate concentration in seawater and photosynthetic activity of the bladelets of Ecklonia cava. Dissolved inorganic nitrogen (DIN) and nitrate concentrations in seawater and the net photosynthetic rates of E. cava were measured every month in Nabeta Bay, Shimoda, Izu peninsula, Japan. The concentrations of DIN and nitrate and the photosynthetic activities of E. cava showed the same seasonal change, high in winter and low in summer. The net photosynthetic rates of bladelets of E. cava were also measured every two months after incubation for two days in the nitrate enriched seawater and in fresh seawater. The maximum photosynthetic rates of bladelets of E. cava were slightly higher in the nitrate enriched seawater than in the fresh seawater in each month, but this difference was not significant by the t-test.