Effects of Suruga Bay [Japan] deep-sea water, irradiance and water temperature on the growth of juvenile Eisenia arborea

Juvenile Eisenia arborea sporophytes were cultured in indoor tanks containing deep-sea water (DSW, known as clean, cold and nutrient-rich) from Suruga Bay, central Pacific Coast of Japan, pumped from depths of 397 m and 687 m using pipelines. This experiment was performed to determine the most suitable growth condition for Eisenia arborea seed production. At the end of culture, blade lengths of the sporophytes cultured in deep-sea water (pumped from depths of 397 m and 687 m) were 122+-15 mm and 128+-15 mm [relative growth rate (RGR), 3.7%/day and 4.1%/day, respectively]. These values of blade length were higher than those obtained for sporophytes cultured in surface sea water (100+-8 mm; RGR, 3.2%/day). Small sporophytes (150 mm) had blade lengths of 141+-19 mm and 138+-17 mm (RGR, 4.1%/day and 3.6%/day) at a water temperature of 12, 17 deg C, and these values were greater than those obtained for sporophytes at 2l deg C (100+-9 mm; RGR, 3.3%/day). At 8 - 18 deg C, large sporophytes ( 150 mm) showed higher growth rate (ca 1.0%/day) in light conditions above 3.6 mol/square m/day.