Abstract
Diel fluctuations in concentrations of nutrients (ammonia-N, nitrate & nitrite-N, phosphate-P) and their flow were determined in an integrated culture system (started on Nov. 18, 2003) using deep seawater (DSW) pipelined from a depth of 321 m in Toyama Bay, Sea of Japan. In the system, ezo-abalone, Nordotis discus hannai (260 shells, 6.19 kg on Aug. 26, 2004) were cultured in two indoor tanks (60l in water volume (w. v.)) by using fresh warmed DSW (18°C) and the wastes were supplied to an indoor tank (14°C, 400l in w. v.) in which barfin flounder, Verasper moseri (30 fishes, 21.0 kg), were cultured. The waste from the latter tank was used in another outdoor tank (10°C, 3600l in w. v.) in which makombu kelp, Saccharina japonica (600 plants, 55.8 kg) were cultured. For chilling, intact DSW (3°C) was supplemented to the barfin flounder and kelp tanks. Nutrient outputs from the abalone and barfin flounder tanks and uptake in the makombu kelp tank were determined every hour on Aug. 25, 2004. On the day, abalones and barfin flounders were fed 450 g/tank of cut-off blade of kelp cultured in the system at 16: 00 and 95 g/tank of artificial compounds at 9: 30, respectively. The two notable features of nutrient variation were (1) increase of ammonium-N level in barfin flounder tank and its uptake in makombu kelp tank and (2) increase of other nutrients in ezo-abalone tank just after feeding. The utilization of ammonia-N, nitrate & nitrite-N and phosphate-P by makombu kelp were calculated to be 38 %, 6 % and 12 % from the difference of nutrient concentrations between supply and drainage. The low utilization rates of nutrients suggest that enlargement of the kelp biomass can improve the nutrient utilization in this system.
