A 3-DIMENSIONAL NUMERICAL-MODEL FOR A MARICULTURE NITROGEN-CYCLE - CASE-STUDY IN SHIZUGAWA BAY, JAPAN

A numerical model is developed for mariculture management, which consi sts of: (1) calculation of spatial distribution of PON (particulate or ganic nitrogen) using simulated current, (2) calculation of spatial di stribution of DO (dissolved oxygen), (3) calculation of DON (dissolved organic nitrogen), (dr) calculation of spatial distribution of DIN (d issolved inorganic nitrogen), and (5) calculation of the horizontal di stribution of accumulated matter which is supplied by deposits from th e mariculture of fish. This model is capable of calculating the detail ed spatial distribution of PON, DON, DIN and DO by dividing the bay in to many grid points. It also takes into consideration the effects of f eed and fish in each raft, and the loading of DIN from rivers. The mod el is applied to Shizugawa Bay, in Miyagi Prefecture, Japan. The model elucidated the oxygen cycle among ecological compartments. The amount of dissolved oxygen supplied by photosynthesis is much greater than t he consumption through respiration by fish and all other conditions fo r mariculture of fish are favourable in this bay.