A three-dimensional numerical model for a mariculture nitrogen cycle: case study in Shizugawa Bay, Japan

A numerical model is developed for mariculture management, which consists of: (1) calculation of spatial distribution of PON (particulate organic nitrogen) using simulated current, (2) calculation of spatial distribution of DO (dissolved oxygen), (3) calculation of DON (dissolved organic nitrogen), (4) calculation of spatial distribution of DIN (dissolved inorganic nitrogen), and (5) calculation of the horizontal distribution of accumulated matter which is supplied by deposits from the mariculture of fish. This model is capable of calculating the detailed spatial distribution of PON, DON, DIN and DO by dividing the bay into many grid points. It also takes into consideration the effects of feed and fish in each raft, and the loading of DIN from rivers. The model 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 the consumption through respiration by fish and all other conditions for mariculture of fish are favourable in this bay.