Abstract
As a result of the simulation of nitrogen budgets in Ariake Bay utilizing a box-type model, we concluded that the lack of nitrogen in nori farms was caused by the following facts: First, when nitrogen loading was delayed, some phytoplankton types consumed large amounts of nitrogen, which then created a lack of nitrogen because of the poor supply of nitrogen from the catchment area during the rainy period of autumn. Second, when the standing stocks of nitrogen in the fields of a nori fishery contributed significantly to the level of available nitrogen, and the fields had a high level of nitrogen consumption by phytoplankton, the supply of nitrogen was not sufficient to restore the nitrogen level to that required for a healthy fishery. Finally, phytoplankton was able to bloom at a favorable water temperature even at the beginning of nori production. Because the uptake of nitrogen depends on the population of phytoplankton, the plankton blooming in August and September causes a lack of nitrogen at the beginning of October.
