Ise Bay is still suffering from eutrophication and hypoxia frequently occurs in the hypolimnion, whereas discoloration of cultivated laver has been repeatedly found in recent years. In this paper, sensitivity analysis was conducted to assess the effect of riverine load reduction on primary productivity and occurrence of hypoxia in Ise Bay using a numerical model. Although riverine load reduction caused a local decrease in primary productivity around river mouths and a delay of hypoxia development, the bay-scale improvement was hardly found from the analytical results. Moreover, internal load of phosphorus, which was equivalent to 58% of riverine load, was hardly affected by the reduction. To summarize, riverine load reduction was considered to be less effective regarding primary production and hypoxia in Ise Bay.
