Primary Production and Physical Structure of the Seto Inland Sea, Japan.

瀬戸内海を鉛直混合強度の季節変動を指標として9海域に区分し, 一次生産量の地理的・季節別変動を調べ, 海洋構造との関係を考察した. 年間平均一次生産量のもっとも大きな海域は大阪湾北部(1.227mgCm^<-1>day^<-1>), ついで広島湾北部(1.013mgCm^<-2>day^<-1>)であった. これらの海域は周年にわたって成層が形成され, 陸域からの大量の栄養塩供給によって一次生産が高く維持されていた. また, これからの海域の一次生産量は夏季と秋季に大きく, 冬季と春季に小さかった. 一方, 年間平均一次生産量の小さな海域は備讃瀬戸(323mgCm^<-2>day^<-1>), 安芸灘(335mgCm^<-2>day^<-1>)であった. これらの海域は周年にわたり鉛直混合が卓越しており, 光不足により一次生産が制限されていると考えられる. 最も鉛直混合が卓越する備讃瀬戸では周年にわたり一次産量は小さく, 季節変動はほとんど見られなかった.According to the seasonal variation of the vertical mixing condition, the Seto Inland Sea were divided into 9 sub areas. Geographical and seasonal variations of primary production were investigated in relation to physical structure of each area. Annual average primary production was high at the northen part of Osaka Bay (1,227 mgC m^<-2> day^<-1>) and the northen part of Hiroshima Bay (1,013 mgC m^<-2> day^<-1>). At these areas, the density stratification developed throughout the year and the primary production was enhanced due to the nutrient supply by river discharge. The primary production at these areas was high during autumn and summer, and was low during winter and spring. While, the annual aveage primary production was low at Bisan Seto (323 mgC m^<-2> day^<-1>) and Aki Nada (355 mgC m^<-2> day^<-1>). At these areas, the vertical mixing was dominant throughout the year. It was suggested that the primary production at these areas was restrained by the light condition for the phytoplankton. At Bisan Seto, where the vertical mixing was the strongest, the primary production was low during all seasons and its seasonal variation was almost negligible