大船渡湾における栄養塩類の平均的季節変動

抄録

Mean seasonal changes of dissolved inorganic nutrients (silicates, phosphates, and nitrogen compounds) in the Ofunato estuary were represented on the basis of monthly measurements from April 1979 to March 1989, and were compared with those in coastal waters. Estuarine nutrients increased in all layers in winter and spring, and decreased in the middle layer in summer and autumn, during which, however, high concentrations were observed in the surface and the bottom layer. A rapid depletion of nutrients occurred from February to March in the estuary in relation to phyto-plankton blooms, and from April to May in coastal waters.
Estuarine nutrients were greatly influenced by fluxes of nutrients from the river into the surface and from bottom sediments into the bottom, as well as fluxes from coastal waters in which the seasonal changes were mainly attributed to those in the oceanographic structure.