2004 Volume 48 Pages 1495-1500
In some lakes and estuaries, yearly maximum chlorophyll a (Chl. a) concentration was observed in winter, however, the mechanism of such blooms are poorly understood. In this study, dynamics of Chl. a of the Kiso and Nagara River estuaries was investigated, by using long-term monitoring data set of water quality during 1995-1998. The chloronity (Cl concentration) was found to be a primary component to govern the temporal variation of the Chl.a concentration in the surface layer of the two estuaries. A mathematical model was constructed to analyze the phytoplankton dynamics as a function of Cl, light intensity, nutrient (DIN), and water temperature. The model calculations satisfactorily reproduced not only year to year variations in the Kiso River estuary, but also spatial difference between the two observational sites located in the Nagara River estuary, in case that nutrient limitation was incorporated.
