Abstract
An investigation was pursued on the eutrophication problem in Hakata Bay from June 1981 to April 1982. By the chemical analysis and the examination for Phytoplankton of the water samples collected from the surface and bottom of several stations, it was proved that eutrophication was remarkable in the eastern region of the bay.
The population density of phytoplankton revealed a range of 44 to 2, 200 cells/ml in the western region, while the density frequently exceeded a level of 20, 000 cells/ ml in the central and eastern regions. Several species of diatoms and flagellates were found in the red tides developed in the bay during the investigation period.
In addition, Algal Growth Potential (AGP) was determined in the water samples by the use of Skeletonema costatum and Olisthodiscus sp., and the ratio of AGP to COD value in Hakata Bay was caluculated. Thus, the range of 0.44 to 0.80 and 0.27 to 0.60 were obtained respectively by the former plankton and by the latter. In conclusion, the results obtained from the ratio suggested the fact that eutrophication more profoundly proceeds in Hakata Bay under the optimal condition of phytoplankton growth.
