Guangwei HUANG （Niigata University）
In this study, field investigations were carried out to shed light on the spatial and temporal variability of water quality in the Sakata lagoon. The objective was to gain a better understanding on the problems the lagoon is faced with. Field works included seasonal surveys, monthly measurements and continuous sampling during summer. It was found that the water quality of the Sakata lagoon was highly variable both spatially and temporally. The transparency of the lagoon water was very low, and the high turbidity might have caused the reduction of dissolved oxygen near the bottom in some portion of the lagoon in summer. In terms of phosphorous and chlorophyll-a concentrations and the Secchi depth, the lagoon can be classified as being hypereutrophic. Besides, the release rates of phosphorus from the lagoon sediment under both aerobic and anaerobic conditions, and the sediment oxygen demand as well were obtained experimentally. They provided valuable insight into the characteristics of the lagoon.
Sakata lagoon, field survey, water quality, spatial and temporal variability