In order to know the magnitude of primary production in the Bingo-nada area in the central part of the Seto Inland Sea, the photosynthesis (by 14 C method) and the chlorophyll contents were measured at the two stations, BG-1 and -2. The measurements were carried out once a month from September 1962 to September 1963.
Seasonal changes of the hydrographic conditions are shown in Text-figs. 2-6. Secchi disc depth is small in this area, especially at BG-2.
The results of primary production measurements are shown in Text-figs. 7-10. The primary production is within the rangeof 0.03-l. 79 g/m2/day as Carbon; it is relatively great in May, June, August and September, and relatively small in November, December and February.
The ratio of the photosynthesis determined by the tank experiment to chlorophyll a content is smaller than 6 in most of the cases. The ratio tends to increase as water temperature rises; at the same temperature, however, it sometimes varies remarkably among stations or layers, suggesting that this ratio is affected not only by temperature but also by some other factor(s) (Text-fig. II).
No correlation is found between the chlorophyll a content (in the water column from Om to the Secchi disc depth) and the Secchi disc depth (Text-fig. 12).