Abstract
The Secchi disk depth, total downward irradiance, beam transmittance and the concentrations of particulate matters were measured at a station located in the coastal region of northern part of Hiroshima Day during April 1979 to December 1981. Compensation depth was estimated from the in situ measurements of photosyntheticc rate.
Three water layers having different attenuation coefficients (K1, K2 and K3) were frequently found in identical water column. Seasonal variation in K1 was quite similar to that of chlorophyll-a concentrations.
Vertical distributions of beam attenuation coefficient representing turbidity were in good accordance with those of chlorophyll-a concentration during the period of active algal growth. On the contrary, in winter season, beam attenuation coefficient increased gradually with depths. These phenomena could be interpreted as being due to suspended matters other than chlorophyll-a.
Compensation depth was about 2.6 times of the Secchi disk depth. Among particulate organic matters (POC, POP and PON) which were a fraction of matters affecting turbidity, the highest correlation existed between POC and attenuation coefficient. In addition to these, the correlations among optical parameters were studied.
