cause the composition of coastal water is full of variety by each region, relationship between chlorophyll-a (chl.a)
concentration as a indicator of primary productivity derived by satellite ocean color data and in situ data of chl.a may not be
same always. Those relations or algorithms should be verified at each coastal water for managing coastal environment. Coastal
ocean color algorithms should be built up at each coastal water or at least should be verified by wide range field data for practical
application at each region. Intensive research cruises were conducted at the Upper Gulf of Thailand. Optical survey using
PRR (Profiling Reflectance Radiometer) showed the character of the Upper Gulf water. Under water optical algorithms for that
water were suggested by these survey data. Optical depths in the Gulf of Thailand were also measured to know the compensation
depth for primary production. Although the transparency measured by Secchi disk is not so large and surface water looks
very turbid, the light energies are reaching to near bottom at almost all stations of the upper Gulf. It suggests that the turbidity
of this water were mainly composed of scattering material like as clay mineral rather than absorbing material like as phytoplankton
pigment or CDOM