Subsurface chlorophyll maxima or deep chlorophyll maxima are well known phenomenon in
temperate, subtropical and tropical oceanic regions. They are usually found at the depths around or
below the seasonal thermocline [Saijo et al. (1969), Furuya and Marumo (1983)]. Thermocline zone is the productive area that thermocline ridges have been found to be the place where tunas aggregate
[Silas and Pillai (1982)]. The most abundance of phytoplankton in the water column and high diversity
were observed in this layer [Boonyapiwat (1999b, 2000)].