In-water algorithms for estimation of chlorophyll a and primary production in the Arabian sea and the eastern Indian ocean

In-water algorithms to estimate the chlorophyll a concentration in the Arabian Sea and the Indian Ocean were set up by computation based on empirical method using subsurface radiance ratio of SeaWiFS bands. A series of investigation for the algorithms was carried out at 16 stations during a cruise in January 1994 from Gulf of Oman to Fremantle, Australia. Photosynthetic productivity of phytoplankton was measured at 12 stations by the stable C-13 isotope method. The algorithm of surface chlorophyll a, that the strongest correlation was observed was Chl.a+Pheo. (mg m(-3)) = 0.26x[Lu(443)/Lu(490)](-3.35) with a coefficient of determination r(2) = 0.93. Most of the standing stock was included in the subsurface chlorophyll maximum (SCM) layer found clearly from 15 to 120 m, Primary production of water column in this area depends on it at the upper layer because of low photosynthetic productivity at SCM. Accordingly a linear relationship with r(2) = 0.90 between the surface chlorophyll a concentration and daily primary production of water column was obtained.