Journal of Oceanography, Vol. 61 (No. 3), pp. 575-589, 2005
Eko Siswanto1, Joji Ishizaka2* and Katsumi Yokouchi3
1Graduate School of Science and Technology, Nagasaki University, Bunkyo, Nagasaki 852-8521, Japan
2Faculty of Fisheries, Nagasaki University, Bunkyo, Nagasaki 852-8521, Japan
3Seikai National Fisheries Research Institute, Fisheries Research Agency, Taira, Nagasaki 851-2213, Japan
(Received 12 September 2003; in revised form 14 September 2004; accepted 14 September 2004)
Abstract: An algorithm was evaluated for estimating primary production in the Kuroshio front of the East China Sea. The algorithm involves three principal inputs: Chlorophyll-a (Chl-a) vertical profile, water column photosynthetic parameter and underwater irradiance parameter. We construct empirical models for estimating those three inputs from sea surface variables accessible by means of satellite remote sensing. Types of Chl-a vertical profile were closely associated with water mass features, and sea surface temperature seemed to be a potential variable to distinguish profile types. The consequence of the deep Chl-a maximum (DCM) presence was investigated by comparing the vertically non-uniform Chl-a profile against the uniform Chl-a profile in terms of the integrated biomass and primary production estimates. Since the DCM in the frontal region occurred in a relatively shallow layer with relatively high light level, allowing intensive photosynthetic processes to take place in the DCM layer. In contrast, as the DCM in the Kuroshio region occurred in the low-light, deep layer, it contributed less to the integrated primary production. We inferred that the DCM formation is more important in the frontal region than in the Kuroshio region, as they potentially contributed within 30.9% (±9.1%) and 20.9% (±5.4%) to the integrated primary production in the frontal and the Kuroshio regions, respectively. Such different degrees in the DCM contribution was then revealed by the higher integrated primary production in the frontal region than in the Kuroshio region.