<title>Two-phytoplankton community model of primary production for ocean color satellite data</title>

Abstract

We developed an algorithm to estimate primary production from ocean color satellite data, and estimated the global distribution of primary production with OCTS and SeaWiFS data. The VGPM is one of the simplest and most usable models for primary production estimation from satellite chlorophyll. We propose two-phytoplankton community model of primary production to improve the VGPM. In general, chlorophyll concentration tends to be proportional to phytoplankton cell size and phytoplankton productivity tends to be inversely proportional to cell size. Based on these facts, we improved P<SUP>B</SUP><SUB>opt</SUB>(maximum carbon fixation rate within a water column), which is one of the most important parameters of the VGPM. We assume that the phytoplankton community is composed of large and small cell size phytoplankton and that there are limits to the biomass of small phytoplankton. Based on this hypothesis, we matched P<SUP>B</SUP><SUB>opt</SUB> to the functions of sea surface temperature and sea surface chlorophyll concentration. The results indicate that small phytoplankton has higher productivity with higher temperature dependency. We estimated the global distribution of primary production using this modified VGPM. The global distribution of primary production is basically similar to that of chlorophyll concentration. The modified VGPM estimates lower productivity than original VGPM in high chlorophyll concentration areas, and conversely estimates higher productivity in low chlorophyll concentration areas. With total global primary production, the modified VGPM results are 12% lower than the original VGPM.