Estimation of Marine Primary Productivity From Satellite-Derived Phytoplankton Absorption Data

Abstract

The global ocean net primary production (NPP) was estimated from satellite-derived information using a phytoplankton pigment absorption ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${a}_{{\bf ph}}$</tex> </formula> )-based model. Satellite-derived spectral-averaged <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${a}_{{\bf ph}}$</tex> </formula> was used as the key predictor of phytoplankton photosynthetic efficiency in the model. The <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${a}_{{\bf ph}}$</tex> </formula> -based model yields an annual integrated NPP of approximately <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\bf 55~\hbox{Pg C year}^{-1}$</tex> </formula> for the global oceans over the period 2003–2010. The accuracy of the model was validated by comparing it with in situ NPP at three sites, and the logarithmic root-mean-square error of the model was approximately 0.18. The model performance was also compared with two existing NPP models (chlorophyll-based model and carbon-based model) in terms of spatial distribution, seasonal cycles, and accuracy. The comparison results indicated that the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${a}_{{\bf ph}}$</tex> </formula> -based model has improved accuracy in describing NPP variation for monthly timescales compared with the other two models. We were surprised to find that the spatial distribution of global ocean NPP provided by the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${a}_{{\bf ph}}$</tex> </formula> -based model is more similar to the carbon-based model than the chlorophyll-based model. Although many additional studies need to be conducted, the performance of the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${a}_{{\bf ph}}$</tex> </formula> -based model in this work may encourage us to estimate ocean NPP from satellite-derived phytoplankton pigment absorption.