Mapping size-specific phytoplankton primary production on a global scale

Abstract

Since the initiation of satellite-borne visible spectral radiometry (ocean colour), oceanographers have developedtechniques to map phytoplankton biomass on a global scale, with a major application being tomodel primary production and the ocean carbon cycle in the context of climate change. However, we nowrecognise that marine carbon cycling links specifically to the activity of particular phytoplankton functionalgroups. From the perspective of primary production and the global carbon cycle, cell size is thoughtto be sufficient for defining these functional groups. This has led to a variety of bio-optical methods thatuse satellite data to differentiate between phytoplankton size classes. Here we combine an establishedphytoplankton size class algorithm which is integrated into an available-light primary production modelin order to partition and map primary production estimates from microplankton (>20μm) and combinednano-picoplankton (<20μm) on a global scale for the year 2005. We estimate global primary production in2005 to be 51.20 ± 0.29 Gt C y-1 of which, combined nano-picoplankton contributes to 48.58 ± 0.34 Gt Cy-1 (94.8%) and microplankton 2.62 ± 0.07 Gt C y-1 (5.2%). This approach can supply data for large-scalemaps of size-specific primary production and an example of May and November 2005 is shown.