Global Distribution of Non-algal Particles From Ocean Color Data and Implications for Phytoplankton Biomass Detection

In the last few decades, phytoplankton biomass has been commonly studied from space. However, satellite analysis of non-algal particles (NAPs), including heterotrophic bacteria and viruses, is relatively recent. In this work, we estimate the backscattering coefficient associated with the NAP fraction that does not covary with chlorophyll based on satellite particulate backscattering coefficient and chlorophyll (b(bp)NAP). b(bp)NAP is computed at 100-km resolution using 19 years of monthly satellite data. We find clear differences in b(bp)NAP between northern and southern oceans. High b(bp)NAP values are found in the Arctic and Southern Oceans, the North Atlantic area influenced by the Gulf Stream current, as well as shelf regions (i.e., Patagonian shelf) affected by upwelling regimes. Low correlation between chlorophyll and backscattering prevents precise b(bp)NAP estimations in oligotrophic areas (e.g., subtropical gyres). These b(bp)NAP estimations lead to a reduction to half in satellite-based phytoplankton biomass estimates respect to previously published results.