Phytoplankton lysis predicts dissolved organic carbon release in marine plankton communities

Abstract. The relationship between the percent extracellular carbon release (PER) and the specific lysis rates of phytoplankton was examined across a range of communities spanning from highly oligotrophic ones in the subtropical Atlantic Ocean to productive ones in the N. African upwelling and the Southern Ocean. Communities in oligotrophic waters supported high phytoplankton cell lysis rates and low particulate primary production rates but high dissolved primary production and PER. The percent extracellular carbon released increased with increasing lysis rates to reach an asymptote at about 80% PER with specific lysis rates > 1.5 d⁻¹, observed in the most oligotrophic conditions tested. These results confirm that high phytoplankton mortality in the oligotrophic ocean leads to high PER, accounting for the large fraction of the photosynthetic carbon channelled through bacteria characteristic of oligotrophic marine communities.