Abstract
We determined the relationship between photosynthetic production of dissolved organic carbon (OC) and phytoplankton cell size and taxonomic composition in cultures of marine phytoplankton at 3 different growth stages. We measured OC exudation in 22 species belonging to 5 phyla and spanning >7 orders of magnitude in cell volume. The extracellular release of OC in our cultures represented on average similar to 2% of total carbon fixation, was not statistically different between growth stages, and was not correlated to cell size. The cell-specific OC exudation rate held an isometric relationship with cell size during the different growth phases (average slope: 0.95), which implies that general allometric models cannot be used to predict exudation in marine phytoplankton.