Measurements of the release of dissolved organic nitrogen (DON) and carbon (DOC) were carried out on an axenic batch culture of the coccolithophorid Emiliania huxleyi. This unicellular marine alga was cultured using a media with nitrate as the sole N source and the changes of DOM concentrations measured over 14 days. Results showed that there was a significant release of DON, i.e.7.6 µM N day⁻¹ during mid-exponential growth phase (days 5–7). The highest release of DOC was also recorded in the same growth phase and accounted for 24.0 μM C day⁻¹.