In the present study we investigated the effects of temperature and light intensity (including daylength) on CH4 formation from three widespread marine algal species Emiliania huxleyi, Phaeocystis globosa and Chrysochromulina sp.. Rates of E. huxleyi increased by 210 % when temperature increased in a range from 10 to 21.5 °C, while a further increase in temperature (up to 23.8 °C) showed reduction of CH4 production rates. Our results clearly showed that CH4 formation of E. huxleyi is controlled by light: when light intensity increased from 30 to 2670 µmol m-2 s-1 CH4 emission rates increased continuously by almost one order of magnitude and was more than one order of magnitude higher when the daylength (light period) was extended from 6/18 h light-dark cycle to continuous light. Furthermore, light intensity is also an important factor controlling CH4 emissions of Chrysochromulina sp. and P. globosa and could therefore be a species-independent regulator of phytoplankton CH4 production.