Lack of an effect of light on methylamine uptake by phytoplankton 1

Light‐dependent ammonium up take was studied with an analogue of ammonium, methylamine. This analogue is nonassimilable by phytoplankton so far examined; a low percentage is incorporated into macromolecules, so that the uptake or membrane transport process can be measured with little complication from assimilatory process. Single label incubations ([ 14 C] methylamine) and dual label incubations ([ 3 H] methylamine and [ 14 C]bicarbonate) were used to show that there is no light‐dependent MeA uptake in an oceanic diatom, dinoflagellate, coccolithophorid, or in natural populations (particles > 1‐ µ m diam).