Nitrogen isotope fractionation during nitrate, ammonium and urea uptake by marine diatoms and coccolithophores under various conditions of N availability

摘要: Stable isotopes of N provide a new approach to the study algal production in ocean, yet knowledge isotope fractionation (epsilon) various oceanic regimes is lacking. Here we report large and rapid changes composition (delta(15)N) 2 coastal diatoms clones (open coastal) coccolithophore grown simultaneous presence nitrate, ammonium urea under varying conditions availability (i.e. N-sufficiency N-starvation followed by N-resupply) hence different physiological states, During N-sufficiency, delta(15)N particulate organic (PON) was well reproduced, using model derived from Rayleigh distillation theory, with constant epsilon similar that for growth on each individual source. However, following N-resupply, variations delta(15)N(PON) could be explained only case open ocean Emiliania huxleyi, N-sufficient conditions. It concluded mechanism changed rapidly 3 clones. E. huxleyi isolated Subarctic Pacific Ocean, no evidence change found, suggesting perhaps species can quickly recover N-depleted