Coupled nitrate N and O stable isotope fractionation by a natural marine plankton consortium

摘要: The stable nitrogen (N) and oxygen (O) isotope ratios (15N/14N 18O/16O, respectively) of nitrate (NO3-) were measured during incubations freshly collected seawater to investigate the effect light intensity on fractionation associated with assimilation possible co-occurring regeneration nitrification by in situ plankton communities. Surface was off coast Vancouver, Canada, late fall summer incubated under different laboratory conditions for 10 30 days, respectively. In experiments, parallel supplemented 15NH4+ H218O tracers monitor nitrification. Differences irradiance resulted reduced consumption at low light, but had no distinguishable impact N-isotope (15e) NO3- assimilation, which ranged between 5 8‰. late-summer community incubations, contrast, showed growth rates more elevated 15e 11.9 ± 0.4‰, compared 8.4 0.3‰ high-light conditions. seasonal differences could reflect physiological adaptations irradiance, such that their incubation did not elicit increase proportional cellular efflux required raise effect. both ratio coincident rises δ15N δ18O comparable previous monoculture phytoplankton a ∆δ18O:∆δ15N ~1, regardless level. A decoupling is expected if occurs concomitantly assimilation. lack best explained absence significant any our study’s treatments, an interpretation supported inability identify tracer 15N 18O uptake into pool incubations.