Bulk vs. amino acid stable N isotope estimations of metabolic status and contributions of nitrogen fixation to size-fractionated zooplankton biomass in the subtropical N Atlantic

摘要: Abstract A comparative analysis of natural abundance stable N isotopes (δ 15 N) in individual amino acids and bulk organic matter size-fractionated plankton revealed the differential impact nitrogen fixation through food web a transect across subtropical North Atlantic. All δ measurements showed low values central region, followed by western zone, while maximum were found eastern zone. These results consistent with prevalence zones, influence west Africa upwelling Use compound-specific acid isotope data (CSI-AA) relatively variability diazotrophic within different size fractions, high size. Explicit CSI-AA trophic position estimates small increase mean class varied narrow range 1.8–2.5), lowest High correlations between (in particular Phe Thr), as well reconstructed total protein values, suggest set new relationships that may be important to tracing direct contributions recycling ocean, including detrital pools. Overall, these represent most detailed investigation classes date, indicated greater importance than suggested concurrent N, large fixing organisms or rates.