Amino acid carbon isotope fingerprints are unique among eukaryotic microalgal taxonomic groups

Eukaryotic microalgae play critical roles in the structure and function of marine food webs. The contribution to webs can be tracked using compound-specific isotope analysis amino acids (CSIA-AA). Previous CSIA-AA studies have defined eukaryotic as a single functional group web mixing models, despite their vast taxonomic ecological diversity. Using controlled cultures, this work characterizes acid δ13C (δ13CAA) fingerprints—a multivariate metric carbon values—of four major groups microalgae: diatoms, dinoflagellates, raphidophytes, prasinophytes. We found excellent separation essential (δ13CEAA) fingerprints among microalgal (mean posterior probability reclassification 99.2 ± 2.9%). also quantified temperature effects, primary driver bulk variability, on fidelity δ13CAA fingerprints. A 10°C range conditions did not significant impacts variance values or diagnostic δ13CEAA These were used identify producers at base supporting consumers two contrasting systems: (1) penguins feeding diatom-based (2) mixotrophic corals receiving directly from autotrophic endosymbiotic dinoflagellates indirectly water column prasinophytes, cyanobacteria, likely via heterotrophic zooplankton. increased specificity developed here will greatly improve future efforts reconstruct diverse sources cycling organic matter dynamics biogeochemical studies.