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Abstract Eukaryotic microalgae play critical roles in the structure and function of marine food webs. The contribution of microalgae to food webs can be tracked using compound‐specific isotope analysis of amino acids (CSIA‐AA). Previous CSIA‐AA studies have defined eukaryotic microalgae as a single functional group in food web mixing models, despite their vast taxonomic and ecological diversity. Using controlled cultures, this work characterizes the amino acidδ13C (δ13CAA) fingerprints—a multivariate metric of amino acid carbon isotope values—of four major groups of eukaryotic microalgae: diatoms, dinoflagellates, raphidophytes, and prasinophytes. We found excellent separation of essential amino acidδ13C (δ13CEAA) fingerprints among four microalgal groups (mean posterior probability reclassification of 99.2 ± 2.9%). We also quantified temperature effects, a primary driver of microalgal bulk carbon isotope variability, on the fidelity ofδ13CAAfingerprints. A 10°C range in temperature conditions did not have significant impacts on variance inδ13CAAvalues or the diagnostic microalgalδ13CEAAfingerprints. Theseδ13CEAAfingerprints were used to identify primary producers at the base of food webs supporting consumers in two contrasting systems: (1) penguins feeding in a diatom‐based food web and (2) mixotrophic corals receiving amino acids directly from autotrophic endosymbiotic dinoflagellates and indirectly from water column diatoms, prasinophytes, and cyanobacteria, likely via heterotrophic feeding on zooplankton. The increased taxonomic specificity of CSIA‐AA fingerprints developed here will greatly improve future efforts to reconstruct the contribution of diverse eukaryotic microalgae to the sources and cycling of organic matter in food web dynamics and biogeochemical cycling studies.
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Variation in gut microbial contribution of essential amino acids to host protein metabolism in a wild small mammal community
Abstract Herbivory is a dominant feeding strategy among animals, yet herbivores are often protein limited. The gut microbiome is hypothesized to help maintain host protein balance by provisioning essential macromolecules, but this has never been tested in wild consumers. Using amino acid carbon (δ13C) and nitrogen (δ15N) isotope analysis, we estimated the proportional contributions of essential amino acids (AAESS) synthesized by gut microbes to five co‐occurring desert rodents representing herbivorous, omnivorous and insectivorous functional groups. We found that herbivorous rodents occupying lower trophic positions (Dipodomysspp.) routed a substantial proportion (~40%–50%) of their AAESSfrom gut microbes, while higher trophic level omnivores (Peromyscusspp.) and insectivores (Onychomys arenicola) obtained most of their AAESS(~58%) from plant‐based energy channels but still received ~20% of their AAESSfrom gut microbes. These findings empirically demonstrate that gut microbes play a key functional role in host protein metabolism in wild animals.
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- PAR ID:
- 10435173
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Ecology Letters
- Volume:
- 26
- Issue:
- 8
- ISSN:
- 1461-023X
- Page Range / eLocation ID:
- p. 1359-1369
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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