A multi‐biomarker approach supports the use of compound‐ specific stable isotope analysis of amino acids to quantify basal carbon source use in a salt marsh consumer

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Great Lakes Research Center


Rationale:Determining the flow of energy from primary producers to higher trophiclevels in complex systems remains an important task for ecologists. Biomarkers can beused to trace carbon or energy sources contributing to an organism's tissues.However, different biomarkers vary in their ability to trace carbon sources based onhow faithfully they transfer between trophic levels. Comparing emerging biomarkertechniques with more commonly used techniques can demonstrate the relativeefficacy of each in specific systems.

Methods:Two common biomarker techniques, fatty acid analysis (FAA) and bulkstable isotope analysis (SIA), and one emerging biomarker technique, compound‐specific stable isotope analysis of amino acids (CSIA‐AA), were compared to assesstheir ability to characterize and quantify basal carbon sources supporting theseaside sparrow (Ammodramusmaritimus), a common salt marsh species.Herbivorous insect and deposit‐feeding fiddler crab biomarker values were analyzedas proxies of major terrestrial and aquatic basal carbon sources, respectively.

Results:All three biomarker techniques indicated that both terrestrial and aquaticcarbon sources were important to seaside sparrows. However, FAA could only beevaluated qualitatively, due to a currently limited understanding of trophicmodification of fatty acids between primary producer and this consumer's tissues.Quantitative stable isotope (SIA or CSIA‐AA) mixing models predicted nearly equalcontributions of terrestrial and aquatic carbon sources supporting seaside sparrows,yet estimates based on CSIA‐AA had greater precision.

Conclusions:These findings support the use of CSIA‐AA as an emerging tool toquantify the relative importance of basal carbon sources in salt marsh consumers.Integrating multiple biomarker techniques, with their differing benefits andlimitations, will help to constrain models of carbon and energy flow in futureecosystem studies.

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Rapid Commun Mass Spectrom