Quantifying terrestrial carbon in freshwater food webs using amino acid isotope analysis: Case study with an endemic cavefish

Jia H. LIEW, Kenny W. J. CHUA, Emily R. ARSENAULT, James H. THORP, Apinun SUVARNARAKSHA, Ahmad AMIRRUDIN, Darren C. J. YEO

Research output: Journal PublicationsJournal Article (refereed)peer-review

21 Citations (Scopus)


1. Flow of terrestrial carbon though aquatic ecosystems (allochthony) is an important but underestimated component of the global carbon cycle. A lack of clear consensus about the importance of allochthonous (terrestrial) organic carbon is sometimes attributed to uncertainties associated with conventional ‘bulk’ isotope data, the most widely used ecological tracer.

2. Amino acid‐specific isotope analysis is an emerging research method promising to address existing limitations of bulk C and N isotope analyses. We tested the efficacy of amino acid δ13C data as a generalizable measure of allochthony by analysing an aggregated dataset (n = 168) of primary and secondary data of carbon sources from disparate geographical locations across the globe.

3. We found the δ13C fingerprints amino acids to be consistently distinct between allochthonous (terrestrial) and autochthonous (aquatic) carbon sources. We also found that our approach is most effective when we use only essential amino acid tracers (i.e. isoleucine, leucine, phenylalanine, threonine and valine). Predictive trends in δ13C fingerprints appear to be largely compatible across studies and/or laboratories.

4. As a case study, we used this approach to quantify the contribution of terrestrial carbon to an endemic cavefish, Cryptotora thamicola, and found that its biomass was comprised largely of autochthonous carbon (~75%).
Original languageEnglish
Pages (from-to)1594-1605
Number of pages12
JournalMethods in Ecology and Evolution
Issue number9
Early online date27 May 2019
Publication statusPublished - 1 Sept 2019
Externally publishedYes

Bibliographical note

We gratefully acknowledge an AcRF Tier 1 grant from the Singapore Ministry of Education (National University of Singapore Grant No. R‐154‐000‐A20‐114), the National Parks Board (National University of Singapore Grant No. R‐154‐000‐A55‐490), the Maehongsorn province Education for Life Project (2017) and the Fish Diversity in North Thailand, Nagao Natural Environment Foundation (2008) for financial support. J.H.T. and E.R.A. were partially supported by the macrosystem ecology grant (#1442595) from the U.S. National Science Foundation. We thank Chris Yarnes from the University of California Davis for sample analysis and Weerapong Dechjinda from the Chiang Mai Fisheries Department for support during field excursions. We also thank David Soto and two anonymous reviewers for helpful and insightful comments.


  • allochthonous organic carbon
  • amino acid-specific isotope analysis
  • aquatic ecosystems
  • carbon cycle
  • community ecology
  • food webs
  • species interactions
  • terrestrial carbon


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