Amino acids compound-specific nitrogen stable isotope analysis (AA-CSIA) is an emerging tool in ecology for understanding trophic system dynamics. While it has been successfully used for several independent studies across a range of environments and study locations, researchers have encountered calculation issues for determining trophic position values. Most studies introduce modifications to the constants of trophic position equation calculations, but then fail to account for the equation variations when comparing across separate research studies. The broad acceptance of this approach is anchored in an underlying presumption that no addition of the exogenous nitrogen atom occurs in the different methods; and therefore, such variations should not affect the outcome. In this paper, we evaluate the use of the EZfaast amino acid derivatization kit (chloroformate) and compare it to the isotopic results of two other derivatization methods. We highlight new considerations for working with AA-CSIA that might account for some of the variations in the results and lead researchers to modify constants in the equation. This study concludes that developing unique constants per derivatization method is required to have more accurate cross-study comparisons of trophic positions.
Bibliographical noteFunding Information:
This research was supported by the Wolfson Foundation, Kahn Foundation, J. Isaacs Charitable Foundation, and the Kadas Charitable Trust.
We would like to thank Drs. Tali Mass, Nir Stern, and Christine Ferrier Pages for their assistance in collecting samples at the various sites. Funding. This research was supported by the Wolfson Foundation, Kahn Foundation, J. Isaacs Charitable Foundation, and the Kadas Charitable Trust.
© Copyright © 2020 Martinez, Lalzar, Shemesh, Einbinder, Goodman Tchernov and Tchernov.
- eastern Mediterranean Sea
- food web
- nitrogen isotopic composition
- trophic discrimination factor
ASJC Scopus subject areas
- Global and Planetary Change
- Aquatic Science
- Water Science and Technology
- Environmental Science (miscellaneous)
- Ocean Engineering