Journal Article

Meta-analysis of amino acid stable nitrogen isotope ratios for estimating trophic position in marine organisms

Popp, Brian N., Nielsen, Jens M., Winder, Monika

2015

Overview

Estimating trophic structures is a common approach used to retrieve information regarding energy pathways, predation, and competition in complex ecosystems. The application of amino acid (AA) compound-specific nitrogen (N) isotope analysis (CSIA) is a relatively new method used to estimate trophic position (TP) and feeding relationships in diverse organisms. Here, we conducted the first meta-analysis of δ¹⁵N AA values from measurements of 359 marine species covering four trophic levels, and compared TP estimates from AA-CSIA to literature values derived from food items, gut or stomach content analysis. We tested whether the AA trophic enrichment factor (TEF), or the ¹⁵N enrichment among different individual AAs is constant across trophic levels and whether inclusion of δ¹⁵N values from multiple AAs improves TP estimation. For the TEF of glutamic acid relative to phenylalanine (Phe) we found an average value of 6.6 ‰ across all taxa, which is significantly lower than the commonly applied 7.6 ‰. We found that organism feeding ecology influences TEF values of several trophic AAs relative to Phe, with significantly higher TEF values for herbivores compared to omnivores and carnivores, while TEF values were also significantly lower for animals excreting urea compared to ammonium. Based on the comparison of multiple model structures using the metadata of δ¹⁵N AA values we show that increasing the number of AAs in principle improves precision in TP estimation. This meta-analysis clarifies the advantages and limitations of using individual δ¹⁵N AA values as tools in trophic ecology and provides a guideline for the future application of AA-CSIA to food web studies.

• Publisher: Springer Berlin Heidelberg,Springer,Springer Nature B.V
• Subject: Amino acids / Amino Acids - analysis / Amino Acids - metabolism / Ammonium / Analysis / Animals / Aquatic Organisms - metabolism / Biomedical and Life Sciences / Carnivores / Compounds-specific isotope analysis / digestive system / Ecology / Ecosystem / Ecosystems / energy / Food Chain / Food webs / Gastrointestinal Contents - chemistry / glutamic acid / guidelines / Herbivores / HIGHLIGHTED STUDENT RESEARCH / Hydrology/Water Resources / Life Sciences / marin ekologi / Marine Ecology / Marine organisms / meta-analysis / Nitrogen / Nitrogen - analysis / Nitrogen enrichment / Nitrogen Isotopes - analysis / Omnivores / Phenylalanine / Plant Sciences / predation / Predatory Behavior / stable isotopes / Trophic ecology / Trophic enrichment factor / Trophic levels / Urea