Virginia Institute of Marine Science
The delta N-15 values of organisms are commonly used across diverse ecosystems to estimate trophic position and infer trophic connectivity. We undertook a novel cross-basin comparison of trophic position in two ecologically well-characterized and different groups of dominant mid-water fish consumers using amino acid nitrogen isotope compositions. We found that trophic positions estimated from the delta N-15 values of individual amino acids are nearly uniform within both families of these fishes across five global regions despite great variability in bulk tissue delta N-15 values. Regional differences in the delta N-15 values of phenylalanine confirmed that bulk tissue delta N-15 values reflect region-specific water mass biogeochemistry controlling delta N-15 values at the base of the food web. Trophic positions calculated from amino acid isotopic analyses (AA-TP) for lanternfishes (family Myctophidae) (AA-TP similar to 2.9) largely align with expectations from stomach content studies (TP similar to 3.2), while AA-TPs for dragonfishes (family Stomiidae) (AA-TP similar to 3.2) were lower than TPs derived from stomach content studies (TP similar to 4.1). We demonstrate that amino acid nitrogen isotope analysis can overcome shortcomings of bulk tissue isotope analysis across biogeochemically distinct systems to provide globally comparative information regarding marine food web structure.
NORTH PACIFIC-OCEAN; AQUATIC FOOD-WEB; GULF-OF-MEXICO; STOMACH CONTENTS; STABLE ISOTOPES; PISCES; DIET; MICRONEKTON; ASSEMBLAGE; ABUNDANCE
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This research was funded by National Science Foundation (NSF) grant # OCE-1041329 to B.N.P. and J.C.D., NSF grant # OCE-0623551 to T.T.S., and by the Pelagic Fisheries Research Program via Cooperative Agreement NA17RJ123 between the Joint Institute for Marine and Atmospheric Research and the National Oceanic and Atmospheric Administration to J.C.D. and B.N.P. Field collections and data analyses for GOM samples were supported by grants to S.W.R. by the Department of the Interior U.S.G.S. (Cooperative Agreement 05HQAG0009, subagreements 05099HS004 and 5099HS0013). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Choy CA, Davison PC, Drazen JC, Flynn A, Gier EJ, et al. (2012) Global Trophic Position Comparison of Two Dominant Mesopelagic Fish Families (Myctophidae, Stomiidae) Using Amino Acid Nitrogen Isotopic Analyses. PLoS ONE 7(11): e50133. doi:10.1371/journal.pone.0050133