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Global trophic position comparison of two dominant mesopelagic fish families (Myctophidae, Stomiidae) using amino acid nitrogen isotopicanalyses
Citation:
CHOY, C. A., P. C. DAVISON, J. C. DRAZEN, A. FLYNN, E. J. GIER, J. HOFFMAN, J. P. MCCLAIN-COUNTS, T. W. MILLER, B. N. POPP, S. W. ROSS, AND T. T. SUTTON. Global trophic position comparison of two dominant mesopelagic fish families (Myctophidae, Stomiidae) using amino acid nitrogen isotopicanalyses. PLOS ONE . Public Library of Science, San Francisco, CA, 7(11):1-8, (2012).
Impact/Purpose:
We examined the biogeochemical and ecological mechanisms responsible for variability in bulk tissue and amino acid (AA) stable nitrogen isotope compositions in two groups of important mesopelagic fish families, Myctophidae (lanternfishes) and Stomiidae (dragonfishes), from five different oceanographic regions across the World’s oceans. Using the ?15N values of individual AAs we quantified trophic positions (TPs) of these fishes and showed that despite large variability in bulk tissue ?15N values, TPs are nearly uniform within both families of fishes across all regions. Differences in the ?15N values of phenylalanine (?15Nphe) and bulk tissue ?13C values confirmed that bulk tissue ?15N values reflect region-specific water mass biogeochemistry controlling ?15N values at the base of the food web. Isotopic variability in phytoplankton is inherited by the fish consumers, confounding the interpretation of TPs derived from bulk tissue ?15N values and regional comparisons. TPs calculated from AA isotopic analyses for the lanternfishes (TP ~2.9) largely align with expectations from stomach content (SC) studies describing these fishes as predominantly zooplanktivorous (TP ~3.2). In contrast, TPs calculated from AA isotopic analyses for dragonfishes (TP ~3.2) were lower than expected given previous SC studies, which report that dragonfishes are piscivorous (TP~4.1) across all regions. Our TP estimates suggest that dragonfishes are more similar to lanternfishes and are not strict piscivores. We discuss food web implications and possible ecological explanations for this trophic re-evaluation and discuss the utility of the AA compound specific nitrogen isotope approach in providing new information to evaluate marine food web structure.
Description:
We examined the biogeochemical and ecological mechanisms responsible for variability in bulk tissue and amino acid (AA) stable nitrogen isotope compositions in two groups of important mesopelagic fish families, Myctophidae (lanternfishes) and Stomiidae (dragonfishes), from five different oceanographic regions across the World’s oceans. Using the ?15N values of individual AAs we quantified trophic positions (TPs) of these fishes and showed that despite large variability in bulk tissue ?15N values, TPs are nearly uniform within both families of fishes across all regions. Differences in the ?15N values of phenylalanine (?15Nphe) and bulk tissue ?13C values confirmed that bulk tissue ?15N values reflect region-specific water mass biogeochemistry controlling ?15N values at the base of the food web. Isotopic variability in phytoplankton is inherited by the fish consumers, confounding the interpretation of TPs derived from bulk tissue ?15N values and regional comparisons. TPs calculated from AA isotopic analyses for the lanternfishes (TP ~2.9) largely align with expectations from stomach content (SC) studies describing these fishes as predominantly zooplanktivorous (TP ~3.2). In contrast, TPs calculated from AA isotopic analyses for dragonfishes (TP ~3.2) were lower than expected given previous SC studies, which report that dragonfishes are piscivorous (TP~4.1) across all regions. Our TP estimates suggest that dragonfishes are more similar to lanternfishes and are not strict piscivores. We discuss food web implications and possible ecological explanations for this trophic re-evaluation and discuss the utility of the AA compound specific nitrogen isotope approach in providing new information to evaluate marine food web structure.
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Global trophic position comparison of two dominant mesopelagic fish families (Myctophidae, Stomiidae) using amino acid nitrogen isotopicanalyses