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Turnover rates of carbon and nitrogen stable isotopes in the amphipod Gammarus aequicauda: insights for trophic studies of Mediterranean macrophytodetritus accumulation.
Remy, François; Melchior, Aurélie; Darchambeau, François et al.
2014 9th IsoEcol, International Conference on the Applications of Stable Isotope Techniques to Ecological Studies
 

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Keywords :
Stable isotope; Turnover rate; Trophic ecology
Abstract :
[en] A quite diverse and abundant macrofauna assemblage is found in the Mediterranean Sea in exported Posidonia oceanica macrophytodétritus accumulations along with meiofauna, microalgae, fungi and bacteria. This study focused on a dominant vagile macroinvertebrate species living and feeding in exported dead P.oceanica leaves litter from Calvi Bay (Corsica, France): Gammarus aequicauda. Results of gut content observations and stable isotope analysis (SIAR data) showed clearly that G. aequicauda is the most important dead P. oceanica consumer with up to 50% of dead leaves contribution. An isotopic turnover experiment was conducted with 3 controlled simultaneous treatments: 1. amphipod feeding for 43 days, 2. Green algae feeding for 30 days and 3. Posidonia oceanica litter feeding for 30 days. Individuals (n = 12 to 16) have been sampled every 7 days and whole individual stable isotope analysis have been conducted. An exponential decay regression model and calculations resulted in half-lives for C ranging from 11.72 days (treatment 1) to 51.62 days (treatment 3). Treatment 2 data did not allow us to fit a curve, consequence of a potentially very low turnover rate. For N, no significant increase or decrease of the δ15N values have been observed, and we thus concluded that δ15N was at the equilibrium from the beginning to the end of the experiment. It appears that amphipods feeding on low quality food (high to very high C/N ratio) like algae and Neptune grass dead leaves, show a lower turnover rate for C than amphipods feeding on a high quality animal food (low C/N ratio). Carbon and Nitrogen stable isotope “Trophic Enrichment Factor” (TEF) were calculated for treatments where δ13C or δ15N were at the equilibrium at the end of the experiment. Calculated TEF for nitrogen ranged from 0.53‰ ± 0.439 to 0.96‰ ± 0.424 for treatment 2 and 3 (consistent with detritus-feeder invertebrate values) and was 2.91‰ ± 0.558 for treatment 1 (consistent with predator invertebrate values). For C calculations, a TEF of 0,81‰± 0.39 for treatment 1 and a TEF of 1.19‰ ± 0.824 for treatment 3 were calculated.
Research center :
MARE - Centre Interfacultaire de Recherches en Océanologie - ULiège
Disciplines :
Zoology
Aquatic sciences & oceanology
Environmental sciences & ecology
Author, co-author :
Remy, François ;  Université de Liège - ULiège > Département de Biologie, Ecologie et Evolution > Océanologie
Melchior, Aurélie
Darchambeau, François ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Océanographie chimique
Lepoint, Gilles  ;  Université de Liège - ULiège > Département de Biologie, Ecologie et Evolution > Océanologie
Language :
English
Title :
Turnover rates of carbon and nitrogen stable isotopes in the amphipod Gammarus aequicauda: insights for trophic studies of Mediterranean macrophytodetritus accumulation.
Alternative titles :
[en] Taux de turnover des isotopes stables du carbone et de l'azote chez l'amphipode Gammarus aequicauda : aperçu pour les études trophiques des accumulations marines de macrophytodétritus en Méditerranée.
Publication date :
04 August 2014
Event name :
 9th IsoEcol, International Conference on the Applications of Stable Isotope Techniques to Ecological Studies
Event organizer :
University of Western Australia, CSIRO
Event place :
Perth, Australia
Event date :
du 03 août 2014 au 08 août 2014
Audience :
International
Funders :
F.R.S.-FNRS - Fonds de la Recherche Scientifique [BE]
Commentary :
Expérience réalisée dans le cadre du mémoire de Mlle Aurélie Melchior.
Available on ORBi :
since 26 August 2014

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