δ13C, δ15N, and C:N ratios as nutrition indicators of zooxanthellate jellyfishes: insights from an experimental approach

Type Article
Date 2020-01
Language English
Author(s) Djeghri Nicolas1, Stibor Herwig2, Lebeau Oanez3, Pondaven Philippe1
Affiliation(s) 1 : Université de Brest, UBO, Institut Universitaire Européen de la Mer, IUEM, Laboratoire des sciences de l'Environnement Marin, UMR 6539 LEMAR, Technopôle Brest Iroise, Rue Dumont d'Urville, 29280 Plouzané, France
2 : Ludwig-Maximilians-Universität München, Department Biologie II, Aquatische Ökologie, Großhaderner Str. 2, 82152, Planegg, Martinsried, Germany
3 : Université de Brest, UBO, Institut Universitaire Européen de la Mer, IUEM, UMS 3113, Technopôle Brest Iroise, Rue Dumont d'Urville, 29280 Plouzané, France
Source Journal Of Experimental Marine Biology And Ecology (0022-0981) (Elsevier BV), 2020-01 , Vol. 522 , P. 151257 (8p.)
DOI 10.1016/j.jembe.2019.151257
WOS© Times Cited 5
Keyword(s) Stable isotopes, C:N ratios, Photosymbiosis, Mixotrophy, Scyphozoa, Zooxanthellae
Abstract

Some jellyfish host zooxanthellae in their tissues (mostly from the family Symbiodiniaceae; Dinophyceae) and supplement their heterotrophic nutrition with their symbiont's photosynthates. The mixotrophy of zooxanthellate jellyfishes (as holobionts) renders the study of their nutrition, growth, and population dynamics complicated. Here, we used an experimental approach to assess how carbon and nitrogen stable isotopes (δ13C and δ15N) as well as the elemental composition (C:N ratios) of zooxanthellate jellyfishes are affected by variations in nutrition sources: i. e. predation (heterotrophic) versus photosynthesis (autotrophic). Our laboratory experiment, conducted on the zooxanthellate jellyfish Cassiopea sp. medusae (including symbionts) in the presence or absence of light and prey during 24 days, showed conclusive results. Presence of light decreased δ15N, increased δ13C and C:N ratios, whereas presence of prey increased δ15N, and decreased δ13C and C:N ratios. The medusae incubated with both light and prey had intermediate δ15N, δ13C and C:N ratios. Variations in zooxanthellate jellyfishes' nutrition sources (autotrophy vs. heterotrophy) are thus reflected by their isotopic and elemental composition. By disentangling the effects of autotrophy and of heterotrophy on zooxanthellate jellyfish isotopic and elemental compositions, these results would help to interpret the values of δ13C, δ15N and C:N ratios that can be observed on these organisms in fieldwork studies.

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