TY - JOUR T1 - Isotopic and elemental compositions reveal density‐dependent nutrition pathways in a population of mixotrophic jellyfish A1 - Djeghri,Nicolas A1 - Pondaven,Philippe A1 - Stockenreiter,Maria A1 - Behl,Stephan A1 - Huang,Jessica Y. T. A1 - Hansen,Thomas A1 - Patris,Sharon A1 - Ucharm,Gerda A1 - Stibor,Herwig AD - Laboratoire des Sciences de l'Environnement Marin, LEMAR Institut Unversitaire Européen, IUEMUniversité de Brest, UBO Rue Dumont d'Urville Plouzané 29280, France AD - Department Biologie II, Aquatische Ökologie Ludwig‐Maximilians‐Universität München Großhaderner Str. 2 Planegg‐Martinsried 82152, Germany AD - Department of Marine Ecology GEOMAR Helmholtz Centre for Ocean Research Kiel Experimental Ecology‐Food Webs Düsternbrooker Weg 20 Kiel24015, Germany AD - Coral Reef Research Foundation PO Box 1765 Koror PW96940, Palau UR - https://archimer.ifremer.fr/doc/00663/77469/ DO - 10.1002/ecs2.3295 KW - density dependence KW - jellyfish KW - marine lakes KW - mixotrophy KW - stable isotopes KW - symbiosis KW - zooxanthellae N2 - Mixotrophic organisms are increasingly recognized as important components of ecosystems, but the factors controlling their nutrition pathways (in particular their autotrophy–heterotrophy balance) are little known. Both autotrophy and heterotrophy are expected to respond to density‐dependent mechanisms but not necessarily in the same direction and/or strength. We hypothesize that the autotrophy–heterotrophy balance of mixotrophic organisms might therefore be a function of population densities. To investigate this relationship, we sampled mixotrophic jellyfish holobionts (host, Mastigias papua etpisoni; symbiont, Cladocopium sp.) in a marine lake (Palau, Micronesia) on six occasions (from 2010 to 2018). Over this period, population densities varied ~100 fold. We characterized the nutrition of the holobionts using the δ13C and δ15N signatures as well as C:N ratios. δ13C values increased and δ15N values decreased with increasing population densities (respectively, R2 = 0.86 and 0.70, P < 0.05). Although less distinct, C:N ratios increased with increasing population densities (R2 = 0.59, 0.1 > P > 0.05). This indicates that the autotrophy–heterotrophy balance tends toward autotrophy when population densities increase. We propose that the availability of zooplanktonic prey is the main driver of this pattern. These results demonstrate that the autotrophy–heterotrophy balance of mixotrophic jellyfishes can be tightly regulated by density‐dependent mechanisms. Y1 - 2020/11 PB - Wiley JF - Ecosphere SN - 2150-8925 VL - 11 IS - 11 ID - 77469 ER -