title: Temporal dietary shift in jellyfish revealed by stable isotope analysis.
abstract: A temporal change in the stable isotope (SI) composition of jellyfish in the Kiel Fjord, Western Baltic Sea, was documented by analyzing δ13C, δ15N and δ34S of bell tissue ofAurelia auritaandCyanea capillatain the period between June and October 2011. A strong and significant temporal change in all SI values ofA. auritawas found, including an increase of ~3 ‰ in δ13C, a decrease of ~4 ‰ in δ15N and sharp decline of ~7 ‰ in δ34S. While knowledge gaps in jellyfish isotope ecology, in particular the lack of reliable trophic enrichment factors, call for a conservative interpretation of our data, observed changes in particular in δ34S, as indicated by means of a MixSIR mixing model, would be consistent with a temporal dietary shift inA. auritafrom mesozooplankton (>150 µm) to microplankton and small re-suspended particles (0.8-20 µm) from the benthos. Presence of a hitherto unidentified food source not included in the model could also contribute to the shift. During the 2-month occurrence ofC. capillata, its isotope composition remained stable and was consistent with a mainly mesozooplanktonic diet. Mixing model output, mainly driven by δ34S values, indicated a lower proportion ofA. auritain the diet ofC. capillatathan previously reported, and thus to a potentially lesser importance of intraguild predation among jellyfish in the Kiel Fjord. Overall, our results clearly highlighted the potential for substantial intraspecific isotopic seasonal variation in jellyfish, which should be taken into account in future feeding ecology studies on this group.
authors.affiliation: GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany.
authors.forename: Jamileh
authors.initials: J
authors.lastname: Javidpour
authors.affiliation: Biological, Earth and Environmental Science, University College Cork, Cooperage Building, Distillery Fields, North Mall, Cork, Ireland.
authors.forename: Ashlie N
authors.initials: AN
authors.lastname: Cipriano-Maack
authors.affiliation: Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543 USA.
authors.forename: Agnes
authors.initials: A
authors.lastname: Mittermayr
authors.affiliation: GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Dierking