Temporal dietary shift in jellyfish revealed by stable isotope analysis.

Jamileh Javidpour,Jan Dierking,Agnes Mittermayr,Ashlie N Cipriano-Maack

doi:10.1007/s00227-016-2892-0

Jamileh Javidpour, Jan Dierking + Show 2 more

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https://doi.org/10.1007/s00227-016-2892-0

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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 of Aurelia aurita and Cyanea capillata in the period between June and October 2011. A strong and significant temporal change in all SI values of A. aurita was 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 in A. aurita from 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 of C. 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 of A. aurita in the diet of C. capillata than 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.Electronic supplementary materialThe online version of this article (doi:10.1007/s00227-016-2892-0) contains supplementary material, which is available to authorized users.

Highlights

Global awareness has been drawn to the increase in jellyfish blooms due to their possible negative impacts on ecosystem goods and services, such as interference with tourism, aquaculture, fishing operations and coastal industrial intakes (Richardson et al 2009; Condon et al 2012)
MixSIR is a graphical user interface (GUI) built on MATLAB that employs an algorithm based on a Bayesian framework to determine the probability distributions for proportional contributions of each food source to the diet mix of a consumer (Semmens and Moore 2008)
MixSIR was run with δ13C, δ15N and δ34S values of A. aurita and C. capillata on a bi-weekly basis

Summary

Introduction

Global awareness has been drawn to the increase in jellyfish blooms due to their possible negative impacts on ecosystem goods and services, such as interference with tourism, aquaculture, fishing operations and coastal industrial intakes (Richardson et al 2009; Condon et al 2012). By comparing SI values of a consumer over time, information on trophic transfer, carbon and energy flux, and contribution of food sources to the diet of an organism can be gained (Kling et al 1992; Cabana and Rasmussen 1996; Ponsard and Arditi 2000). Δ13C and δ15N have been most commonly used to address ecological questions (review by Grey 2006), since carbon (C) isotopes are well suited to identify the primary carbon sources at the base of a food web (Peterson 1999) and nitrogen (N) isotopes are a good tracer of the trophic position of an organism (Cabana and Rasmussen 1996). The use of additional elements has increased recently, e.g., sulfur (S) isotopes can reveal whether a food web is driven by benthic or pelagic primary production (Hansen et al 2009; Jaschinski et al 2008)

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