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MEPS prepress abstract   -  DOI: https://doi.org/10.3354/meps13707

High trophic plasticity in the mixotrophic Mastigias papua-Symbiodiniaceae holobiont: implications for the ecology of zooxanthellate jellyfishes

Nicolas Djeghri*, Philippe Pondaven, Fabienne Le Grand, Antoine Bideau, Nolwenn Duquesne, Maria Stockenreiter, Stephan Behl, Jessica Y-T Huang, Thomas Hansen, Sharon Patris, Gerda Ucharm, Herwig Stibor

*Corresponding author:

ABSTRACT: The trophic ecology of mixotrophic, zooxanthellate, jellyfishes potentially spans a wide spectrum between autotrophy and heterotrophy. However, their degree of trophic plasticity along this spectrum is little known. To better characterize their trophic ecology, we sampled the zooxanthellate medusae Mastigias papua in contrasted environments and sizes in Palau (Micronesia). We characterized their trophic ecology using isotopic (bulk δ13C and δ15N), elemental (C:N ratios), and fatty acid compositions. The different trophic indicators used were correlated or anti-correlated as expected (Pearson’s correlation coefficient > 0.5 or < -0.5 in 91.1% of cases, p-values < 0.05) indicating a good agreement. The M. papua sampled were ordered in a trophic spectrum between autotrophy and heterotrophy (supported by decreasing δ13C, C:N, NLFA:TLFA, n-3:n-6 and increasing δ15N, EPA:DHA). This trophic spectrum was mostly driven by sampling location with only little influence of medusae size. Moreover, previous observations show that in a given location, the trophic ecology of M. papua can change over time. Thus, the positions on the trophic spectrum of the populations sampled here are not fixed, suggesting a high trophic plasticity in M. papua. The heterotrophic end of the trophic spectrum was occupied by non-symbiotic M. papua, whereas the literature indicates that the autotrophic end of the spectrum corresponds to dominant autotrophy where > 100% of carbon requirements are obtain by photosynthesis. This high trophic plasticity has critical implications for the trophic ecology and blooming ability of zooxanthellate jellyfishes.