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Marine Ecology Progress Series

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MEPS 412:103-112 (2010)  -  DOI: https://doi.org/10.3354/meps08674

Stable isotopes reveal limitations in C and N assimilation in the Caribbean reef corals Madracis auretenra, M. carmabi and M. formosa

C. Maier1,2,3,*, M. G. Weinbauer2,3, J. Pätzold4

1Royal Netherlands Institute for Sea Research (NIOZ), PO Box 59, 1790 AB Den Burg, Texel, The Netherlands
2CNRS-INSU, Laboratoire d’Océanographie de Villefranche, BP28, 06234 Villefranche-sur-Mer Cedex, France
3Université Pierre et Marie Curie-Paris6, Laboratoire d’Océanographie de Villefranche, 06230 Villefranche-sur-Mer, France
4MARUM – Center for Marine Environmental Sciences, University of Bremen, PO Box 330440, 28334 Bremen, Germany

ABSTRACT: We used tissue δ15N and δ13C to elucidate nitrogen and carbon utilization in 3 branching coral species of the genus Madracis. Coral branches were sampled between 5 and 47 m water depth, and tissue was sub-sampled from the tips and sides of branches. Photosynthetically active radiation (PAR) ranged between 1 and 71% of surface PAR. There was a good correlation between δ15N and δ13C, and these had similar ranges of 5.6 and 5.2‰, respectively, suggesting that light-driven photosynthesis is a strong factor in isotope fractionation. However, at shallow depths, δ13C decreased more strongly while δ15N remained constant, while at deeper depths δ15N decreased while δ13C remained constant. Comparisons of δ13C in polyps and zooxanthellae revealed that prey capture at the tips of branches was more pronounced than at the corresponding sideward-facing positions and that corals at deeper depths did not increase their food uptake to compensate for a decrease in photosynthetic carbon assimilation. This indicates that foraging in branching Madracis depends on current regimes and prey encounter rather than selective food capture. The systematic analysis of tissue δ15N along a steep depth gradient revealed that the shallow-water coral M. auretenra was nitrogen limited throughout its entire depth range.


KEY WORDS: Stable isotopes · Nitrogen limitation · Carbon · Heterotrophy · Scleractinian coral


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Cite this article as: Maier C, Weinbauer MG, Pätzold J (2010) Stable isotopes reveal limitations in C and N assimilation in the Caribbean reef corals Madracis auretenra, M. carmabi and M. formosa. Mar Ecol Prog Ser 412:103-112. https://doi.org/10.3354/meps08674

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