Tracing carbon flow through coral reef food webs using a compound-specific stable isotope approach
Coral reefs support spectacularly productive and diverse communities in tropical and sub-tropical waters throughout the world’s oceans. Debate continues, however, on the degree to which reef biomass is supported by new water column production, benthic primary production, and recycled detrital carbon (C). We coupled compound-specific stable C isotope ratio (δ13C) analyses with Bayesian mixing models to quantify C flow from primary producers to coral reef fishes across multiple feeding guilds and trophic positions in the Red Sea. Analyses of reef fishes with putative diets composed primarily of zooplankton (Amblyglyphidodon indicus), benthic macroalgae (Stegastes nigricans), reef-associated detritus (Ctenochaetus striatus), and coral tissue (Chaetodon trifascialis) confirmed that δ13C values of essential amino acids from all baseline C sources were both isotopically diagnostic and accurately recorded in consumer tissues. While all four source end-members contributed to the production of coral reef fishes in our study, a single-source end-member often dominated dietary C assimilation of a given species, even for highly mobile, generalist top predators. Microbially reworked detritus was an important secondary C source for most species. Seascape configuration played an important role in structuring resource utilization patterns. For instance, Lutjanus ehrenbergii showed a significant shift from a benthic macroalgal food web on shelf reefs (71 ± 13 % of dietary C) to a phytoplankton-based food web (72 ± 11 %) on oceanic reefs. Our work provides insights into the roles that diverse C sources play in the structure and function of coral reef ecosystems and illustrates a powerful fingerprinting method to develop and test nutritional frameworks for understanding resource utilization.
KeywordsAmino acids Bayesian mixing model Diet Fish Red Sea
This research was based on work supported by Awards USA 00002 and KSA 00011 from King Abdullah University of Science and Technology (KAUST); additional funding was provided by the Woods Hole Oceanographic Institution (WHOI), a KAUST-WHOI award (SPCF-7000000104), and KAUST baseline research funds. We thank E. Mason and the Dream Divers crew for boat and dive operation support, C. Braun for creating the site map, and the following people for field assistance: C. Braun, T. Sinclair-Taylor, M. Priest, G. Nanninga, N. desRosiers, P. de la Torre, J. Bouwmeester, L.-L. Hamady. We also thank two anonymous reviewers and the handling editor for valuable comments on this paper.
Author contribution statement
K. W. M., S. R. T., and M. L. B. conceived of and designed the study; K. W. M. and M. L. B. conducted the fieldwork; K. W. M. and L. A. H. conducted the laboratory analyses; K. W. M. and S. R. T. analyzed the data and wrote the manuscript; M. L. B. and L. A. H. revised and edited the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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