title: Tracing carbon flow through coral reef food webs using a compound-specific stable isotope approach.
abstract: 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 (δ(13)C) 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 δ(13)C 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.
authors.affiliation: Division of Biological and Environmental Science and Engineering, Red Sea Research Center, King Abdullah University of Science and Technology, Thuwal, 23955, Saudi Arabia. kemcmaho@ucsc.edu.|Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA, 02543, USA. kemcmaho@ucsc.edu.|Institute of Marine Sciences, University of California, Santa Cruz, Santa Cruz, CA, 95064, USA. kemcmaho@ucsc.edu.
authors.forename: Kelton W
authors.initials: KW
authors.lastname: McMahon
authors.affiliation: Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA, 02543, USA.
authors.forename: Simon R
authors.initials: SR
authors.lastname: Thorrold
authors.affiliation: Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA, 02543, USA.
authors.forename: Leah A
authors.initials: LA
authors.lastname: Houghton
authors.affiliation: Division of Biological and Environmental Science and Engineering, Red Sea Research Center, King Abdullah University of Science and Technology, Thuwal, 23955, Saudi Arabia.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Berumen
mesh_terms: D000601:Amino Acids, Essential / Q000378:metabolism; D000818:Animals; D037421:Anthozoa / Q000378:metabolism; D059001:Aquatic Organisms / Q000378:metabolism*; D001499:Bayes Theorem; D018533:Biomass; D002244:Carbon / Q000378:metabolism*; D057486:Carbon Cycle; D002247:Carbon Isotopes / Q000378:metabolism; D057894:Coral Reefs; D004032:Diet; D020387:Food Chain; D009792:Oceans and Seas; D010473:Perciformes / Q000378:metabolism*; D011235:Predatory Behavior; D012624:Seaweed / Q000378:metabolism
chemical_list: D000601:Amino Acids, Essential; D002247:Carbon Isotopes; D002244:Carbon
keywords: Amino acids; Bayesian mixing model; Diet; Fish; Red Sea