Primary producer contribution to a coral reef exometabolome

Andreas Haas1, Craig Nelson2, Lihini Aluwihare3, Milou Arts1, Craig A Carlson4, Jacqueline Comstock5, Pieter Dorrestein6, Ellen C Hopmans7, Irina Koester8, Daniel Petras9, Zachary Quinlan10 and Linda Wegley Kelly11, (1)Royal Netherlands Institute for Sea Research, Marine Microbiology & Biogeochemistry, Den Burg, Netherlands, (2)University of Hawaii at Manoa, School of Ocean, Earth Science, and Technology, Honolulu, HI, United States, (3)Scripps Institution of Oceanography, La Jolla, United States, (4)University of California Santa Barbara, Marine Science Institute/Department of Ecology, Evolution and Marine Biology, Santa Barbara, CA, United States, (5)University of California Santa Barbara, Ecology, Evolution, and Marine Biology, Santa Barbara, CA, United States, (6)University of California San Diego, Collaborative Mass Spectrometry Innovation Center, La Jolla, CA, United States, (7)NIOZ Royal Netherlands Institute for Sea Research, Department of Marine Organic Biogeochemistry, Texel, Netherlands, (8)University of California San Diego, Scripps Institution of Oceanography, La Jolla, CA, United States, (9)University of California San Diego, Scripps Institution of Oceanography, La Jolla, United States, (10)San Diego State University, Department of Biology, San Diego, CA, United States, (11)San Diego State University, Department of Biology, San Diego, United States
Abstract:
Despite the recognized importance of marine dissolved organic matter (DOM), its molecular composition and contribution to energy cycling is basically unknown. A detailed chemical characterization of this nutrient and energy source is pivotal to predict influences on the microbial community metabolism and accurately determine rates of marine carbon cycling. In coastal environments a portion of the bioavailable DOM is provided by benthic primary producer exudates. Depending on the respective functional group of producers these exudates can vary significantly in quantity and quality. Here we present an untargeted liquid chromatographic separation tandem mass spectrometry analysis of exometabolites released by dominant benthic primary producers in the reefs of Moorea, French Polynesia. Overall we could identify more than 13000 distinct features (different compounds) in these exometabolomes. The relative contribution of these features to the exometabolome shows specific patterns depending on their origin. Fleshy algae, and especially turf algae had the most distinct signal containing 317 features that were significantly enriched in turf and/or Dictyota exudates. Crustous coralline algae and the coral species had more similar feature signals, but noticeably distinct from the seawater controls. Turf algal and Dictyota exudates contained on average the most reduced carbon and lowest O to C ratio of exudates. The higher energy gained by metabolizing substrates with lower oxidation state likely presents a readily available food source for heterotrophic organisms. Turf algal exudates contained a high proportion of a single, nitrogen rich aliphatic component. All together this study represents the first in-depth metabolomic analysis of coral reef primary producer exudates. It shows the complexity of coral reef producer derived organic material and highlights the significant qualitative and energetic differences of organic substrates provided by different functional groups to the ecosystem.