title: Nitrogen fixation in the mucus of Red Sea corals.
abstract: Scleractinian corals are essential constituents of tropical reef ecological diversity. They live in close association with diazotrophs [dinitrogen (N2)-fixing microbes], which can fix high rates of N2. Whether corals benefit from this extrinsic nitrogen source is still under debate. Until now, N2 fixation rates have been indirectly estimated using the acetylene reduction assay, which does not permit assessment of the amount of nitrogen incorporated into the different compartments of the coral holobiont. In the present study, the (15)N2 technique was applied for the first time on three Red Sea coral species. Significant (15)N enrichment was measured in particles released by corals to the surrounding seawater. N2 fixation rates were species specific and as high as 1.6-2 ng N day(-1) l(-1). However, no significant enrichment was measured in the symbiotic dinoflagellates or the coral host tissues, suggesting that corals do not benefit from diazotrophic N2 fixation.
authors.affiliation: Centre Scientifique de Monaco, Avenue Saint-Martin, MC-98000, Monaco rgrover@centrescientifique.mc.
authors.forename: Renaud
authors.initials: R
authors.lastname: Grover
authors.affiliation: Centre Scientifique de Monaco, Avenue Saint-Martin, MC-98000, Monaco.
authors.forename: Christine
authors.initials: C
authors.lastname: Ferrier-Pagès
authors.affiliation: Laboratoire de l'Environnement Marin (LEMAR), UMR 6539, UBO/CNRS/IRD/IFREMER, Institut Universitaire Européen de la Mer, Place Nicolas Copernic, F-29280 Plouzané, France.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Maguer
authors.affiliation: Centre Scientifique de Monaco, Avenue Saint-Martin, MC-98000, Monaco.
authors.forename: Leila
authors.initials: L
authors.lastname: Ezzat
authors.affiliation: The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel The Interuniversity Institute for Marine Science, 88000 Eilat, Israel.
authors.forename: Maoz
authors.initials: M
authors.lastname: Fine
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000382:microbiology* / Q000502:physiology; D004141:Dinoflagellida / Q000378:metabolism*; D019156:Indian Ocean; D009093:Mucus; D009584:Nitrogen / Q000032:analysis*; D009586:Nitrogen Fixation; D009587:Nitrogen Isotopes; D012623:Seawater / Q000737:chemistry*; D013559:Symbiosis
chemical_list: D009587:Nitrogen Isotopes; D009584:Nitrogen
keywords: Diazotrophy; Scleractinia; Stable isotopes; Symbiosis