title: Photosymbiosis and the expansion of shallow-water corals.
abstract: Roughly 240 million years ago (Ma), scleractinian corals rapidly expanded and diversified across shallow marine environments. The main driver behind this evolution is uncertain, but the ecological success of modern reef-building corals is attributed to their nutritional symbiosis with photosynthesizing dinoflagellate algae. We show that a suite of exceptionally preserved Late Triassic (ca. 212 Ma) coral skeletons from Antalya (Turkey) have microstructures, carbonate13C/12C and18O/16O, and intracrystalline skeletal organic matter15N/14N all indicating symbiosis. This includes species with growth forms conventionally considered asymbiotic. The nitrogen isotopes further suggest that their Tethys Sea habitat was a nutrient-poor, low-productivity marine environment in which photosymbiosis would be highly advantageous. Thus, coral-dinoflagellate symbiosis was likely a key driver in the evolution and expansion of shallow-water scleractinians.
authors.affiliation: Institute of Paleobiology, Polish Academy of Sciences, Twarda 51/55, PL-00-818 Warsaw, Poland.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Frankowiak
authors.affiliation: Department of Geosciences, Princeton University, Princeton, NJ 08544, USA.
authors.forename: Xingchen T
authors.identifier: 0000-0001-5316-789X
authors.initials: XT
authors.lastname: Wang
authors.affiliation: Department of Geosciences, Princeton University, Princeton, NJ 08544, USA.
authors.forename: Daniel M
authors.identifier: 0000-0002-7923-1973
authors.initials: DM
authors.lastname: Sigman
authors.affiliation: School of Oceanography, University of Washington, 1492 NE Boat Street, Seattle, WA 98105, USA.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Gothmann
authors.affiliation: Marine Sciences Department, Federal University of São Paulo, Santos, São Paulo 11030-400, Brazil.
authors.forename: Marcelo V
authors.initials: MV
authors.lastname: Kitahara
authors.affiliation: Department of Chemistry, University of Warsaw, Pasteura 1, PL-02-093 Warsaw, Poland.
authors.forename: Maciej
authors.initials: M
authors.lastname: Mazur
authors.affiliation: Laboratory for Biological Geochemistry, School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, and Center for Advanced Surface Analysis, Institute of Earth Sciences, Université de Lausanne, CH-1015 Lausanne, Switzerland.
authors.forename: Anders
authors.initials: A
authors.lastname: Meibom
authors.affiliation: Institute of Paleobiology, Polish Academy of Sciences, Twarda 51/55, PL-00-818 Warsaw, Poland.
authors.forename: Jarosław
authors.initials: J
authors.lastname: Stolarski
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000382:microbiology / Q000502:physiology; D004141:Dinoflagellida / Q000502:physiology*; D010788:Photosynthesis / Q000502:physiology*; D013559:Symbiosis / Q000502:physiology*
keywords: Symbiosis; dinoflagellate algae; microstructures; nitrogen isotopes; reefs; scleractinian corals