title: Ecological complexity of coral recruitment processes: effects of invertebrate herbivores on coral recruitment and growth depends upon substratum properties and coral species.
abstract: BACKGROUND
  The transition from planktonic planula to sessile adult corals occurs at low frequencies and post settlement mortality is extremely high. Herbivores promote settlement by reducing algal competition. This study investigates whether invertebrate herbivory might be modulated by other ecological factors such as substrata variations and coral species identity.
  
  
  RESULTS
  The experiment was conducted at the Flower Garden Banks, one of the few Atlantic reefs not experiencing considerable degradation. Tiles of differing texture and orientation were kept in bins surrounded by reef (24 m). Controls contained no herbivores while treatment bins contained urchins (Diadema antillarum) or herbivorous gastropods (Cerithium litteratum). Juvenile corals settling naturally were monitored by photography for 14 months to evaluate the effects of invertebrate herbivory and substratum properties. Herbivory reduced algae cover in urchin treatments. Two genera of brooding coral juveniles were observed, Agaricia and Porites, both of which are common but not dominant on adjacent reef. No broadcast spawning corals were observed on tiles. Overall, juveniles were more abundant in urchin treatments and on vertical, rough textured surfaces. Although more abundant, Agaricia juveniles were smaller in urchin treatments, presumably due to destructive overgrazing. Still, Agaricia growth increased with herbivory and substrata texture-orientation interactions were observed with reduced growth on rough tiles in control treatments and increased growth on vertical tiles in herbivore treatments. In contrast to Agaricia, Porites juveniles were larger on horizontal tiles, irrespective of herbivore treatment. Mortality was affected by substrata orientation with vertical surfaces increasing coral survival.
  
  
  CONCLUSIONS
  We further substantiate that invertebrate herbivores play major roles in early settlement processes of corals and highlight the need for deeper understanding of ecological interactions modulating these effects. The absence of broadcast-spawning corals, even on a reef with consistently high coral cover, continues to expose the recruitment failure of these reef-building corals throughout the Caribbean.
authors.affiliation: Integrative Biology Section, The University of Texas at Austin, Austin, Texas, United States of America ; Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Sarah W
authors.initials: SW
authors.lastname: Davies
authors.forename: Mikhail V
authors.initials: MV
authors.lastname: Matz
authors.forename: Peter D
authors.initials: PD
authors.lastname: Vize
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000254:growth & development*; D044822:Biodiversity; D000460:Chlorophyta / Q000254:growth & development; D057894:Coral Reefs; D017753:Ecosystem; D060851:Gulf of America; D060434:Herbivory
references.citation: Zoolog Sci. 2005 Apr;22(4):391-9
references.pmid: 15846048
references.citation: Mar Pollut Bull. 2005;51(1-4):408-14
references.pmid: 15757739
references.citation: Oecologia. 2010 Jul;163(3):747-58
references.pmid: 20169452
references.citation: Proc Natl Acad Sci U S A. 2001 Apr 24;98(9):5067-71
references.pmid: 11274358
references.citation: Curr Biol. 2007 Feb 20;17(4):360-5
references.pmid: 17291763
references.citation: Ecol Lett. 2006 Mar;9(3):271-80
references.pmid: 16958892
references.citation: Proc Natl Acad Sci U S A. 2007 May 15;104(20):8362-7
references.pmid: 17488824
references.citation: Science. 1984 Oct 19;226(4672):335-7
references.pmid: 17749884
references.citation: Proc Natl Acad Sci U S A. 2001 Apr 24;98(9):4822-4
references.pmid: 11320228
references.citation: Science. 1994 Sep 9;265(5178):1547-51
references.pmid: 17801530
references.citation: PLoS One. 2011;6(10):e26411
references.pmid: 22065994
references.citation: Proc Natl Acad Sci U S A. 1988 Jan;85(2):511-4
references.pmid: 16593907
references.citation: Ecology. 2010 Dec;91(12):3572-83
references.pmid: 21302829
references.citation: Dev Biol. 2011 May 15;353(2):411-9
references.pmid: 21338599
references.citation: Mol Ecol. 2011 Sep;20(17):3599-616
references.pmid: 21801258
references.citation: Oecologia. 2013 Oct;173(2):431-8
references.pmid: 23525803
references.citation: PLoS One. 2009 Nov 26;4(11):e8043
references.pmid: 19956632
references.citation: Science. 2006 Jan 6;311(5757):98-101
references.pmid: 16400152