NOTE Endolithic community composition of Orbicella faveolata (Scleractinia) underneath the interface between coral tissue and turf algae N. Gutie´rrez-Isaza • J. Espinoza-Avalos • H. P. Leo´n-Tejera • D. Gonza´lez-Solı ´s Received: 8 December 2013 / Accepted: 13 February 2015 Ó Springer-Verlag Berlin Heidelberg 2015 Abstract We evaluated the species composition, rich- ness, and total abundance of the endolithic community in the skeleton of Orbicella faveolata under coral tissue and under turf algae using cores that were extracted at different distances (0.5, 2.5, and 7.0 cm) from both sides of the external coral tissue–turf algae competitive boundary. We found high endolith richness as never before reported for Orbicella species. Nineteen endolith taxa were found within the O. faveolata skeleton, seven below the coral tissue zone, and twelve exclusively below the turf algae zone. Significant differences existed in the community composition, species richness, and the total abundance of endoliths in the cores that were extracted from the turf algae zone compared with those of the coral tissue zone. The endolithic community composition and species rich- ness changed abruptly across the coral–turf algae interface, forming a clear boundary between different endolithic communities just underneath the interface between the coral tissue and turf algae zones. Keywords Endolithic organisms Á Microflora Á Competition Á Turf algae Á Cyanoprokaryota Á Ostreobium quekettii Introduction Caribbean coral reefs are losing coral cover as a result of different disturbances (Hughes 1994; Alvarez-Filip et al. 2011), while the cover of turf algae and macroalgae is increasing in reef environments that were previously dominated by coral species (Hughes 1994; Mumby and Steneck 2011). The loss of dominance of corals sig- nificantly affects coral reef biodiversity because corals provide a structural complexity that serves as shelter for multiple species (Rasher et al. 2011). Coral colonies (holobionts; Rohwer et al. 2002) also host complex and diverse communities of archaea, viruses, bacteria, di- noflagellates (Symbiodinium spp.), fungi, protists, and en- dolithic algae (Wegley et al. 2004, 2007) that function as a symbiome in which each member of the multi-species assemblage is found in potential symbiotic interactions with the coral host (Gates and Ainsworth 2011). In this study, we focused on describing the endolithic community interacting with a coral host (Orbicella, prev Montastraea faveolata) in light of the growing advance in the cover of turf algae and macroalgae in degraded reefs. In the sym- biotic endolithic algae–coral interaction, algae translocate photoassimilates to the coral host (Schlichter et al. 1995, 1997; Fine and Loya 2002) and may confer photoprotec- tion to the coral–dinoflagellate symbiosis (Yamazaki et al. 2008). In turn, nitrogen-containing metabolites from corals may serve as significant sources of nitrogen for the algae (Titlyanov et al. 2008, 2009). However, aside from the symbiotic interactions between corals and endolithic algae, Communicated by Ecology Editor Dr. Stuart Sandin Electronic supplementary material The online version of this article (doi:10.1007/s00338-015-1276-0) contains supplementary material, which is available to authorized users. N. Gutie´rrez-Isaza Á J. Espinoza-Avalos (&) Á D. Gonza´lez-Solı ´s El Colegio de la Frontera Sur, Av. Centenario km 5.5, Apdo. Postal 424, 77014 Chetumal, Q. ROO, Mexico e-mail: jespino@ecosur.mx H. P. Leo´n-Tejera Laboratorio de Ficologı ´a, Facultad de Ciencias, Universidad Nacional Auto´noma de Me´xico, Apdo. Postal 70-620, 04510 Coyoaca´n, D. F., Mexico 123 Coral Reefs DOI 10.1007/s00338-015-1276-0