title: Prevalent endosymbiont zonation shapes the depth distributions of scleractinian coral species.
abstract: Bathymetric distributions of photosynthetic marine invertebrate species are relatively well studied, however the importance of symbiont zonation (i.e. hosting of distinct algal endosymbiont communities over depth) in determining these depth distributions still remains unclear. Here, we assess the prevalence of symbiont zonation in tropical scleractinian corals by genotyping the Symbiodinium of the 25 most common species over a large depth range (down to 60 m) on a Caribbean reef. Symbiont depth zonation was found to be common on a reef-wide scale (11 out of 25 coral species), and a dominant feature in species with the widest depth distributions. With regards to reproductive strategy, symbiont zonation was more common in broadcasting species, which also exhibited a higher level of polymorphism in the symbiont zonation (i.e. number of different Symbiodinium profiles involved). Species with symbiont zonation exhibited significantly broader depth distributions than those without, highlighting the role of symbiont zonation in shaping the vertical distributions of the coral host. Overall, the results demonstrate that coral reefs can consist of highly structured communities over depth when considering both the coral host and their obligate photosymbionts, which probably has strong implications for the extent of connectivity between shallow and mesophotic habitats.
authors.affiliation: Global Change Institute , The University of Queensland , St Lucia, Queensland 4072, Australia ; ARC Centre of Excellence for Coral Reef Studies , The University of Queensland , St Lucia, Queensland 4072, Australia ; CARMABI , Piscaderabaai z/n, PO Box 2090 , Willemstad, Curaçao.
authors.forename: Pim
authors.initials: P
authors.lastname: Bongaerts
authors.affiliation: Global Change Institute , The University of Queensland , St Lucia, Queensland 4072, Australia.
authors.forename: Margaux
authors.initials: M
authors.lastname: Carmichael
authors.affiliation: Global Change Institute , The University of Queensland , St Lucia, Queensland 4072, Australia.
authors.forename: Kyra B
authors.initials: KB
authors.lastname: Hay
authors.affiliation: Global Change Institute , The University of Queensland , St Lucia, Queensland 4072, Australia ; ARC Centre of Excellence for Coral Reef Studies , The University of Queensland , St Lucia, Queensland 4072, Australia.
authors.forename: Linda
authors.initials: L
authors.lastname: Tonk
authors.affiliation: CARMABI , Piscaderabaai z/n, PO Box 2090 , Willemstad, Curaçao ; Department of Limnology and Bio-Oceanography, Division of Marine Biology , University of Vienna , Althanstrasse 14, Vienna 1090, Austria.
authors.forename: Pedro R
authors.initials: PR
authors.lastname: Frade
authors.affiliation: Global Change Institute , The University of Queensland , St Lucia, Queensland 4072, Australia ; ARC Centre of Excellence for Coral Reef Studies , The University of Queensland , St Lucia, Queensland 4072, Australia.
authors.forename: Ove
authors.initials: O
authors.lastname: Hoegh-Guldberg
keywords: Symbiodinium; coral reef; depth distribution; mesophotic; symbiont zonation