Title: EXPLORING CORAL-ASSOCIATED BACTERIA OVER AN EXTREME DEPTH GRADIENT: ASSESSING THE PRESENCE OF UBIQUITOUS SYMBIONTS

Abstract: Bacteria have an important functional contribution to the health, nutrition, and nutrient cycling of coral reefs, yet almost nothing is known about the bacterial and microbial communities of corals in the mesophotic zone. Coral-associated bacteria are responsive to coral host habitat and the high observed variability of coral-bacterial interactions has lead to the hypothesis that there are only a few ubiquitous bacterial symbionts. We assessed bacterial communities from shallow down to lower mesophotic depths (0-80 m), using this steep environmental gradient to test the ubiquity of specific bacteria interactions in corals. Utilizing 16S rRNA amplicon sequencing on the Illumina MiSeq platform, we conducted an exhaustive characterization of the coral bacterial community in three dominant depth-generalist coral species (Pachyseris speciosa, Acropora aculeus and Mycedium elephantotus) from nine reef locations on the Great Barrier Reef and the Coral Sea (n = 312). We identified a range of ubiquitous bacteria along the depth gradient and spatial scales, suggesting the existence of permanent and stable coral-bacteria symbioses across reef environments. Nonetheless, mesophotic corals showed persistent bacterial communities different in richness compared to shallow corals, supporting the argument of habitat partitioning and ecological diversification over depth. The identification of ubiquitous bacteria highlights important candidates for in-depth functional studies regarding their role in the health and survival of scleractinian corals under a wide range of environmental conditions.

Authors: Hernandez AI, Bongaerts P, Leggat W, Ainsworth TD

Presentation: Oral

Session: 29

Date: 06/21/16

Time: 16:30

Location: 308 A/B

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