Deep down on a Caribbean reef: lower mesophotic depths harbor a specialized coral-endosymbiont community.

ABSTRACT: The composition, ecology and environmental conditions of mesophotic coral ecosystems near the lower limits of their bathymetric distributions remain poorly understood. Here we provide the first in-depth assessment of a lower mesophotic coral community (60-100?m) in the Southern Caribbean through visual submersible surveys, genotyping of coral host-endosymbiont assemblages, temperature monitoring and a growth experiment. The lower mesophotic zone harbored a specialized coral community consisting of predominantly Agaricia grahamae, Agaricia undata and a "deep-water" lineage of Madracis pharensis, with large colonies of these species observed close to their lower distribution limit of ~90 m depth. All three species associated with "deep-specialist" photosynthetic endosymbionts (Symbiodinium). Fragments of A. grahamae exhibited growth rates at 60?m similar to those observed for shallow Agaricia colonies (~2-3?cm yr(-1)), but showed bleaching and (partial) mortality when transplanted to 100?m. We propose that the strong reduction of temperature over depth (?5°C from 40 to 100?m depth) may play an important contributing role in determining lower depth limits of mesophotic coral communities in this region. Rather than a marginal extension of the reef slope, the lower mesophotic represents a specialized community, and as such warrants specific consideration from science and management.

SUBMITTER: Bongaerts P 

PROVIDER: S-EPMC4285725 | biostudies-literature | 2015 Jan

REPOSITORIES: biostudies-literature