The deeper the coral settles in the ocean, the more difficult it is for the zooxanthellae to get enough daylight, and then above a certain depth it is simply too dark to do the synthesis.
There are amazing water depths where corals with zooxanthellae can still live, a record is held here by the stony coral Leptoseris fragilis, which can still live on the metabolic products of photosynthesis at depths below 200 meters. Due to special adaptations, e.g. fluorescent pigments in tissues of Leptoseris fragilis, it can live almost at the edge of the photic zone, below 200 meters!
Other corals do not form symbiotic relationships with energy-rich endosymbionts, and rely on zooplankton or marine snow for energy. such as the gorgonian Antipathes atlantica, which occurs to depths of 152 meters.
Antipathes atlantica forms large colonies that are 50 cm or higher, there is a source that speaks of 130cm,
Antipathes atlantica is densely branched with most branches lying in a single plane like a fan, the adjacent branches are sometimes fused together forming a net-like pattern, an optimal mesh for drifting zooplankton to get caught in.
The polyps are arranged on only one side of the corallum, they generally have a transverse diameter of 0.5 -1.1 mm and are spaced 1.1 -1.7 mm apart.
The Antipathes atlantica colonies observed in the above study were grayish white in situ, however greenish colonies have also been reported for this species at other sites.
Very similar species: Antipathes gracilis Gray, 1860
The black coral fauna (Cnidaria: Antipatharia) of Bermuda with new records
Daniel Wagner & Andrew Shuler, 2017
Licensed under a Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0