Deep Sea Corals: Octocorals

 
Yellow octocoral, front. Photo credit: "expl5235" (CC BY 2.0) by NOAA Photo Library.

This second post (if you missed the first one it can be found here) will focus on one of the two subclasses (class Anthozoa) of corals present in the Gulf of Mexico, octocorals. This subclass includes most Octocoralcorals except stony corals and black corals, which are hexacorals.  Many octocorals share similar traits: most are non-reef building, but they can provide vertical relief over areas that are otherwise soft bottoms, such as sandy bottoms. In general, octocorals tend to have large, erect frames that stretch up into the water column above the substrate, but they can also occur as smaller forms, as demonstrated by the two octocorlas found living on a deep sea chimney in the image to the left. Being above the seafloor and in the water column allows the polyps to more easily capture food from the water as it passes by the colony.  Researchers have found colonies so large that the polyps in the center have starved because the polyps on the outside of the colony have captured all the food.Up-close octocoral polyp
 
Octocorals get their name because each polyp has eight hollow tentacles containing pinnules, which are small branches. The images to the right and left show upclose views of the polyps, and demonstrate how octocorals get their name.  Different species of octocorals are classified according to their sclerites, structures made of calcium carbonate contained within the animal's tissues, as opposed to hexacoral (our next topic) which have their skeleton outside of the polyp bodies.  In octocorals, sclerites can have multiple morphologies, and because they give the coral shape they are how biologists classify different species of octocorals. Right now, there are two DSC groups that octocorals can be divided into: sea pens, and soft corals and sea fans.

Upclose pink octocoralOctocorals include blue corals (the only group that lives exclusively in shallow water), sea fans, sea pens, and sea whips, all of which may be familiar to those familiar with shallow water corals. Overall, there are at least 162 named and described species of octocorals in the Gulf of Mexico.
 
Because octocorals provide vertical relief in otherwise flat areas, there are often other species associated with them.  There have been observations of other animals, such as brittle stars and marine worms, that live on the octocoral, sometimes seen climbing up high, in what scientists think may be an effort to increase their ability to capture food.  Additionally, sometimes these other animals have been observed both feeding on the coral polyps themselves. These corals can also provide an anchor for other organisms, as there have been observations of catshark eggs attached to species of octocoral at depths greater than 1,310 ft. 
 
ROV technology has allowed us to see these interactions that previously may have only been dreamed of by scientists who study the deep ocean.  Here is one example of such an interaction: never-before seen behavior of a sea urchin eating octocoral, taken by NOAA.


Sources: http://oceanexplorer.noaa.gov/explorations/12lophelia/background/corals/... http://oceanexplorer.noaa.gov/explorations/03mountains/background/octoco... http://gulfcouncil.org/wp-content/uploads/N-4-Coral-9-draft-options-May-... France, S.C. (2009) {Page title}. Version 29 June 2009. In Deep-Sea Corals Portal,http://www.ucs.louisiana.edu/~scf4101/Bambooweb/Public.html

Hannah Leis is GRN’s Fishery Associate

Recent Posts

"If a little rain can flood us, what will a hurricane do?" – Public Comment,...
Written by Scott Eustis
Friday, 18 August 2017
Sea fans, sea whips and bamboo coral are all members of the order Alcyonacea, one...
Written by Hannah Leis
Friday, 18 August 2017
Trump's EPA is trying to remove valuable protections for our rivers, streams, and wetlands! The...
Written by Matt Rota
Friday, 18 August 2017
This article is excerpted from the Summer 2017 issue of Gulf Currents, GRN's bi-annual printed...
Written by Andrew Whitehurst
Thursday, 17 August 2017
The August 5th flooding was rough on many New Orleanians - with floodwaters swamping homes,...
Written by Harry Lowenburg
Tuesday, 15 August 2017
This summer, Gulf Restoration Network and our members Bobby Tubre and his grandfather, Don Williams,...
Written by Andrew Whitehurst
Tuesday, 15 August 2017
Black corals, contrary to their name, do not appear black but instead come in a...
Written by Hannah Leis
Friday, 11 August 2017

Latest Actions

SHARE THIS PAGE