Topic: Coral

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Pillar coral
Credit: Credit: NOAA Photo Library
A beautiful pillar coral located in the Florida Keys.


Soft corals
Credit: Credit: Florida Keys NMS
Often mistaken for plants, soft corals including the deep water sea fan (Iciligorgia schrammi), and the giant slit-pore sea rod (Plexaurella nutans), attach themselves to a hard substrate and slowly move with the natural wave action. Sponges like this orange elephant ear sponge (Agelas clathrodes) are water filters for the reef. They filter up to 30,000 times their body volume every day.


Soft coral
Credit: Credit: NOAA Photo Library
Soft coral with polyps extended.


Corals
Credit: Credit: Florida Keys NMS
Corals are large colonies of small animals called polyps. These polyps reside within a cup-like calcium carbonate skeleton. They have a central opening surrounded by tentacles which can be extended to feed on phytoplankton in the water column. Corals are a member of the phylum cnidaria, which also includes jellyfish and anemones.


Pillar coral
Credit: Harold Hudson
Pillar coral (Dendrogyra cylindrus), although beautiful, is rare in the Florida Keys. Pillar coral is unusual in that its polyps are usually extended.


Tongue Snail
Credit: NOAA Photo Library
Flamingo tongue snail on a sea fan close-up.


Staghorn coral
Credit: NOAA Photo Library
Close-up of staghorn coral with polyps extended.


Elkhorn coral
Credit: Paige Gill - Florida Keys NMS
Elkhorn coral (Acropora palmata) is a branching coral. Branching corals grow in the shallow areas of the reef crest and serve to break up the wave action as it comes onto the reef. The branches of Elkhorn coral resemble an elk's rack of antlers, thus its name.


Coral bleaching
Credit: Florida Keys NMS
Coral bleaching is a growing phenomenon for coral reefs globally. It is caused by the expulsion of the symbiotic algae, zooxanthelle, from the coral polyps. The zooxanthelle gives the coral its color and is also the source of most of the coral's nutrients. Coral can survive for a short time without the zooxanthelle, but if the algae remain expelled for an extended period of time, the coral will die.


Brain coral
Credit: NOAA Photo Library
A reticulated brittle star lies on the ridges of brain coral.

Flower coral
Credit: NOAA Photo Library
Beautiful Flower coral -- (Eusmilia fastigiata).


Soft corals
Credit: Larry Zettwoch
In addition to the hard corals, there are a variety of soft corals like this common sea fan (Gorgonia ventalina). The calcium carbonate skeleton of soft corals is located within their bodies, allowing them to move with the wave action. Sea fans typically grow so that the wave action is moving over the broad plane of their bodies, so all of the sea fans in an area will be oriented in the same direction.


Elkhorn and clubtip finger coral
Credit: NOAA Photo Library
Elkhorn coral and a clubtip finger coral in the foreground.


Star coral
Credit: NOAA Photo Library
In the photograph, a vase sponge with star coral inside.


Orange cup coral
Credit: Frank and Joyce Burek
Orange cup coral (Tubastraea coccinea) found in oil platforms.


Star corals
Credit: William Harrington
Boulder and massive corals, like this boulder star coral (Montastrea annularis), are the "builders" of the reef. A coral head is a colony of small animals called polyps. Polyps the size of a pencil eraser build an external skeleton of calcium carbonate around their bodies. The walls of these skeletons form a rock-like structure. Over time, as new polyps build their skeletons on top of each other, a large coral head is formed. The boulder and massive coral skeletons develop the main reef structure. Coralline algae and encrusting corals glue everything together.


Anemones
Credit: Cordell Bank Expeditions
Tiny strawberry anemones stretch their starry crowns of tentacles to catch prey from the food-rich currents.