Corals fall into two general categories: hard and soft coral. In our first Caribbean coral identification story, we talked about 10 common stony corals. Today we’ll cover 10 common soft corals. The biggest difference between them is that stony corals have a hard calcium-carbonate skeleton while soft corals are flexible. You’ll often see soft corals swaying with the current. Also, when you look closely, you will see the stony coral polyps are built on a six-fold symmetry, while soft coral polyps are built on an eight-fold symmetry. Next time you dive, try to find one soft coral, and you’ll see there are eight tentacles on each polyp. Hard-coral polyps will have more than you can count. Here are 10 common soft corals in the Caribbean to look for on your next dive.
Common sea fan (Gorgonia ventalina)
The common sea fan is easily the first coral most people will notice diving or snorkeling. These corals grow into a flat fan shape and can be more than six feet (2 m) in diameter. The common sea fan is usually purple but can also be gray or sometimes yellow. When it extends its polyps, the sea fan looks fuzzy brown. You can find the common sea fan close to the surface and down to 100 feet (30 m).
Venus sea fan (Gorgonia flabellum)
The first time you see a Venus sea fan, you may mistake it for a common sea fan with ragged edges. But in fact, this is a different species, adorned with secondary frilly branches that grow off the main fan. Like the common sea fan, the Venus fan will look fuzzy when the polyps are extended.
Wide-mesh sea fan (Gorgonian mariae)
The wide-mesh sea fan is much smaller than the common and Venus sea fans, growing no larger than 3 feet (1 m) in diameter. The wide-mesh fan grows in a flat plane, and the branches have a wider spacing compared to the common and Venus sea fans. They are pale in color, usually yellow, gray or blue.
Encrusting gorgonian (Erythropodium caribaeorum)
Divers always seem intrigued by this coral, and have often asked me, “what is that fuzzy carpet-looking thing?” This is a perfect way to describe the encrusting gorgonian. This coral grows along rocks into a thick mat. When the polyps are extended, they look like brown or pinkish hairs. When the polyps are retracted, the coral surface is a reddish gray.
Corky sea finger (Briareum asbestinum)
Corky sea fingers, as the name implies, grow into wide, fingerlike stalks. The polyps seem to be long and hairy, also appearing larger than other gorgonian corals. The coral tissue below the polyps will be purple or gray. At times the corky sea finger will outcompete other gorgonians and encrust over these colonies.
Grooved-blade sea whip (Pterogorgia guadalupensis)
The grooved-blade sea whip is one of the easiest soft corals to identify in the Caribbean. The branches grow into long, flattened blades with polyps growing out of the edges. The grooved blade is purple, but there is also a yellow species of blade sea whip, appropriately called the yellow sea whip.
Sea plume (Pseudopterogorgia sp.)
These are common on reefs at any depth. Sea plumes grow with a central stalk and can be quite tall, around 3 feet (1 m) long. Growing off the main stem are small feathery branches. The shape is slightly flat and, when the coral retracts the polyps, it looks like smooth sticks. Sea plumes are commonly purple and sometimes pale yellow in color.
Split-pore sea rod (Plexaurella sp.)
To identify this coral, you need to find a colony with closed polyps. Then it’s easy to see the split-pore opening rather than a circular opening on the coral’s rind. Another recognizable feature is that the coral rods are generally thick and often bend over because of their own weight.
Black sea rod (Plexaura homomalla)
Black sea rods form bushy colonies, almost looking like a candelabra. The branches extend from a central attachment point and reach upward. Sometimes branches can appear laterally off the front or back of the coral, but usually they grow in a single plane. This coral grows to a height of about one foot (35 cm). The central stalk and branches are black or dark brown and the polyps are cream-colored, yellow or pale brown.
Bent sea rod (Plexaurella flexuosa)
The bent sea rod grows into a flat plane or bushy shape and can get quite large. The branches are not perfectly straight, with small bends in each. These corals can be cream, yellow or golden brown, sometimes with a purple tint. When the polyps are extended, this coral looks soft and furry. You can find the bent sea rod in very clear water and growing on patches of rocky reef.