A sea plume.

A sea plume.

by Johnny Rader

Have you ever come across a plant-like thing attached to a small, white shell on the beach? Most of the time, the plant-like part is bright purple, if it washed ashore recently, or a dull shade of grey if the living body has died. These are not actually plants, but animals called gorgonians.

Sea fans in the Caribbean.

Sea fans in the Caribbean.

Although the classification of these organisms is not well understood, scientists place them in a group with soft corals. This is because of their eight branching tentacles on each polyp, unlike hard or stony corals, which have six branching tentacles on each polyp. What sets gorgonians aside from true soft corals is the presence of a central rind, the dull grey structure left behind after the animal dies.  

A gorgonian on Sanibel.

A gorgonian on Sanibel.

Gorgonians come in many forms – they can be bushy and feather-like, branching and fan-like, or simple and whip-like. Regardless of their shape, all can be found in beautiful shades of purple, yellow, and green. They are benthic organisms that attach themselves to a hard surface, and they are widespread and quite diverse throughout the Caribbean Sea and the Gulf of Mexico. Although a few species have a global range, most of the diversity is found in the Caribbean and off the coast of Florida.

They have eating habits that match those of both stony and soft corals. Consuming most of their food – plankton – at night, gorgonian polyps will extend their eight long tentacles, which contain stinging cells called nematocytes or cnidoblasts. These can stun prey, allowing the gorgonian to maneuver the food item into its central opening.

A sea whip attached to a ponderous arc on Sanibel.

A sea whip attached to a ponderous arc on Sanibel.

Additionally, like almost all corals and jellies, gorgonians have phytoplankton (plant-like plankton), called zooxanthellae, in their stomach. This symbiotic relationship is one of the most perfect on our planet. The zooxanthellae not only provide sugars produced during photosynthesis to the gorgonian, but also produce all the oxygen it may need. In return, the animals will provide a home and any nutrients that the zooxanthellae may not be able to obtain from sea water. Pretty amazing, if you ask us!

On Sanibel, the most common gorgonian you will find is called a sea whip, which is usually attached to a small, white shell called a ponderous arc or a larger piece of rock. Travel down to the Florida Keys and you will find fields of sea whips, sea fans, and sea plumes.

Corals are under stress from human impacts and our ocean changing environment, so here are a few things you can do today to help protect them: 

  • Turn your lights off when you are not in the room

  • Choose to bike, skate, or walk instead of driving if you’re not traveling too far

  • Use sunscreen that is marked “reef safe” when you are in the ocean, avoid the ingredients avobenzone and oxybenzone

  • Opt for reusable alternatives to single-use, disposable plastic items

  • Plant a tree

  • Snorkel responsible, be mindful of your movement to avoid damaging your surroundings

  • Raise awareness by talking to friends

  • Donate or volunteer in support of a conservation effort

  • Organize a coastal clean up

 

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