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Dive Dry with Dr. Bill

#397: Soft Coral or Sea Fans

It's been a few years since I've had the luxury (or, more accurately, the money) to dive tropical waters. I think back fondly to my dives in places like Tahiti, Thailand, Belize and elsewhere. And, of course, how could I forget the time I spent in the "Soft Coral Capitol of the World" (Fiji) diving as the guest of Jean-Michel Cousteau at his resort in Savusavu. I spent the previous two weeks nursing a cold in New Zealand and couldn't dive, so the day I landed at the airport in Nadi I located a dive operation to re-submerge with before making the trip to Vanua Levu and the resort. I just had to get my gills wet! Turned out the dive master with that outfit was a cousin of the one I dove with at the Cousteau resort!

The flight from Nadi to Savusavu was absolutely beautiful. We flew low over the coral reefs of the islands and I only wished I had a high definition camcorder to record their beauty from the air. Standard def had to suffice. The only other passengers were two women from New York City. They spent the 45 minute flight looking out over that beauty and expressing their terror about crashing in what they considered a rickety old plane. They were definitely white knucklers and screamed every time the plane hit an air pocket. I guess they were used to 737s, but with my experience in our seaplanes decades ago I was quite comfortable and simply marveled at the sights below.

However, you don't need to fly to Fiji to see soft corals, known as gorgonians to us scientists. We have several species right here in Catalina waters that are visible even to snorkelers. They come in reds, browns and golden colors. I was reminded of their beauty a few weekends ago when I came across one of the brown gorgonians bathed in unusual lighting from the sun (yes, it DID come out that Sunday!). Gorgonians are related to corals, sea anemones, jellyfish and the other members of the phylum Cnidaria (formerly Coelenterata) which possess stinging cells to capture their prey. However, I've never felt a sting from ours here. Of course I am wearing a full wetsuit and have pretty thick skin!

Our brown and golden gorgonians are members of the same genus (Muricea fruticosa and Muricea californica respectively) and look similar except for their color. The colony of the former is brownish to reddish and the individual polyps are white. The latter has brownish branches covered with golden yellow polyps. Both are found from Pt. Conception down into Baja California. The red gorgonian (Lophogorgia chilensis) has thinner, red branches with white polyps. It is known from Monterey down to Cedros Island off Baja, and is often seen in much deeper water especially at Ship Rock. However, they can be found even in water as shallow as 20-30 ft in our dive park. Other local species such as the purple and orange gorgonians exist, but they are usually at depths most divers avoid... except yours truly and a few of our local tech divers.

The branching colony is composed of a protein known as gorgonin. It gives the structure firmness, yet the ability to flex and yield as the colony sways with the surge and currents. This is one reason they are also known as "sea fans." The branching colonies are often oriented perpendicular to the prevailing current. This allows the tiny polyps to grasp passing food with their tentacles and pull it in. Like most Cnidarians, they use stinging cells or nematocysts to assist in capturing small critters and organic matter. Colonial gorgonians are an interesting example of actual working socialism (although I doubt they have economic or political systems on their minds... if they had any... just good old "munching" and "mating"). The feeding polyps or zooids in a colony all have a common gut or digestive system so when one feeds, the others benefit as well. Some day I hope to meet a lovely lady who can cook so I'll get good meals at least every other day!

The individual polyps have eight tentacles as is typical of the octocorals (no relation to Octo Mom). Under certain conditions each polyp may retract into the horny branches of the colony. Hmmm, that word reminds me that in many species each colony consists of polyps of a single gender... the guys on one and the gals on another. And they have much better luck keeping the two separate than we did back at the Toyon School when being in the "dorm of the opposite sex" was "rewarded" with demerits... or even expulsion... if caught. To reproduce, the polyps cast off their gametes into the water and hope they will be much luckier than I am with the lottery. A new colony is slow growing and not sexually mature for a few years. Each one may survive 50 years or more.

It is interesting to note that I rarely see anything feeding on gorgonians. Of course the stiff protein-based colony would not seem very palatable, at least to my refined and delicate taste. In addition, the soft polyps have crystals of calcium carbonate in them. Their hard coral relatives build their stony colonies with this same material. Crunching down on it would likely give most predators a toothache. I did once film a sheep crab munching away on a gorgonian. It didn't seem to mind. Recently, while diving with three lady-go-divers, Ruth Harris showed me two snails known as Simnia on a golden gorgonian. I have seen them "munching" away on red gorgonians in our waters, but this was the first time I've seen them on a golden gorgonian. Of course diving without prescription lenses made it nearly impossible to recognize them underwater, but I have the high definition video footage to prove it! And, by the way, they were "mating" rather than "munching..." and laying strings of tiny eggs on a branch of the colony suggesting they felt the golden gorgonian would be good food for their youngsters. Other snails are also known to eat them.

In addition to predators, gorgonians are often parasitized by a relative known as a zoanthid (Parazoanthus lucificum). The first time I saw such parasitism, I thought the zoanthids were simply gorgonian polyps on steroids. They are much larger than the gorgonian polyps and have longer tentacles. Of course the poor gorgonian colonies failed to see the humor in that as they died a slow and "agonizing" death. I wouldn't like it either if some alien from outer space started growing right over my body and eventually choked me to death. Of course the only such aliens I know are from the planet Xanadu, and they ensure we humans receive a quick death as they "munch" on us, or don't feel pain when they "mate" and lay their eggs on our paralyzed bodies for their young 'uns to eat. Just ask anyone involved with Project Blue Book if you don't believe me.

© 2010 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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Golden and brown gorgonians; red gorgonian and the polyps showing the eight tentacles
of a tropical species down in Belize off Half Moon Caye Wall.

This document maintained by Dr. Bill Bushing.
Material and images © 2010 Star Thrower Educational Multimedia