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Dive Dry with Dr. Bill

#592: Catalina's Coral "Reefs"

As I write this, I'm thinking about my upcoming birthday surprise. No, no one will be throwing me a party on my birthday. By the time you read this I'll away from the island. A few weeks ago, I decided to do something completely different from anything I've ever done on a birthday. That means I certainly won't be diving... but I will be on my way to a diver's paradise. Starting at midnight, I'll be on a plane heading for Atlanta to make a connection to Aruba in the Dutch Antilles and then on to Bonaire the next day. Yes... on a plane on my birthday!

Anyone who knows me well, is aware that I didn't fly in commercial airplanes for 22 years. I had two potentially fatal incidents in one day way back in the early 70s and decided I had no desire for a third strike. It wasn't until then girlfriend Janet said she would not take a three day train ride back to Boston for my Harvard reunion that I got back on board a jet liner. Good thing she held my hand on take-off, but I've been flying ever since (at least when I could afford it). I missed many great dive adventures during those Earth-bound years and am trying to make it up now.

The thought of heading back to the tropics has me contemplating coral reefs rather than kelp forests... oh, and warm water as well! My two trips last year, the Bahamas and the Philippines, were wonderful and provided lots of opportunity to film coral reef residents. I expect the same down in Bonaire which is considered a diver's paradise by many. Personally I prefer the far greater biodiversity of the Asian tropics (not to mention the beautiful ladies) to the Caribbean, but I had a free flight on AirTran to take advantage of so the A-B-C islands are where I'm headed... Aruba, Bonaire and Curacao.

Now I don't really have to go to the tropics to find true stony corals. We actually have a few right here in our cooler waters. I'm referring to the cup corals which I see every time I dive our waters. The difference is that these small corals are not hermatypic, that is they do not form large reefs like the ones I've dived in Australia, Belize, Tahiti, Fiji and elsewhere. Today I'll talk a bit about the colonial cup coral, Coenocyathus bowersi, rather than its lone wolf cousin, the solitary cup coral (Paracyathus stearnsii).

This species is known from Monterey down to Baja California and into the Sea of Cortez at depths down to nearly 500 feet. Colonies are usually only a few inches in any dimension and the color of the living coral is usually orange or pink. Other species of cup corals can be seen in the tropics, and members of the group are also known from very cold water (unlike me). In general the cup corals are found on the shaded vertical surfaces of rocky reefs or on the under side of overhangs and in caverns where the sun don't shine. Cup corals are related to the reef-building coral as well as sea anemones, hydroids, jellyfish and other members of the phylum Cnidaria.

What do the Cnidarians have in common? The answer is stinging cells known as nematocysts. These are used primarily to capture food like as plankton, suspended organic matter, or even fish and other invertebrates by the bigger species in the group. Fortunately we Homo sapiens are not among their menu choices. However, the nematocysts are also used by Cnidarians for defense. Most of my readers are undoubtedly aware of the stings that can come from encountering jellyfish or siphonophores such as the Portuguese man-of-war in the water.

The individual polyps of colonial cup corals have a six-fold symmetry or less. There is just a single ring of tentacles. There is a single opening which leads into a digestive cavity so food is ingested and wastes expelled through it. Speaking of which, I think it's time to get my colonoscopy! To reproduce they release sperm and eggs which fertilize to develop into a planula larva. These attach to the bottom and develop into polyps. Now if the vast majority of climate scientists are right, and the waters around Catalina warm up, we may see coral reefs forming here, too! OK, maybe not in my lifetime, but...

© 2014 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. You can also watch these episodes in iPod format on YouTube through my channel there (drbillbushing). 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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Several clusters of colonial cup corals and close-up of tentacles; tentacles showing stinging nematocysts
and true reef-building coral of tropical waters like Bonaire

This document maintained by Dr. Bill Bushing.
Material and images © 2014 Star Thrower Educational Multimedia