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Tuesday, September 1, 2009

Sea Things #13: Corals

Sea Things is a regular feature on my blog where I profile a different sea creature. Look for it weekly, or something close to weekly.

Here's a little bit of interesting things about corals, which are everywhere, and which comprise an entire group of sea things rather than something specific. I'll go into more details on various types of corals in future installments of sea things, but just talking about corals in general is pretty interesting as a start.

First of all, corals, if you are not aware, are animals. This is a big deal because they don't move, and apparently people generally want to classify things that don't move as plants. I, however, have trouble imagining that coral, sea fans and the like are plants or animals - they seem like a whole different thing to me. But, that's just me. They're animals, and this was first discovered in 1753 by french biologists in the Atlantic.

The animals themselves are tiny. The photo below shows star coral, with polyps that are around 1/4 - 1/2 inches in size (and the fish is a friendly Goby). These tiny creatures amass themselves into huge colonies that form coral reefs. Corals have a skeleton of calcium carbonate, which they gather from seawater, and over a very long time form a limestone base of a reef. These can even build themselves up into islands and atolls. Without coral, we wouldn't have the Cayman Islands, for example. Pictured at the top of the page is Lettuce Coral from Belize, one of the many shapes and types of corals out there.

So, with this particular phylum of animals that are corals (called Cnidaria), there are animals that hang out alone and solitary throughout their lives - anemone. There are other animals that group together and amass themselves - most corals. And then there are others that go off and free float around in the water, and those are jellyfish. That's right, jellyfish and coral are really about the same thing. The thing that really makes them about the same is that they have some sort of stinging tentacle that they use to catch prey. Most of the time, divers aren't affected, but sometimes they are (like with jellyfish and fire coral).

Corals are delicate. They require light, so the water must be clear. They also require a very strict temperature range - about 70 to 85 degrees. The problem these days with global warming is that water temperatures have been rising, and this leads to mass amounts of corals dying off (called coral bleaching). In fact, when we were in Bonaire in August 2008, my dive computer was registering surface temps of 84 degrees, so we were close. However, that was on the surface and the water temperature dropped once we got down on to the reef. There hasn't been a major bleaching event since 2002, when a large portion of the Great Barrier Reef became bleached. When corals die, it can take a crazy amount of time for them to repair themselves. Corals grow at less than an inch a year most of the time.

Corals are fascinating and I hope to talk about more of them in the future. I just wanted to go over some basic facts about corals in general before going into more detail on each individual species.

Is there a creature that you would like to see featured in Sea Things? If so, shoot me an email and if I can, I'll write about it. Photos on this post are courtesy of Todd Krebs.

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