Florida Keys Marine Ecology The Florida Keys are a national treasure. Not only do these islands provide a near-tropical vacation paradise in own back yard, but they have the reefs. The barrier reef alongside the Florida Keys are the northernmost barrier reef in the world. There is an amazing variety of marine found here, the only living coral reef in the continental USA. Living here are over forty species of coral with more than 500 types of fish swimming around it. It's a symbiotic relationship that forms this delicate underwater life system, and some of the reef is very very old.
The foundation of the coral reef is the coral polyp, which is the size of a mini marshmallow, at its largest, and sometimes much much smaller. These tiny polyps build the coral reef with the help of tiny algae that are called zooxanthellae. These algae, through the process of photosynthesis, take in carbon dioxide and nitrogen (which is waste from teh polyp) and give out oxygen and nutrients. The polyp uses the oxygen and nutrients, and the whole process, since it is based on photosynthesis, can occur only in clear water that's not very deep. The zooxanthellae also somehow encourage the coral polyps to secrete calcium carbonate, and this is what makes the hard basis of the reef, the skeleton. Coral polyps also get nutrients from other souces, such as plankton that become entangled in the long fingers of the coral. These tentacle-like protrusions have little stingers on them, called nematocysts. Plankton are out mostly at night, so the coral polyps don't bother to send out the tentacles during the day. Since they constantly need nutrients, they rely on their symbiotic relationship with the zooxanthellae to feed them during the day.
There are soft corals and there are hard corals. You can tell the difference of course by touch, but you really aren't supposed to touch coral at all. They are also different in that soft corals have eight tentacles and hard corals have six. Remember, it's the calcium carbonate that makes the hard skeletal formation of coral, so you can logically conclude that soft coral does not produce calcium carbonate. And remember also that it's the zooxanthellae that stimulates the production of calcium carbonate in the corals, so you might guess that soft corals are somehow not in any relationship with the zooxanthellae. That's correct, actually. And remember about the zooxanthellae feeding the hard coral during the day, well now that you know soft coral has no symbiotic relationship with the zooxanthellae, you can also guess that soft coral doesn't get fed during the day by the zooxanthellae. Therefore, the tentacles stay out during the day, which is perhaps why they have eight instead of six. They do double duty.
Keep these hard-working tentacles in mind when you're out diving...they're trying to eat, and grow, and the more they eat the more reef we have. Some of the reef around the Florida Keys has been there since before the United States became a country. There are some areas of reef that have become famous, at least amongst divers, residents and travellers to the Florida Keys. Maybe you've heard of Molasses Reef or Carysfort Reef. These are two very old reefs. To read about other reefs in the Florida Keys, check out the main Keys areas across the top of this page.