Did you know that our Coral Reefs in the Florida Keys are carnivorous?
Our beautiful colorful coral reefs are responsible for bringing many visitors to the Florida Keys each year. They are one of the most diverse and productive communities on earth. They’re found in warm, clear tropical, nutrient free oceans all around the world. They provide food and shelter to all forms of marine life. In some places they protect the shore line from erosion.
There’s something truly magic about diving over and along the reef, observing all the marine life that is so busy there. It scares me to think about how fragile this underwater world is that I so enjoy watching.
The coral reefs is made up of calcium carbonate. It’s produced by tiny coral polyps. These guys are the main builders of the reef, they get help from coralline algae which cements different corals together with calcium.
Corals live in colonies made up of thousands and thousands of polyps. These guys are carnivorous, yes, they eat meat. They’ll grab small particles
of plankton out of the water column as they float by. They have a sticky mucous that helps them with the capture. Most species feed during the night. That’s when the zooplankton is floating in the water.
Corals reproduce both sexually and asexually. Mostly the branching corals such as the Elkhorn and Staghorn produce asexually. When a piece is broken off, it will develop into a totally new coral stand. The others reproduce sexually. In the Florida Keys this happens in August, usually seven to ten days after the full moon, and it happens at night. If you want to witness this, you’ll need to dive at night. It’s called a coral bloom. People come from all over to see this explosion in nature. The polyps in a colony will all release their eggs and sperm at the same time. They drift in the current together and become fertilized. The water is so thick with them you can’t see anything else. Lots of them are eaten by other marine animals.
Some do survive. After being carried in the current they will drift back down to the ocean floor where just one fertilized polyp can start a whole new coral colony.
Coral reefs can tolerate only a narrow range of environmental conditions. They’re very sensitive to any environmental change. Water temperature, turbidity and mainly pollution from man puts great stress on our reefs. Artificial Reefs
are one way to take pressure away from the reefs. Many have been sank into the waters of the Florida Keys
They can tolerate water temperatures ranging from 75 degrees to around 88 degrees. When the water temperatures are outside this range for a prolonged period of time, it causes stress on the corals. When the temperature reaches 92 degrees for a prolonged period of time and the water becomes still and is no longer clear coral bleaching occurs. This is when the coral turns white. The skeleton is exposed. The symbiotic algae leaves the polyps. This algae gives them their nutrients and building blocks. Without it they die. This happened here in the Florida Keys in 1996 and 1997. Lots of corals were affected by the warm still water. The El Nino affecting us those years caused the waters to get warm early in the season and stay that way all summer long.
In 1988 there was a mass die off of the Sea Urchins that inhabit the coral reefs of the Florida Keys. They graze on the algae keeping it in check. As a result of them missing from the environment, the fast-growing algae got out of control growing thick all over the reef smothering large areas of it. The urchins have made a great comeback. I see them in all stages of growth all over the reef. There were lots more of them before Hurricane Wilma last year, but I am seeing more of them each time I dive.
White band and black band disease are two other diseases seen out on the reef. It’s a bacterial infection. It’s thought to migrate from one coral to another when they are touching each other. Warmer waters and stress seem to speed up the chance of infection. It’s easy to spot the corals that are affected because of the white or black band around them. The disease progresses in the band leaving the white coral skeleton.
Other threats to the coral reefs are man and nature. The biggest threat is human growth and development. Runoff caused by development contains pollutants which find their way to the oceans leaving sediments and causing turbidity leading to coral bleaching and death of the reef. It's also responsible for algae blooms . This in turn sometimes leads to some species of fish carrying a fish poisoning called Ciguatera .
Over fishing is another problem. Lots of the reef fish eat algae. When they’re fished out in large numbers as they are today the algae takes over and smothers the reef.
Hurricanes are a big threat to the coral reefs. They build huge waves that pound the corals and fish for an extended time. The last two hurricane seasons have really beat up our coral reefs. Some areas are nothing but rubble. Large coral heads that used to have lobster hiding in them had gotten cracked when hurricane’s Frances and Jean came thru. Then the next season brought Wilma close by here and finished the job. I can’t even find these heads. They have been beaten into many pieces and scattered all around the sandy bottom of the ocean floor. It’s amazing to see the large chunks of coral that have been rolled over a long distance, crushing everything in its path. The soft corals such as sea whips and gorgonians are crushed laying under lots of these large pieces. All my landmarks under the water are gone. I used to really know my way around because I recognized the different outcropping and heads and now they’re nothing but rubble.
Parrotfish are considered a predator to the corals. You can hear them crushing it with their teeth while diving. Some of these guys are at least three feet long and quite thick. I read that each parrotfish is responsible for generating a ton of sand each year. It’s the by-product from them eating the coral.
Spur and groove are the most abundant coral formation here. It’s fingers of corals with sandy channels in between. We have large areas of patch reefs in Hawk Channel. Some of the heads there are 15 to 20 feet tall. They’re mostly star and brain coral. I see lots of pillar coral. It’s one of the most interesting. It looks like fuzzy fingers. Some of them are two and 3 feet tall. Fire coral is my least favorite. That stuff gets me every time I dive. It’ll grow on almost anything and takes the shape of whatever it grows onto. My favorite one is the Elkhorn coral. There’s not much of it left here. It seems to be a favorite place for large schools of fish to hide.
The groundings of ships have forced us to help rebuild the structure of the coral reefs to give these corals a surface on which to grow. Several of these restoration projects have been carried out right here at Looe Key Reef and in the Upper Keys at Molasses reef inside John Pennekamp State Park . The good news is that it’s working.
Our coral reefs seem to be in danger in the Florida keys and around the world. But research is being done to better understand how we can help this beautiful fragile environment to rebuild and have clean, clear waters to grow in.
Return from Coral Reefs to Diving and Snorkeling
Return from Coral Reefs to N The Florida Keys