Corals

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Corals are tiny, soft-bodied creatures, that usually exist as part pf a large limestone community (coral reefs). A coral begins life as a polyp, a tiny individual that looks very similar to a sea anemone or jellyfish. Corals can live singly, but most attach themselves to a hard substrate on the sea floor, then divide (buds) into thousands of clones. They draw calcium carbonate from seawater to build a skeleton, which connects the polyps to each another, creating a colony that acts as a single organism. As these colonies grow over hundreds and thousands of years, they produce massive skeletons that form the limestone framework of coral reefs. Some of the coral reefs on the planet today began growing for more than 10 million years!


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Barrel sponge, Jupiter Beach

Corals live in tropical oceans worldwide, usually in clear, sunny areas within the first 100 feet of water. Corals have two methods of acquiring food. Corals (like their close cousins the jellyfish) can catch zoo-plankton using their stinging cells (nemotocysts) on their tentacles. However, corals obtain most their nutrition from a symbiotic relationship they have with tiny host algae that live within their bodies. This algae is responsible for giving the coral its color. The algae produce their own food by photosynthesis, and give a portion of it to the coral, in return for shelter and protection.


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Brain coral

Coral reefs only cover 1% of the ocean floor, but support 25% of marine creatures!! Coral reefs are the most biologically diverse marine ecosystems on earth, rivaled only by the tropical rainforest's on land. However despite their importance in marine ecosystems, they are under severe threats from man made pollution, global warming and natural disturbances to name but a few.

Natural disturbances such as storms affect coral reefs in many ways. Run off from land causes increased sedimentation in shallow waters, which literally smothers the coral. The increased nutrient load that run off brings, deteriorates the water quality. A range of coral diseases have been documented in recent years. Various diseases have hit most of the reefs in the Caribbean. Corals react to all these stressors by expelling their symbiotic algae, which causes coral bleaching, and eventual death of the coral reef.

Globally, more than 30% of coral reefs are already damaged. Even under the best conditions, coral reef grows very very slowly, usually less than an inch per year. This makes coral especially vulnerable to environmental changes.


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Sea rod coral

Interestingly, deep cold water corals have been discovered in most the worlds oceans, living at depths of up to 8000 feet!! They have been well studied in the deep water trenches off the coasts of Ireland and Scotland. As they live far below the depth that sunlight penetrates to, the do not have the symbiotic algae that their tropical cousins have. They thrive in areas of strong water currents, as their sole method of acquiring food is to grab prey items from the water column with their sticky tentacles.


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Diver and Brain Coral
Photo by Kevin Redfield

Brain coral is one of the most abundant types of coral in Florida.


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Close up of barrel sponge, West Palm Beach

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Bluehead juveniles over a barrel sponge, Lantana Beach

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Sea rod coral

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Lavendar rope sponge, Key Largo
Photo by Courtney Redfield

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Ridged Cactus Coral, Mycetophyllia lamarckiana, Lantana Beach
Photo by Robert Palmer
This species of coral prefers shadier and deeper water.


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Smooth flower coral, Eusmilia fastigiata, West Palm Beach
This species is common throughout the Caribbean, and extends as far north as Carolina.


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Bleached (dead) coral, West Palm Beach
Photo by Robert Palmer