This Purple Tube Sponge colony lives on a dead coralhead. The coral may have succombed to the algae and sponges that grew over the polyps and killed them. Now the skeleton of the coral supports a variety of sponges and algae.

Sponges are colonies of thousands of individual cells. The cells work together, pumping water through the body of the sponge. The tall tube is in the shape of a "chimney." This chimney is an exhaust tube, where the water pumped by the sponge comes out. The sponge eats the plankton it filters out of the water as the water is pumped through the body of the sponge.

Animals that eat sponges and algae help to keep a healthy balance on the reef. If there are too few of these animals, then the sponges and algae may take over. Examples of algae eaters are Parrotfishes, Sea Urchins, and Crabs. Examples of sponge eaters are Hawksbill Turtles and Loggerhead Turtles.

Learn more about the reefs of Bimini on the ReefNews Bimini webpages.