-November 14, 2011-
On our latest trip we went to the Great Barrier Reef . We saw several different types of corals some that are only found in that area. Some of the hard corals were Elkhorn coral,
Staghorn coral,
Table coral,
and Brain coral.
Some of the soft corals we encountered were: Mushroom coral,
Yellow Tree coral,
Sea Plume Gorgonian,
and the Red Tree Gorgonian.
Corals are like people, they need food, water, and shelter to survive. Coral filter feed on plankton and detritus, but nematocycts on the polyp’s tentacles also paralyze small fish and shrimp swimming by to eat.
The water temperature and salinity also need to be at certain levels for different species of coral in shallow water to allow sunlight to reach them. Pollution and debris in the water can damage and clog polyps. Polyps also live in hard calcium carbonate skeletons and stay inside during the day, protruding to catch food during the night. When polyps die the new polyps form on the skeletons of the old, slowing building the coral colony.
Coral can reproduce both sexually and asexually. During spawning one or two nights of the year, polyps release eggs and sperm that float out into the water. When they meet and become the fertilized, the larva will settle somewhere and begin to try and grow into a polyp. Asexual reproduction is accomplished by budding.
Coral also have beneficial relationships with other organisms, the most important being with the zooxanthellae. The zooxanthellae are algae inside of the coral that are used as food for the coral, and in return the the coral’s waste gives nutrients to the zooxanthellae. Sea Anemones are a type of soft coral that we saw have a symbiotic relationship with Clownfish. The anemones provide protection to the Clownfish that live in them and the Clownfish provide food for the anemone with any leftover scraps from their food. Crabs and shrimp also use the coral to hide from predators and will live under or inside the coral colony.
We also saw a few of the corals predators, including the crown-of-thorns starfish, parrotfish and butterfly fish. These organism eat the coral and the fish destroy parts of the calcium carbonate skeleton as they take bites out of the coral. Parrotfish however also can keep algae from covering the coral and so have a love-hate relationship with the coral.
- Alaric Pfitzinger