Feeding
Coral polyps can feed on minute organic particles and plankton using their tentacles to capture and then engulf their prey. However, many Anthozoan and all hermatypic coral species have a close symbiotic relationship with zooxanthellae, microscopic brown algae which are found in the coral tissue. These algal cells produce excess sugars through photosynthesis, which is taken up by the coral. In return the zooxanthellae are provided with a stable environment away from predators and variable environmental conditions.
These corals are completely dependent on these algae partners to provide them with 80% of their nutrients. It is the zooxanthellae, living within the coral polyps' cells which often provide the coral with its colour. Coral bleaching occurs when the corals expel their zooxanthellae in stressed conditions such as unusually high temperatures, which can be fatal for the coral colony. (photos)
