Coral Reef Reproduction is amazing.

Coral reef reproduction is done in two ways: asexually and sexually.

Some corals divide to form new individuals. This is known as asexual reproduction.

Sexual coral reef reproduction takes place as mass spawning, where polyps release millions of eggs and sperm. Polyps are either male or female or both male and female. After the eggs and sperm are released, they float to the surface. The fertilised eggs that escape predation by other animals hatch into larvae and drift with the plankton. The tiny percent that survive and settle on the reef then begin new coral colonies. Mass Spawning by corals.

Releasing massive amounts of eggs and sperm by many animals (or plants) at once is called mass spawning. This increases the chances of successful fertilisation in two ways.

Firstly, with more sperm and eggs in the water the probability of successful fertilisation is increased, and secondly with such a large number of fertilised gametes in the water the percentage lost to predation is reduced.

Mass spawning occurs in a spectacular fashion at Coral Bay and some other reefs in the world including the Great Barrier Reef.

Corals spawn en masse on only one or two nights a year. This event occurs on the night when the tides are at their lowest so that the draining water takes the fertilised gametes away from the reef and increases dispersal to other reefs or other areas of the reef. Mass spawning on the reef has also been recorded in some algae and other invertebrates, such as palolo worms.

Many millions of eggs and sperm are released, forming slicks on the sea surface. Before release, each egg is supplied with the symbiotic zooxanthellae so important to the coral animals’ success on the reef. A few days after fertilisation, a swimming larva (a planula larva) develops and these larvae may travel great distances to start new colonies. After a certain time, the larva starts to head to the bottom and if it finds a suitable substrate to grow on it will settle there and metamorphose (change) into a coral polyp and start a new coral colony. Very few larvae make it to this stage - they are eaten, cannot find a place to settle, or killed by unsuitable water conditions or lack of food.

Other related pages: