How Corals Feed

In this video we take a look at coral nutrition and understand how they obtain food.

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Let us now take a look at an individual coral polyp.

Coral reefs, as I mentioned in the last lesson, are built up and made up of thousands of tiny coral polyps. These polyps are related to sea anemones and also jellyfish.

The polyps can live individually or in large colonies that make up the entire reef structure. The polyp has a sack-like body, and an opening or a mouth. Surrounding the mouth are tentacles that have stinging cells called nematocysts.

The bodies of corals are clear. The color which you see in the corals occurs because of the zooxanthellae that live inside their tissues.

But how do the corals feed?

The corals help several different strategies for obtaining food. One of those strategies is to prey on tiny organisms that swim in the water column. These organisms can be zooplankton and other small organisms that pass over the coral colony.

If they venture too close to the tentacles, they will be paralyzed by the stinging cells, captured by the tentacles, and transported toward the mouth of the coral polyp.

Some coral polyps have short tentacles that produce mucus, and it is covered with cilia, which are like tiny hairs. During feeding, these cilia beat toward the mouth and create a water current that traps these small organisms within the mucus and draws it into the mouth of the polyp.

However, the greatest amount of nutrients that the coral receives is from the zooxanthellae. In fact, the zooxanthellae provide up to 90% of the nutritional needs of the coral. The zooxanthellae provide glucose, glycerol, and amino acids.