What Corals Need to Grow

In this tutorial, we will look at what coral reefs need to grow.

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You may have seen beautiful coral reefs flourishing with plants and animals and you may have also seen devastated, destroyed, diseased and unhealthy reefs.

What makes the difference between these two sets of reefs?

That is what we’re going to look at today. In this tutorial, we’re going to look at the conditions necessary for optimum coral reef growth. In a previous lesson, I mentioned that a coral consists of a polyp, which is an animal, and also a zooplankton, which is a plant.

And while plants and animals have some common needs, there are also some differences. 

So let us look at the first condition necessary for coral growth. One of the first conditions needed for coral growth is warm water. Coral reefs are found around the world, and although you can find them in temperate areas, some of the best-known reefs are found in waters that range in temperature between 23 and 25 degrees Celsius.

A second condition needed for coral growth is sunlight. To keep the zooplankton thriving and growing well, there must be sufficient sunlight for the zooplankton to carry out photosynthesis. 

Once the zooplankton is thriving, it helps the coral polyp and the entire reef to thrive as well. In fact, the depth at which a coral will grow in a particular area depends on how much light can penetrate into the water depth. 

Corals also need salt water to survive. Corals need a certain balance of salt and water, not too little, not too much. This is one of the reasons you will not find coral reefs growing at the mouth of rivers where there is a large flow of fresh water mixing with the ocean. 

Another condition needed for corals is clear water. Many activities take place on land that can affect coral reefs such as farming, construction, dredging, and sewage treatment. Also, rainwater runoff can take particles from the land and deposit them into empty nearby water streams, which can end up in the ocean. 

Too many of these particles known as sediments can smother the tiny polyps and block out sunlight, so clear water is best for their survival. 

The amount of wave action in the water is also important for healthy reef growth. There should be moderate wave action to move about the oxygen in the water, which the animal needs for survival.

The waves not only bring oxygen, but also help to remove any broken pieces of rock, grains of sand, or any sort of sediment that would otherwise smother the polyps.

When wave action is too strong, such as in the case of hurricanes, it can uproot the reef and destroy the reef’s habitat. 

Coral reefs also need inundation. This means they need to be flooded or covered by water. Although some reefs may grow as tall as the surface of the water, they are careful not to grow so tall that they grow to pass the height of the low tide mark. 

But why is this? If a coral reef grows above the low tide mark, it will be exposed to air between the low and high tides during the day. This is enough time for the reef organisms to dry out, and although some coral species can survive a few hours in the air, most cannot, and they will die from too much air exposure. 

So let’s now do a quick recap. To get optimum growth, coral reefs need conditions that are suitable for both the polyp and the symbiotic zooxanthellae.

These conditions include warm water, sunlight, salt water, clear water, moderate wave action, and inundation.

In the next lesson, we’ll look at competition grazing and predation among organisms on the reef. See you then.