We describe a method that makes quite a realistic reef using a plastic box, clay and sand, but feel feel free to adapt this activity using building blocks or other shapes.

Activity steps - making a reef

1. You will first need to make your model reef. Take your plastic box and place the heavy items in the bottom that will make up the structure of your reef. You are looking for the shape shown below: a reef flat or lagoon, gently sloping up to the reef crest and then curving down to the fore reef and then the reef slope.
2. If you are using clay to create your reef, then roll out a layer of clay using a rolling pin or glass bottle and lay this over the heavy items.
3. Decorate the wet clay with sand to create a more realistic effect, then leave this to dry out for at least an hour.

Activity steps - adding coral

1. You are now going to add five different types of coral to your reef zone model. These are: branching coral, boulder coral, encrusting coral, branching plate coral and plate coral.
2. Make models of each of these out of play dough or modelling clay. You can use the Gallery: Zones on the reef or Gallery: Coral ID to help with your coral modelling.
3. Think about how depth and wave action might affect the zones where these different corals can be found.

• Clear plastic box
• Heavy items to build the structure of the reef
• Clay
• Sand (optional)
• Rolling pin or glass bottle
• Coloured play dough or modelling clay

Factors affecting zonation on the reef

There are two main factors that affect zonation on the reef: wave action and depth. The wave action is strongest on the shallower areas facing the open ocean, i.e. reef crest and fore reef. It is less likely to find corals with a fragile shape in these zones. Larger corals are unlikely to be found in the shallow areas of the reef such as the lagoon or reef crest. In the deeper waters, corals will need to have adapted to the lower light conditions. This may involve darker colours, which you can investigate using the Activity: Exploring deep coral. Deeper corals also try to maximise access to the lower light conditions at depth by growing in flat plate-like shapes.