The reef crest is the part of the coral reef that usually lets us know where the reef is actually located. Reef crests come in all shapes and sizes, and although corals rarely actually grow here, there are many useful qualities associated with these reef zones.
Understanding the role played by reef crests in the structure and balanced continuity of coral reefs can be extremely important when trying to explain exactly how coral reefs work.
Any coral reef is formed by three main reef zones: reef crests, back reef and fore reef. While the back reef and fore reef – as the name would suggest – are found on the innermost and outermost side of the reef, and are usually completely submerged, reef crests are the uppermost areas of coral reefs, and are almost always visible above water at low tide.
Because of this, corals are almost never able to thrive on the reef crest, so you will rarely find any coral colonies here. Constantly uncovered, the crest of most coral reef formations is also bombarded with waves coming from the open sea, so that even plants and animals are rarely able to grow and find refuge in this hostile environment.
Nevertheless, the crest plays a vital role due to this fact, being assigned with the task of protecting the inner reef, the shoreline and any lagoons present from the strong ocean waves that would otherwise make the survival of small, fragile creatures, corals and plants almost impossible.
Another significant trait associated with reef crests located near most Indo-Pacific islands and coasts is the presence of a seaweed margin known as the algal ridge. The algal ridge is often exposed at low tide, and it is the area of the crest where the wave action is strongest. Calcareous red algae are most common here, and the ridge may also be a refuge for certain types of more resilient corals in areas where the waves aren’t as strong and the ridge is not usually exposed to open air during low tide.
Although the reef crest is normally not a good place for animals – and certainly not for most types of corals – some coral colonies are actually able to live here, as long as the wave action is less severe.
Elkhorn corals are usually quite prevalent on the reef crests of coral reef formations located in the Caribbean. At the same time, there are a number of short branching corals that can also survive, and are found on less exposed areas of reef crests even more often.
Even though they may be the highest point of the reef, reef crests are teeming with life just below the surface where the effects of the tide and waves are not as strong and the irregular texture of the reef can offer protection against predators and stronger waves. Only small animals can thrive here, however, such as small crabs and shrimp.
The protective and often vital qualities of the reef crest are essential for any fish, sea creatures and plants that live on the reef flat, and as time goes by and the coral structure continues to grow, this trait becomes even more important, especially in a more dynamic environment.