Understanding the main reef zones is essential to having a broader view of how corals actually work, and the reef flat is among the most significant reef zones, as well as the largest.
This is the entirety of the flat area that separates the shore from the coral reef crest. It includes both the back reef and the lagoon area (if present), and is often uncovered during low tide periods, extending the shoreline in some cases right to the reef itself.
Structure of the Reef Flat
Smooth, sandy areas that extend from the shore to the reef crest, reef flats commonly start with a low downward slope, and in most cases are just a few feet deep. Also known as the inner reef, this area sustains most of the damage incurred from sediments, due to being adjacent to the land. Because of this, coral colonies rarely survive here, and you can only find a few soft corals in more protected parts of the inner reef.
On the other hand, seagrass and seaweed grow in abundance on the reef flat, particularly near the reef slope, where coral growths are also more significant. At this point, an ascending slope begins, also known as the back reef, and can extend from a few feet to several miles, depending on how large and old the coral reef actually is.
The inner reef’s lowest depths are usually known to form a lagoon zone that allows for significant species diversity, due to the much warmer and tamer currents, compared to those hitting the reef crest and fore reef zone.
A Thriving Underwater World
Mangroves and various plants found in the area between land and the main areas of the inner reef protect the shoreline by trapping sediments. They often turn these sediments into ideal habitats for small marine animals and fish. At the same time, seagrass beds can also be found in this reef zone, providing vital nourishment for a variety of species.
The inner reef is home to many types of underwater fauna, including hundreds of species of colorful fish, as well as sea turtles, as well as many other fascinating species of animals and plants alike, including sea cucumbers, sponges, anemones and conch.
It’s important to note that the zone may differ greatly in some areas, depending on the types of reef formations present and their distance from the actual shoreline. The reef flat can, in some cases, be much more difficult to navigate by larger fish and sea mammals, particularly due to it being separated from the open sea and offering far less space than the fore reef.
Nevertheless, due to the common presence of lagoons, as well as the larger depth and smoothness of these areas, inner reef zones can, in some cases, allow larger fish to thrive as well as herbivore ones that feed on the abundant seagrass, making it easy for the ecosystem to fully develop the food chain that makes it possible for the wide range of coral reef species and marine life to survive most successfully.
Whether you consider the multiple complex reef formations of the Great Barrier Reef or the volcanic islands of the Pacific, the reef flat reef zone plays an essential role in both the continuing growth and expansion of corals themselves and the marine life species thriving in the areas around them.