CORAL FORMATIONS

This is the fun stuff now.

Coral species (of the order Scleractinia) secrete calcium carbonate, form hard skeletons that protect their soft bodies and build coral reefs.

Coral reefs are considered to be the most diverse and complex marine ecosystem on Earth. Yet well developed reefs grow under a restricted set of environmental parameters. Factors most significantly influencing coral growth and distribution include temperature, light, and nutrient levels.

Optimal conditions for coral growth are warm (18-30 C), clear, nutrient-poor waters.

The classification of coral reefs dates back to Darwin who placed them in three main categories: fringing reefs, barrier reefs, and atolls. Many scientists also recognize bank reefs and patch reefs as distinct reef types. Still other scientists have put forth their own theories or developed their own classifications. From my recreational viewpoint, fringing reefs, barrier reefs and atolls are described below.

Coral reefs are defined by their structure and the geological conditions under which they evolved. Generally, reef types may be described as follows;

Fringing Reefs. Fringing reefs grow out from the shore or are separated by a shallow lagoon. They generally parallel the coastline and at their shallowest, often break or nearly reach the water's surface. They are common around most Caribbean islands but are virtually absent along both the Florida coasts and Florida Keys. Geologically, they are considered the youngest type of reef.

Barrier Reefs. Barrier reefs generally grow parallel to a coastline but are separated by extensive distance and a relatively deep lagoon. Belize is a perfect example of this in the western hemisphere.

The distance to a barrier reef may vary from one mile to 25 miles and the water in the lagoon often exceeds depths of 60 feet. At their shallowest, barrier reefs often break the surface or almost reach the surface, forming a barrier to navigation. The outer edge of a barrier reef drops sharply from a platform or continental shelf into very deep water.

Atolls. An atoll is a open water reef that forms a ring or an oval shape around a shallow lagoon. Atolls are generally found in the tropical Pacific, like Bora Bora or Rangiroa, where large geological plates supporting volcanic peaks gradually sink, forming a ridge around the extinct volcano. As the plate sinks, the reefs become more distant from the land and grow upwards, forming barrier reefs.

The final stage of an atoll's development occurs when the volcanic island is completely submerged, leaving the lagoon in its place.

There are three good examples of atolls in Belize, Glovers Atoll, which we have visited on several occasions, and is a spectacular place to dive, and the Turneffe and Lighthouse Atoll, home to the Great Blue Hole.