Thailand Coral Reefs
There are two types of coral; hard coral and soft coral. Hard corals, like brain coral and staghorn coral, are the reef makers. Soft corals, like broccoli corals and mushroom coral, do not contribute to reef building.
Coral reef refers to the limstone structure produced when coral polyps excrete an exoskeleton of calcium carbonate. Even though this exoskeleton grows at a very slow rate, typically 1-2cm annually, it accumulates over hundreds of years to form massive reef networks. These are the largest structures on earth of biological origin.
Worldwide Distribution of Coral
Coral reefs occure in both temperate and tropical waters. The tropical reefs are much more prolific with 92% of the world's reefs exisiting in the Indo-Pacific region Atlantic and Caribbean coral reefs are much less significant accounting for only 7.6% of the worlds total reef coverage.
Reefs are rare on the west coasts of America and Africa as strong cold coastal currents prohibits coral growth. They are also rare around the north eastern fringe of South America due to the freshwater release from the Amazon basin.
The coral reef at Koh Pling - located on the west coast of Koh Phra Thong near Golden Buddha Resort.
The delicate branches of a hard coral. This structure is a calcium carbonate exoskeleton excreted by the coral polyps.
The tentacles of a coral polyps collect and direct plankton towards the mouth at the centre.
Coral Polyps Structure
All coral polyps share two basic structural features. The first is that they all have a gastrovascular cavity and mouth. Food is consumed and some waste prodcuts are expelled through this mouth. The second feature is that all corals contain a circle of tentaclees at the hood of the mouth. The tentacles help the coral to capture and ingest plankton for food and also to clear away debris from the mouth.
Better Living Through Symbiosis
Most corals live in a symbiotic relationship with an algae called zooxanthellae. The coral provides the algae with a protected environment and the compounds necessary for photosynthesis. These include carbon dioxide, produced by coral respiration, and inorganic nutrients such as nitrates, and phosphates, which are metabolic waste products of the coral.
In return, the algae produce oxygen and help the coral to remove wastes. Most importantly, they supply the coral with organic products of photosynthesis. These compounds, including glucose and amino acids, are utilized by the coral in the manufacture of proteins, fats, and carbohydrates, as well as the synthesis of calcium carbonate (CaCO3).
The large reliance on zooxanthellae photosynthesis explains why the tropical shallow water corals only exist above 50m depth and thrive in a temperature of 26°C - 27°C.
Richelieu Rock is a limestone pinnacle in the Andaman Sea covered in beautiful soft corals
Coral Reef Biodiversity
Coral reefs are considered to be the marine equivalent of tropical rainforests.They harbor more than 25 percent of all known fish and provide our oceans with the highest biodiversity of any marine ecosystem.
These are astounding statistics within themselves, yet are even more so when you also consider that coral reefs grow in nutrient poor waters. It is the symbiotic relationship between the coral polyps and zooxanthellae that provides a basis for high nutrient recycling with the system, which in turn supports this extraordinary level of biodiversity.
Threats to the World's Coral Reefs
Coral reefs are under significant threat from a range of macro and micro stressors. Most of these are rooted in the increasing burden that mankind is putting on the planet.
Natural events such as storms, coral diseases and temperature changes from El Nino events also play a role. The El Nino of 1997-1998 increased water temperature to such an extent that 70-80% of shallow waters were killed in some regions of the Indo-Pacific
The quantity and mechanisms of other threats are too numerous to be explained here. A summary of the most significant ones is listed below.
Ocean Warming - From greenhouse gases. Stresses the coral polyps leadin to coral bleaching.
Ocean Acidification - Carbon Dioxide dissolving into seawater, acidifying it. This weakens the skeletons of coral and shell based organisms.
Water Pollution - Oil, gas, pesticides poison coral. Human waste causes an overgrowth of algae which smothers the reef by cutting off sunlight.
Sedimentation - Coastal development destroys mangroves and seagrasses. Increases sedimentation which again smothers the reef.
Destructive Fishing Practices - cyanide fishing poisons the coral, dynamite fishing blows the reef apart, overfishing strains the interdependent relationships found on a healthy reef.
Coral Mining - For construction purposes and for tourists trade.
Dynamite fishing is a highly destructive practice where hundreds of years of coral growth can be destroyed in a moment.
Cyanide fishing is a practice where exotic fish are stunned and captured for the aquarium & restaurant trades with disastrous side effects.
Scuba divers checking the species and monitoring the health of a hard coral reef colony.
Get involved with Coral Reef monitoring by joining an eco dive with Blue Guru Diving. By doing this you will also be contributing to diving and marine eucation of the local youth. The key to a sustainable future for these tropical marine habitats.