Coral Reefs: Formation, Distribution, and Features

• Coral reefs are deposits of calcium carbonate built by coral polyps.
• Coral polyps are tiny soft-bodied animals that create coral reefs.
• Corals are generally located 30 degrees north and south of the equator.
• Corals are scattered throughout the tropical and subtropical western Atlantic and Indo-Pacific oceans.
• Western Atlantic reefs include Bermuda, the Bahamas, the Caribbean Islands, Florida, and the Gulf of Mexico.
• The Indo-Pacific ocean region extends from the Red Sea and the Persian Gulf through the Indian and Pacific oceans to the western coast of Panama.
• Corals grow on rocky outcrops in some areas of the Gulf of California.
• The Great Barrier Reef in Northern Australia has great biodiversity and can be seen from space.
• Coral reef distribution depends on temperature, light, water depth, and salinity.

Coral Reef Features

• Corals cannot tolerate water temperatures below 18°C but grow best at 23-29°C.
• Some corals can withstand temperatures up to 40°C for short periods.
• Coral thrives between the Tropics of Capricorn and Cancer.
• Corals need light for photosynthesis because of zooxanthellae.
• Zooxanthellae are tiny algae that live inside the cells of coral and help by providing food through sunlight.
• Corals are generally found at depths less than 25m where sunlight can penetrate.
• Optimum photosynthesis requires clear and clean water.
• As marine animals, corals need salty water to survive, with salinity ranging between 32-42% saltwater.
• Corals require well-oxygenated waves and clean water.
• They cannot be exposed to air for too long.
• Coral reefs support high levels of biodiversity.

Types of Coral Reefs

• Fringing reefs form around a land mass.
• Barrier reefs run parallel to the shore, separated by channels, e.g., the Great Barrier Reef, Australia.
• Atolls are horseshoe-shaped rings consisting of a coral rim that encircles a lagoon.

Mangrove Distribution

• Mangroves and coral reefs are found in warm tropical waters.
• Mangroves are adapted to changing conditions, unlike coral reefs.
• Mangroves cover 25% of tropical coastlines.
• Mangroves are primarily located in warm tropical waters and coastal swamps within 30 degrees north and south of the equator.

Mangrove Characteristics

• Mangroves are trees that grow along the coastline.
• Mangrove trees grow in water between 0.5 to 2.5 meters high.
• Tree sizes range from over 60m high.
• High levels of humidity are needed.
• The ideal temperature for mangrove growth is around 27 degrees.
• Mangrove root systems features numerous tangled roots that grow above ground, forming dense thickets.
• Mangroves have a filtration system that keeps salt out.
• Some mangroves have snorkel-like roots that help them take in air.

Sand Dune Distribution

• Coastal dunes are found worldwide.
• Sand dunes consist of sand shaped into mounds and ridges by the wind.
• Sand dunes are located at the back of a beach, above the maximum reach of the tide.
• Sand dunes develop best when there is a wide beach with a large quantity of sand.
• Sand dunes develop when the prevailing wind is onshore.
• Sand dunes develop when there is a large tidal range.
• Characteristics of sand dunes: small or large ridges are usually found at the back of the beach.
• Sand dunes extend backwards for many miles.

Sand Dune Formation

• Wind blows over sand and hits pebbles.
• More sand particles are caught, and dunes grow in size, forming rows at right angles.

Types of Sand Dunes

• Embryo dunes: dry sand blows over and gets trapped by debris.
• Sea couch grass and other plants grow in embryo dunes.
• Embryo dunes have poor soil with high pH levels.
• Embryo dunes are fragile and have a maximum height of 1 meter.
• Fore dunes: act as protection against prevailing winds such as marram grass up to 5 meters.
• Yellow dunes: initially yellow but darken over time due to organic matter, with a maximum height of 8 meters.
• Grey dunes: more stable, with shrubs and bushes between 8-10 meters.
• Mature dunes: oldest and most stable, hundreds of meters from the shoreline.

Salt Marshes Distribution

• Salt marshes are found all over the world and are not temperature-dependent.
• Salt marshes have very flat numerous channels running through them.
• Salt marshes form in sheltered coastal areas, areas behind spits, and brackish water.
• Brackish water is partly salty and partly fresh.

Salt Marsh Features

• Salt marshes build up to and above the level of tidal flooding, remaining muddy and sticky.
• Salt marshes begin as tidal mud flats that gain height as more sediment is deposited.
• The process of vegetation over time is called succession.