The zooxanthellae use the waste products of the coral during photosynthesis, and the coral can use the nutrients provided by the zooxanthellae during photosynthesis.
Most reef-building corals are located in shallow water where they have plenty of access to the sunlight needed for photosynthesis. The presence of the zooxanthellae helps the reef to thrive and become larger. Some coral reefs are very large.
The Great Barrier Reef , which stretches more than 1, miles off the coast of Australia, is the world's largest reef. An important part of coral reefs is their calcium carbonate skeleton. If you follow ocean issues, you know that animals with calcium carbonate skeletons are under stress from ocean acidification Ocean acidification causes a lowering of the ocean's pH, and this makes it difficult for corals and other animals that have calcium carbonate skeletons.
Other threats to reefs include pollution from coastal areas, which can affect reef health, coral bleaching due to warming waters, and damage to corals due to construction and tourism.
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The first stage of the formation of a coral reef is the coral larvae attaching themselves to rocks or soil near the coasts. The coasts may be of an island or a continent. The larvae become polyps and excrete calcium carbonate, which forms their exoskeleton. The polyps live only in those waters which have enough sunlight seeping though. They have a symbiotic relation with the microscopic algae Zooxanthellae, which helps them grow.
As they grow, they secrete more calcium carbonate. The secreted calcium carbonate sediments on the rocks and provides a substrate for more polyps coming to attach themselves to the formation. As more and more polyps attach to the substrate, a coral reef is formed. Calcareous Algae also add their sediments to the structure. The marine animals and plants also add their own remains to the reef as they die and sink.
It strengthens the reef and now it can withstand any storm. The reefs that are initially formed near the coast are known as fringing reefs. Over a period the calcium carbonate converts into lime stone due to pressure. Patch reefs are small, isolated reefs that grow from the open bottom of the island platform or continental shelf. They usually occur between fringing reefs and barrier reefs. They vary in size and rarely reach the surface of the water.
The information in this chapter is thanks to content contributions from Haley Zanga and Emily Michaeles. Skip to content Have you ever wondered how coral reefs are formed?
Fringing Reefs: Fringing reefs grow near the coastline around islands and continents. Wilson [CC by 2. An Atoll Reef is a ring-like shaped coral reef or small islands of reefs in a circle with a lagoon in the middle and are usually located in the middle of the sea. These types of reefs are formed when an island has sunk completely or nearly in the middle of the ocean from rising sea levels around a pre-existing structure these islands are often the tops of underwater volcanoes.
Most atoll reefs can be found in the Pacific ocean where the waters are warm and salty. They can grow between the sizes of However, there are three classic structures that need to be understood: Fringe Reefs; Barrier reefs and Atoll reefs. For a coral reef to form you need several conditions: shallow water, warm water and of course, reef building corals in attendance.
These are the corals which have developed the ability to live in colonies and build up a calcium carbonate skeleton. The most common way for a coral reef to grow is when a new tropical volcanic island is produced at a hot spot on the oceanic plate or at the plate boundary.
The corals require a solid surface to settle on, often found on the new volcanic islands formed. A basic idea to remember is that coral reefs grow upwards toward sunlight, but as they are marine creatures they must continue to be under the surface of the water, so when they can no longer grow upwards they will begin to grow outwards.
The first reef structure to understand is Fringe Reefs , by far the most common type of coral reef. They grow along the coastline, forming a boarder along the coastline, sometimes even completely surrounding the volcanic island.
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