What is a Coral reef?
Coral Facts

The Great Barier Reef is the       largest living thing on the       planet.
A quarter of the world's fish       rely on coral reefs as       nurseries.
More than 450 million people       live within 60 kilometres of       coral reefs, with the majority       directly or indirectly deriving       food and income from them

Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny animals found in marine waters that contain few nutrients.Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps belong to a group of animals known as Cnidaria, which also includes sea anemones and jellyfish. Unlike sea anemones, coral polyps secrete hard carbonate exoskeletons which support and protect their bodies. Reefs grow best in warm, shallow, clear, sunny and agitated waters.

Often called "rainforests of the sea", coral reefs form some of the most diverse ecosystems on Earth. They occupy less than 0.1% of the world's ocean surface, about half the area of France, yet they provide a home for 25% of all marine species, including fish, mollusks, worms, crustaceans, echinoderms, sponges, tunicates and other cnidarians. Paradoxically, coral reefs flourish even though they are surrounded by ocean waters that provide few nutrients. They are most commonly found at shallow depths in tropical waters, but deep water and cold water corals also exist on smaller scales in other areas.

Coral reefs deliver ecosystem services to tourism, fisheries and shoreline protection.They are under threat from climate change, oceanic acidification, blast fishing, cyanide fishing for aquarium fish, sunscreen use, overuse of reef resources, and harmful land-use practices, including urban and agricultural runoff and water pollution, which can harm reefs by encouraging excess algal growth.

Location of Coral Reefs around the World

Coral reefs can be found around the world and even in some places that you would not expect. In recent years scientists have discovered cold water coral reefs off the coast of Norway and deep underwater in the Mediterranean Sea.

Coral Structure

Coral reefs begin to form when free-swimming coral larvae (planulae) attach to the submerged edges of islands or continents. As the corals grow and expand, reefs take on one of three major characteristic structures-fringing, barrier or atoll.Fringing reefs, which are the most common, project seaward directly from the shore, forming borders along the shoreline and surrounding islands. Barrier reefs also border shorelines, but at a greater distance. They are separated from their adjacent land mass by a lagoon of open, often relatively deep water. If a fringing reef forms around a volcanic island that subsides completely below sea level while the coral continues to grow upward, an atoll forms. Atolls are usually circular or oval, with a central lagoon. Parts of the reef platform may emerge as one or more islands, and breaks in the reef provide access to the central lagoon

Coral and their Kinds

The three principal reef types are:

Fringing reef - directly attached to a shore, or borders it with an intervening     shallow channel or lagoon
Barrier reef - reef separated from a mainland or island shore by a deep channel or     lagoon
Atoll reef - more or less circular or continuous barrier reef extends all the way around a lagoon without a central     island

Importance of Coral Reefs

Coral reefs do a number of amazing things! Reefs

Protect shorelines from big waves by absorbing wave energy
Provide a safe place for fish to spawn (release eggs into the water)
Provide habitats for a large variety of organisms
Provide food (fish and shellfish) for many people living along    coastlines
Are a source of medication-some anti-cancer drugs and painkillers    come from reefs
Help in the carbon cycle
Are a good sign of ocean water quality: Healthy reefs = Healthy    water.

Coral Reefs under threat

Major threats to coral reefs and their habitats include:

When I first saw a coral, I thought that it was a plant. Is that right?

Are polyp and coral the same?

How does the polyp make its skeleton?

How does sunlight affect the growth of a coral?

Monograph:101 questions on corals:towards awareness
Destructive fishing practices:
These include cyanide fishing, blast or dynamite fishing, bottom trawling, and muro-ami (banging on the reef with sticks). Bottom-trawling is one of the greatest threats to cold-water coral reefs.
This affects the ecological balance of coral reef communities, warping the food chain and causing effects far beyond the directly overfished population.
Careless tourism:
Careless boating, diving, snorkeling, and fishing happens around the world, with people touching reefs, stirring up sediment, collecting coral, and dropping anchors on reefs. Some tourist resorts and infrastructure have been built directly on top of reefs, and some resorts empty their sewage or other wastes directly into water surrounding coral reefs.
Urban and industrial waste, sewage, agrochemicals, and oil pollution are poisoning reefs. These toxins are dumped directly into the ocean or carried by river systems from sources upstream. Some pollutants, such as sewage and runoff from farming, increase the level of nitrogen in seawater, causing an overgrowth of algae, which 'smothers' reefs by cutting off their sunlight.
Erosion caused by construction (both along coasts and inland), mining, logging, and farming is leading to increased sediment in rivers. This ends up in the ocean, where it can 'smother' corals by depriving them of the light needed to survive. The destruction of mangrove forests, which normally trap large amounts of sediment, is exacerbating the problem.
Coral mining:
Live coral is removed from reefs for use as bricks, road-fill, or cement for new buildings. Corals are also sold as souvenirs to tourists and to exporters who don't know or don't care about the longer term damage done, and harvested for the live rock trade.
Climate change:
Corals cannot survive if the water temperature is too high. Global warming has already led to increased levels of coral bleaching, and this is predicted to increase in frequency and severity in the coming decades. Such bleaching events may be the final nail in the coffin for already stressed coral reefs and reef ecosystems.

The Great Barrier Reef and the coal mine that could kill it

The Great Barrier Reef is sick. Almost half of its coral is already dead and a massive new coal mine, which was given final approval this week, will only cause further damage. This is not just an issue for Australia, it affects us all

Source: http://www.theguardian.com/environment/2014/aug/01/-sp-great-barrier-reef-and-coal-mine-could-kill-it

Solution to threats

Marine Protected Areas (MPAs):

The MPAs play a major role in protecting the Coral Reefs. An MPA is any marine area reserved by laws or regulations to provide protection for part or all of the resources within the area. The protected resources can be natural or cultural (e.g., a historical shipwreck). An MPA may include areas zoned for specific uses, including "no-take" areas, where no resources can be removed.

When we follow the below mentioned points, the coral reefs can be easily protected.

Conserve water
Help reduce pollution
Use only ecological or organic fertilizers
Dispose of your trash properly
Support reef-friendly businesses
Plant a tree
Practice safe and responsible diving and snorkeling
Volunteer for a coral reef cleanup
Contact your government representatives
Spread the word