Coral Reefs

Coral reefs are warm, clear, shallow ocean habitats that are rich in life. The reef’s massive structure 1) forms / is formed / had been formed from coral polyps, tiny animals that live in colonies; when coral polyps 2) are dying / die / will die, they leave behind a hard, stony, branching structure 3) making / having been made / made of limestone.

The coral 4) provides / is provided / was provided shelter for many animals in this complex habitat, 5) included / including / having included sponges, nudibranches, fish (like Blacktip Reef Sharks, groupers, clown fish, eels, parrotfish, snapper and scorpion fish), jellyfish, anemones, sea stars (including the destructive Crown of Thorns), crustaceans (like crabs, shrimp and lobsters), turtles, sea snakes, snails, and 33olluscs (like octopuses, nautilus and clams). Birds also 6) are feasted / feast / feasts on coral reef animals.

There are two types of coral, hard coral and soft coral. Hard corals (like brain coral and elkhorn coral) have hard, limestone skeletons which 7) are forming / form / are being formed the basis of coral reefs. Soft corals (like sea fingers and sea whips) 8) do not build / does not build / are not built reefs.

Coral reefs 9) are developed / will develop / develop in shallow, warm water, usually near land, and mostly in the tropics; coral prefer temperatures between 70 and 85 ° F (21 – 30 °C). There are coral reefs off the eastern coast of Africa, off the southern coast of India, in the Red Sea, and off the coasts of northeast and northwest Australia and on to Polynesia. There 10) is / are / were also coral reefs off the coast of Florida, USA, to the Caribbean, and down to Brazil.

The Great Barrier Reef (off the coast of NE Australia) 11) has been / is / are the largest coral reef in the world. It is over 1,257 miles (2000 km) long.

The different types of reefs 12) have included / includes / include the following. Fringing reefs, that form along a coastline, 13) grows / grow / are grown on the continental shelf in shallow water.

Barrier reefs 14) will grow/ are grown / grow parallel to shorelines, but farther out, usually 15) separating / to separate / separated from the land by a deep lagoon. They are called barrier reefs because they form a barrier between the lagoon and the seas, 16) impeding / impeded / to impede navigation.

Coral Atolls are rings of coral that 17) is grown / grow / are grown on top of old, 18) sunken / sinking / to sink volcanoes in the ocean. They 19) have begun / begin / began as fringe reefs 20) to surround / surrounded / surrounding a volcanic island; then, as the volcano 21) sink / sinks / is sunken, the reef 22) continue / continues / will continue to grow, and eventually only the reef 23) remains / is remained / is remaining.

Many coral reefs 24) are dying / had died / has died. Major threats to coral reefs are water pollution (from sewage and agricultural runoff), dredging off the coast, careless collecting of coral specimens, and sedimentation (when silt or sand from construction or mining projects muddies the waters of a reef and kills coral, which needs light to live).

(Based on http://www.enchantedlearning.com/subjects/ocean/Coralreef.shtml)

Task 9. Read the text and complete the tasks after it: