<<

Department of Primary Industries and Regional Development

Reefs provide habitat for a diverse range of a horseshoe or ring around a central marine organisms that also interact with the lagoon. Parts of the reef platform may adjacent habitats, such as shallow sheltered poke through the surface as one or more bays and lagoons, seagrass meadows and islands. coastal . Reefs create a natural buffer or barrier against strong winds and waves that would normally erode coastlines and affect coastal communities and infrastructure, such as ports and boat moorings, canals and marina developments. They also act as ‘ sinks’ locking up the carbon Investigating the reef structures along our dioxide in the form of . coast will give you an indication of the type Reefs can take on various forms such as: of you can expect to find washed up on the . Plants and animals are • Fringing reefs extend directly out to found in places where they are best adapted sea, forming protective ‘borders’ along to survive. Reefs in Western Australia can be shorelines and around islands. Ningaloo broadly split into two groups – reef in Western Australia’s North-West is Australia’s largest fringing reef. limestone reefs (generally found in temperate climates) and coral reefs (generally found in tropical climates). Limestone reefs Limestone reefs along the Western Australian coast are formed from continuous deposits of . These reefs have taken thousands of years to develop. Organic • Barrier reefs are separated from the matter such as skeletal remains and shells, mainland by a wide channel, or lagoon. have formed deposits that have been An example is Queensland’s 2300km-long compressed and hardened over time. The Great Barrier Reef, the longest barrier reef wind and sea have eroded some deposits, but in the world. others remained and formed the coastal reef systems as they are today. Limestone reefs may also be the remnants from the previous mainland. About 18,000 years ago, the edge of the coastal plain, including the mouth of the Swan , was about 20 km west of Rottnest. • Atoll reefs are created when a fringing was just a hill rising from a vast plain until reef forms at the edges of a volcanic rising seas submerged it and cut it off from island that has sunk below sea level. the mainland. Many of Western Australia’s Atolls are usually circular or oval, forming offshore islands formed this way.

Beachcombers Kit, more resources like this can be found at – beachcombers-kit.fish.wa.gov.au Page 1 Reef continued...

Limestone reefs provide platforms to which hitchhikers are deposited at various spots algae attaches itself. Algae begins a process along the way, where they help to populate that encourages other plants and animals spectacular coral communities. to live on limestone reefs and support a The most significant coral reefs are found complex marine habitat. along Western Australia’s so-called Coral Higher order animals in the food web come Coast, stretching some 1000 kilometres from in search of food on limestone reefs, and Cervantes in the south to Exmouth in the may also use its holes and overhangs for north. protection. As these animals are not on the are colonies of tiny tubular animals reef all the time, they are unlikely to be highly called polyps. Generally classified as either adapted for survival on a reef. hard or soft corals, the hard coral polyp Limestone reefs and ‘bombies’ (or outcrops) secretes a cup-shaped limestone skeletal provide important habitat for many fisheries case, known as a corallite that supports and in Western Australia including our abalone protects the soft body of the coral polyp. and western lobster fisheries. When the coral polyp dies, the corallite stays behind as a hard skeleton. Coral reefs are Coral reefs formed over thousands of years with the build up of millions of these coral skeletons. Coral reefs grow off Western Australia’s coastline from the far north all the way south A coral reef is not made entirely of coral. to Rottnest Island. Algae plays an important role by producing calcium type materials. These materials help Strongest in autumn and winter, the warm to together , pieces of coral and Leeuwin Current makes an epic coastal other materials either living or dead, to form voyage from north to south, carrying with it the reef. the larvae of tropical corals and fish. These

Beachcombers Education Kit, more resources like this can be found at – beachcombers-kit.fish.wa.gov.au Page 2