Stimulating investment in pearl farming in ... - World Fish Center

Suitability of Habitats for Growth of Black-Lip and Silver-Lip Pearl Oysters Final, June 20084.0 OVERVIEW OF CORAL REEF AND LAGOON HABITATS INKEY PACIFIC REGIONS4.1 AustraliaThe following overview of tropical Australian reef systems is based on Veron (2000). Subtropicalcoral reef systems have not been described, because they are not comparable tothose in the South Pacific region. In the tropical region of Australia, the best-developedcoral reefs are found along the northeast coast, there is less development of coral reefs alongthe northwest coast and only limited development along the north coast. On the north-eastcoast, the major reef structure is the Great Barrier Reef (GBR), which comprises about 3,000fringing reefs, submerged reefs, platform and barrier reefs spanning the continental shelf ofthe Pacific coast of Queensland and merging in the north with the reefs of the Torres Straitand Papua New Guinea (Figure 1a). There are also scattered and remote reefs in the CoralSea. The GBR extends from the tropics into the subtropics and has various regions whichdiffer in terms of climate (wind patterns and rainfall), tidal regimes, water quality,bathymetry, island types, substrata and even geological histories.Capricorn and Bunker reefs, in the southern section of the GBR, are characterised by welldefined,distinctly elevated platform reefs with entire, steeply sloping sides, moderatelydeep water between reefs and vegetated cays. The Pompey Complex and Swain Reefs, twoof the most offshore extensions of this section of the GBR, have a greater range of habitatsand more diverse corals than the Capricorn/Bunker Reefs. The Pompey Complex, consistsof interlocking reefs, channels, sandbars and lagoons and has ‘deltaic’ reefs composed ofsolid limestone on its outer edge which are separated by U-shaped channels characterisedby very strong, reversing, tidal currents. This complex experiences the greatest tidal rangeof the GBR and is a major barrier to tidal water movement. The Swain complex forms asouthward pointing wedge. The reefs on both sides of the wedge have exposed outer facesand protected inner margins, but are ecologically dissimilar.The central section of the GBR is characterised by lower reefs than the southern andnorthern sections, a lack of cays and well-defined outer barrier reefs. The coastal waters arerelatively shallow, turbid, protected from strong wave action and subject to seasonalterrigenous inputs of silt, freshwater and organic nutrients when rivers are in flood. Thefauna and flora of the inshore reefs and inter-reefal areas are conseqently very different fromthose occurring offshore.In the northern section of the GBR, ribbon reefs are found where the GBR shelf meets theQueensland Trough. These ribbon reefs occur all the way along the shelf-edge break toTorres Strait (720 km). Those on the eastern side are exposed to ocean swells and dropsteeply into the abyssal depths of the Queensland Trough. The band of water inside theribbon reefs is largely devoid of reefs. The mid-shelf, however, supports extensive areas ofreefs with roughly parallel east-west margins, that were cut in the past by rivers at low sealevels. The inner shelf contains a variety of reef types, high islands and coral cays, many ofwhich are vegetated. In the far north, where the continental shelf widens, there areextensive shelf edge reefs and numerous nearshore reefs. In the Torres Strait, the outerbarrier reefs are broken up into a series of delta-like formations similar to the reefs of thePompey Complex, and an almost impenetrable line of 'dissected' reefs. Inside this barrier,there is a variety of reef complexes, high islands and cays. The sea gradually becomes moreshallow and turbid towards the west, finally forming the Warrior Reefs, a series ofenormous mud flats fringed in the east by coral.The Ecology Lab Pty Ltd – Marine and Freshwater Studies Page 12