Seagrasses of Western Australia

The Seagrasses of Western Australia are submerged flowering plants found along the coast, around islands, and in Estuaries of Western Australia. The region contains some of the largest seagrass meadows in the world, and is the most diverse in the number of species. The variety of habitats along its western and southern coasts is often soft sands in shallow subtropical waters, ideal for these plants.

Marine grasses are flowering plants that evolved from terrestrial grasses to habitat in coastal waters. In contrast to seaweeds, usually found on rocks, seagrass colonises sandy ocean beds to form dense stands and meadows.

The Western Australian coastline, along with its islands, is over 20,000 km long. These tropical to temperate waters extend from latitudes 32-34°S to 12°S. The great diversity of habitat in these coastal regions of Western Australia are occupied by seagrasses, frequently 'engineering' habitat through colonisation of shallow ocean floors. These plants possess rhizomes which extend under the sand, stems emerge from these with one, or many, flattened and elongated leaves. These features allow the plants to stabilise the substrate, anchor themselves against currents, and change the environment.

A colony may have one or several species of seagrass, and a large number of other species living within it. The area covered by seagrass in Western Australian waters is equivalent to Australia's rainforest.

The range extends to the temperate regions of the Southern Ocean. Some areas of the southern coast provide suitable habitat, such as those at King George Sound and the Archipelago of the Recherche, the warmer water of the Leeuwin Current contributes the diversity of these seagrass communities. The western coast contain notable and diverse seagrass beds; Cockburn Sound and the Swan River estuary, and the Houtman Abrolhos, Rottnest and other islands. The Wooramel Seagrass Bank 12 species - estimated 4,500 km² of seabed - at Shark Bay is the largest reported seagrass meadows in the world (Walker, 1989). The Timor Sea is largely unsurveyed.

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