Seagrasses
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Seagrass beds |
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Close-up view of seagrass |
More than 5000 km2 of seagrass habitat have been mapped so far within the Great Barrier Reef Marine Park. While this is an impressive area, it represents less than 1.5 per cent of the total area of the Park.
Seagrasses are of great ecological importance as food sources for threatened or endangered species such as green turtles and dugongs, and as nursery areas for juvenile prawns and fishes, some of which, such as tiger prawns, are of great commercial significance.
Seagrass habitat is found throughout the Marine Park - in estuaries, shallow coastal bays and inlets, coral reef platforms and in areas between reefs to a depth greater than 60 metres.
Fourteen species of seagrasses have been identified. Most are widespread, but at least two may be endemic to north-eastern Australia.
Even under natural conditions, seagrasses tend to die in some areas and colonise others fairly quickly. Consequently, the distribution of seagrass habitat also changes.
While there have been few detailed studies of changes to seagrass habitat over time, there is agreement among scientists that seagrass is coming under increasing pressure from human urban and agricultural development, trawling, and natural events such as cyclones.
Land run-off is regarded as the greatest threat, as seagrasses are extremely susceptible to changes in water quality.
