Waycott et al., 2007:

Diversity and Distribution 

"Seagrass diversity in Australia is amongst the highest in the world, in part due to the overlap of already diverse tropical and temperate floras^141,31. The bays, estuaries, lagoons and reef platforms of the Great Barrier Reef (GBR) region provide habitat for 12 seagrasses including one endemic species, Halophila tricostata. The seagrasses of this region are typically found growing in waters less than ten metres below mean sea level. However, some species of the genus Halophila can be found to depths of 56 metres^82,25. Shallow and intertidal seagrass meadows are influenced by coastal topography and shelter, as a result, most larger seagrass meadows are found in north facing bays and estuaries that are protected from the dominant south-easterly winds. The highest densities of seagrass occur between Princess Charlotte Bay and Cairns (13.5 to 17 °S) and below Rockhampton (23 °S). Seagrass meadows are sparse north of Princess Charlotte Bay and south of Mackay in the area where tidal velocities are high. The total area of seagrass habitat along the Queensland coast has remained relatively stable during the past 5 to 10 years.

The mapped area of seagrass is approximately 1741 km2 (Figure 8.2), while best estimates of total area of seagrass meadows along the east coast are 5668 km2 of intertidal and shallow subtidal habitat (down to 15 metres water depth)^{66,4,83,84,91,26,27,28,29,30,92,93} (Queensland Department of Primary Industries and Fisheries unpublished data) (Figure 8.2). The area of seagrass meadows in reef lagoon waters of the GBR deeper than 15 metres may be as high as 40,000 km2 25, however these seagrasses are little studied. We present the seagrass areas of the GBR in four regions to facilitate discussion regarding the different general environments seagrass occur."

Seagrass beds as habitat 

"Tropical seagrass meadows have been documented to create habitat complexity compared with unvegetated areas – providing up to 27 times more habitable substrate115 – as well as providing refuge and food for a range of animals. At least 20 species of prawns (mostly commercially important juveniles) can be found in seagrasses of the GBR in densities eight times that of adjacent bare areas^23,80,24. Seagrass meadows are also crucial habitat for at least 134 species of fish, predominantly gobies, leatherjackets, pony fish and trumpeters^23,80,24.

In the GBR, the abundance of fauna occupying seagrass meadows correlates strongly with seagrass biomass or living space (leaf area)^103,61,74. The fish and prawns occupying these seagrass meadows are predominantly carnivorous, feeding not directly on the seagrass but on a range of fauna occupying the meadows including amphipods, isopods, gastropods and copepods^145,74. These smaller invertebrates form an important trophic link between seagrasses, epiphytes and the carnivorous fauna⁶⁸. In contrast, as much as 99 percent of dugong and 97 percent of adult green turtle diets consist of seagrass75 with the remainder comprising invertebrates and algae that are usually, though not always, incidental foods^50,116."

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Citation and/or URL

Waycott, M., Collier, C., McMahon, K., Ralph, P., Mckenzie, L., Udy, J. and Grech, A., 2007, Chapter 8, Vulnerability of seagrasses in the Great Barrier Reef to climate change, In: Climate change and the Great Barrier Reef: a vulnerability assessment, eds J.E., Johnson and P.A. Marshall, Great Barrier Reef Marine Park Authority and Australian Greenhouse Office, Australia, 193-235 

Spatial Coverage

Reef-wide

Temporal Coverage

 Not applicable - a synthesis report

Update Frequency

 Not applicable - a synthesis report

Other Information

 None