De'ath et al., 2008: 

"This report summarises a preliminary analysis of changes in seagrass distribution over the scale of the whole of the Great Barrier Reef World Heritage Area. Although similar numbers of sites were visited in both surveys fundamental differences in approach evident in the sample location (Figure 1) limit the amount of information that can be obtained from a comparison.

The comparison does show that ten years after the first survey large areas of the inter-reef waters of the Great Barrier Reef World Heritage Area are still populated with seagrass meadows. There is no evidence to suggest seagrasses have been lost from any region in the ten year period. Highest probabilities of finding seagrasses are in the central wet tropics from Princess Charlotte Bay to Upstart Bay and in the south offshore from Gladstone. There is a region south of Mackay of high tidal velocities where seagrasses are least likely to be found. These general patterns are present in the data from both surveys suggesting that these large spatial scale patterns are stable over time.

Most seagrass in deep water are of the genus Halophila (Coles et al 2000). The least common species HT and HC are the most clumped with HT in particular mostly limited in distribution to the central wet tropics. The small colonizing species HD and HO are widely distributed through the GBR apart from the region to the south of Mackay. HS is a larger plant with a non leaf replacing di-meristematic growth strategy (as has HT) enabling it to develop large leaf surface. It can form extensive deep water meadows and can be found in offshore areas at depths of sixty metres or more.

In July 2004 The Great Barrier Reef Marine Park Authority introduced a new zoning plan that was developed in part from biological information on the nature of the seafloor. This biological information was used to establish bioregions each of which is represented and protected in the new plan. The 1994-1999 seagrass data set was a key data set used to establish the interreef bioregions. Our analysis is the first attempt to establish whether the spatial distribution of this key habitat type is consistent through time or highly variable. The results suggest that seagrass meadows in the deep water of the Great Barrier Reef World Heritage Area have only a 15-25 % variation in spatial extent after ten years – a remarkably small change for a biological system. The designers of the new zoning plan can be reassured that spatial decisions to protect seagrass based on the 1994-1999 data set are likely to remain relevant over long time scales."

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Citation and/or URL

De’ath, G., Coles, R., McKenzie, L. and Pitcher, R., 2008 'Spatial distributions and temporal change in distributions of deep water seagrasses in the Great Barrier Reef region', Report to the Marine and Tropical Sciences Research Facility, Reef and Rainforest Research Centre Limited, Cairns 21pp.

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Spatial Coverage

 Reef-wide

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Temporal Coverage

Two surveys:

1) QDPI&F 1994-1999

2) CSIRO 2003-2006 

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Update Frequency

Not applicable 

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Other Information

 None