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Changing the flow of the Mary River, as well as the volume and frequency of its sediment load, will have a negative impact on the seagrass beds within the Great Sandy Strait and in turn, the habitat and lifecycle of native species dependent upon them for survival.
Threatened migratory marine mammals like the Dugong dugon (dugong), Caretta caretta (loggerhead turtle), and Chelonia mydas (green turtle), are all known to feed on these seagrass beds.
Seagrass, mud flat and mangrove areas are sensitive to changes in hydrology, water quality and sedimentation, which can result from the discharge of polluting substances, dredging and filling, disruption of drainage patterns or construction activity leading to alterations in tidal movement or wave direction.
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Seagrass Survival—A Delicate Balance |
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Halophila Spinulosa |
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Dugong, grazing |
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ourgreatsandy.com Celebrating and Defending the Great Sandy Strait
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PROPOSED MARY RIVER DAM
IMPACTS ON THE GREAT SANDY
ABOUT THE GREAT SANDY |
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Over time, the emptying of fresh water into the Bay has created a delicate balance in oceanic saline solutions and a number of other subtle ecological processes that ensure the survival of seagrass, as well as bank/silt stabilisation, and in turn other fresh water and marine microbiology.
The fragility of this balance was illustrated during the severe flooding of the Mary River in 1992. The run-off from the river’s upstream siltation that year threatened the dugongs with extinction, with some 1000 dugongs dying due to loss of seagrass. The suspended siltation prevented sunlight from penetrating to the ocean floor and providing the necessary chlorophyll to sustain the seagrass nutrient balance.
With the damming of the Mary River the nutrient and freshwater flow already impeded by the Tidal Barrage (See Mary River Tidal Barrage) will be cut off completely for significant periods of time. This will severely impact on the seagrass populations of the Bay and Sandy Strait, and in turn threaten the very survival of the species that rely upon it.
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¨ ‘Seagrass - Meadows in the Sea’ ... click here
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