The Coorong Lagoon System in southern Australia near Adelaide contains salt levels two to three times higher than those in the ocean, making for a truly unique ecosystem around the mouth of the Murray River. But according to a new report, this one-of-a-kind locale may now be under threat, strangely enough, from a new source of salty water.
Plans are under way to cut drains through to the lagoon to clear water from nearby agricultural lands, rendered useless by salt. "The land has lost its productivity because of the loss of native vegetation," explains David Paton of the University of Adelaide. "Those plants are relatively deep-rooted, and they keep the water table low. Since the water table is saline, taking off those deep-rooted plants allows the saline water to rise to the surface, and we now have salinized and unproductive lands."
The proposed drain water, while salty, would be nowhere near as salty as the water in the Coorong, and Paton fears that it will dilute the water in the lagoon. "In five to 10 years, the hypermarine south lagoon system will have changed to an estuarine system," Paton says. And that will threaten the remarkable mix of creatures¿among them such aquatic plants as Ruppia tuberosa and some species of fish¿that have managed to adapt to the lagoon's high-salt surroundings.
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"One fish prominent here now is the hardihead, which is very important for a number of birds such as horny-headed grebes and fairy terns," Paton says. "The southern lagoon has the biggest population of fairy terns in the country. If you suddenly change the system from high salinity where these whitebait do very well, you bring in predatory fish and the whitebait fish population drops, affecting the fish-eating birds."
Instead of cutting drains, Paton suggests a different strategy: "The solution is to use much more strategic revegetation to absorb the water before it gets into the groundwater system to eliminate dryland salinity with a sustainable outcome instead of something that will continue to destroy natural assets."
