Ruppia tuberosa is a small aquatic plant with flowers that float on the water. They shed their pollen there, so the flower heads must be kept above the Coorong's water, which may form waves 30 cm high. Each flower head has a spiral like a loose spring. As the waves come and go, it rises and falls, remaining on the surface.
The plants produce pollen and then seeds, but more important for plant-eating birds are the starchy food stores called turions. Other birds depend on fish adapted to the hypermarine system.
"One fish prominent there now is the hardihead," said Dr Paton. "It's commonly known as whitebait, a small 10cm fish which is very important for a number of birds such as horny headed grebes and fairy terns," said Dr Paton. "The southern lagoon has the biggest population of fairy terns in country," he said..
" 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."
Changes to the salinity of the southern lagoon are not just an academic threat. There are plans to cut drains through to the lagoon in order to clear water from areas of the south east.
"It is part of process to rehabilitate large areas of agricultural land from dryland salinisation," said Dr Paton. "The land has lost its productivity because of the loss of native vegetation," he said. "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 salinised and unproductive lands."
The drains are intended to solve this problem by carrying the surface water into the Coorong but, if they do, they will carry it into the hypermarine system of the southern lagoon. Despite the salt loads in the drained water, it cannot match the hypermarine salinity of the Coorong water, and will grad
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Contact: Dr David Paton
david.paton@adelaide.edu.au
618-83034742
Adelaide University
8-Apr-2001