On 2 February 1971, an international convention came into being. Known as the Ramsar convention after the Iranian city where it was adopted, it committed its signatories to the conservation and wise use of wetlands, primarily to provide habitat for water birds.
Australia is a signatory to the RAMSAR convention, and one of our important wetlands lies around the mouth of the Murray River. For years, Dr David Paton of the Department of Environmental Biology has been studying the estuarine waters of the River, Lakes, Murray Mouth and Coorong.
"A line of sandhills called Younghusband Peninsula runs for 150 kilometres from the mouth to Kingston," said Dr Paton. "Behind it is this great lagoonal system like a big appendix. About 50 km along its length it gets very narrow and breaks into two. The southern lagoon is the bottom half of it," he said.
This lagoonal system is known as the Coorong. As you move along it from the mouth, its salinity increases well beyond the level of seawater.
"It's a natural laboratory," said Dr Paton. "You can test the performance of organisms under different salinity regimes. The southern lagoon may be 2 times saltier than seawater in winter time but 3 times saltier in summer because of evaporation. It fills up in late autumn and winter with freshwater runoff, so you get a seasonal change," he said.
This high salinity means that the southern lagoon is a hypersaline sytstem; one that Dr Paton describes as "really simple."
"High salinity causes all sorts of problems for animals," said Dr Paton. "Near the mouth you'll find marine worms, but not 30 kilometres back from it, " he said. " They've been replaced by other organisms like tiny ostracods; distant relatives of shrimps."
These peculiarities of the hypersaline system govern the food sources of many birds protected under the Ramsar convention. "In the high salinity you'll have plants like Ruppia tuberosa," said Dr Paton. "A flowering plant that is a lifelin
Contact: Dr David Paton