Tiny glass plants reveal salinity change in Murray River

Monday, 25 October 2004

Scientists at the University of Adelaide and Monash University have developed a new tool for assessing the degree of salinity increases in the Murray River and its wetlands.

In a recently published study in Marine and Freshwater Research, Dr John Tibby, ARC Research Associate, Geographical and Environmental Studies, Faculty of Humanities and Social Sciences, University of Adelaide, and Dr Michael Reid, a Research Fellow at the Cooperative Research Centre for Freshwater Ecology, University of Canberra, used microscopic plants - known as diatoms - to develop a model for inferring subtle changes in salinity in the river and its wetlands.

"Because of its glass cell wall, diatoms are preserved anywhere where mud accumulates. By doing sediment coring and dating the sediments, diatoms provide a record of past salinity conditions, in particular those before European arrival," Dr Tibby says.

Dr Tibby says where sediments accumulate, there is a potential to use these sensitive organisms to tell us what salinity was 10, 100 or even 1000 years ago.

"This information is important as there are major efforts to rehabilitate the River and its wetlands, yet in most places we just don't know what conditions used to be like," Dr Reid says.

"This type of work is important since salinity measurements in the River are, at best, less than 100 years old," Dr Tibby says.

The two researchers were surprised how sensitive the diatoms were to changes in salinity. "We're picking up changes in the species observed, despite the fact that most people couldn't taste the salt in the water we're studying," Dr Reid says.
"We weren't looking to develop a method for detecting past salinity. However, the salinity signal was just too strong to ignore," Dr Tibby says.

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