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Southern Ocean’s health affected by River Murray

Thursday, 7 December 2017

Source: University of Adelaide

Reductions in the flow of water out of the River Murray could be harmful to marine life in the Southern Ocean, according to research findings.

Up until now there has been almost no research into the effect of the river’s flow on the ocean beyond its mouth.

In contrast, changes in flow and how it affects the river’s own ecology and the economy which depends on it, have been widely studied.

University of Adelaide researchers analysed satellite images over 15 years to determine the amount of phytoplankton (microscopic plants that float in the sea) outside the Murray Mouth during various flow conditions.

Their findings have been published in the journal Marine and Freshwater Research

Lead author Hannah Auricht – a PhD candidate from the School of Biological Sciences – said that marine life up to 60km out to sea was being affected by water leaving the river.

“Ocean health can be gauged by the levels of phytoplankton present in the water as it is the basis for the food web and hence critical for marine ecosystem function. Higher concentrations indicate a more productive system,” Ms Auricht said.

“We suspect that the coastal ecosystems beyond the mouth are dependent on the outflows from the river and significant breaks in these flows are likely to have long-term impacts on marine life - including commercially fished species.”

“Populations of marine species such as mulloway fish (Argyrosomus japonicus) and Goolwa cockles (Donax deltoides) could be devastated by reduced flows, especially considering future climate change projections,” Ms Auricht said.

Senior Research Fellow at the School of Biological Sciences Dr Luke Mosley said the research demonstrated that the river outflows were a "stimulus for productivity in the sea, causing phytoplankton blooms up to 60km from the coast" and that severe drought – for example that experienced from 2007 to 2010 – could reduce flows to the point where this stimulation effect vanished completely. 

“At present, management plans for the river do not take into account the effect it has on the marine ecosystems of the Southern Ocean,” Dr Mosley said.

With increasing frequency and severity of droughts likely in future, the potential impact of reduced outflows from the River Murray should be considered as part of Murray-Darling Basin management plans.

The results also highlight the importance of implementing the current Murray-Darling Basin plan, which is recovering water for the environment.

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Media Contacts:

Hannah Auricht
PhD candidate and lead author
School of Biological Sciences, University of Adelaide.
P: +61 (8) 8313 2790

Dr Luke Mosley
Senior Research Fellow, School of Biological Sciences
Faculty of Sciences, University of Adelaide.
P: +61 (8) 8313 5453
M: 0428 103 563

Crispin Savage
Media Officer, External Relations
The University of Adelaide
P: +61 (8) 8313 7194
E: crispin.savage@adelaide.edu.au