Reduced flow in water out of the Murray could be harmful to Southern Ocean marine life

THREATENED: The River Murray is home to unique ecosystems, which are under threat due to reduced flow in the water out of the Murray River. Photo: Supplied.

THREATENED: The River Murray is home to unique ecosystems, which are under threat due to reduced flow in the water out of the Murray River. Photo: Supplied.

Discoveries have been made by researchers from the University of Adelaide that reduced flow in the water out of the River Murray could pose as a threat to marine life in the Southern Ocean.

Researchers analysed satellite remote-sensing data (MODIS) of the coastal ocean zone that receives outflows from the Murray River.

Populations of marine species such as mulloway fish and Goolwa cockles could be devastated by reduced flows

The data was collected over the course of 15 years to determine the amount of phytoplankton outside the Murray Mouth during various flow conditions.

The research was published in the Marine and Freshwater Research journal.

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

“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 eco system function. Higher concentrations indicate a more productive system,” she 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 and Goolwa cockles could be devastated by reduced flows, especially considering future climate change projections.

School of Biological sciences senior research fellow Dr Luke Mosley said the research demonstrated that river outflows were a stimulus for productivity in the sea.

“(This causes) phytoplankton blooms up to 60km from the coast, and that severe drought, for example from 2007-2010, can reduce flows to the point where this stimulation effect vanishes completely,” he said.

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

As the likelihood of increased frequency and severity of droughts could occur in the future, it was suggested that  the potential impact of reduced outflows from the River Murray should be considered as part of the Murray-Darling Basin management plans.

Dr Ken Clark, School of Biological Sciences, said the findings were not entirely unexpected.

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