Southern Ocean's health affected by River Murray's ebb and flow

December 7, 2017 by Crispin Savage, University of Adelaide

Researchers at the University of Adelaide have found that reductions in the flow of water out of the River Murray could be harmful to marine life in the Southern Ocean.

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.

The research, published in the journal Marine and Freshwater Research, 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 conditions.

"Marine life is being affected by the water leaving the river up to 60 km out to sea," says lead author Hannah Auricht, Ph.D. candidate from the School of Biological Sciences.

"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."

"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 —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," says Ms. Auricht.

"The research demonstrates that the river outflows are a stimulus for productivity in the sea, causing phytoplankton blooms up to 60 km from the coast, and that severe drought, for example from 2007-2010, can reduce flows to the point where this stimulation effect vanishes completely," says Dr. Luke Mosley, senior research Fellow at the School of Biological Sciences.

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

With increasing frequency and severity of droughts likely to occur in the 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.

Explore further: First long-term study of Murray-Darling Basin wetlands reveals severe impact of dams

More information: Hannah C. C. Auricht et al. Have droughts and increased water extraction from the Murray River (Australia) reduced coastal ocean productivity?, Marine and Freshwater Research (2017). DOI: 10.1071/MF17226

Related Stories

Dam risk to Murray-Darling wetlands may be underestimated

June 7, 2011

(PhysOrg.com) -- Computer modelling used to develop the Murray-Darling Basin Plan may have significantly underestimated the effects of building dams and diverting water on the internationally listed Macquarie Marshes wetlands, ...

World's rivers running on empty, paper finds

November 26, 2012

(Phys.org)—Four of the world's great rivers, including the Murray Darling, are all suffering from drastically reduced flows as a direct result of water extraction, according to new ANU research.

Australia pumps $1.83 bln into food bowl river

October 26, 2012

The government on Friday pledged Aus$1.77 billion (US$1.83 billion) to pump more than 450 billion litres of water into the ailing Murray-Darling River and help rejuvenate a crucial system supplying Australia's food bowl.

Fake flooding impacts considered

July 21, 2014

Artificial flooding may be a water-efficient way to irrigate dry landscapes but scientists warn it is not a solution for all problems and the ecological impact needs more thorough monitoring.

Recommended for you

A damming trend

December 14, 2018

Hundreds of dams are being proposed for Mekong River basin in Southeast Asia. The negative social and environmental consequences—affecting everything from food security to the environment—greatly outweigh the positive ...

Data from Kilauea suggests the eruption was unprecedented

December 14, 2018

A very large team of researchers from multiple institutions in the U.S. has concluded that the Kilauea volcanic eruption that occurred over this past summer represented an unprecedented volcanic event. In their paper published ...

The long dry: global water supplies are shrinking

December 13, 2018

A global study has found a paradox: our water supplies are shrinking at the same time as climate change is generating more intense rain. And the culprit is the drying of soils, say researchers, pointing to a world where drought-like ...

Death near the shoreline, not life on land

December 13, 2018

Our understanding of when the very first animals started living on land is helped by identifying trace fossils—the tracks and trails left by ancient animals—in sedimentary rocks that were deposited on the continents.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.