Drought On The Murray River Harms Ocean Life Too
Hannah Auricht, Kenneth Clarke, 8 Dec 17
       

The mouth of the Murray River delivers vital nutrients to marine life in the ocean beyond. SA Water, Author provided

Drought in the Murray River doesn’t just affect the river itself – it also affects the ecosystems that live in the ocean beyond.

In a study published in Marine and Freshwater Research today, we found that the very low flows in the river over the past decade reduced the abundance of microscopic marine plants called phytoplankton, which are ultimately the base of all marine food webs.

This shows that the health of the Murray River has a much bigger influence on the marine environment than we previously realised. With climate change poised to make droughts more frequent and severe in the river, it will be crucial to monitor the health not just of freshwater species, but of the local marine ones too.

Phytoplankton depend on nutrients, which are often delivered to the ocean by rivers. In turn, these tiny plants are a source of food for almost all marine ecosystems. Worldwide, they are responsible for half the production of organic matter on the planet.

In South Australia, a dry period dubbed the Millennium Drought (2001 to 2010) and overallocation of water resources (primarily for agriculture) meant that very little water was delivered from the Murray Mouth to the coastal ocean. Between 2007 and 2010, no water was discharged at all. The water in the river’s lower reaches became much saltier and cloudier.

We used historical flow records and satellite imagery, taken between early 2002 and late 2016, to figure out how much phytoplankton and other organic matter were in the coastal ocean each month. We broke up the area into incremental zones, venturing up to 130km from the river mouth.

We found that during and after high-flow events, Murray River discharge resulted in a huge increase in phytoplankton concentrations – as far as 60km beyond the river’s mouth. Surprisingly, before our research it wasn’t known that the river played such an important role in stimulating phytoplankton growth over such a large area.

The mouth of the Murray River, where sometimes no water flows into the ocean at all. CSIRO/Wikimedia Commons, CC BY

Armed with an understanding of how river flows influenced phytoplankton growth, we used historic flow records to estimate phytoplankton concentrations back to 1962. Our results showed that large flows used to occur more often and in greater volumes, and consequently that phytoplankton populations would have gone through more frequent and larger booms.

This in turn would have benefited all of the species that ultimately depend on phytoplankton for food, either directly or indirectly. This food web encompasses almost the whole marine ecosystem.

Sign in to view full article

       
Enough’s Enough: Buying More Stuff Isn’t Always the Answer to Happiness
The average German household contains 10,000 items. That’s according to a study cited by Frank Trentmann in his sweeping history ...
Anthony James
Thu, 5 Jan 17
Facebook’s New Anti-Fake News Strategy Is Not Going To Work – But Something Else Might
Over the past year, the social media company has been scrutinized for influencing the US presidential election by spreading fake ...
Paul Ralph
Mon, 1 May 17
Every Picture Tells A Story, But Visualisation Can Tell The Right One
They say a picture is worth a thousand words.
Quang Vinh Nguyen
Thu, 4 May 17
Is Violent Political Protest Ever Justified?
The mass protests against Donald Trump’s election, inauguration, and executive actions might subside – but based on the scale and ...
Christopher J. Finlay
Thu, 30 Mar 17
Singapore’s Ageing Population, a Challenge for Hospitals and Nurses
The increase in hospital admission and ensuing demands on intensive medical care will trigger the need for more hospital beds: ...
Epoch Newsroom
Mon, 2 Jan 17
Sports Elements
An Epoch Times Survey
Get your November/December 2017 issue at Kinokuniya stores today!
BUCHERER
Sports Elements
Read about Forced Organ Harvesting