Dr Chris Hepplewhite and Dr Ralf Haese from Geoscience Australia collect sediment core samples from the Coorong in South Australia.

Nutrient sources and sinks in the Coorong

Geoscience Australia and the Coorong, Lower Lakes and Murray Mouth Ecology Research Cluster (CLLAMMecology) have established a partnership to investigate nutrient sources and sinks in the Coorong in South Australia.

• 15 November 2007 | Updated 14 October 2011

• Background
• Project aims
• Partnership

Background

The Coorong, Lower Lakes and Murray Mouth (CLLAMMecology) region of the River Murray is an environmental asset of international significance.

Home to large numbers of migratory birds, as well as many species of fish and invertebrates, the area also has significant cultural, social and economic values.

But the area is threatened by low flows, rising salinity and other issues of environmental degradation.

In response to the need for a detailed bio-physical characterization of the Coorong under present-day conditions, this Geoscience Australia project will develop an understanding on nutrient sources and sinks, their importance for algal growth and implications for food-webs and habitats.

Project aims

Geoscience Australia will undertake a detailed bio-physical characterization of the Coorong under present-day conditions to support the calibration and validation of a bio-physical model used as a tool to predict how the Coorong ecosystem will respond to different scenarios.

The following key research questions will be addressed:

1. What is the magnitude of nutrient release from sediments into the overlying water and how important are these benthic nutrient fluxes for primary production and the composition of algal groups?
   
   
2. Given the importance of Nitrogen (N) fixation and N₂ production in surface sediments as main mechanism to enrich and remove bioavailable N from the system, respectively, how do these processes vary along the salinity gradient?
   
   
3. Given preliminary thermodynamic calculations suggesting possible precipitation of Phosphorous (P)-containing minerals under hypersaline conditions, do sediments act as permanent sink for P under given salinity conditions and to what degree does possible P sequestration affect nutrient limitation of primary production?

Sample collection and experiments in the field will be carried out during the winter of 2007 and the 2007-08 summer.

Nutrient and gas fluxes across the sediment-water interface will be measured using benthic chambers, rates of benthic and water column primary production will be determined, and the pore water chemistry will be determined to predict mineral precipitation using thermodynamic models.

Partnership

This project is a collaboration between

• Geoscience Australia
• the CLLAMMecology Research Cluster.

Geoscience Australia's collaboration through this project will develop synergies with ongoing ecological research leading to a better process-based understanding on interactions between nutrient cycles and food webs.

The CLLAMMecology Cluster involves:

• The University of Adelaide, South Australia
• Flinders University of South Australia
• South Australian Research and Development Institute (SARDI)
• the South Australian Department of the Environment and Heritage.

It is developing tools to predict how changes in management practices, such as environmental flow releases and the operation of the Lower Lakes barrages, are likely to impact on ecosystem function and biodiversity.