Scientists observe post-flood benefits in the Coorong and Lower Lakes

The Coorong’s underwater plant community provides a vital food source for birds and habitat for fish and were almost lost from the system during the Millennium Drought.

Associate Professor Jason Nicol, Senior Research Scientist with South Australian Research and Development Institute (SARDI) has observed positive changes in the plant community since the recent flood.

“The reduced salinity and extended high water levels in the Coorong resulting from the flood event have provided favourable conditions for the submergent plant community with the highest biomass recorded since the Millennium Drought,” Associate Professor Nicol said.

Principal Scientist with SARDI, Associate Professor Qifeng Ye, has been monitoring the Coorong’s native fish.

Fish sampling in December 2022 showed a substantial increase in the abundance of fish species including congolli, black bream, greenback flounder and yelloweye mullet compared to previous dry years.

“Species numbers doubled in the South Lagoon following the reduction of salinity to less than 60 grams per litre,” Associate Professor Ye said.

“The increase in fish biomass will also now benefit the many fish-eating birds and larger fish within the waters.”

Associate Professor Luke Mosley from the University of Adelaide has been engaged through the Healthy Coorong, Healthy Basin program to analyse information on water quality and nutrients in the Coorong.

“Early indications from the data we’ve collected post the big flood is that there has been marked reductions in salinity and nutrient levels in most of the Coorong, particularly the South Lagoon,” Associate Professor Mosley said.

“These conditions should enable a wider diversity of invertebrates and aquatic plants to recolonise the southern region of the Coorong, which could further improve water quality as they oxygenate the sediment and remove nutrients.”

The lowered salinity has also seen macroinvertebrate populations extending further south into the lagoons.

Flinders University’s Professor Sabine Dittmann explained that the macroinvertebrate community found near Noonameena has now become more similar to the community previously confined to the Murray Mouth region.

“This brings multiple benefits, such as a potential for bioremediation of the sediments through bioturbation by the larger worms, and the provision of food for shorebirds and fish preying on them,” Professor Dittmann said.

These scientists are part of the Coorong, Lower Lakes and Murray Mouth Scientific Advisory Group (SAG) who provide scientific advice on water delivery and water for the environment in the region.

SAG is a reference group of the Department for Environment and Water established to collect and analyse fish, vegetation, invertebrate and water quality data in the Coorong and Lower Lakes.

These projects will be among the latest research on show at the Healthy Coorong, Healthy Basin Science Forum to be held in Goolwa on Tuesday 16 May.

Presentations will include key findings from the extensive Trials and Investigations (T&I) research project, which is informing the restoration of the Coorong. Attendees will also be able to participate and provide feedback during a Coorong Restoration Roadmap workshop.

This is a free event, but venue capacity will be limited. Registration is essential via https://hchbforum.eventbrite.com.au/

Ecological monitoring programs in the Coorong are funded by The Living Murray and Healthy Coorong, Healthy Basin programs. The Living Murray is a joint initiative funded by the South Australian, New South Wales, Victorian and Commonwealth governments, coordinated by the Murray-Darling Basin Authority.