The long dry is over and environmental flows are being restored to our rivers. Managing re-emerging wetlands to ensure plant and animal life returns rapidly to its former health is now a national priority.

Transcript

Narrator:

The long dry is over and environmental flows are being restored to our rivers. Managing re-emerging wetlands to ensure plant and animal life returns rapidly to its former health is now a national priority. Helping with this is La Trobe University freshwater plant ecologist, Dr Caitlin Johns, at the Murray Darling Freshwater Research Centre on the University's Mildura campus. Hers is one of the first revegetation studies of its kind, at Lake Walla Walla, part of the Chowilla and Lindsay-Wallpolla Islands flood plain, an 840 hectare refuge for waterbirds and other native wildlife.

Dr Caitlin Johns:

We've decided to look at this because there has been some work done overseas that's shown that waterborne plant dispersal can be a pretty important factor for re-establishing aquatic vegetation at a site that has been dry. There has been some work done on this overseas, but very little in Australia.

Narrator:

Before water was pumped back into the lake in April, Dr Johns and her team collected soil cores from the lake's drought-ravaged seed banks, and from a dry wetland nearby that acted as a 'control'.

Dr Caitlin Johns:

We are growing that in the glass house, we're going to see which species emerge and we'll be able to compare those results with germination trial results we have using sediment from more recently wet wetlands.

Narrator:

As the water began to flow, the scientists laid out sediment mats and drift nets to capture floating seeds and stem fragments to see what washes into the wetland during pumping.

Dr Caitlin Johns:

There have been previous studies which have shown that, for example, fish communities can develop in pumped sites, you do get movement of eggs and larvae through the pump, and we're expecting to find the same thing with the plant community and we're interested in two things there: one is seed capture, but the other is capturing all those species that regenerate by stem fragments, rhizomes and other vegetative means.

Narrator:

Refilling the lake has provided a wonderful natural laboratory for this.

Dr Caitlin Johns:

One of the interesting things that we're seeing is some of the floating species, some of the submerged species that don't withstand drying are washing into our nets, they're things which we wouldn't expect to come up from the soil seed bank because they do reproduce primarily by fragmentation. From the soil cores we've started to have some of our first plants begin to grow and get to a stage where we can identify them, and we've only had dry land species emerge to date, but we might get wetland species or flood dependent species coming up later on, that's still to be seen.

Narrator:

A proper balance of plants is critical for wetland nutrient cycles. Too much nutrient can lead to environmental disasters like algal blooms. And the correct plants are a vital habitat to shelter fish, water birds and other animals.

Dr Caitlin Johns:

One of the main benefits is that it will help us select sites that have a good regeneration potential so that when we do deliver environmental water we are delivering it in places where it will be most effective.

Narrator:

After the lake has been refilled at the end of the year, Dr Johns will create an inventory of all vegetation at the lake and at the control wetland. This study has been funded by the Murray-Darling Basin Authority.

Note: This project was funded by the Murray-Darling Basin Authority's 'The Living Murray' program, a joint initiative funded by the New South Wales, Victorian, South Australian, Australian Capital Territory and the Commonwealth governments.

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