Littoral vegetation is found on or along a shoreline or riverbank, and is an vital component of riverine ecosystems. It is an important carbon source for both instream and adjacent riverbank and floodplain ecosystems, providing habitat for fish, macroinvertebrates and birds, as well as stabilising river banks with its strong root network.
In addition to having a high environmental value, littoral species have provided indigenous people with sources of food, materials for weaving, hunting and fishing, as well as for the construction of shelters and watercraft.
Purchased, 1999 ©️ Yvonne Koolmatrie courtesy Aboriginal & Pacific Art Gallery
At the heart of Yvonne Koolmatrie’s work is her homeland: Njarringjeri Country. Stretching from the Lower Murray to its mouth at the Coorong is the land of the artist’s mother and ancestors.
The littoral zone extends from the high water mark (rarely inundated) to shoreline areas that are usually submerged. These zones are hot spots for biodiversity because they contain specialised species adapted to wetting and drying that are not found in the adjacent land and instream ecosystems.
Examples of plant species that are adapted to stable water levels and variable water levels.
The largely stable water levels brought about by river regulation and water abstraction has changed the littoral vegetation in the lower River Murray which is now, unsurprisingly, dominated by species adapted to static water levels.
Our research is investigating whether the delivery of environmental water will reinstate more variable water levels, and enable a greater diversity of littoral vegetation. We are hoping that native vegetation which responds rapidly to changes in water level will re-establish. The quick response time of littoral vegetation also makes it an excellent indicator to assess the benefit of the delivery of environmental water.
| Stable water level species | Variable water level species |
|---|---|
| Weeping willow (Salix babylonica) | River red gum (Eucalyptus camaldulensis) |
| Crack willow (Salix fragilis) | Spiny sedge (Cyperus gymnocaulos) |
| Tortured willow (Salix tortuosa) | Common rush (Juncus usitatus) |
| Cumbungi/bulrush (Typha domingensis) | Blue rod (Stemodia florulenta) |
| Common reed (Phragmites australis) | Tangled lignum (Duma florulenta) |
| Prickly bottlebrush (Callistemon brachyandrus) | |
| Water primrose (Ludwigia peploides) |
Stable water level species
Variable water level species
This research project is part of the Lower Murray Selected Area, which is within the larger Commonwealth Environmental Water Holder Flow- Monitoring Evaluation and Research (Flow-MER) project. Over the next few years we will monitor the diversity and productivity of vegetation in the littoral zones immediately downstream of Locks 1, 4 and 6. We undertake this sampling in tailwaters, as small volumes of water can result in large water level fluctuations that inundate substantial areas.
So far we have undertaken vegetation surveys in December 2019 after the spring flow pulse, when water levels had returned to normal pool level (as most littoral species recruit as water levels fall). Results showed (see graph) that native plant species richness was higher in areas inundated by environmental water, compared to the adjacent areas not inundated. In addition, numerous River red gum seedlings were observed in the area inundated by environmental water.
These results showed the spring flow pulse provided by environmental water benefited the littoral plant community by creating conditions suitable for the recruitment of littoral species, including the iconic River red gum.
We will continue to monitor to see what the ongoing delivery of environmental water will enable for the recruitment and survival of native littoral species. We are hopeful that we will see an increasing diversity of littoral species adapted to fluctuating water levels and a decrease in those littoral species adapted to stable water levels.
Our long-term hope is that environmental water delivery will enable littoral vegetation comprised of a diverse and dynamic community, dominated by native species adapted to variable water levels. Follow up surveys are planned for late 2020/early 2021 depending on the delivery of environmental water.
The study is led by plant ecologist Dr Jason Nicol from SARDI Aquatic Sciences.
