Tookayerta Creek, near Tooperang
2010 Aquatic Ecosystem Condition Report
- Slow-flowing freshwater creek in autumn and spring
- Moderately diverse macroinvertebrate community with many rare and sensitive species
- Obvious signs of moderate nutrient enrichment
- Riparian vegetation limited to reeds and introduced grasses
About the location
Tookayerta Creek is a moderately large stream in the southern Mount Lofty Ranges, rising south of Mount Compass and flowing east where it ultimately discharges into the Finniss River. The major land uses are cattle grazing and cropping, with minor areas of native vegetation and rural residential living also present.
The monitoring site was located downstream of a track off Cleland Gully Road in the mid reaches of the creek, about one kilometre west of Tooperang.
The creek was given a Good rating because the site sampled showed evidence of relatively minor changes in ecosystem structure and function. There was evidence of human disturbance, including nutrient enrichment and a poor riparian habitat but the creek provides habitat for many rare and sensitive species of macroinvertebrates and fish.
A moderately diverse community of about 38 species of macroinvertebrates was collected from the slow-flowing creek, three metres wide and 50 centimetres deep, in autumn and spring 2010. The community included some species tolerant to poor water quality as well as some rarer and more sensitive species.
Large numbers of amphipods, springtails, chironomids and small water striders were collected, along with smaller numbers of freshwater limpets, introduced snails (Physa), leeches, mites, beetles, biting midges, mosquitoes, blackfly larvae, mayflies, waterbugs (waterboatmen and backswimmers), damselflies and caddisflies. The site was notable because it provided habitat for many rare or sensitive species, including four mayflies (Offadens, Tasmanophlebia, Atalophlebia australasica and Koorrnonga inconspicua) and three caddisflies (Taschorema, Ulmerochorema membrum and Orthotrichia bishopi). The community also included many species normally associated with flowing water, including a blackfly (Austrosimulium furiosum), dytiscid beetle (Platynectes), chironomid (Rheotanytarsus) and most of the rare mayflies and caddisflies. The only fish collected was the introduced mosquitofish (Gambusia) in autumn.
The water was fresh (salinity of 197-199 mg/L), well oxygenated (81-88% saturation), slightly turbid and coloured, with moderate to high concentrations of nutrients such as nitrogen (0.43-1.1 mg/L) and phosphorus (0.05-0.12 mg/L).
The sediments were dominated by detritus with some clay, silt and algae also present; samples taken from below the surface were blackened, sulphidic and anaerobic, indicating that too much organic matter had entered the creek in the past. A deposit of 1-5 centimetres of silt covered the creekbed in autumn and over 10 metres of the bank showed signs of erosion due to flood and stock damage.
A moderate amount of phytoplankton was recorded and filamentous algae comprised 15% of the sediment cover in spring. Over 35% of the site was covered in aquatic plants, including floating (Azolla and Spirodela), submerged (Stuckenia pectinata) and emergent species (Typha and introduced Rorippa).
The very narrow riparian zone lacked any trees or shrubs and only consisted of the Common Reed (Phragmites australis) and introduced grasses. The surrounding vegetation was grazed grassland.
Special environmental features
Tookayerta Creek provides a significant habitat for several sensitive and rare species of macroinvertebrates, and a range of flow-dependent species. Many of these are particularly sensitive to disturbances and have highly restricted distributions in the region and State. The mayfly from the Family Oniscigastridae (Tasmanophlebia), for example, has only been collected from Tookayerta Creek and three other creeks from the Fleurieu Peninsula in South Australia.
Recent fish surveys in the catchment have also recorded the presence of at least three threatened fish species (Mountain Galaxias, River Blackfish and Southern Pygmy Perch) from the mid to lower sections of the creek (M. Hammer, Aquasave Consultants, 2009).
Pressures and management responses
|Livestock have direct access at the site and upstream, causing sediment erosion and adding excessive nutrients (which leads to habitat disturbance, algal growth and aquatic weeds).||The SA Murray–Darling Basin NRM Board acknowledges the significant impacts that livestock have on aquatic environments and seeks to provide free technical advice and incentives to land managers for fencing and other works as funding permits. Funding incentives are limited in value and extent and require land managers to volunteer to be involved.|
|Limited riparian vegetation at the site and upstream, providing minimal buffer protection from catchment landuses (reducing habitat quality).||The SA Murray–Darling Basin NRM Board recognises that the management of riparian vegetation requires a long-term, integrated approach to achieve ecosystem benefits. The board therefore provides free technical advice on a range of topics for land managers and various incentives for works as funding permits.|
|Insufficient natural water flows resulting from water extraction and climate variability (reducing ecological integrity.||The SA Murray–Darling Basin NRM Board is working with the Department for Water and the community to develop a water allocation plan and licensing system which aim to balance social, economic and environmental needs for water. The objective for providing water to the environment is to maintain and/or restore self-sustaining water-dependent ecosystems which are resilient in times of drought.|
|Large nutrient inputs from numerous diffuse sources in the catchment (leading to extensive growth of algae and aquatic weeds).||The SA Murray–Darling Basin NRM Board’s Land Management Program provides free technical advice and education to land managers to minimise fertiliser, manure, or effluent sources of nutrients. The NRM Board also works closely with local government and developers to pursue industry best practice and manage sediment loads entering waterways. The water Allocation Planning and Water Affecting Activities policies of the NRM Board also seek to minimise nutrient inputs and allow for natural flows to dilute naturally occurring nutrient loads in waterways.|
|Feral predatory fish (trout and redfin) (reducing ecological integrity).||Local volunteer groups are undertaking works at some sites. The SA Murray-Darling Basin NRM Board opportunistically removes pest fish during monitoring activities. Other agencies are responsible for the control of pest fish and have undertaken some awareness-raising activities throughout the region.|