Tookayerta Creek, near Mount Observation
2010 Aquatic Ecosystem Condition Report
- Permanently wet, slow-flowing, freshwater creek in autumn and spring.
- Sparse macroinvertebrate community with some rare or sensitive species.
- Obvious signs of moderate to gross nutrient enrichment.
- Riparian vegetation dominated by reeds, introduced grasses and a few gum trees.
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 use is cattle grazing.
The monitoring site was located off the Tooperang–Cleland Gully Road, about three kilometres south of Mount Observation.
SA Murray–Darling Basin NRM Regional Summary 2010
The creek was given a Fair rating because the site sampled showed moderate changes in ecosystem structure and some changes to the way the ecosystem functions. There was evidence of human disturbance, including nutrient enrichment and poor riparian habitat, although the stream still provided an important refuge for some sensitive macroinvertebrate species.
A sparse community of about 18 species of macroinvertebrates was collected from the slow-flowing creek, five metres wide and over a metre deep, in spring 2010. The site was not sampled in autumn because it was overgrown by reeds and too difficult to access. The community was dominated by moderate numbers of chironomids and blackfly larvae. It also included smaller numbers of mites, amphipods, isopods, freshwater shrimps, mayflies, waterbugs, dragonflies and caddisflies.
Several rare and sensitive species were collected, including a baetid mayfly (Offadens), stonefly (Dinotoperla evansi) and caddisfly (Triplectides similis). The site also provided habitat for several species normally associated with flowing water, including a blackfly (Austrosimulium furiosum), chironomid (Rheotanytarsus) and the above mentioned mayfly, stonefly and caddisfly.
The water was fresh (salinity of 225 mg/L), well oxygenated (77% saturation), slightly turbid and coloured, with moderate to high concentrations of nutrients such as nitrogen (0.91 mg/L) and phosphorus (0.08 mg/L).
The sediments were dominated by detritus and silt; samples taken from below the surface were sulfidic, presumably in response to the decomposition of the large amount of detritus in the sediments.
Only a small amount of phytoplankton was recorded from the site and no filamentous algae was observed in 2010. Over 90% of the site was, however, covered by the Common Reed (Phragmites australis), with smaller patches of introduced watercress (Rorippa) also noted.
The riparian zone consisted of reeds, introduced grasses, broom, and gum trees. The surrounding vegetation at the site was grazed grassland with a few gums.
Special environmental features
The lower reaches of Tookayerta Creek provides habitat for some rare and sensitive species, including a stonefly, mayfly and caddisfly. A more diverse assemblage of significant species also occurs further upstream in the upper and mid reaches of this creek.
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.|
|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.|
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