Pine Creek, near Dutton
2010 Aquatic Ecosystem Condition Report
- Permanently wet with isolated saline pools present in autumn and spring.
- Sparse macroinvertebrate community with no rare or sensitive species.
- Obvious signs of moderate to gross nutrient enrichment.
- Riparian vegetation was mostly native trees over introduced grasses and weeds.
About the location
Pine Creek is a small stream in the northern Mount Lofty Ranges. It rises near Mount Rufus and flows in an easterly direction through Dutton and eventually disappears underground in the Murray mallee, several kilometres east of Accommodation Hill. The major land use is sheep grazing.
The monitoring site was located off Dutton Mail Road, about one kilometre east of Dutton.
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, silt deposition and a degraded riparian zone.
A sparse community of about 29 species of macroinvertebrates was collected from the isolated pool habitats, up to 10 metres wide and over one metre deep, in autumn and spring 2010. The community was dominated by species tolerant to poor water quality such as amphipods (Austrochiltonia australis), chironomids (including Dicrotendipes and Kiefferulus) and culicid mosquito larvae. It also included smaller numbers of introduced hydrobiid snails (Potamopyrgus), mites, freshwater shrimps, yabbies, springtails, beetles, biting midges, soldierflies, waterbugs, damselflies and dragonflies. No sensitive or rare species were found.
The water was saline (salinity ranged from 5,939–5,989 mg/L), moderately well to well oxygenated (50–92% saturation), clear, and with low to moderate concentrations of nutrients such as nitrogen (0.29–0.39 mg/L) and phosphorus (<0.005–0.02 mg/L).
The sediments were dominated by detritus, silt, sand, gravel and algae; samples taken from below the surface were sulfidic in autumn, indicating that the sediments were occasionally lacking in oxygen. Large deposits of silt, over 10 centimetres thick, covered the creekbed in places. Small areas of bank erosion caused by roadworks were also recorded in autumn.
The creek had low amounts of phytoplankton present in both seasons sampled and about 20% of the sediment was covered by filamentous algae (Spirogyra and Cladophora) in autumn. Over 65% of the channel was covered by aquatic plants, including both submerged (Chara) and emergent species (Typha, Phragmites and the introduced weed Juncus acutus).
The riparian zone consisted of native trees (River Red Gums, acacias and sheoaks) over introduced grasses, weeds (including Juncus acutus) and reeds (Phragmites). The surrounding vegetation was cropping and grazing land with a few scattered gum trees.
Special environmental features
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.|
|Widespread introduced trees and weeds in the riparian zone at the site and upstream in the catchment (reducing habitat quality).||The SA Murray–Darling Basin NRM Board recognises the limitations of available funds relative to the scale of the degradation caused by introduced trees and weeds. The NRM Board provides free technical advice and community education to assist land managers in dealing with the integrated management of aquatic weeds. The NRM Board also has a targeted process, as directed by State Government, to strictly prioritise its investment in weed control activities as funds are limited. The NRM Board actively seeks funding opportunities for weed control; most opportunities are for locations where biodiversity outcomes can be achieved.|
|Saline groundwater inflow (reducing ecological integrity).||Saline groundwater inflows may be exacerbated by two things; vegetation clearing and resultant increase in rainfall recharge, or the extraction of surface water reducing the dilution factor in natural saline discharge zones. The SA Murray–Darling Basin NRM Board’s Land Management Program strategically invests in salinity ‘hotspots’ by providing incentives to land managers to plant perennial pasture/fodder crops/ or revegetation to reduce recharge. The NRM Board works with various agencies to minimise any further vegetation clearing which may impact on the catchment’s water balance. The NRM Board seeks to manage and provide for environmental flows to allow natural dilution of saline waters through the development of Water Allocation Plans and Water Affecting Activity policies across the region.|