Little Timber Creek, N from Murray Lagoon
2013 Aquatic Ecosystem Condition Report
- Permanently flowing stream in autumn and spring 2013
- Moderately diverse macroinvertebrate community with no rare or sensitive species and only one flow-dependent species recorded in spring
- Water was saline, clear and high in nitrogen concentrations
- Riparian vegetation comprised native trees over rushes and weeds
About the location
Little Timber Creek is a moderately sized stream on the south-central part of Kangaroo Island. It rises in the middle of the island about 8 km east from Parndana and flows in a south-easterly direction for about 14 km before merging with Timber Creek, and eventually discharging into Murray Lagoon. The major land uses in the 3,332 hectares catchment upstream from the site sampled included grazing modified pastures (50%), cropping (20%) and other minimal uses (17%), with smaller areas also used for plantation forestry, nature conservation, transport and communication, irrigated horticulture and dams. The site was located in the middle of the catchment off Birchmore Road, about 7 km north from Murray Lagoon and 16 km south-east from Parndana.
The creek was given a Poor rating because the site sampled showed evidence of major changes in ecosystem structure and moderate changes to the way the ecosystem functions. There was evidence of human disturbance due to nitrogen enrichment, high salinity and a weedy riparian zone.
A moderately diverse community of at least 22 species of macroinvertebrates was collected or seen from the creek (5 species in autumn and 18 in spring), 1.3-3.4 m wide and up to 24 cm deep, in autumn and spring 2013. The creek consisted of shallow still to slow-flowing pools connected by small areas of flowing riffle habitats, in both seasons sampled. The community was not dominated by any species but included low to moderate numbers of nematodes, mites, amphipods, beetles (including Berosus queenslandicus), craneflies, mosquitoes, biting midges, chironomids, waterbugs, dragonflies and caddisflies. The presence of crayfish holes in the banks indicated that yabbies occurred at the site and blackfly larvae were seen among the riffle habitats in spring. All of these are tolerant, generalist macroinvertebrates that have a wide distribution in the State, particularly from brackish to saline, nutrient enriched streams. The site lacked any rare or sensitive species; the high salinity probably prevents many macroinvertebrates from being able to inhabit this creek.
The water was saline (salinity ranged from 5,491-7,346 mg/L), well oxygenated (96-104% saturation), clear and slightly coloured, and with low concentrations of phosphorus (0.02 mg/L) but high nitrogen concentrations (1.03-1.13 mg/L).
The sediments were dominated by detritus, with smaller amounts of sand, silt and clay also present. Samples taken from below the surface were grey sands, silts and clays that appeared to be well-aerated, despite the abundance of organic matter at the site. There was no evidence of any significant areas of bank erosion recorded, and the only animal droppings seen in the vicinity of the creek were from kangaroos.
There was a small amount of phytoplankton recorded from the creek (chlorophyll a 1.4-2.7 μg/L) but no filamentous algae was seen during either survey in 2013. There were also no aquatic plants observed in the creek. The riparian zone extended over 5 m wide and was dominated by patches of gums and wattles over rushes (Juncus) and introduced grasses and weeds. The surrounding vegetation near the creek comprised blue gum plantation forests on one bank and native woodland merging into cleared agricultural land on the other bank.
Special environmental features
Little Timber Creek provides a permanently flowing habitat on the southern part of the island but lacks any significant aquatic animals or plants, presumably due to the high salinity of this watercourse.
Pressures and management responses
|Saline groundwater inflows into the creek (reducing ecological integrity).||This information is not available at the moment but it will be updated as soon as possible.|
|Large nutrient inputs from diffuse sources in the catchment (potentially leading to extensive growth of algae and aquatic weeds).||The Kangaroo Island NRM Board has funded the fencing of significant areas of riparian vegetation in the catchment and continues to work with landowners to increase the fencing of watercourses.|