Mosquito Creek, near Langhorne Creek
2010 Aquatic Ecosystem Condition Report
- Dry in autumn and a fresh, isolated waterhole present in spring.
- Sparse macroinvertebrate community with no rare or sensitive species.
- Obvious signs of gross nutrient enrichment.
- Riparian vegetation was mostly River Red Gums and sedges.
About the location
Mosquito Creek is a small stream in the southern Mount Lofty Ranges. It rises east of Langhorne Creek and initially flows in an easterly direction before turning southwards and flowing into Boggy Lake at the northern end of Lake Alexandrina. The major land uses are sheep grazing and minor areas of native vegetation.
The monitoring site was located on Gollan’s waterhole, accessed via a track off the Wellington Road, about five kilometres east of Langhorne Creek.
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 considerable evidence of human disturbance in terms of nutrient enrichment and the extent of grazing in the catchment.
A sparse community of about nine species of macroinvertebrates was collected from a recently flooded in-stream pool, up to 70 metres wide and nearly 50 centimetres deep, in spring 2010; the site was dry in autumn. The community was dominated by species tolerant to poor water quality and temporary waters such as chironomids (Chironomus), notonectid waterbugs (Anisops) and culicid mosquito larvae (Culex). It also included smaller numbers of dytiscid and hydrophilid beetles, marshflies and corixid waterbugs. No sensitive or rare species were found.
The water was fresh (salinity of 593 mg/L), poorly oxygenated (19% saturation), and clear but strongly coloured, with very high concentrations of nutrients such as nitrogen (3.07 mg/L) and phosphorus (0.76 mg/L).
A large amount of phytoplankton was recorded from the waterhole and less than 10% of the site was covered by filamentous algae (Cladophora). Over 10% of the site was covered with emergent aquatic plants (Typha, Baumea and Cyperus).
The riparian zone mostly consisted of sedges, lignum and River Red Gums. The surrounding vegetation included River Red Gums over a remnant native shrub understorey and introduced grasses.
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.|