Aaron Creek, near Cobbler Hill
2012 Aquatic Ecosystem Condition Report
Ephemeral freshwater creek with isolated pools in spring 2011 and slow-flowing water in autumn 2012
Diverse macroinvertebrate community with some rare and sensitive species
Emerging signs of nutrient enrichment
Riparian vegetation comprising of native species with some weeds also present.
About the location
Aaron Creek is a small creek on the bottom of the Fleurieu Peninsula. It rises near Goondooloo Cottage, about 6.5 kilometres south from Delamere and flows in the south-westerly direction to the Southern Ocean. The 247 hectare catchment is entirely located within a conservation park. The monitoring site was located at the end of a track near Eagle Waterhole Campground, approximately 8.5 kilometres south from Delamere.
The creek was given a Very Good rating because the site sampled showed evidence of very little changes in ecosystem structure and function. There was evidence of human disturbance including emerging signs of nutrient enrichment but the stream still provided an important refuge for many macroinvertebrate species in the region.
A diverse community of at least 46 species of macroinvertebrates was collected from this stream which consisted of isolated pools in spring 2011 and a long slow-flowing pool in autumn 2012. The creek was approximately 1.5 m wide and up to 36 cm deep. The community consisted of mostly generalist taxa, however some rare and sensitive species were also collected. The community was dominated by the caddisfly Leptorussa, with smaller numbers of hydrobiid snails, segmented worms, five mites, springtails, four beetles, fly larvae from the family Dixidae, mosquitoes, biting midges, soldier flies, at least 11 species of non-biting midge, mayflies, small water striders, dragonflies, stoneflies and caddisflies also collected. A number of more sensitive species were also collected including a mayfly (Thraulophlebia inconspicua), a stonefly (Austrocerca tasmanica), and a dragonfly (Synthemis eustalacta). Several specimens of the frog Brown Tree Frogs (Litoria ewingi) and tadpoles of the same species were seen in spring 2011.
The water was moderately fresh (salinity ranged from 2,015-2,048 mg/L), moderately-well oxygenated (26-55% saturation) and clear, with high concentrations of nutrients such as nitrogen (1.09-1.14 mg/L) and phosphorus (0.055-0.062 mg/L).
The sediments were dominated by detritus, with silt and clay also present. Samples taken from below the surface were grey/black clays and silt and were anaerobic, or lacking oxygen, in autumn 2012. Small deposits of silt covered the streambed to a depth of 5 cm in places and small amounts of bank erosion were evident over less than 10 m of the stream. Kangaroo droppings were present on the banks.
A small amount of phytoplankton (chlorophyll a ranged from 0.51-0.61 µg/L) was recorded but no filamentous algae was seen. Less than 10% of the site was covered by aquatic plants including Cyperus, Isolepis, Juncus and Triglochin. The riparian vegetation consisted of large eucalypts with an understorey of native shrubs and weedy species such as lilies and thistles. The surrounding vegetation at the site was native vegetation with eucalypts, Xanthorrhoea, native shrubs and bracken present.
Special environmental values
Aaron Creek provides important habitat within a conservation park for a number of rare and sensitive aquatic macroinvertebrate from the region.
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