Unnamed Creek, Deep Creek Conservation Park
2012 Aquatic Ecosystem Condition Report
Permanently wet freshwater creek which was flowing in spring 2011 and autumn 2012
Diverse macroinvertebrate community with many rare and sensitive species
Obvious signs of nutrient enrichment
Riparian vegetation comprised of mostly native species
About the location
This unnamed creek is a small stream in the Deep Creek Conservation Park on the bottom of the Fleurieu Peninsula. It rises near the Deep Creek Homestead and flows south, directly to the Southern Ocean. This 228 hectare catchment is entirely located within the Deep Creek Conservation Park. The monitoring site was located just upstream of a track crossing across the creek, approximately 9 kilometres south-east from Delamere.
The creek was given a Fair rating because the site sampled showed evidence of moderate changes in ecosystem structure, and some changes to the way the ecosystem functions. There was evidence of human disturbance including nutrient enrichment and fine sediment deposition but the stream still provided habitat for some rare and sensitive macroinvertebrate species.
A diverse community of at least 58 species of macroinvertebrates was collected from pools in this flowing creek, approximately 1.8 m wide and up to 26 cm deep in spring 2011 and autumn 2012. The community consisted of mostly generalist species tolerant to pollution, such as round worms, segmented worms, the scud Austrochiltonia and mosquitoes. Other species collected in smaller numbers included a range of commonly collected species such as hydrobiid snails, freshwater limpets, 4 mites, yabbies, springtails, three beetles, craneflies, three biting midges, 15 non-biting midges, mothflies, soldier flies, dance flies, a common species of mayfly, waterbugs and dragonflies. Many sensitive and rare species were also found, including non-biting midges (Stictocladius and Harnischia), mayflies (Atalophlebia and Thraulophlebia), a stonefly (Austrocerca) and caddisflies (Oxyethira Columba and Notolina fulva). Deer, a water skink and adult stoneflies were also seen at the site.
The water was fresh (salinity ranged from 497-513 mg/L), well oxygenated (75-83% saturation) and clear, with high concentrations of nutrients such as nitrogen (0.79-0.88 mg/L) and phosphorus (0.107-0.117 mg/L).
The sediments were dominated by detritus and silt; samples taken from below the surface were blackish-brown clays and silts and were anaerobic, or lacking in oxygen. The sediments were also sulphidic in spring 2011. Large deposits of silt covered the streambed to a depth of more than 10 cm in places and more than 10 m of bank erosion was evident, likely caused by flood damage.
A moderate to large amount of phytoplankton (chlorophyll a ranged from 7.04-11.8 µg/L) and small amounts of blue-green algae (chlorophyll b ranged from <0.1-0.24 µg/L) were recorded but no filamentous algae was seen. More than 35% of the site was covered by aquatic plants including Berula, Carex, Isolepis and Polygonum. The riparian zone consisted of mainly grasses and gum trees with Carex, Berula and bracken also present. The surrounding vegetation was native scrubland on the left bank but open grassland on the right bank.
Special environmental values
This unnamed creek in Deep Creek Conservation Park provides important habitat for a rich assemblage of aquatic macroinvertebrates, including several rare and sensitive species from the region.
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