The Deep Creek, at the waterfall
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
Emerging signs of nutrient enrichment
Riparian vegetation comprised of native species
About the location
The Deep Creek is located on the bottom of the Fleurieu Peninsula. It rises near Parawa and flows in a southerly direction through grazing land and pine forests before entering Deep Creek Conservation Park. The lower reaches of the creek are located within the boundaries of the park until it discharges into the Southern Ocean. The major land uses in the 1,360 hectare catchment are conservation park (66%) and grazing pasture (31%). The monitoring site was located at the waterfall in the lower reaches of the catchment, approximately 2 kilometres from the mouth of the creek.
The creek was given a Very Good rating because the site sampled showed evidence of very little changes in ecosystem structure and function, with many rare and sensitive macroinvertebrate species present. 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 78 species of macroinvertebrates was collected from this flowing creek, approximately 5 m wide and up to 35 cm deep in spring 2011 and autumn 2012. The community included a range of generalist and pollution tolerant species, as well as more sensitive species. The generalist and pollution tolerant species included round worms, hydrobiid snails, freshwater limpets, segmented worms, seven different species of mites, the scud Austrochiltonia, craneflies, biting midges, dance flies, at least 20 species of non-biting midge, a common species of mayfly, waterbugs, two dragonflies and three common species of caddisfly. The more sensitive species collected from this site included the riffle beetle Simsonia leai, three different types of blackfly larvae (Austrosimulium and Simulium), the fly larvae Austrothaumalea, non-biting midges (Cardiocladius, Bryophaenocladius, Bortyocladius and Riethia), the mayfly Thraulophlebia, stoneflies (Dinotoperla, Illiesoperla, Newmanoperla and Austrocerca) and caddisflies (Taschorema, Orphninotrichia maculata, Orthotrichia bishop, and Lingora). The introduced snail Potamopygrus was also present and the frog Crinia was heard calling near the site. Marron, an introduced crayfish, while not caught in either spring 2011 or autumn 2012 is also known to inhabit this stream. Three rare species of caddisfly (Tasimia, Notalina fulva and Anisocentropus) and a mayfly (Centroptilum) were also found at this site on a previous visit.
The water was moderately fresh (salinity ranged from 994-1034mg/L), well oxygenated (86-101% saturation) and clear, with moderate to high concentrations of nutrients such as nitrogen (0.64-0.9 mg/L) and phosphorus (0.035-0.044 mg/L).
The sediments were dominated by cobbles, detritus and silt. Samples taken from below the surface were grey silts and clays and showed no signs of being anaerobic or lacking oxygen. Small deposits of silt covered the streambed to a depth of 5 cm in places but there was no evidence of bank erosion at the site.
A small amount of phytoplankton (chlorophyll a ranged from 2.11-3.09 µg/L) was recorded and small amounts of filamentous algae (Cladophora) was present at the site in spring 2011. More than 10% of the site was covered in aquatic plants, including Berula, Carex, Cyperus, Hydrocotyle, Juncus pauciflora, Phragmites and Triglochin. The riparian zone consisted of native scrubland, Carex and Cyperus and some weedy species. The surrounding vegetation was native scrubland with an overstorey of gums and acacias and an understorey of Melaleucas, other native shrubs and Xanthorrhoea.
Special environmental values
The Deep Creek provides important habitat for a wide range of rare, sensitive, flow-dependent aquatic macroinvertebrates from the region. It has consistently supported a large number of regionally important species over the past two decades and is among the most notable streams in the Mount Lofty Ranges.
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