The Wither Swamp, near Deep Creek Conservation Park
2012 Aquatic Ecosystem Condition Report
Permanently wet freshwater creek with slow-flowing water in spring 2011 and autumn 2012
Diverse macroinvertebrate community with many rare and sensitive species
Obvious signs of nutrient enrichment
Riparian vegetation comprised of native species.
About the location
The Wither Swamp is a small tributary of The Deep Creek on the bottom of the Fleurieu Peninsula which then flows into the Southern Ocean. The upper reaches of this stream is located in grazing land, however, the lower reaches occur are within Deep Creek Conservation Park. The major land uses in this 289 hectare catchment are grazing pasture (59%), native vegetation (24%) and conservation park (15%). The monitoring site was located on the boundary of the Deep Creek Conservation Park, about 7 kilometres south from Delamere.
The creek was given a Good rating because the site sampled showed evidence of relatively minor changes in ecosystem structure and function. There was evidence of human disturbance including emerging signs of nutrient enrichment but the stream provides habitat for several rare and sensitive species of macroinvertebrates.
A diverse community of at least 49 species of macroinvertebrates was collected from this slow-flowing creek, approximately 1.8 m wide and up to 30 cm deep in spring 2011 and autumn 2012. The community was dominated by hydra, worms and the scud Austrochiltonia. Other species collected in smaller numbers included a range of generalist and pollution tolerant species, such as round worms, hydrobiid snails, nine mites, two beetles, craneflies, mosquitoes, three biting midges, nine non-biting midges, mothflies, soldier flies, dance flies, a common species of mayfly, two dragonflies and a common species of caddisfly. Many sensitive and rare species commonly found in flowing water habitats were also found, including the rare mite family Momoniidae, the non-biting midge Riethia, mayflies (Atalophlebia and Thraulophlebia), the dragonfly Synthemis eustalacta and the caddisfly Triplectides similis. The frog Crinia was also heard calling.
The water was fresh (salinity ranged from 474-485 mg/L), well oxygenated (78-88% saturation) and clear, with high concentrations of nutrients such as nitrogen (0.84-0.98 mg/L) and phosphorus (0.129-0.157 mg/L).
The sediments were dominated by detritus, with clay and silt also present. Samples taken from below the surface were grey clays and silts and showed no signs of being anaerobic or lacking oxygen. Minor deposits of silt covered the streambed to a depth of 1 cm in places and no bank erosion was evident.
A moderate amount of phytoplankton (chlorophyll a ranged from 1.08-9.45 µg/L) and small amounts of blue-green algae (chlorophyll b ranged from 0.53-0.69 µg/L) were recorded but no filamentous algae was seen. More than 10% of the site was covered by aquatic plants including Triglochin, Rorrippa and Polygonum with some Carex also present near the water’s edge. The riparian zone and beyond consisted of native vegetation with some tall gums trees and an understorey of bracken and Xanthorrhoea with Gahnia and Carex present closer to the stream banks.
Special environmental values
The Wither Swamp provides important habitat for a number of rare, sensitive and flow-dependent species, as well as many common macroinvertebrates from the region.
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