Tributary of Hindmarsh River, near Hindmarsh Tiers
2012 Aquatic Ecosystem Condition Report
Ephemeral freshwater creek with pools in spring 2011 and flowing water in autumn 2012.
Diverse macroinvertebrate community with many rare and sensitive species
Emerging signs of nutrient enrichment
Riparian vegetation mostly introduced species
About the location
Tributary of Hindmarsh River rises near Woodcone Hill, approximately 5 kilometres south from Mount Compass and joins the Hindmarsh River about 1 kilometre upstream from Hindmarsh Falls. The major land uses in the 510 hectare catchment are grazing pasture (63%) and native vegetation (36%). The monitoring site was located upstream of Hindmarsh Valley Road, approximately 3 kilometres upstream from the junction with the Hindmarsh River.
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 emerging signs of nutrient enrichment, fine sediment deposition and weeds dominating the understorey vegetation on the banks but the stream still provided habitat for some rare and sensitive macroinvertebrate species.
A diverse community of at least 79 species of macroinvertebrates was collected from this 2 m wide and up to 54 cm deep creek. The creek consisted of still pools in spring 2011 but had fast-flowing water in autumn 2012 due to considerable early autumn rainfall. The community was dominated by worms, the scud Austrochiltonia, springtails, and the mayfly Thraulophlebia. Other species collected from the site included generalists and pollution tolerant species such as flatworms, roundworms, five snails (including the introduced species Physiella), four mites, the isopods Heterias and Haloniscus, freshwater shrimp, at least 14 different species of beetle, craneflies, mosquitoes, at least four species of biting midge and at least 12 species of non-biting midge, waterbugs and a common species of caddisfly. Some rare and sensitive species were also found including flow-dependent blackfly larvae, two stoneflies (Dinotoperla and Austrocerca) and three caddisflies (Apsilochorema and Taschorema). Yabbies were also seen at the site.
The water was fresh (salinity ranged from 422-575 mg/L), moderately well oxygenated (45-92% saturation), slightly coloured and slightly turbid, and with high concentrations of nutrients such as nitrogen (0.59-1.83 mg/L) and phosphorus (0.03-0.08 mg/L).
The sediments were dominated by clay, with some silt and detritus also present. Samples taken from below the surface were brown clays and silts, and were sulphidic and lacking in oxygen in spring 2011. Moderate deposits of silt covered the streambed to a depth of 5 cm in the pools and more than 10 m of bank erosion was evident due to stock damage.
A small amount of phytoplankton (chlorophyll a ranged from 0.78-3.29 µg/L) and small amounts of blue-green algae (chlorophyll b ranged from <0.1-0.72 µg/L) were recorded but no filamentous algae was seen. More than 10% of the site was covered by aquatic plants including submerged (Chara and Callitriche) and emergent plants (Eleocharis, Isolepis, Juncus articulatus, Polygonum and Triglochin). The riparian zone consisted of thistles, introduced species of grasses, willows and some eucalypts. The surrounding vegetation was grazing land with pasture grass, although the region upstream was predominantly native vegetation.
Special environmental values
The Tributary of Hindmarsh River provides important habitat for several mayflies, stoneflies and caddisflies and a rich assemblage of common and tolerant macroinvertebrates.
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