Tributary of Cox Creek, south from Uraidla
2011 Aquatic Ecosystem Condition Report

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 degraded riparian habitats. Despite this, the stream still provided habitat for some rare and sensitive macroinvertebrate species.

A sparse community of at least 23 species of macroinvertebrates was collected from the slow-flowing creek, 0.5-1 m wide and up to 10 cm deep, in autumn and spring 2011. The community was dominated by generalists and species tolerant to poor water quality such as hydrobiid and introduced physid snails, worms, chironomids and leptocerid caddisflies (Lectrides varians). It also included smaller numbers of flatworms, limpets, bivalves, mites, springtails, beetles, craneflies, blackflies, waterbugs, dragonflies, stoneflies and other types of caddisflies. Several rare, sensitive and/or flow-dependent species were recorded, including a blackfly (Austrosimulium furiosum), dytiscid beetle (Platynectes decempuncatus), stonefly (Austrocerca tasmanica) and hydrobiosid caddisfly (Taschorema evansi); most were detected in spring when flows were highest (0.2 metres/second). A threatened species of native fish called Mountain Galaxias (Galaxias olidus) was collected in autumn and a juvenile galaxiid fish was also found in spring.

The water was fresh (salinity ranged from 75-169 mg/L), well oxygenated (85-87% saturated), clear, and with high concentrations of nutrients such as nitrogen (1.5-2 mg/L) and phosphorus (0.06-0.16 mg/L).

The sediments were dominated by detritus and silt, with sand and gravel also present. Samples taken from below the surface were grey and anaerobic in autumn but the sediments appeared to be well-aerated in spring when the creek was flowing more extensively. A small amount of fine silt was deposited in the channel and no bank erosion was noted during either survey in 2011.

Over 90% of the creek was covered by aquatic plants, mostly comprising introduced watercress (Rorippa) and patches of dock (Rumex). The limited riparian zone was dominated by woody weeds (blackberries and broom) and the surrounding terrestrial vegetation was cleared grassland and rural gardens.

This creek was the only first order stream sampled in 2011 that sustained flowing pool habitats and aquatic biota; the other 9 similar stream types were all dry. The creek was also notable because several rare, sensitive and flow dependent species of macroinvertebrates were present and it provided habitat for a state-listed, threatened native fish.

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