First Creek, flows to Tunkalilla Beach on the Fleurieu Peninsula
2013 Aquatic Ecosystem Condition Report

The creek was given a Very Good rating because the site sampled showed evidence of minor changes in ecosystem structure and function. There was some evidence of human disturbance due to the extent of algal and plant growth in the stream but it provides significant habitat for a large number of rare, sensitive and flow-dependent species of macroinvertebrates and two threatened fish species.

A diverse community of at least 52 species of macroinvertebrates was collected from the creek (30 species in autumn and 43 in spring), 0.7-4.1 m wide and up to 32 cm deep, in autumn and spring 2013. The creek consisted of mostly slow to moderately fast-flowing riffle habitats and smaller areas of still to slow-flowing deeper pools in both seasons sampled. The community comprised low to moderate numbers of mites (including Procarticacarus and Oxidae), introduced snails (Potamopyrgus and Physa), limpets, amphipods, springtails, beetles (including the elmid Simsonia), craneflies, dixid flies, biting midges, chironomids (including Riethia, Cardiocladius and Rheotanytarsus), blackflies (including Austrosimulium furiosum and Simulium melatum), thaumaleid flies (Austrothaumalea), empidid flies, mayflies (including Offadens and Atalophlebia australasica), stoneflies (Dinotoperla evansi and Austrocerca tasmanica), dragonflies (including Austrogomphus guerini) and caddisflies (including Taschorema, Ulmerochorema, Oxyethira columba andLingora aurata). The community included a wide range of tolerant and generalist species, as well as many rare, sensitive and/or flow-dependent species. The more significant species included the above-listed mites, elmid beetle, chironomids, blackflies, thaumaleid, mayflies, stoneflies, dragonflies and caddisflies. The only fish seen or collected at the site were two regionally threatened species; a Climbing Galaxias (Galaxias brevipennis) was recorded in autumn and a Mountain Galaxias (Galaxias olidus) in spring.

The water was fresh (salinity ranged from 642-649 mg/L), well oxygenated (92-99% saturation), clear, and with low concentrations of nutrients such as phosphorus (0.02 mg/L) and nitrogen (0.43-0.45 mg/L).

The sediments were dominated by bedrock, detritus and boulder, with smaller amounts of cobble, silt, gravel, sand and filamentous algae also present on occasion; samples taken from below the surface were mostly grey silts and showed no evidence that they had recently been anaerobic or lacking in oxygen. There was no sign of any bank erosion at the site and the only animal droppings seen near the creek were from kangaroos.

There was a large amount of phytoplankton present in autumn (chlorophyll a ranged from 0.5-34 μg/L) at a time when about 10% of the channel was covered by a filamentous alga (Cladophora). These clear nutrient enrichment effects were seen despite the stream being well shaded (55% shading) and having generally low nutrient concentrations in water samples taken from the flowing stream. Over 65% of the channel was covered by several types of aquatic plants (Cyperus, Typha, Persicaria, Triglochin, and introduced Rorippa and Rumex), which also supports the nutrient enriched status for this creek. The riparian zone was dominated by native vegetation, including gums, wattles, tea-trees, sedges and various herbaceous plants. The surrounding vegetation near the creek comprised dense native woodland buffering the creekline for about 300 m, comprising gums, wattles, correas and yaccas. Beyond that the landscape has been cleared and used for grazing cattle.

First Creek at Tunkalilla provides a permanently flowing, freshwater stream and supports a diverse range of rare, sensitive and flow-dependent macroinvertebrate species and at least two threatened native fish species. These features make it one of the most significant streams in the region and the State.

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