Riparian vegetation consisted of mostly native gums, and tea-tree over sedges
Area map
About the location
First Creek is a small stream in the Southern Mount Lofty Ranges that rises near ‘Tunkalilla’ and flows southwards, where it discharges onto Tunkalilla Beach in the Southern Ocean. The monitoring site was located off Tunkalilla Road, about 2 km east from Deep Creek Conservation Park on the Fleurieu Peninsula. The major land uses in the 229 hectare catchment are stock grazing (77%) and remnant native vegetation (17%), with minor areas also used for roads.
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 plant growth in the stream and the presence of algae but it provides significant habitat for a large number of rare, sensitive and flow-dependent species of macroinvertebrates.
Findings
A diverse community of at least 60 species of macroinvertebrates was collected from the creek (36 species in autumn and 47 in spring), 3 m wide and up to 26 cm deep, in autumn and spring 2016. The creek consisted of mostly moderately fast-flowing riffle habitats and smaller areas of still and slow-flowing pools. The macroinvertebrate community comprised large numbers of caenid mayflies and leptocerid caddisflies, and low to moderate numbers of introduced snails (Potamopyrgus and Physiella), mites, amphipods, beetles, dixid flies, biting midges, chironomids (including Rheotanytarsus), blackflies (including Austrosimulium furiosum), mayflies, waterbugs, dragonflies, stoneflies and caddisflies. Many rare, sensitive and flow dependent species were recorded at this site including the chironomid and blackfly mentioned above, the riffle beetle Simsonia, mayflies Atalophlebia australasica, Atalophlebia australis and Thraulophlebia inconspicua, dragonfly Austrogomphus, stoneflies Dinotoperla evansi, Illiesoperla mayi and Newmanoperla thoreyi, and the caddisflies Taschorema, Orthotrichia bishop, Oxyethira columba, Lingora aurata, Atriplectides dubius and Triplectides similis. Juvenile Galaxias were also collected at the site.
The water was fresh (salinity ranged from 340-741 mg/L), well oxygenated (84-89% saturation), clear but slightly coloured with some froth present in autumn, and with moderate to high concentrations of nutrients such as phosphorus (0.02-0.1 mg/L) and nitrogen (0.45-1.03 mg/L).
The sediments were dominated by detritus with a mixture of rocks (boulders, cobbles, pebbles) and fine sediment (gravel, sand, silt). Samples taken from below the surface were mostly grey silts and clays 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 but sheep and kangaroo droppings were present on the banks, suggesting animals are accessing the creek.
A small amount of phytoplankton was present at the site (chlorophyll a ranged from <0.1-2.22 μg/L). Over 35% of the channel was covered by a wide variety of aquatic plants (Aponogeton, Carex, Cyperus, Hydrocotyle, Isolepis, Juncus, Persicaria, Ranunculus and Triglochin, and introduced Rorrippa and Rumex). The riparian zone was dominated by native vegetation, including gums, tea-trees and sedges and the surrounding vegetation beyond comprised dense native woodland, comprising gums, and yaccas.
Special environmental features
First Creek at Tunkalilla provides a permanently flowing, freshwater stream and supports a diverse range of rare, sensitive and flow-dependent macroinvertebrate species. These features make it one of the most significant streams in the State.
Pressures and management responses
Pressures
Management responses
Nutrient inputs to the creek from numerous diffuse sources (potentially leading to excess growth of algae and aquatic weeds)
The Adelaide and Mount Lofty Ranges NRM Board land management program encourages and promotes managing land to improve water quality. This includes working with industry and landholders to ensure efficient use of fertilisers and discuss ways to reduce runoff of nutrients into waterways.
Insufficient natural water flows in the creek resulting from water extraction and climate variability
Through water allocation planning the Adelaide and Mount Lofty Ranges NRM Board seeks to manage a sustainable water supply for the region so that there is enough water available for everyone (including the environment) even in drought conditions.
This aquatic ecosystem condition report is based on monitoring data collected by the EPA. It was prepared with and co-funded by the Adelaide and Mount Lofty Ranges NRM Board.
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Observed Condition
Expected Condition
