Riparian vegetation included numerous blackberries under native trees and shrubs
Area map
About the location
Tunkalilla Creek rises near Parawa on the bottom of the Fleurieu Peninsula and flows in a southerly direction to the Southern Ocean. The swamps in the upper part of the Tunkalilla catchment have been included in a group of wetland habitats known as the Fleurieu Peninsula Swamps which have been listed as ‘critically endangered’ under the Environment Protection and Biodiversity Conservation Act 1999. The major land uses in the catchment upstream from the site sampled include grazing pastures, native vegetation and softwood production. The monitoring site was located in the mid to lower reaches of the creek at an elevation of about 200 metres near Arthur Hill, about 1 km south from Rymill Road and 3.5 km east from Deep Creek Conservation Park.
The creek was given a Very Good rating because the site sampled showed evidence of only minor changes in ecosystem structure and function. There were emerging signs of nutrient enrichment but the stream provided an important habitat for many rare and sensitive macroinvertebrate species in the region.
Findings
A diverse community of at least 43 species of macroinvertebrates was collected from the creek, 3-3.8 m wide and up to 50 cm deep, in spring; the site was not accessed or sampled in autumn 2016. The creek consisted of mostly fast flowing riffles (70%) connecting slow flowing to still pool (30%) habitats when sampled. The community was dominated by moderate numbers of amphipods, chironomids and leptophlebiid mayflies in the pools, and by elmid beetles, blackflies, chironomids and hydrobiosid caddisflies in the riffles. It also included smaller numbers of hydrobiid snails, worms, yabbies, beetles, dixids, biting midges, another three families of mayflies (Baetidae, Oniscigastridae and Caenidae), waterbugs, dragonflies, stoneflies, and another four families of caddisflies (Hydroptilidae, Ecnomidae, Conoescucidae and Leptoceridae). A large number of rare and sensitive species were collected, including elmid beetle larvae and adults (Simsonia leai), blackflies (Paracnephia and Austrosimulium furiosum), mayflies (Tasmanophlebia, Offadens, Atalophlebia australasica and Thraulophlebia inconspicua), a gomphid dragonfly (Austrogomphus), a stonefly (Austrocerca tasmanica), and several caddisflies (Taschorema evansi, Ulmerochorema membrum, Oxyethira columba, Lingora aurata and Triplectides similis).
The water was fresh (salinity of 170 mg/L), well oxygenated (87% saturation), clear but slightly coloured, and with moderate to high concentrations of nutrients such as phosphorus (0.06 mg/L) and nitrogen (1.06 mg/L).
The sediments were dominated by bedrock, boulder and sand in the riffles and by detritus and gravel in the pools; samples taken from below the surface were mostly grey sand that did not release any sulfide when tested, indicating that the sediments were well aerated. There was some minor evidence of bank erosion which appeared to have been caused by recent flood damage. The only animal droppings seen in the vicinity of the creek were some rabbit faeces on the banks.
Only a small amount of phytoplankton was recorded (chlorophyll a 1.42 μg/L) but a filamentous alga (Spirogyra) covered nearly 10% of the channel in spring. A slightly larger area was also covered by aquatic plants, including sedges (Carex and Isolepis), rushes (Juncus), water ribbons (Triglochin) and weedy blackberries. The narrow riparian zone extended over less than 5 m wide along the edge of the stream and comprised sedges, rushes and a large growth of blackberries under a few wattles and gums. The surrounding terrestrial vegetation was dense eucalypt woodland.
Special environmental features
The rich number of mayfly and caddisfly families recorded and presence of so many rare and sensitive species of macroinvertebrates from only one sampling period, highlights the regional significance of this stream.
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.
Widespread introduced weeds in the riparian zone at the site and upstream
The Adelaide and Mount Lofty Ranges NRM Board has several pest plant (weed) mitigation and control programs. They work closely with landholders to control weeds on their property and to help stop the spread to other properties and waterways.
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.
Observed Condition
Expected Condition
