Riparian vegetation comprised scattered gums over native sedges and weeds
Area map
About the location
Jacobs Creek is a tributary of the North Para River that is located in the Southern Mount Lofty Ranges. It rises at an elevation of about 540 m south from Kaiserstuhl Conservation Park and flows in a north-easterly direction, where it eventually discharges into the North Para River upstream from Rowland Flat. The major land use in the 4,011 hectare catchment was stock grazing (77%), with smaller areas also used for other minimal uses, plantation forestry, irrigated horticulture and pastures, cropping, nature conservation, roads, dams and some rural housing. The site was located at the Kaiser Gauge Station (505518) accessed off Lily Farm Road, about 3 km east from Rowland Flat.
The creek was given a Good rating because the site sampled showed evidence of relatively minor changes in ecosystem structure and function. There was minor evidence of human disturbance due to the limited and weedy riparian zone and presence of extensive growths of filamentous algae and macrophytes. The stream provides habitat for a large number of macroinvertebrates and a threatened fish species.
Findings
A diverse community of at least 54 species of macroinvertebrates was collected from the creek (34 species in autumn and 41 in spring), 2-5 m wide and up to 45 cm deep, in autumn and spring 2016. The creek consisted of a slow-flowing to still channel in autumn but was wetter and dominated by fast-flowing riffles (60%) connecting pool habitats (40%) in spring. The community was dominated by amphipods, dytiscid beetles, chironomids and leptophlebiid mayflies. It also included lower numbers of snails, limpets, leeches, shrimp, springtails, other families of beetles, mosquitoes, biting midges, blackflies, long-legged flies, houseflies, baetid and caenid mayflies, waterbugs, damselflies, dragonflies, stoneflies and caddisflies. Most were generalist and tolerant groups and species, commonly found from other agricultural streams in the region. Several rare and sensitive species which are normally associated with flowing water were also collected, including a beetle from the Family Psephenidae (Sclerocyphon), a blackfly (Simulium ornatipes), caddisfly (Cheumatopsyche sp. 2), and mayflies (Offadens sp. 5, Atalophlebia australasica and Thraulophlebia inconspicua) and stoneflies (Dinotoperla evansi and Austrocerca tasmanica). The only fish seen at the site were a few threatened Mountain Galaxias (Galaxias olidus) in the deeper pools during the spring survey.
The water was fresh (salinity ranged from 458-706 mg/L), well oxygenated (60-77% saturation), clear but with patches of iron floc present, and with generally moderate concentrations of nutrients such as phosphorus (0.01-0.02 mg/L) and nitrogen (0.38-0.44 mg/L).
The sediments were dominated by detritus and filamentous algae; samples taken from below the surface were mostly grey clay and silt that did not release any sulfide when tested but had an anaerobic odour in autumn, indicating that the sediments were occasionally low in oxygen. There was some evidence of bank erosion which was attributed to recent flood damage. Sheep droppings were seen on the banks in autumn but only kangaroo and rabbit droppings were recorded in spring.
Only a small amount of phytoplankton was recorded (chlorophyll a ranged from 0.59-0.82 μg/L) but filamentous algae was more extensive, with 10% of the creek covered in autumn (Spirogyra) and more than 35% of the channel covered in spring (Cladophora). A similar area was also covered by aquatic plants, including submerged (Callitriche) and emergent sedges (Cyperus, Isolepis, Eleocharis and Schoenoplectus), rushes (Juncus), water ribbons (Triglochin), cumbungi (Typha), buttercups (Ranunculus) and introduced watercress (Rorippa). The narrow riparian zone comprised scattered gums over sedges and various weeds. The surrounding vegetation was mostly cleared sheep and cattle grazing land with a few isolated gums in the local landscape.
Special environmental features
The site supported a rich assemblage of macroinvertebrates which included a number of rare, sensitive and flow-dependent species. It also provided habitat for a threatened native fish species.
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
