Minniribbie Creek is a small stream in Eyre Peninsula that originates as the outflow from Lake Wangary and discharges into Kellidie Bay (which is a marine sanctuary zone). The creek represents the downstream extent of Glengyle Creek that flows into Lake Wangary. The major land uses are sheep and cattle grazing and cropping, although a large yabby and marron aquaculture farm was located in the lower reaches of the stream. The monitoring site was located upstream from Kellidie Bay Road, about four kilometres south from Wangary.
The creek was given a poor rating because the site sampled showed evidence of major changes in ecosystem structure and moderate changes to the way the ecosystem functions. There was considerable evidence of human disturbance, including salinization, nutrient enrichment and poor riparian habitat.
Findings
A sparse community of about 14 species of macroinvertebrates (9 in autumn and 10 in spring) was collected from isolated pool habitats that extended 8.5-10 metres wide and over 70 centimetres deep, in autumn and spring 2015. The community was dominated by large numbers of salt-tolerant snails (Coxiella) and beetles (Necterosoma penicillatus), and included smaller numbers of other salt-tolerant species such as hydrophilid beetles (Berosus), biting midges (Culicoides), chironomids (Tanytarsus barbitarsus and Procladius), brineflies from the Family Ephydridae, mosquitoes (Aedes and Culex) and waterbugs (Sigara). The presence of claws, moulted skin casts and active holes indicates that yabbies (Cherax destructor) also occurred at the site; salt levels in the stream probably approached their upper salt tolerance in autumn (Bailey, unpubl salt tolerance database) but they can survive for extended periods in their burrows if fresher groundwater is available. No rare or sensitive species were collected, and many freshwater macroinvertebrate orders and classes found elsewhere in the state do not occur in this stream. The only fish seen were a large number of juvenile hardyheads in spring.
The water was saline (salinity of 21,748 mg/L in autumn and 12,221 mg/L in spring), poorly oxygenated (34-84% saturation), clear and slightly coloured, and very high nutrient concentrations such as nitrogen (2.85-7.11 mg/L) and phosphorus (0.05-0.24 mg/L); poorer water quality (dissolved oxygen and nutrients) was recorded in autumn when the creek was drying.
The sediments were dominated by sand and silt in autumn and by detritus and filamentous algae in spring, and also included smaller amounts of bedrock, boulder, cobble, pebble, clay and dead detritus. Samples taken below the surface showed considerable evidence to indicate the sediments consistently lacked oxygen and were a harsh environment for most benthic species to be able to tolerate; the sediments had a strong anaerobic odour, they appeared to be black clays and silts, they released sulfide when tested, and the underside of rocks embedded in the sediments were completely black. Over 10 centimetres of silt covered the streambed in autumn, which contributed to the anaerobic nature of the sediments at the site. No significant areas of bank erosion were noted and the only droppings seen on the banks and within the channel were from kangaroos.
A large amount of phytoplankton (chlorophyll a ranged from 13-34 µg/L) was recorded but filamentous algae was only seen in spring when Cladophora covered more than 10% of the creek. Over 65% of the site was also covered by salt-tolerant samphire and rushes (Juncus). The riparian zone consisted of the same rushes, samphire and included monkey-flowers (Mimulus) and weeds. The surrounding vegetation at the site was mostly open woodland within a fenced area near the creekline, with cleared grazing land further away from the stream.
Special environmental features
None detected in 2015.
Pressures and management responses
Pressures
Management responses
Livestock have direct access at the site and upstream in the catchment, causing sediment erosion and adding excessive nutrients.
The Eyre Peninsula NRM Board administer the Water Affecting Activities permits and polices for the region. This process allows the Board to grant or refuse permits to undertake certain activities affecting water resources. The process is the region’s primary means of preventing any potential impact on the environmental integrity of surface water catchments.
The Eyre Peninsula NRM Board continues to promote managing land to improve water quality. This includes incentives for:
Waterway and wetland fencing to exclude or limit stock from entering riparian zones and the best practice managements of springs, soaks and waterholes as stock water supplies.
Revegetation programs around waterways and wetlands and stock exclusion as well as educating landholders about the importance of riparian vegetation in managing soil erosion.
The Eyre Peninsula NRM Board also undertakes a native freshwater fish monitoring program throughout this catchment.
Two water quality monitoring stations have also been installed in Kellidie and Coffin Bays. These stations provide real time data for pH, salinity, water temperature, dissolved oxygen and chlorophyll.
Limited natural riparian vegetation at the site and upstream in the catchment, providing minimal buffer protection from catchment land uses.
Observed Condition
Expected Condition
