Mine Creek, near Tumby Bay
2010 Aquatic Ecosystem Condition Report
- Dry in autumn and flowing saline stream in spring.
- Sparse macroinvertebrate community with no rare or sensitive species.
- Obvious signs of moderate nutrient enrichment.
- Riparian vegetation consisted of native species and weeds.
- Some bank erosion evident and silt deposits occurred in the channel.
About the location
Mine Creek is a small stream in Eyre Peninsula that rises west of Yallunda Flat and flows east before discharging to swampland near the airport at Tumby Bay. The major land uses are grazing, cropping, with minor areas of native vegetation and the disused Port Lincoln Mine.
The monitoring site was located at the ford off Stirlings Road, about six kilometres north-west of Tumby Bay.
Eyre Peninsula NRM Regional Summary 2010
The creek was given a Fair rating because the site sampled showed moderate changes in ecosystem structure and some changes to the way the ecosystem functions. There was evidence of human disturbance, including nutrient enrichment, bank erosion and fine sediment deposition.
A sparse community of about 24 species of macroinvertebrates was collected from the flowing creek, seven metres wide and 70 centimetres deep, in spring 2010; the site was dry in autumn. The community was dominated by species tolerant to poor water quality and high salinity such as amphipods, chironomids, notonectid waterbugs and leptocerid caddisflies (Triplectides). It also included low abundances of snails (including the salt tolerant Coxiella), mites, beetles (dytiscids and hydrophilids), flies (blackfly, soldierfly and mosquito larvae), waterbugs (corixids and veliids), odonates (two damselflies and two dragonflies) and other types of caddisflies. Two flow-dependent species were recorded from the flowing riffle habitat (dytiscid beetle Platynectes decempunctatus and blackfly Simulium ornatipes). No sensitive or rare species were found.
The water was saline (salinity of 7,931 mg/L), well oxygenated (98% saturation) and clear, with moderate to high nutrient concentrations such as nitrogen (0.66 mg/L) and phosphorus (0.02 mg/L).
The sediments were dominated by detritus, sand, silt and algae in the non-flowing pools, and the riffle habitat was dominated by silt, gravel, pebbles, sand and algae. Samples taken from below the surface were well aerated and showed no signs of being anaerobic despite the high silt and detrital content of the creek. A deposit of 1-5 centimetres of silt covered the site upstream of a ford in spring and less than 10 metres of the bank showed signs of erosion due to past flood damage.
More than 10% of the site was covered by filamentous algae (Cladophora) in spring, and also covered about 20% of the dry channel in autumn. Aquatic plants covered over 10% of the site and included submerged (Chara) and emergent species (Cyperus, Juncus, Rumex and Baumea).
The riparian zone consisted of a mixture of native species such as acacias, gum trees, sheoaks and paperbarks over samphire and introduced weeds and grasses. The surrounding vegetation was mainly native scrubland and agricultural cropping land.
Special environmental features
The most notable feature of this stream was the presence of at least two flow-dependent species in the riffle habitats in spring. Only five other sites sampled from the region in spring 2010 had sufficient flowing habitat to sample, which highlights the presence of a rare habitat type for Eyre Peninsula.
Pressures and management responses
|Livestock have direct access at the site and upstream in the catchment, causing sediment erosion and adding excessive nutrients (which leads to habitat disturbance, algal growth and aquatic weeds).||
The Eyre Peninsula NRM Board promotes managing land to improve water quality. This includes incentives for:
|Limited natural riparian vegetation at the site and upstream in the catchment, providing minimal buffer protection from catchment landuses (reducing habitat quality).|
|Saline groundwater inflow (reducing ecological integrity).||The Eyre Peninsula NRM Board promotes the revegetation of recharge areas known to contribute to dryland salinity and encourages the adoption of perennial pastures as an alternative to annual cropping in these areas.|
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