Unnamed creek, near Green Patch
2010 Aquatic Ecosystem Condition Report
- Permanently wet with non-flowing pool habitats in autumn and slightly flowing channel present in spring.
- Sparse macroinvertebrate community with no rare or sensitive species.
- Obvious signs of moderate to gross nutrient enrichment.
- Riparian vegetation dominated by introduced grasses and sedges.
About the location
This unnamed creek is a small stream in Eyre Peninsula that rises at Green Patch and flows south before discharging into the northern end of Little Swamp. The major land uses are sheep grazing and cropping.
The monitoring site was located off Green Patch Road, about eight kilometres west of North Shields.
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 nutrient enrichment, fine sediment deposition and a lack of vegetative cover in the riparian zone.
A sparse community of about 19 species of macroinvertebrates was collected from the still to slow-flowing creek, 2–3 metres wide and 50 centimetres deep, in autumn and spring 2010. The community was dominated by species tolerant to poor water quality such as mites, springtails and chironomids, and included smaller numbers of amphipods, beetles and mosquito larvae. No sensitive or rare macroinvertebrate species were found, although a native fish was collected.
The water was moderately fresh to saline (salinity of 3,824 mg/L in autumn and 2,885 mg/L in spring), well oxygenated (66–70% saturation), slightly turbid and coloured, with moderate to high concentrations of nutrients such as nitrogen (0.61–1.14 mg/L) and phosphorus (0.03–0.06 mg/L).
The sediments consisted of a layer of detritus over clay and silt. Samples taken from below the surface were blackened and sulfidic, indicating that too much organic matter was entering the creek. A deposit of 1–5 centimetres of silt was recorded in the channel during both seasons sampled.
Filamentous algae (Cladophora) covered more than 10% of the site in spring and a similar area of the site was covered by emergent aquatic plants (Juncus and Bolboschoenus).
The riparian zone was limited to an area of less than five metres along the creek and consisted of introduced grasses, rushes and planted trees and shrubs. The surrounding vegetation consisted of crops and grazing land.
Special environmental features
This creek provides habitat for a native fish called the Common Galaxias (Galaxias maculatus), a species that has rarely been recorded from the Eyre Peninsula but is commonly found in the lower reaches of streams in the Mount Lofty Ranges, River Murray catchment and coastal streams and lakes in the South East.
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).|
|Large nutrient inputs from numerous diffuse sources in the catchment (leading to extensive growth of algae and aquatic weeds).|