Light River, Pinkerton Plains
2008 Aquatic Ecosystem Condition Report
- Significantly affected by nutrient enrichment and high salinity.
- Macroinvertebrate community dominated by species tolerant of pollution.
- Highly disturbed riparian zone with little native vegetation.
About the location
The Light River rises on the western slopes of the Tothill Ranges, near Waterloo in the Mid North. It flows south to Kapunda before turning west and ultimately discharging through mangroves into Gulf St Vincent, north of Middle Beach. Sheep grazing and cereal cropping are the main land uses in the river’s large catchment area.
The site selected for monitoring was located off Murphys Crossing Road, about five kilometres southwest of Hamley Bridge.
The river was given a Poor rating at this site because the ecosystem showed evidence of major changes in the animal community and plant life, and moderate changes to the way the ecosystem functions. Evidence confirmed very high levels of nutrient and salinity, presumably as a result of the widespread clearing of native vegetation in the catchment.
Deep, isolated pools formed the river at this site when it was sampled in November 2008.
A moderately diverse community of 31 macroinvertebrate species tolerant to high salinity and enriched nutrient levels was collected. The community was dominated by snails from the Family Hydrobiidae, small crustaceans called water scuds (Eusiridae) and chironomids (Procladius). No sensitive or rare species were collected. The introduced mosquitofish (Gambusia) was the only fish collected and formed large schools throughout the site.
The water was saline (salinity of 8,850 mg/L), well oxygenated (64% saturation), and clear although slightly coloured by tannins. It contained moderate to high levels of nutrients such as nitrogen (1.03 mg/L) and phosphorus (0.05 mg/L).
Common Reed (Phragmites australis) covered more than 90% of the channel, and there were patches of stonewort (Chara), an introduced weedy rush (Juncus acutus) and Creeping Monkey-flower (Mimulus repens).
The riparian zone was highly disturbed, with only a few River Red Gums and melaleucas growing along the riverbanks as well as extensive stands of reeds, woody weeds and introduced grasses. Surrounding areas were planted to cereal crops, with some introduced pine trees and patches of pasture grasses.
Special environmental features
Pressures and management responses
|Livestock have direct access at the site and upstream, causing sediment erosion and adding excessive nutrients (which leads to habitat disturbance, algal growth and aquatic weeds).||
The Northern and Yorke Regional NRM Plan has the following Resource Condition Targets:
|Limited riparian zone vegetation at the site and upstream, providing minimal buffer protection from catchment landuses (reducing habitat quality).|
|Saline groundwater inflow (reducing ecological integrity).|