King George Creek, Kangaroo Island
2008 Aquatic Ecosystem Condition Report
- Significantly affected by nutrient enrichment and salinity.
- Macroinvertebrate community dominated by species tolerant of pollution and saline conditions.
- Excessive growths of algae and aquatic plants.
About the location
King George Creek rises about seven kilometres south of Stokes Bay, on the northern coast of Kangaroo Island. It flows northwest through large areas of remnant native vegetation and agricultural land used for livestock grazing and cropping, before discharging into Investigator Strait at King George Beach.
The site selected for monitoring was located off North Coast Road, about 17 kilometres north-west of Parndana.
The creek 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 the creek had been affected by high nutrient levels and moderately high salinity, making it difficult for more sensitive, freshwater species to survive.
A series of wide, shallow pools connected by narrow areas of moderately flowing riffles formed the creek at this site when it was sampled in December 2008.
A limited community of 22 macroinvertebrate species was collected from the pool edges, and 21 from the riffles. The species from both habitats were tolerant of saline conditions and high nutrient levels, with chironomids (Procladius, Chironomus and Paramerina), worms and the tiny crustacean called a water scud (Austrochiltonia australis) dominating the community. A single fly larva from the Empididae family was the only example collected of a species moderately sensitive to high nutrient levels. No sensitive or rare species such as mayflies, stoneflies or caddisflies were found.
The water was saline (salinity of 4,600mg/L), well oxygenated (102% saturation), and slightly coloured and cloudy, or turbid. It contained high levels of nutrients such as nitrogen (1.03 mg/L), phosphorus (0.26 mg/L) and organic carbon (15 mg/L). Moderate amounts of phytoplankton were suspended in the water, and green filamentous algae (Cladophora and Enteromorpha) covered more than 10% of the creek.
Aquatic plants such as clubrush (Isolepis), saw-sedge (Gahnia) and Sea Rush (Juncus kraussii) also covered up to 65% of the channel.
Clay and gravel dominated sediments at the edges of the pools, while sediments the riffle areas were mostly sand, detritus and cobbles. They were blackened and anaerobic, an indication too much organic matter was entering the creek.
The riparian zone extended up to 30 metres from the creekbanks and featured a mix of native gums, melaleucas, Tea-tree and sedges which merged into the surrounding landscape in places.
Special environmental features
The creek provides habitat for flies from the Empididae family, and includes some quite extensive areas of remnant native vegetation.
Pressures and management responses
|Drought in the catchment, reducing natural water flows (reducing ecological integrity).||The Kangaroo Island NRM Board have adopted policies to ensure the sustainable water use limits of the catchment are not exceeded.|
|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 Kangaroo Island NRM Board has funded the fencing and re-vegetation of significant areas of riparian vegetation in the catchment and continues to work with landowners to increase the presence of protected riparian vegetation by funding the fencing of watercourses.|
|Limited riparian zone vegetation at the site and upstream, providing minimal buffer protection from catchment landuses (reducing habitat quality).||The Kangaroo Island NRM Board has funded the fencing and re-vegetation of significant areas of riparian vegetation in the catchment and continues to work with landowners to increase the presence of protected riparian vegetation by funding the fencing of watercourses.|
|Altered flow regime resulting from catchment clearing or modification (reducing ecological integrity).||The Kangaroo Island NRM Board have adopted policies to ensure the sustainable water use limits of the catchment are not exceeded.|
|Saline groundwater inflow (reducing ecological integrity).||The Regional NRM Plan includes a target to address saline groundwater.|