Eleanor River, Kangaroo Island
2008 Aquatic Ecosystem Condition Report
- Significantly affected by nutrient enrichment, fine sediments and salinity as a result of extensive land clearing in past decades.
- Sparse macroinvertebrate community dominated by species tolerant of pollution.
- Excessive growths of algae and aquatic plants.
About the location
Eleanor River flows through the south-central part of Kangaroo Island, before discharging into the Southern Ocean east of Vivonne Bay. Large parts of the catchment have been cleared for livestock grazing, although well vegetated areas of riparian vegetation have been retained along many sections of the stream.
The site selected for monitoring was located off South Coast Road, about 15 km south of Parndana.
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 due to excessive loads of nutrients, sediment and salt.
The general biological diversity appears to be limited to a small range of plants and animals that are able to tolerate prolonged periods of high salinity and exploit the high levels of organic matter present in this stream. The inflow of shallow saline groundwater and a rise in watertables due to vegetation clearance over past decades has contributed to its poor condition.
A series of slow-flowing connected pools provided habitat for a sparse community of only 16 macroinvertebrate species when the site was sampled in December 2008.
The community was dominated by species typically found in saline waters around the state, including the tiny crustacean, water scud (Austrochiltonia australis) and chironomids (Tanytarsus and Procladius). Species tolerant of pollution accounted for 94% of the community, including several potentially nuisance insects such as mosquitoes and biting midge larvae. No sensitive species were found.
The water was saline (salinity of 8,515 mg/L), well oxygenated (96% saturation) and clear. It contained moderate to high concentrations of nutrients such as nitrogen (0.7 mg/L), phosphorus (0.02 mg/L) and organic carbon (13.9 mg/L).
Moderate amounts of phytoplankton were found in the pools despite 70% of the stream being shaded, and up to 35% of the channel was covered with mats of dead green filamentous algae. There were also extensive growths of plants such as samphire, stonewort (Chara) and rushes (Juncus acutus) along the edges of the river.
Sands with smaller amounts of detritus and silt, and some rocks, covered the riverbed; these sediments were sulphidic and the undersides of the rocks were blackened, indicating too much organic matter had entered the stream.
Low growing native woodland and shrubland dominated by eucalypts, wattles and paperbark trees grew in the riparian zone and surrounding areas.
Special environmental features
Pressures and management responses
|Drought in the catchment, reducing natural water flows (reducing ecological integrity).||The Regional NRM Plan includes a target to address surface water flow management.|
|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 of significant areas of riparian vegetation in the catchment and continues to work with landowners to increase 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 of significant areas of riparian vegetation in the catchment and continues to work with landowners to increase the fencing of watercourses.|
|Saline groundwater inflow (reducing ecological integrity).||The Regional NRM Plan includes a target to address saline groundwater.|
|Altered flow regime resulting from catchment clearing or modification (reducing ecological integrity).||The Regional NRM Plan includes a target to address surface water flow management.|