Kangaroo Island NRM Regional Summary
2008 Aquatic Ecosystem Condition Report
Six sites were sampled on Kangaroo Island in spring 2008, including one site in Flinders Chase National Park at the western end of the island, four close to the south coast and one on the northern side of the island.
- Nutrient enrichment affecting all streams sampled.
- Degraded riparian zones invaded by weeds.
- Extensive dam developments disrupting flow patterns and affecting refuge habitats for aquatic species.
- High salinity levels significantly affecting eastern sites.
- Diverse aquatic animal life with many rare and sensitive species found in the higher rainfall areas.
The three sites sampled on Stunsail Boom, Harriet and Breakneck rivers were assigned Fair ratings because the ecosystems showed moderate changes to animal and plant life, and some changes to the way the ecosystems functioned. Several lines of evidence confirmed each stream was affected by nutrient enrichment. This included the Breakneck River which would normally be expected to rate better because its entire catchment falls within the Flinders Chase National Park. However, the stream had clearly been affected by a major bushfire in the park the previous summer. The other two sites showed evidence of nutrient enrichment as a result of a range of agricultural practices in their catchments. However, they were in better condition than other sites assessed on the island, most likely due to their location in the higher rainfall part of the island and lower salinity levels (less than or around 1,000 mg/L).
The three more easterly sites on Timber Creek, King George Creek and Eleanor River were all assigned Poor ratings because the ecosystems showed evidence of major changes in the animal community and plant life, and moderate changes to the way the ecosystems functioned due to the combined effects of high salinity and moderate to high nutrient enrichment. These streams receive less average rainfall compared with the island’s western side, contributing to the generally poorer water quality and habitat condition.
Special environmental features
A number of streams on Kangaroo Island support rare and sensitive species of macroinvertebrates. All the streams in Flinders Chase National Park and Stunsail Boom, North-West, Harriet, upper Eleanor, upper Middle and upper Cygnet rivers have provided refuge for at least one of the following species in the past: scorpionfly larvae (Nannochorista), stoneflies (Newmanoperla thoreyi, Austrocerca tasmanica, Illiesoperla mayi, Riekoperla naso), mayflies (Centroptilum elongatum, Atalophlebia, Koorrnonga inconspicua, Nousia fuscula), caddisflies (Apsilochorema gisbum, Tasimia, Orthotrichia bishopi, Oxyethira columba, Lingora, Atriplectides dubius), uncommon chironomids (Stempellina and Podonomopsis) and riffle beetle larvae (Kingolus).
These species prefer cool, wet climates and permanently flowing streams; they are most commonly found when streams consist of flowing riffle habitats interspersed with deep, shaded pool habitats. Large numbers of these species tend to occur together in similar conditions on western Kangaroo Island and the high rainfall (>600 mm) parts of the Fleurieu Peninsula and southern Mount Lofty Ranges.
Persistent drought across much of the state since 2005 has resulted in many of these streams ceasing to flow and drying to form only isolated pools during summer and autumn, so most of these rare species have not been found during recent field trips to these regions. Presumably they are well adapted to persist during extended dry periods by taking advantage of isolated refuge areas or possessing some sort of special lifecycle adaptation that allows them to survive in this type of stream habitat.
Pressures and management responses
|Drought in most catchments, reducing natural water flows (reducing ecological integrity).||The Regional NRM Plan includes a target to address surface water flow management.|
|Bushfire in some catchments, causing sediment erosion (habitat disturbance).||Bushfires are disturbances that can occur naturally. The affected areas can take approximately 5 years or more to naturally recover.|
|Livestock have direct access at some creeks, 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 adjacent to creeks, 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.|
|Altered flow regime in several creeks resulting from catchment clearing or modification (reducing ecological integrity).||The Regional NRM Plan includes a target to address surface water flow management.|
|Large nutrient inputs from diffuse sources in the catchments (leading to extensive growth of algae 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.|
|Saline groundwater inflows in creeks towards the eastern end of the island (reducing ecological integrity).||The Regional NRM Plan includes a target to address saline groundwater.|
|Feral pigs in some catchments causing sediment erosion and adding excessive nutrients (leading to habitat disturbance, algal growth and aquatic weeds).||The Kangaroo Island NRM Board continues to work with landowners to reduce the impact of pigs on riparian vegetation by trialling coordinated pig management. We have trialled a number of new control options including Pigout baits and bait delivery systems such as the Boerbuffets and Hog hoppers developed by the Invasive Animal CRC but these were not reliably effective on KI.|