Eyre Peninsula NRM Regional Summary
2010 Aquatic Ecosystem Condition Report
A total of 30 sites were sampled in the region during autumn and spring 2010. They were located along the south-eastern and south-central parts of the peninsula. Land use mostly consisted of agriculture (grazing and cereal cropping) with patches of remnant native vegetation largely confined to the steeper, rocky hills, gullies, roadside vegetation and along creeklines.
- Low rainfall and the largely flat topography limits the occurrence and extent of creeks and rivers in the region.
- Most streams occur in the wetter, south-eastern and south-central parts of the peninsula
- No sites were assessed in Excellent, Very Good or Good condition, and 43%, 43% and 13% of sites were assessed as Fair, Poor and Very Poor, respectively.
- Macroinvertebrate communities consisted of a low to moderate diversity of saline tolerant species with few rare or sensitive species collected.
- Most streams were probably naturally saline prior to European settlement but have been further salinised by extensive vegetation clearance that began in the region from the 1880's to the mid-1970's.
- All streams were either moderately fresh or saline and were affected by nutrient enrichment.
- Riparian zones were often reduced and degraded due to the lack of trees and shrubs and dominance by introduced grasses and weeds that were frequently grazed by stock.
Sites monitored in the Eyre Peninsula were considered to be in a Fair to Very Poor condition. No sites were assigned to either of the Excellent or Very Good condition classes and may no longer exist in the region given the scale of vegetation clearance, salinisation and nutrient enrichment evident in 2010.
Of the sites assessed, 13 (43%) were in Fair condition, with moderate changes to animal and plant life, and some changes to the way the ecosystems functioned; 13 (43%) were considered to be in Poor condition, with evidence of major changes in the animal and plant life, and moderate changes to the way the ecosystems functioned; and four (13%) were considered to be in Very Poor condition, with evidence of major changes in the animal and plant life and the way the ecosystems functioned.
The better sites were located on the Tod River and Mine, Uranno, Pokalalie and Poonana creeks. They were characterised by generally moderate levels of nutrient enrichment and low to moderately diverse macroinvertebrate communities that included most of the major groups typically found from stream environments.
In contrast, the worst sites sampled included Salt Creek near Mangalo, Edillilie Creek near Edillilie, Stinky Creek near Port Lincoln and Salt Creek near Lipson. These sites had very sparse aquatic faunas, poor riparian habitats and very high salinity and nutrient levels.
Salinity is a major issue on Eyre Peninsula with most streams considered to be saline (e.g. salinity > 3,000 mg/L). Only three sites assessed in 2010 were considered to be moderately fresh (salinity 1,000–3,000 mg/L), including Poonana and Yeldulknie creeks near Cleve and Coonta Creek near Tumby Bay.
All sites showed obvious evidence of nutrient enrichment by the large growths of filamentous algae, large amounts of phytoplankton present, excessive amounts of reeds or other aquatic plants, and/or high concentrations of nitrogen and phosphorus in the water. Many streams sampled had significantly disturbed riparian zones with cropping or other introduced grasses and weeds often being the main plants growing on the banks. Surface runoff from agricultural lands and bank erosion from stock accessing riparian zones were considered to be significant stressors affecting the condition of streams in the region. Saline groundwater, enriched with nutrients from agricultural land uses, discharges into and forms the baseflow for most, if nor all, streams in the region and also contributes to the generally poor condition of creeks and rivers on Eyre Peninsula.
The aquatic macroinvertebrate communities of most streams were typically dominated by a small number of very tolerant species, and included few rare or sensitive species. The amphipod crustacean (Austrochiltonia australis) was usually the most abundantly collected macroinvertebrate along with chironomids and hypogastrurid springtails. Other commonly collected species that were occasionally present in large numbers included mosquito larvae, beetles (Necterosoma, Laccobius and Berosus), waterbugs (Micronecta, Anisops and Microvelia), snails (hydrobiids and Coxiella) and caddisflies (Triplectides and Notalina). Worms, soldierflies, damselflies (e.g. families such as Coenagrionidae and Lestidae), and various chironomids (e.g. Procladius, Tanytarsus, Chironomus and Dicrotendipes) were also often collected in low numbers from most sites.
The only rare or specialised species collected in the region in 2010 included a leptocerid caddisfly (Symphitoneuria wheeleri) and flow-dependent hydropyschid caddisfly (Cheumatopsyche species 2). The former only occurs in very saline streams and coastal saltmarshes, and was collected from Uranno Creek and Salt Creek near Sheoak Hill Conservation Park in 2010. The latter species was only recorded from the Tod River at White Flat, where it was collected from the slightly flowing channel in both autumn and spring.
The limited distribution of Cheumatopsyche on the Eyre Peninsula is probably related to the lack of permanently flowing streams, apart from the lower sections of the Tod River, because it commonly occurs in riffle habitats from fresh and saline streams elsewhere in South Australia. Other flow-dependent species collected from the region included blackfly larvae (Simulium ornatipes) and a dytiscid beetle (Platynectes) that were both recorded from slow-flowing habitats in the Tod River catchment, Mine, Coonta and Poonana creeks; Platynectes larvae were also collected from a fast-flowing riffle in spring from Millalie Creek. Presumably, these latter species are well adapted to survive in ephemeral streams that often cease to flow for many months of the year.
Special environmental features
Few rare or sensitive species were found in the region in 2010. Only one rare and regionally restricted macroinvertebrate species (Symphitoneuria wheeleri) was found. A limited number of flow-dependent species that frequent saline riffles elsewhere in the state were also recorded but the region lacked many groups (e.g. bivalve molluscs, shrimps and prawns, mayflies and stoneflies) that are typically found in freshwater habitats from the wetter parts of South Australia.
No threatened species of fish were collected from the region in 2010, although the galaxiid fish observed from the Tod River near Whites Flat may have been Climbing Galaxias (Galaxias brevipinnis). The other fish recorded from the region included Small-mouth Hardyhead from Glengyle, Salt and Minniribbie creeks; Common Galaxias collected from the Unnamed Creek near Green Patch; and an introduced pest called mosquitofish that was recorded from several locations on the Tod River.
Previous sampling on Eyre Peninsula since the mid 1990's has included several additional rare and uncommon species that were not recorded in 2010. A subterranean crustacean (Family Parabathynellidae) has only been collected once from the Tod River, and several other uncommon species recorded from the region include a mayfly (Cloeon), beetles (Copelatus and Paroster), chironomids (Botryocladius grape 'th', Apsectrotanypus and Paraheptagyia), biting midge (Atrichopogon), caddisflies (Ecnomus cygnitus, Hellyethira simplex and Oecetis) and the water measurer (Hydrometra). Most of these records came from the Tod River catchment, Coonta and Yeldulknie creeks.
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).
|Saline groundwater inflow (reducing ecological integrity).
|The Eyre Peninsula NRM Board promotes the revegetation of recharge areas known to contribute to dryland salinity and encourages the adoption of perennial pastures as an alternative to annual cropping in these areas.