Pedler Creek, near Moana
2008 Aquatic Ecosystem Condition Report
- Significantly affected by nutrient enrichment and fine sediment.
- Macroinvertebrate community dominated by species tolerant of pollution.
- Excessive aquatic plant growth and weedy riparian vegetation.
About the location
Pedler Creek is formed by smaller streams rising among the steep slopes of Sellicks Hill Range, south of Adelaide. The streams flow west and join near Landcross Farm before eventually discharging into Gulf St Vincent between Moana and Seaford. Vineyards (46%) and livestock grazing (35%) are the major land uses in the catchment, which also includes townships such as McLaren Vale and McLaren Flat.
The site selected for monitoring was located off Pedler Road, downstream from the Pedler Creek Rubbish Dump.
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 due to high loads of nutrient and fine sediment.
The creek was about seven metres wide and consisted of mostly deep pool habitats when it was sampled in November 2008.
A moderately diverse community of 27 macroinvertebrate species was collected. The community was dominated by species tolerant of nutrient enrichment such as the tiny crustacean called a water scud (Austrochiltonia australis) and chironomids. No waterbugs or damselflies were found, and only limited numbers of caddisflies, mayflies and molluscs were collected. The introduced Mosquitofish (Gambusia) was the only fish detected in the creek.
The water was moderately fresh (salinity of 1,400 mg/L), well oxygenated (80% saturation), and slightly cloudy, or turbid. It contained moderate to high concentrations of nutrients such as nitrogen (0.53 mg/L) and phosphorus (0.05 mg/L).
The creekbed comprised large amounts of silt and detritus, with the silt more than 10 cm deep throughout the deeper areas of the channel. The sediments were smelly, blackened and anaerobic, further indications that too much organic material and nutrients were entering the creek.
Extensive areas of Common Reed (Phragmites australis) and patches of Cumbungi (Typha domingensis) grew along the edge of the water, which also contained submerged stoneworts (Chara) and patches of green filamentous algae (Cladophora).
Gum trees grew in the riparian zone as well as introduced herbaceous species and grasses such as lawn varieties from houses recently built adjacent to the creek. Away from the creek, urban housing and areas of gums over introduced grasses dominated the landscape.
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 Adelaide and Mount Lofty Ranges NRM Board's land management program encourages and promotes managing land to improve water quality. This includes incentives for waterway and wetland fencing to exclude or limit stock from entering riparian zones.|
|Limited riparian zone vegetation at the site and upstream, providing minimal buffer protection from catchment landuses (reducing habitat quality).||The Adelaide and Mount Lofty Ranges NRM Board's land management program encourages and promotes managing land to improve water quality. This includes incentives for revegetation programs around waterways and wetlands and stock exclusion as well as educating landholders about the importance of riparian vegetation in managing soil erosion.|
|Stormwater runoff causing high water velocities, containing nutrients and sediments (causing habitat disturbance, algal growth and aquatic weeds).||The Adelaide and Mount Lofty Ranges NRM Board has a well developed stormwater quality improvement, harvesting and reuse program which has installed (and maintains) gross pollutant (and silt) traps in several watercourses across the region to catch litter, debris and silt in order to minimise impacts and damage to seagrass in the receiving marine environment. Stormwater captured is also treated through artificial wetlands across the region which act as suspended solid and nutrient filters; these wetlands also provide important habitat for many native species.|
|Extensive weed growth in the riparian zone at the site and upstream (reducing habitat quality).||The Adelaide and Mount Lofty Ranges NRM Board has several pest plant (weed) mitigation and control programs. They work closely with landholders to control weeds on their property and to help stop the spread to other properties and waterways.|
This aquatic ecosystem condition report is based on monitoring data collected by the EPA and prepared in conjunction with the Adelaide and Mount Lofty Ranges NRM Board.