Tributary of Maslin Creek, SE from Maslin Beach
2013 Aquatic Ecosystem Condition Report
- Non-flowing, drying channel in autumn and dry creek in spring 2013
- Sparse macroinvertebrate community with no rare or sensitive species
- Water was saline, clear and enriched with nutrients
- Riparian vegetation consisted of introduced grasses and reeds
About the location
Tributary of Maslin Creek is a small stream that rises at an elevation of about 350 m off the northern slopes of Sellicks Hill Range, flows west through a disconnected network of channels, and may occasionally discharge into Gulf St Vincent at Maslin Beach during exceptionally wet winter flows. Major land uses in the 2,814 hectare catchment were irrigated horticulture (46%) and stock grazing (34%), with minor areas used for residential living, roads, other minimal uses, plantation forestry, cropping, industry and dams. The site was located in the lowland section of creek off Bayliss Road, 2 km south-east from Maslin Beach.
The creek was given a Poor rating because the site sampled showed evidence of major changes in ecosystem structure and function. There was evidence of human disturbance due to the extent of nutrient enrichment and degraded riparian habitats associated with the creek.
A sparse community of at least 17 species of macroinvertebrates was collected or seen from creek in autumn; it was dry in spring 2013. The creek consisted of a 5.4 m wide and 35 cm deep, non-flowing, connected channel that was clearly drying when sampled in autumn. The community was dominated by moderate numbers of mosquitoes (Culex and Anopheles) and amphipods (Austrochiltonia), and included lower numbers of worms, flatworms, introduced and native snails, yabbies, isopods, springtails, beetles, waterbugs, chironomids and damselflies. All were common generalists and opportunistic species that are often associated with organically enriched habitats and able to tolerate poor water quality. No rare, sensitive or flow-dependent species were collected. The site lacked many of the major groups of macroinvertebrates that are commonly found from streams in the region, including mites, mayflies, stoneflies, caddisflies, dragonflies, and a wider range of waterbugs and chironomids.
The water was saline (salinity of 3,997 mg/L), moderately well oxygenated (54% saturation), clear and with high concentrations of nutrients such as phosphorus (0.08 mg/L) and nitrogen (1.67 mg/L); nearly half the nitrogen was in an inorganic oxidised form, and was probably sourced from seepage of groundwater into the creek near the site sampled.
The sediments were dominated by detritus, with smaller amounts of boulder, cobble, sand, silt, clay and bedrock also present; samples taken from below the surface were grey sands, lacked any anaerobic odours and tested negative for sulfide, which indicate that the sediments were generally well aerated when sampled. There were no significant areas of bank erosion despite the presence of cow manure on the banks and in the channel in autumn, which shows that cattle regular access the creek.
There was a small amount of phytoplankton (chlorophyll a 1 μg/L) in the creek but no sign of any filamentous algae was seen during 2013. Over 65% of the channel was covered by aquatic plants, including extensive growths of common reed (Phragmites) and patches of submerged sea tassel (Ruppia), introduced watercress (Rorippa) and cumbungi (Typha). The narrow riparian zone was mostly about 5 m wide was dominated by introduced grasses and reeds, and had few trees present. The surrounding vegetation near the creek comprised cleared cattle grazing paddocks and vineyards.
Special environmental features
Pressures and management responses
|Widespread introduced weeds 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.|
|Livestock having direct access at the site and upstream (causing sediment erosion and adding excessive nutrients).||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 creek and upstream (reducing habitat quality, increasing sediment erosion).||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.|
This aquatic ecosystem condition report is based on monitoring data collected by the EPA. It was prepared with and co-funded by the Adelaide and Mount Lofty Ranges NRM Board.