Piccaninnie Blue Lake Outlet, Piccaninnie Ponds Conservation Park
2009 Aquatic Ecosystem Condition Report
- Permanently wet with a slow-flowing channel present in autumn and spring 2009.
- Sparse macroinvertebrate community with a few rare, sensitive and specialist species.
- Emerging signs of nutrient enrichment.
- Riparian vegetation consists of native coastal heath and shrubland.
- Minor erosion in an area around a jetty that was removed in 2009.
About the location
Piccaninnie Blue Lake Outlet is a very small stream in the lower South East that drains the Piccaninnie Ponds Conservation Park and discharges into the Southern Ocean at Discovery Bay. The only land use is the conservation of the vegetation and fauna in the park.
The monitoring site was located near the gauge station at the downstream extent of the stream on a walking track off Piccaninnie Ponds Road, about 20 kilometres east from Port MacDonnell.
The stream was given a Good rating because the site sampled showed evidence of relatively minor changes in ecosystem structure and function. There was some evidence of nutrient enrichment due to the extent of plant and algal growths recorded in 2009, which may have been exacerbated by the reduced flow in this waterway as a result of the recent drought in the region.
A sparse community of about 20 species of macroinvertebrates was collected from the slow-flowing channel, up to six metres wide and 62 centimetres deep, during autumn and spring 2009. The community consisted of low abundances of all species in autumn but was dominated by insects such as leptocerid caddisflies, chironomids and baetid mayflies in spring. The community included at least two sensitive, rare and specialised species; namely, a baetid nymph (Centroptilum elongatum) and blackfly larvae (Austrosimulium furiosum). Both favour freshwater and permanently flowing habitats, and neither species is widely found in the South East. No introduced species were recorded in 2009.
The water was moderately fresh (salinity ranged from 1,184–1,389 mg/L), well oxygenated (75–92% saturation) and clear, with low phosphorus concentrations (0-0.02 mg/L) and high nitrogen concentrations (2.24–2.41 mg/L); the latter was mostly in the form of oxidised nitrogen, sourced from the inflows of local groundwater into the watercourse.
The sediments were dominated by detritus, sand, algae, silt and cobbles; samples taken from below the surface were blackened, sulfidic and anaerobic, or lacking in oxygen. A small deposit of silt, less than one centimetre deep, was present in the channel and nearly 10 metres of the bank showed signs of erosion due to the recent removal of an old jetty.
Several submerged (Stuckenia or Ruppia) and emergent plants (Triglochin and Rorippa) were growing in the channel or on the water’s edge. The presence of Watercress (Rorippa), an introduced herbaceous plant, shows that the stream is slightly disturbed because this plant is typically found wherever there are excessive nutrients entering waterways. The extent of plant cover exceeded 35% of the channel in spring, at a time when the growth of filamentous algae extended over 10% of the channel. The levels of phytoplankton were low in both seasons sampled. Consequently, there are signs of nutrient enrichment leading to excessive growths of plants, particularly in spring.
The riparian zone consisted of native coastal heaths and shrubs that merged into the surrounding terrestrial vegetation.
Special environmental features
Piccaninnie Blue Lake Outlet provides habitat for at least two sensitive and rare species of macroinvertebrates, a baetid nymph (Centroptilum elongatum) and blackfly larvae (Austrosimulium furiosum). It would also be expected to support other significant species of macroinvertebrates, fish and aquatic species with more frequent sampling in this waterway, particularly during non-drought periods.
Pressures and management responses
|Some nutrient inputs from unknown diffuse sources in the catchment (leading to growth of algae and aquatic weeds)||Given the Conservation Park does not include any agricultural landuses, the source of nutrients is currently unknown. The Department of Environment and Natural Resources have released the Piccaninnie Ponds Conservation Park Management Plan (696kb pdf).|