Dog Trap Creek, near Deep Creek Conservation Park
2012 Aquatic Ecosystem Condition Report
Permanently wet, moderately fresh creek in spring 2011 and autumn 2012
Diverse macroinvertebrate community with many rare and sensitive species
Emerging signs of nutrient enrichment
Riparian vegetation mostly native species but some invasion by weeds
About the location
Dog Trap Creek forms the westerly catchment for The Deep Creek at the bottom of the Fleurieu Peninsula, where it flows through the Deep Creek Conservation Park and into the Southern Ocean. The major land uses in the 2196 hectare catchment are grazing pastures (47%), softwood production (13%), native vegetation (13%) and conservation park (12%). The monitoring site was located on Tappanappa Road just upstream of the confluence with The Deep Creek, about 5.5 kilometres south from Delamere.
The creek was given a Good rating because the site sampled showed evidence of relatively minor changes in ecosystem structure and function. There was evidence of human disturbance including emerging signs of nutrient enrichment and some weedy plants in the riparian zone but the stream provides habitat for several rare and sensitive species of macroinvertebrates.
A diverse community of at least 47 species of macroinvertebrates was collected from the still pools of this creek, 4 m wide and more than 85 cm deep in places in spring 2011 and autumn 2012. The community was dominated by amphipods (scuds) with other generalist and pollution tolerant species also present including worms, mites, mosquito larvae, thirteen different types of non-biting midges, and waterbugs. However, many sensitive and rare species were also found including the non-biting midges Stempellina and Riethia, the mayfly Thraulophlebia, the stonefly Austrocerca and the caddisflies Taschorema, Oxyethira and Triplectides similis. The frog Crinia was heard calling and introduced brown trout and marron have been found in this section of the creek in the past.
The water was moderately fresh (salinity ranged from 1,476-1,621 mg/L), well oxygenated (64-77% saturation) and slightly turbid, with high concentrations of nutrients such as nitrogen (0.79-1.59 mg/L) and phosphorus (0.01-0.06 mg/L).
The sediments were dominated by clay and detritus. Samples taken from below the surface were brown with black silt present in places, and were anaerobic, or lacking in oxygen, in spring. Only small deposits of silt covered the streambed to a depth of 1 cm and only small amounts of bank erosion were noticed due to undercutting of the banks.
A small to moderate amount of phytoplankton (chlorophyll a ranged from 1.23-4.32 µg/L) was recorded but no filamentous algae was seen. More than 35% of the site was covered by emergent aquatic plants including Berula, Carex, Isolepis, Juncus, Ranunculus, Triglochin and Gahnia. The riparian zone comprised native vegetation including eucalypts, Melaleuca, yaccas and also Gahnia, Berula, Carex and some introduced grasses and weed species. The surrounding vegetation was also mainly native vegetation with eucalypts, bracken, yaccas and other native shrubs present.
Special environmental values
Dog Trap Creek provides important habitat for two uncommon species of fly larvae, one mayfly, one stonefly and three caddisflies.
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