Mackereth Creek, near Scott Bottom
2012 Aquatic Ecosystem Condition Report
Ephemeral freshwater creek with slow-flowing water in spring 2011 but dry in autumn 2012
Moderately diverse macroinvertebrate community with a few rare and sensitive species
Emerging signs of nutrient enrichment
Riparian vegetation comprised mostly native species but areas invaded by blackberries
About the location
Mackereth Creek is a small stream in the southern Mount Lofty Ranges that rises within the Scott Creek Conservation Park and flows in a westerly direction before joining Scott Creek at Scott Bottom which then meets the Onkaparinga River just downstream from Mount Bold Reservoir. The major land uses in the 349 hectare catchment include the conservation park (82%) and grazing pasture (12%). The monitoring site was located just downstream of the Scott Creek Conservation Park, about 4 kilometres south from Cherry Gardens.
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 weeds in the riparian zones but the stream provides habitat for several rare and sensitive species of macroinvertebrates.
A moderately diverse community of at least 32 species of macroinvertebrates was collected from this slow-flowing creek, 1.5 m wide and 11 cm deep in spring 2011; the creek was dry in autumn 2012. The community was dominated by worms, the non-biting midge Tanytarsus and the stonefly Austrocerca. The community also included smaller numbers of snails (Glyptophysa), springtails, beetles (Necterosoma, Copelatus, Bidessinae, Paracymus, Scirtidae), ten different types of non-biting midge, and the mayfly Thraulophlebia. One rare species was also found, the caddisfly Maydenoptila rupina. The frog Crinia was heard calling near the site.
The sediments were dominated by clay and detritus. Samples taken from below the surface were brown and showed no evidence of being anaerobic or lacking oxygen. Only small deposits of silt covered the streambed to a depth of about 1 cm in places and no significant areas of bank erosion were seen. A considerable amount of koala droppings were seen in the creek, possibly contributing to nutrient concentrations in the stream.
A small amount of phytoplankton (chlorophyll a 4.76 µg/L) was recorded but no filamentous algae was seen. More than 35% of the site was covered by a range of aquatic plants, including the submerged plant Crassula and several emergent plants (Carex, Cyperus, Isolepis, Juncus and Polygonum). The riparian zone was dominated by bracken and eucalypts, although some blackberry bushes were also present. The surrounding vegetation was mostly native and dominated by bracken, with grasses also present.
Special environmental values
Mackereath Creek provides important habitat for a diverse assemblage of species including a rare species of caddisfly, one species of mayfly and one species of stonefly.
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