Little Timber Creek, N from Murray Lagoon
2013 Aquatic Ecosystem Condition Report

The creek was given a Poor rating because the site sampled showed evidence of major changes in ecosystem structure and moderate changes to the way the ecosystem functions. There was evidence of human disturbance due to nitrogen enrichment, high salinity and a weedy riparian zone.

A moderately diverse community of at least 22 species of macroinvertebrates was collected or seen from the creek (5 species in autumn and 18 in spring), 1.3-3.4 m wide and up to 24 cm deep, in autumn and spring 2013. The creek consisted of shallow still to slow-flowing pools connected by small areas of flowing riffle habitats, in both seasons sampled. The community was not dominated by any species but included low to moderate numbers of nematodes, mites, amphipods, beetles (including Berosus queenslandicus), craneflies, mosquitoes, biting midges, chironomids, waterbugs, dragonflies and caddisflies. The presence of crayfish holes in the banks indicated that yabbies occurred at the site and blackfly larvae were seen among the riffle habitats in spring. All of these are tolerant, generalist macroinvertebrates that have a wide distribution in the State, particularly from brackish to saline, nutrient enriched streams. The site lacked any rare or sensitive species; the high salinity probably prevents many macroinvertebrates from being able to inhabit this creek.

The water was saline (salinity ranged from 5,491-7,346 mg/L), well oxygenated (96-104% saturation), clear and slightly coloured, and with low concentrations of phosphorus (0.02 mg/L) but high nitrogen concentrations (1.03-1.13 mg/L).

The sediments were dominated by detritus, with smaller amounts of sand, silt and clay also present. Samples taken from below the surface were grey sands, silts and clays that appeared to be well-aerated, despite the abundance of organic matter at the site. There was no evidence of any significant areas of bank erosion recorded, and the only animal droppings seen in the vicinity of the creek were from kangaroos.

There was a small amount of phytoplankton recorded from the creek (chlorophyll a 1.4-2.7 μg/L) but no filamentous algae was seen during either survey in 2013. There were also no aquatic plants observed in the creek. The riparian zone extended over 5 m wide and was dominated by patches of gums and wattles over rushes (Juncus) and introduced grasses and weeds. The surrounding vegetation near the creek comprised blue gum plantation forests on one bank and native woodland merging into cleared agricultural land on the other bank.

Little Timber Creek provides a permanently flowing habitat on the southern part of the island but lacks any significant aquatic animals or plants, presumably due to the high salinity of this watercourse.

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