Springy Creek, SW from Stokes Bay
2013 Aquatic Ecosystem Condition Report
- Permanent wet stream in autumn and spring 2013
- Sparse macroinvertebrate community with no rare, sensitive or flow-dependent species
- Water was generally saline, clear and high in nitrogen concentrations
- Riparian vegetation comprised native trees over sedges
About the location
Springy Creek is a small, second-order stream on the northern side of Kangaroo Island. It rises at an elevation of about 135 m and flows in a northerly direction for nearly 5 km before discharging into Investigator Strait about 2 km east from Cape Dutton. Major land-uses in the 560 hectare catchment upstream from the site sampled included grazing modified pastures (77%) and other minimal uses (20%), with minor areas also used for cropping, dams and roads. The site sampled was located upstream from the North Coast Road, about 3 km south-west from Stokes Bay.
The creek was given a Fair rating because the site sampled showed evidence of moderate changes in ecosystem structure and some changes to the way the ecosystem functions. There was evidence of human disturbance due to nitrogen enrichment and high salinity of this second-order stream located within a largely cleared catchment used for grazing stock.
A sparse community of at least 12 species of macroinvertebrates was collected or seen from the creek (only 4 species in autumn and 8 in spring), 0.9-1.2 m wide and up to 55 cm deep, in autumn and spring 2013. The creek consisted of a shallow, still to slow-flowing channel in both seasons sampled. The community was not dominated by any species in autumn but included low numbers of a beetle (Family Curculionidae), biting midge (Bezzia), soldierfly (Family Stratiomyidae) and chironomid (Thienemanniella). In spring, low numbers of amphipods, yabbies, scirtid beetles, mosquitoes, chironomids (Dicrotendipes), waterbugs, aeschnid dragonflies and caddisflies (Triplectides) were collected. These species are all tolerant, generalist insects and crustaceans that frequent other saline, nutrient enriched streams in South Australia. The site lacked any rare, sensitive, or flow-dependent species, and many macroinvertebrates that commonly occur in other streams on the island and the wetter parts of the State were also absent, including worms, mites, snails, shrimp, blackflies, mayflies, stoneflies and damselflies, and a wider range of beetles, waterbugs and chironomids. The limited range of species collected from what is a small second-order stream indicates that it is probably a temporary creek that dries during most years. These conditions would favour a sparse assemblage of insects and crustaceans adapted to exploit temporarily wet habitats, due to their ability to either fly and exploit newly created pools, or by sheltering in burrows and damp sediment and emerging when surface water is present.
The water was moderately fresh to saline (salinity ranged from 2,354-3,574 mg/L), well oxygenated (83-117% saturation), alkaline (pH 7.57-8.04), clear, and with low to moderate concentrations of phosphorus (0.02-0.03 mg/L) and high nitrogen concentrations (0.83-1.02 mg/L).
The sediments were dominated by detritus, sand, silt and clay; cobble was only evident in autumn. Samples taken from below the surface were grey silts and clays, and showed no evidence to suggest that the sediments were sulphidic, anaerobic or lacked oxygen. A small amount of bank erosion was noted over about 10% of the banks, presumably caused by past flood damage of very soft banks. The only animal droppings seen in the vicinity of the river were from kangaroos.
There was a large amount of phytoplankton present in the creek in spring (chlorophyll a ranged from 1.2-11.7 μg/L) but no significant growths of filamentous algae recorded during 2013. The only aquatic plants seen in the creek were a sedge (Carex) and rush (Juncus) which extended over 35% of the channel in spring; these plants are normally found on the wet edge of streams, so their presence within the channel indicates that this creek does not remain permanently wet throughout the year. The riparian zone was dominated by gums, sheoaks and wattles over extensive growths of the same sedge listed above. The surrounding vegetation near the creek comprised areas of cleared land and open woodland.
Special environmental features
None noted in 2013.
Pressures and management responses
|Large nutrient and sediment inputs from diffuse sources in the catchment (leading to extensive growth of algae and aquatic weeds as well as increased turbidity and smothering of habitat).||The Kangaroo Island NRM Board has funded the fencing of significant areas of riparian vegetation in the catchment and continues to work with landowners to increase the fencing of watercourses.|