First Creek is a small stream in the Southern Mount Lofty Ranges that rises near ‘Tunkalilla’ and flows southwards, where it discharges onto Tunkalilla Beach in the Southern Ocean. The monitoring site was located off Tunkalilla Road, about 2 km east from Deep Creek Conservation Park on the Fleurieu Peninsula. The major land uses in the 229 hectare catchment are stock grazing (77%) and remnant native vegetation (17%), with minor areas also used for roads.
The creek was given a Very Good rating because the site sampled showed evidence of only minor changes in ecosystem structure and function. There were emerging signs of nutrient enrichment but the stream provided an important habitat for many rare and sensitive macroinvertebrate species in the region.
Findings
A highly diverse community of at least 59 species of macroinvertebrates was collected from this flowing creek, approximately 2 m wide and up to 40 cm deep, in autumn and spring 2015. The creek consisted of slow-flowing pools with fast-flowing riffle sections between the pools in both autumn and spring 2015. The site was dominated by mayflies, stoneflies and caddisflies, as well as fly larvae from the families Dixidae, Simuliidae and Chironomidae. Other species collected in smaller numbers included a range of generalist and pollution tolerant species, such as worms, snails, beetles, mites, six different families of fly larvae including a diverse range of non-biting midges, mayflies, waterbugs, stoneflies, dragonflies and caddisflies. Some sensitive and rare species, as well as flow-dependent species, were also collected, including the riffle beetle Simsonia leai, two different types of blackfly larvae (Austrosimulium and Simulium), mayflies (Atalophlebia, Nousia and Thraulophlebia), stoneflies (Dinotoperla, Illiesoperla, Newmanoperla and Austrocerca), the dragonfly Austrogomphus and the caddisflies Triplectides similis, Taschorema, Orthotrichia, Oxyethira, Tasimiidae and Lingora. Introduced snails (Physiella) were seen in the creek and the fish Climbing Galaxias (Galaxias brevipinnis) were also seen in both seasons.
The water was fresh (salinity ranged from 465-787 mg/L), well oxygenated (89-100% saturation) and clear but slightly coloured, with low to moderate concentrations of nutrients such as nitrogen (0.33-0.45 mg/L) and phosphorus (0.025-0.03 mg/L). Small amounts of froth were noticed at the site in both autumn and spring.
The sediments consisted of almost equal amounts of large and fine sediments with detritus also present. Samples taken from below the surface were grey sands with some silt present and showed evidence of being anaerobic, or lacking oxygen for at least part of the year. 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. Sheep and kangaroo faeces were evident on the banks of the creek suggesting sheep may have access to the creek and could trample the banks trying to access the water. This may in the future lead to erosion problems as well as increase the nutrient input to the stream.
A small amount of phytoplankton (chlorophyll a ranged from 0.44-0.59 µg/L) but no filamentous algae were recorded from the site. More than 35% of site was covered by a range of aquatic plants, including the submerged plant Chara, and several emergent plants (Carex,Cyperus, Hydrocotyle,Isolepis, Juncus, Polygonum, Ranunculus, Rorrippa, and Triglochin). The riparian zone consisted of a strip of sedge with isolated gums and wattles. The surrounding vegetation was native scrubland.
Special environmental features
First Creek provides important habitat for a wide range of species sensitive to pollution and dependent on the near permanent flows that occur in this creek. It provides important habitat for many species of mayflies, stoneflies and caddisflies as well as fish such as Climbing Galaxias. This creek is one of the few “least disturbed” creeks in South Australia and provides important habitat for rare species on the Fleurieu Peninsula.
Pressures and management responses
Pressures
Management responses
Livestock having direct access at the site and upstream (causing sediment erosion and adding excessive nutrients).
The Adelaide and Mount Lofty Ranges NRM Board’s land management program encourages and promotes managing land to improve water quality. This includes incentives for waterway and wetland fencing to exclude or limit stock from entering riparian zones.
Insufficient natural water flows in the creek resulting from water extraction and climate variability (reducing ecological integrity).
Through water allocation planning the Adelaide and Mount Lofty Ranges NRM Board seeks to manage a sustainable water supply for the region so that there is enough water available for everyone (including the environment) even in drought conditions.
This aquatic ecosystem condition report is based on monitoring data collected by the EPA. It was prepared with and co-funded by the Adelaide and Mount Lofty Ranges NRM Board.