A total of 14 sites were sampled from streams in the Western Mount Lofty Ranges that drain into the sea. The10 sites from the Torrens River catchment sampled included First Creek upstream from the waterfall in Cleland Conservation Park, Cudlee Creek in the Adelaide Hills, and 8 main channel sites were adjacent to residential housing from Klemzig to Henley Beach. A site on the Field River downstream from Glenthorne National Park-Ityamaiitpinna Yarta and 3 coastal streams on the Fleurieu Penisula (Callawonga, First and Boat Harbor creeks) were sampled in 2020. Land use was dominated by either residential living or agriculture (stock grazing and cereal cropping), with remnant native vegetation often largely confined to conservation parks, steep hills, gullies, along creek-lines, and as part of roadside vegetation.
Sites monitored in 2020 were considered to be in a Very Good to Fair condition. No sites were assigned to the Excellent, Poor or Very Poor condition classes, and given the scale of vegetation clearance, it is unlikely that any stream in the region remains unaffected by human activities. Of the sites assessed, one site (7%) was in Very Good condition with little change to animal and plant life; 5 sites (36%) were rated in a Good condition with only minor changes to animal and plant life, and 8 sites (57%) were in Fair condition with moderate changes to animal and plant life, and some changes to the way the ecosystems functioned.
The best sites were located in higher rainfall catchments (>600 mm annual rainfall) from the coastal creeks on the Fleurieu Peninsula and from the Southern Mount Lofty Ranges (eg First Creek in Cleland Conservation Park). These sites were characterised by their moderately diverse to diverse macroinvertebrate communities that included many rare, sensitive and/or flow-dependent species, presence of well vegetated riparian zones, and waters with low salinity and low to moderate nutrient concentrations. The Cudlee Creek site was located downstream from the major bushfire that extended across the Adelaide Hills in the summer of 2019–20 but showed no indications that large amounts of ash entering the stream in winter runoff had degraded pool and riffle habitats for the resident aquatic life that included a few sensitive mayflies, stoneflies and caddisflies.
In contrast, the poorer sites were from cleared or urbanised catchments, and were characterised by macroinvertebrate communities dominated by tolerant and generalist species. The sites lacked sensitive and rare species, riparian habitats with limited extent and highly degraded, and waters enriched with nutrients and sometimes fine sediment.
The aquatic macroinvertebrate communities of most streams in the region were typically dominated by a small number of tolerant species and included low numbers of rare and sensitive species. Macroinvertebrates commonly present in sampled streams included the amphipod crustacean (Austrochiltonia) and different species of chironomids (including Procladius, Cricotopus, Cladotanytarsus, Paratanytarsus, Chironomus, Dicrotendipes and Polypedilum). Sites in Fair condition were dominated by introduced snails (Potamopyrgus and Physa), native molluscs (Angrobia, Ferrissia and Glyptophysa), freshwater shrimp (Paratya australiensis), waterbugs (Micronecta, Agraptocorixa, Microvelia and Anisops), the mayfly Tasmanocoenis tillyardi), and damselflies and dragonflies (Ischnura and Hemianax).
Species present at the better rates sites and those that frequent flowing water habitats included blackfly larvae (Austrosimulium, Simulium and Paracnephia), a range of mites (including Oxidae, Hygrobatidae, Unionicolidae, Momoniidae and Arrenuridae), chironomids (Stictocladius, Thienemaniella, Paralimnophyes, Eukiefferiella, Rheotanytarsus, and Paratanytarsus), fly larvae from the family Dixidae, biting midge (Ceratopogon), beetles (Simsonia and Sclerocyphon), mayflies (Offadens confluens, Tasmanophlebia, Atalophlebia australasica, and Thraulophlebia), dragonflies (Austrogomphus, Hemigomphus and Austroaeschna), stoneflies (Dinotoperla evansi, Illiesoperla mayii, Newmanoperla thoreyi and Austrocerca tasmanica) and caddisflies (Taschorema evansi, Ulmerochorema membrum, Oxyethira columba, Tasimia, Lingora aurata, Atriplectides dubius, Lectrides varians and Triplectides similis).
Other species have been present in the region in previous years but were not collected in 2020. These include the mite (Piona), beetles (Chostonectes and Limnoxenus), dipterans (Aphroteniella, Parametriocnemus, Simulium melatum and Austrothaumalea), mayflies (Centroptilum, Nousia fuscula, Atalophlebia and australis), the stonefly (Riekoperla naso), hemipteran (Hydrometra), and caddisflies (Apsilochorema, Orthotrichia, Orphninotrichia, Anisocentropus, Leptorussa and Notolina).
Most streams in the region were distinguished by the presence of a narrow riparian zone lined with River Red Gums and acacias and occasionally Ti Tree over introduced grasses and weeds.
Sites in better condition, located in the Adelaide Hills and on the Fleurieu Peninsula, were fresh (salinity <500 mg/L), and well oxygenated, with nitrogen concentrations ranging from 0.4–1.2 mg/L and phosphorus concentrations ranging from 0.007–0.04 mg/L. These sites were often well shaded and had low amounts of phytoplankton (chlorophyll <5 µg/L) and filamentous algae but aquatic plants sometimes covered up to 90% of the stream channel. Sites in poorer condition in the more urbanised areas were fresh to slightly saline (360–2,000 mg/L), usually well oxygenated, and with nitrogen concentrations ranging up to 4.6 mg/L and phosphorus concentrations up to 0.16 mg/L. These sites had generally less shade provided by riparian vegetation and higher phytoplankton concentrations (chlorophyll >5 µg/L), filamentous algae was usually present, and aquatic plants covered more than 35% of each stream.
Many rare and sensitive macroinvertebrates were recorded in 2020, including several mites, stoneflies, mayflies, dragonflies, caddisflies, beetles, and some significant species of dipterans. They were typically found from the better streams in the Adelaide Hills and Fleurieu Peninsula, which were characterized by the presence of native vegetation in their catchments, flowing freshwater habitats and good water quality.
The most notable record was the presence of the riffle beetle larvae Sclerocyphon (Family Psephenidae) from the Field River upstream from Cormorant Drive in Hallett Cove. This beetle is most commonly recorded from the lower reaches of the permanently flowing Sixth Creek in the Adelaide Hills but has been found from a number of flowing riffles from a few other streams in the Mount Lofty Ranges. Its presence in the lower Field River indicates that flowing riffle habitats have not been adversely affected in the past by urban development adjacent to and upstream from the sampled site; maintaining natural flow patterns will be critical to the continued presence of this rare South Australian aquatic beetle.
The presence of introduced marron (Cherax cainii) in Boat Harbor Creek indicates that the illegal stocking of streams with this species has extended beyond the nearby Deep Creek catchment and Callawonga Creek. The environmental effects of this introduced species is unknown but it is expected to outcompete native yabbies and may suppress aquatic plant growth, and degrade any stream that is stocked with this large freshwater crayfish that is native to Western Australia.
A number of fish species were recorded in spring 2020, including juvenile Galaxias in First Creek at waterfall Gully (probably Mountain Galaxias) and Common Galaxias in both the Field River and Cudlee Creek. Catfish were seen in the Torrens River at Cresswell Court and Flathead Gudgeon were seen in several sites on the Torrens River along with introduced mosquitofish.
Recent comprehensive fish surveys have shown that a rich assemblage of rare, threatened and significant species occurs in the more permanently flowing freshwater streams in the Western Mount Lofty Ranges, including Mountain Galaxias, Climbing Galaxias, Southern Pygmy Perch, Congolli, Freshwater Catfish and various eels and lampreys (Hammer et al 2009, Schmarr et al 2018).
