Fifteen sites were sampled from the region in spring 2018, ranging from the North Para River in the north to several coastal streams from the bottom of the Fleurieu Peninsula in the south. Land use was dominated by agriculture (stock grazing and cereal cropping) and residential living, 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 the Adelaide and Mount Lofty Ranges region during 2018 were considered to be in a Very Good to Poor condition. No sites were assigned to the Excellent or Very Poor condition classes; given the scale of vegetation clearance and nutrient enrichment evident in 2018 (and sampled in previous years), it is unlikely that any stream in the region remains unaffected by human activities. Of the sites assessed, 3 sites (20%) were in Very Good condition with little change to animal and plant life; 8 sites (53%) were considered to be Good condition with only minor changes to animal and plant life; 3 sites (20%) were in Fair condition with moderate changes to animal and plant life, and some changes to the way the ecosystems functioned; and 1 site (7%) was in Poor condition with evidence of major changes in animal and plant life, and moderate changes to the way the ecosystems functioned.
The best sites were located in high rainfall catchments (>600 mm annual rainfall) from the Fleurieu Peninsula (eg First Creek and Callawonga Creek north from Taylors Rd) and Southern Mount Lofty Ranges (eg First Creek upstream from the waterfall in Cleland Conservation Park). These sites were characterised by their moderately diverse to diverse macroinvertebrate communities, presence of many rare, sensitive and/or flow-dependent species, well vegetated riparian zones, and low to moderate nutrient concentrations.
Streams that were rated as Good also supported diverse aquatic communities but generally provided habitat for fewer and lower numbers of significant macroinvertebrates. These streams included three sites on Tunkalilla Creek, Callawonga Creek at Callawonga, and Boat Harbor Creek on the Fleurieu Peninsula, and First Creek downstream from the waterfall in Cleland Conservation Park, Sixth Creek and Brownhill Creek downstream from Tilleys Rd in the Southern Mt Lofty Ranges. They generally showed increased evidence of nutrient enrichment or disturbance to riparian habitats from adjacent grazing or urban development.
In contrast, the worst sites were from cleared or developed catchments and were characterized by the presence of limited and degraded riparian habitats, enriched with nutrients and often fine sediment, and were dominated by tolerant and generalist macroinvertebrate communities that lacked sensitive and rare species.
The sites assigned to either the Fair or Poor ratings showed evidence of significant nutrient enrichment (eg high nutrient concentrations, large growths of algae and/or aquatic plants, anaerobic sediments) and were distinguished by the lack of rare and sensitive species and dominance by tolerant and generalist macroinvertebrate species. The Fair sites tended to occur in streams with more extensive riparian habitats and some remnant native vegetation in their catchments, including sites from the North Para River near Chateau Yaldara, Little Para River off One Tree Hill Rd, and Brownhill Creek downstream from the caravan park. The Poor site from Pedler Creek off Stump Hill Rd receives runoff from nearby agricultural and urban land uses, and is characterized by its poor riparian zone, high nutrient concentrations, and a sparse macroinvertebrate community comprising pollution tolerant species.
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. The amphipod crustacean (Austrochiltonia) was usually the most abundantly collected macroinvertebrate along with chironomids (including Paramerina, Procladius, Cricotopus, Thienemanniella, Parametriocnemus, Tanytarsus, Chironomus, Dicrotendipes and Polypedilum). Where flowing water was present, large numbers of blackfly larvae (Austrosimulium furiosum and Simulium ornatipes), chironomids (Rheotanytarsus), mayflies (Atalophlebia and Thraulophlebia) and caddisflies (Cheumatopsyche) were often recorded. The slow to non-flowing pools usually provided habitat for waterbugs (Micronecta and Microvelia), beetles (Necterosoma, Platynectes, Paracymus and Scirtidae), yabbies (Cherax destructor), shrimp (Paratya), introduced snails (Physa and Potamopyrgus), mosquitoes (Aedes, Anopheles and Culex), biting midges (Bezzia and Culicoides), mayflies (Cloeon and Tasmanocoenis), caddisflies (Hellyethira, Lectrides and Triplectides australis), stoneflies (Dinotoperla evansi) and flies from the families Stratiomyidae and Dixidae. Low numbers of a range of worms, mites, craneflies, dragonflies and damselflies were also found at most sites.
Streams that flow provided more habitat complexity and supported a wider range of aquatic species than those that ceased to flow or dried up for at least part of the year. A large number of rare and sensitive species that frequent freshwater flowing riffle habitats were collected from the better sites, including several mites (Austrolimnochares, Flabellifrontipoda, Procorticacarus, and Coaustraliobates), stoneflies (Illiesoperla mayii and Newmanoperla thoreyi), mayflies (Offadens and Tasmanophlebia), dragonflies (Hemigomphus gouldii and Austrogomphus guerini), caddisflies (Taschorema, Ulmerochorema, Oxyethira, Tasimia palpata, Lingora, Atriplectides and Triplectides similis), and an elmid beetle (Simsonia leai), blackfly (Paracnephia), thaumaleid fly (Austrothaumalea), and chironomid (Ablabesmyia).
Many rare and sensitive macroinvertebrates were recorded in 2018, including several mites, stoneflies, mayflies, dragonflies, caddisflies, an elmid beetle, and a number of 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 presence of introduced marron (Cherax cainii) in Callawonga and Boat Harbor Creeks indicates that the illegal stocking of streams with this species has extended beyond the nearby Deep Creek catchment. The environmental effects of this introduced species is unknown but it is expected to outcompete with 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 (see https://www.pir.sa.gov.au/biosecurity/aquatics/aquatic_pests).
The only fish recorded from the region were some juvenile Galaxias from above the waterfall on First Creek in Cleland Conservation Park. Recent comprehensive fish surveys have shown that a rich assemblage of rare, threatened and significant species occurs in the more permanently flowing freshwater streams, including Mountain Galaxias, Climbing Galaxias, Southern Pygmy Perch, Congolli, Freshwater Catfish and various eels and lampreys (Hammer et al 2009, Schmarr et al 2018).
