Thirty-one sites were sampled from Kangaroo Island during autumn and spring 2013. They were located throughout the island and included sites from the lower, middle and upper reaches of all the major streams, and some of the smaller coastal creeks that drain the more developed parts of the island. Land use was dominated by nature conservation throughout the western end, and cropping, stock grazing and forestry dominated the middle and eastern parts of the island. The latter typically only retained patches of remnant native vegetation along hilltops, creeklines, roadsides, and around salt lakes and swamps.
Sites monitored in the Kangaroo Island NRM region during 2013 were considered to be in a Very Good to Poor condition. No sites were assigned to the Excellent or Very Poor condition classes and neither probably occurs on the island; all streams appear to have been degraded to some extent by the presence of introduced marron and snails (Potamopyrgus) which prevents sites being assessed with the best condition rating, and the lack of extensive urban areas and associated industries and discharges indicates that the worst condition class may not occur on the island.
Of the sites assessed, three sites (10%) were in Very Good condition with little change to animal and plant life; three sites (10%) were considered to be Good condition with only minor changes to animal and plant life; 15 sites (48%) were in Fair condition with moderate changes to animal and plant life, and some changes to the way the ecosystems functioned; and 10 sites (32%) were in Poor condition with evidence of major changes in animal and plant life, and moderate changes to the way the ecosystems functioned.
The better sites were located in the high rainfall catchments (>600 mm annual rainfall) from the western end of the island, in and around Flinders Chase National Park, Ravine des Casoars Wilderness Protection Area and Kelly Hill Conservation Park (eg Rocky, Breakneck, De Mole and North West rivers and Ravine des Casoars). These sites were characterised by the presence of several rare, sensitive and/or flow-dependent macroinvertebrates. They also had well vegetated riparian zones that were dominated by native plants, and generally lacked any evidence of nutrient enrichment, apart from a few streams that had higher than expected nitrogen concentrations during at least one of the sampling periods.
The sites assigned to either the Fair or Poor ratings showed evidence of moderate to significant nutrient enrichment (eg high nutrient concentrations, large growths of algae and/or aquatic plants, anaerobic sediments) and were largely distinguished by the number of rare and sensitive aquatic species and the extent of damage that has occurred to the riparian zone. The Fair sites tended to occur in streams with at least some riparian habitats and remnant native vegetation in their catchments, and included many of the larger streams from across the middle of the island (eg Middle, Western, Harriet, Cygnet and South West rivers, Stun’Sail Boom, and Smith and Springy creeks). These streams provided habitat that supported at least a few significant aquatic macroinvertebrates on the island in the spring months of the year.
The Poor sites included streams receiving significant runoff from the most cleared agricultural land from around the middle to the eastern end of the island (eg lower Cygnet River, Timber and Emu Bay creeks, and Willson and Chapman rivers). These streams lacked extensive areas of remnant native vegetation in their catchments, had limited and ineffective riparian zones, and showed evidence of gross nutrient enrichment (eg very high nutrient concentrations; large algal or plant growths; anaerobic fine sediments; dominance by organic-feeding, tolerant species of macroinvertebrates and lack of any rare or sensitive species).
The aquatic macroinvertebrate communities of most streams comprised at least 15-25 species, and ranged from a low of 9 species from Emu Bay Creek to a maximum of 35 species from the mid-reaches of the Cygnet River at Huxtable Forest Gauge Station; the tributary of Western River was the only site that remained dry during autumn and spring 2013. Most stream communities were dominated by low to moderate numbers of amphipod crustaceans (Austrochiltonia) and chironomids (including Procladius, Paramerina, Larsia, Cricotopus, Paralimnophyes, Parakiefferiella, Tanytarsus, Chironomus and Dicrotendipes). Where flowing water was present, low to moderate numbers of blackfly larvae (Austrosimulium and Simulium ornatipes), chironomids (Rheotanytarsus), mayflies (Atalophlebia and Thraulophlebia) and caddisflies (Cheumatopsyche) were often recorded. The slow to non-flowing pools generally provided habitat for low numbers of waterbugs (Micronecta, Microvelia and Anisops), beetles (Liodessus, Sternopriscus, Necterosoma, Platynectes, Macrogyrus, Paracymus, Limnoxenus, Ochthebius and Scirtidae), yabbies (Cherax destructor), introduced marron (Cherax tenuimanus), introduced snails (Potamopyrgus), mosquitoes (Aedes, Anopheles and Culex), biting midges (Bezzia and Culicoides), soldierflies (Family Stratiomyidae), mayflies (Cloeon and Tasmanocoenis) and caddisflies (Lectrides, Notalina, Leptorussa and Triplectides australis). Low numbers of worms, different families of mites, 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 number of rare and sensitive species that frequent freshwater flowing riffle and edge habitats were collected from the better sites, including stoneflies (Illiesoperla mayii, Newmanoperla thoreyi and Dinotoperla evansi), caddisflies (Taschorema, Ulmerochorema and Oxyethira), mayflies (Centroptilum elongatum, Atalophlebia australasica and Thraulophlebia inconspicua) and blackflies (Simulium melatum and Austrosimulium furiosum).
The only fish seen or collected from these sites in 2013 were a few commonly occurring coastal species, including Common Galaxias (Galaxias maculatus) and Western Blue-spotted Goby (Pseudogobius olorum); no State-listed threatened fish were recorded.
The riparian zone of most streams on the island comprised native overstorey trees and shrubs (mostly gums, paperbarks and wattles) over a variable assemblage of understorey plants. The streams from the more vegetated catchments typically had few weeds present and were dominated by sedges, rushes and bracken, whereas the more disturbed catchments from the middle and eastern end of the island were usually dominated by introduced grasses and herbaceous weeds among patches of rushes and sedges.
The median water quality data from sites sampled during 2013 indicated that Kangaroo Island streams were generally moderately fresh (salinity of about 1,500 mg/L), well oxygenated (>90% saturation and 9 mg/L), alkaline (pH>7) and had low phosphorus concentrations (0.02 mg/L) but were enriched with nitrogen (0.85 mg/L).
A number of rare and sensitive macroinvertebrates were found on the island in 2013, including several mites (Oxus, Australiobates and Coaustraliobates), a stonefly (Riekoperla naso), and most of the above-listed mayflies, stoneflies, caddisflies and blackflies that are typically found in or associated with flowing streams.
Only two common native fish species were recorded in 2013 but previous fish surveys have shown that several coastal streams (eg Stun’Sail Boom, South West, De Mole, Eleanor, Harriet, Willson and Chapman rivers) have supported two threatened species in the past few decades; they included Short-finned Eels and Climbing Galaxias (Hammer et al. 2009).
