Molonglo River Research Articles

The spatial legacy of Australian mercury contamination in the sediment of the Molonglo River

Mercury (Hg) contamination is an environmental concern as a by-product of legacy mining in Australia. Here we investigate the spatial and temporal distribution of Hg in the Molonglo River system in New South Wales, Australia, and assess the physical and chemical factors influencing that distribution. Mercury concentrations in sediment cores were measured in conjunction with 210Pb and 137Cs dating to establish historical contamination. This was done at the source mine site of Captains Flat, New South Wales, and the system’s sink in Lake Burley Griffin, Australian Capital Territory. Additionally, surficial sediment Hg concentrations along the Molonglo River were analyzed to determine the spatial distribution of Hg. Analytical results showed the primary physical and chemical factors influencing Hg dispersion to be distance, total organic matter, and the presence of iron oxides and oxyhydroxides. The highest Hg concentrations were near the mine site at Captains Flat and decreased significantly with distance. Sediment core analyses in both Captains Flat and the lake showed reductions in Hg concentrations toward surficial sediment layers. It is suggested government-funded rehabilitation programs are playing a part in reducing the release of metal contamination.

Identifying sex-linked markers in Litoria aurea: a novel approach to understanding sex chromosome evolution in an amphibian

Few taxa exhibit the variability of sex-determining modes as amphibians. However, due to the presence of homomorphic sex chromosomes in many species, this phenomenon has been difficult to study. The Australian frog, Litoria aurea, has been relatively well studied over the past 20 years due to widespread declines largely attributable to chytrid fungus. However, it has been subject to few molecular studies and its mode of sex determination remained unknown. We applied DArTseq™ to develop sex-linked single nucleotide polymorphisms (SNPs) and restriction fragment presence/absence (PA) markers in 44 phenotypically sexed L. aurea individuals from the Molonglo River in NSW, Australia. We conclusively identified a male heterogametic (XX-XY) sex determination mode in this species, identifying 11 perfectly sex-linked SNP and six strongly sex-linked PA markers. We identified a further 47 moderately sex-linked SNP loci, likely serving as evidence indicative of XY recombination. Furthermore, within these 47 loci, a group of nine males were found to have a feminised Y chromosome that significantly differed to all other males. We postulate ancestral sex-reversal as a means for the evolution of this now pseudoautosomal region on the Y chromosome. Our findings present new evidence for the ‘fountain of youth’ hypothesis for the retention of homomorphic sex chromosomes in amphibians and describe a novel approach for the study of sex chromosome evolution in amphibia.

A new genus and species of Australian Tanypodinae (Diptera: Chironomidae) tolerant to mine waste.

For over 25 years an undescribed Tanypodinae (Diptera: Chironomidae) has been known to dominate the lotic invertebrate assemblage associated with long-term polluting mine adits in Captains Flat, on the Molonglo River, southern New South Wales, Australia. Although known in all life stages, it has been impossible to allocate the species to any described genus. Renewed interest in the taxonomy of the Tanypodinae, particularly associated with molecular investigations and pollution indicator status warrants formal description. All stages conform to tribe Pentaneurini, but each life stage differs in morphological resemblance. Yarrhpelopia Cranston gen. n. is proposed for the taxon previously referred to under the informal code name of 'genus A'. The genus name derives from south-east Australian aboriginal word yarrh, in recognition of its core distribution and presence in flowing waters. A single species, A. norrisi Cranston sp. n., is described, acknowledging the late Professor Richard Norris, an influential Australian limnologist. Larvae dominate the benthos immediately adjacent to mine adits that continue to leach heavy metals (zinc, cadmium, copper and lead) into downstream sediments. A wider distribution includes cleaner near pristine, eastern Australian rivers between 30° and 42°S, but these records are excluded from the type series pending molecular insights into species limits.

Exposure of the freshwater bivalve Hyridella australis to metal contaminated sediments in the field and laboratory microcosms: metal uptake and effects.

Metal uptake and induced toxic effects on Hyridella australis were investigated by establishing 28 day exposure-dose-response relationships (EDR) of transplanted H. australis at four sites along a sediment metal contamination gradient in the mine affected Molonglo River, NSW. Laboratory exposure of this organism to the same sediments, collected from in situ sites, was run concurrently. Metal concentrations in whole organisms, individual tissues and sub-cellular tissue fractions were measured as organism metal dose. Total antioxidant capacity (TAOC), lipid peroxidation (MDA) and lysosomal membrane destabilisation (LMS) were measured as biological responses. H. australis accumulated significantly highertissue zinc concentrations compared to the other metals. In situ organisms at the mine affected sites accumulated more metals than organisms in laboratory microcosms. Accumulated zinc, cadmium and the total metal concentrations in whole organism tissues reflected exposure-dose relationships. Sub-cellular analysis showed that most of the accumulated metals, both in the field and laboratory exposed organisms, were detoxified over 28 days exposure. Clear exposure and dose dependent responses of decreased TAOC and measurable increases in MDA and LMS with increased metal exposure and dose were evident in H. australis caged in the river. In contrast, a dose-response relationship was only evident for cadmium in laboratory exposed organisms. Organisms caged at mine affected sites showed stronger EDR relationships than those exposed in laboratory microcosms as they were exposed to additional sources of dissolved zinc and cadmium. Exposure in laboratory microcosms underestimated metal uptake and effects, thus assessment of metal contaminated sediments should be undertaken "in situ".

The freshwater bivalve Corbicula australis as a sentinel species for metal toxicity assessment: An in situ case study integrating chemical and biomarker analyses.

A weight of evidence approach in environmental assessment includes the use of biomonitor organisms to measure biologically available contaminant concentrations and lethal and sublethal responses in an exposure, dose, and response framework. Corbicula australis was assessed as a test species for metal toxicity using in situ river sediment exposures at 4 locations in the Molonglo River (New South Wales, Australia), which has a legacy of sediment metal contamination, following 8 decades of mining in its upper reaches. A sediment metal contamination gradient was evident from 12.5 km to 47 km downstream of the mine, as follows: zinc (851-130 mg/kg) > lead (104-7 mg/kg) > copper (31-5 mg/kg) > cadmium (2-0.3 mg/kg). Exposed C. australis accumulated the following metals in tissue: zinc (1358-236 μg/g) > copper (24-20 μg/g) > cadmium (4.7-0.7 μg/g) = lead (4.2-1.8 μg/g). Biomarker responses showed increased sublethal impairment with increased tissue metal concentrations. Total antioxidant capacity was mildly impaired, with corresponding increased lipid peroxidation and lysosomal membrane destabilization at the higher tissue metal concentrations. Corbicula australis proved to be an effective biomonitor organism for sediment metal assessment, as it is able to accumulate metals relative to sediment concentrations and showed a pattern of increased sublethal impairment with increased tissue metal concentration. It is recommended as a suitable species for incorporation into local freshwater monitoring and assessment programs. Environ Toxicol Chem 2017;36:709-719. © 2016 SETAC.

Sediment Metal Concentration Survey Along the Mine-Affected Molonglo River, NSW, Australia

Metal concentrations were measured in sediments of the mine-affected Molonglo River to determine current metal concentrations and distribution along the river. Compared with an uncontaminated site at 6.5 km upstream of the Captains Flat mine, sediments collected from the river at ≤12.5 km distance below the mine had a significantly higher percentage of finely divided silt and clay with higher concentrations of cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn). The measured metal concentrations in the mine affected sites of the river were in the following order: Zn = 697-6818 > Pb = 23-1796 > Cu = 10-628 > Cd = 0.13-8.7 µg/g dry mass. The highest recorded metal concentrations were Cd at 48, Cu at 45, Pb at 240, and Zn at 81 times higher than the background concentrations of these metals in the river sediments. A clear sediment metal-contamination gradient from the mine site to 63 km downstream was established for Cd, Cu, Pb, and Zn in the river sediments. Compared with sediment metal concentrations before a major flood in 2010, only Zn concentrations increased. For all of the mine-affected sites studied, Cd and Zn concentrations exceeded the (ANZECC/ARMCANZ, Australian and New Zealand guidelines for fresh and marine water quality. Australian and New Zealand Environment and Conservation Council/Agriculture and Resource Management Council of Australia and New Zealand, 2000) interim sediment-quality guidelines low values for Cd (1.5 µg/g dry mass) and the high value for Zn (410 µg/g dry mass). Existing metal loads in the riverbed sediments may still be adversely affecting the river infauna.

Detection and tracing of the medical radioisotope131I in the Canberra environment

The transport and radioecology of the therapeutical radioisotope 131 I has been studied in Canberra, Australia. The isotope has been detected in water samples and its activity quantified via characteristic J-ray photo peaks. A comparison of measurements on samples from upstream and downstream of the Canberra waste water treatment plant shows that 131 I is discharged from the plant outflow into the local Molonglo river. This is consistent with observations in other urban environments. A time-correlation between the measured activities in the outflow and the therapeutical treatment cycle at the hospital identifies the medical treatment as the source of the isotope. Enhanced activity levels of 131 I have been measured for fish samples. This may permit conclusions on 131 I uptake by the biosphere. Due to the well-defined and intermittent input of 131 I into the sewage, the Canberra situation is ideally suited for radioecological studies. Furthermore, the 131 I activity may be applied in tracer studies of sewage transport to and through the treatment plant and as an indicator of outflow dilution following discharge to the environment.

Preliminary observations on a highly-restricted tableland population of Green and Golden Bell frogs on the Upper Molonglo River, NSW.

The Green and Golden Bell Frog Litoria aurea disappeared from the Southern Tablelands of New South Wales in the early 1980's and despite many years of opportunistic survey, it was not until 1999 that it was rediscovered near the Upper Molonglo River east of Queanbeyan. The nearest known populations of the species occur at Kioloa, 85 km east of the site. In order to determine the distribution of the population we undertook surveys and monitoring over a two-year period (September 2000 to April 2002) to establish the extent of the population in the region, and to describe the breeding sites that are still occupied. Fieldwork was hampered considerably by extended drought and in some cases by restrictions on access imposed by landholders. All sites surveyed were within 300 m of the Molonglo River. The species was found to occupy 8 of the 10 wetlands (small billabongs) surveyed, 4 of 5 river sites surveyed on the Molonglo River, and at only 1 of 52 farm dams surveyed. It was also heard calling from a small lake...

Conditional value-at-risk for water management in Lake Burley Griffin

As the centrepiece of Canberra, Lake Burley Griffin provides the setting for buildings of national importance and a venue for aquatic recreation while, as part of the Molonglo River, the lake has a role in the ecological processes of its broader setting. For the purposes of recreation and landscape a constant water level is preferred: the management plan requires the lake to be maintained at a prescribed normal level. In years of low rainfall this requirement could conflict with the water demands of other users. Episodes of high rainfall may also require compromise between competing objectives. For example, drawdown of lake levels for flood mitigation could impact on the lake's recreational and amenity values and the spill may not be a good use of water. Conditional Value at Risk, a risk measure developed by the financial industry for portfolio management, is defined as the expected loss given that some loss threshold is exceeded. Here, Conditional Value at Risk is applied as decision support for strategic planning and day-to-day operational problems in the hydraulic management of Lake Burley Griffin.

Relationship of AUSRIVAS-based macroinvertebrate predictive model outputs to a metal pollution gradient

AbstractBiological assessment of river health often involves making comparisons between the biota observed at a site and the biota expected to occur in the absence of damage. Our study aimed to determine whether observed-to-expected (O/E) ratios of macroinvertebrate taxa showed a monotonic (dose–response) relationship and were correlated with pollution levels along a gradient of trace-metal contamination. The study was conducted on the Molonglo River, Australia, which exhibits a clear gradient of trace-metal contamination, resulting from previous mining activities. Macroinvertebrate samples were collected from riffle habitats at 16 test sites and 5 sites representative of reference conditions. The sites’ O/E taxa ratios, generated by a regional predictive model, ranged from 0.21 (severely impaired) to 1.13 (equivalent to reference). Physical and chemical variables measured at each site included Cd, Cu, Pb, and Zn concentrations in the water and sediment. A factor analysis reduced 19 physical and chemical ...

Zinc in the sediments, water and biota of Lake Burley Griffin, Canberra

Zinc concentrations and total amounts in the sediment, water and biota of Lake Burley Griffin were measured to identify where zinc originating from an upstream mine was being accumulated once it entered the lake and to identify potential lake management problems. Estimates were made based on lake wide sampling on a single occasion. Sediments contained most zinc with 4.2 × 10 5 kg. Of this 11 ± 4% was gut soluble (pepsin released). Water contained the second largest store at the time of sampling with 597 kg of zinc. Estimated lakewide stores of zinc in fish ( Cyprinus carpio) macrophytes (mostly Typha orientalis), zooplankton and macroinvertebrates were 144 kg, 1.4 kg, 0.55 kg and 0.14 kg zinc, respectively. Zinc stores in the water and biota will exhibit large changes depending on rainfall and seasonal growth but they will still be small relative to the amounts held in sediments. Comparison of zinc concentrations in surface sediments (561 ± 81 mg/kg) and water (0.018 ± 0.002 mg/kg) with those before remedial works were performed in 1974 to control a metal contamination source upstream at Captain's Flat show that there has been a reduction in the levels of zinc recorded in the lake (pre-1974 sediment, 1109–1670 mg/kg; water, 0.1 mg/kg). Concentrations of zinc in lake water were well below those reported to be toxic to phytoplankton, zooplankton and fish or to cause degeneration of gill structures. Levels of zinc in fish are below the Australian National Health and Medical Research Council's recommended maximum levels for human consumption. Examination of the oxygen status of Lake Burley Griffin indicates that zinc release from lake sediments under reducing conditions is unlikely to be a potential problem. The major source of zinc to the lake is considered still to be from the mine waste polluted Molonglo River with little contribution from other creeks in the catchment.

Survival of Salmo gairdneri (rainbow trout) in the zinc polluted Molonglo River near Captains Flat, New South Wales, Australia.

Gold, lead, zinc and copper were mined continuously at Captains Flat between 1938 and 1962. The Molonglo River was polluted from a number of sources at the mine site. The mine was finally abandoned in 1962, but it was not until 1974 that a program was instituted to stabilize and rehabilitate the mine workings and waste deposits. Field experiments showed that the water quality of the river was unsuitable for the survival of Salmo gairdneri both before and after the closure of the mine. In order to determine whether the remedial works had effectively improved water quality of the Molonglo River the study reported here was designed to repeat that portion of the work published previously which examined the survival of rainbow trout held in cages in the Molonglo River.

Mine waste pollution of the Molonglo River, New South Wales and the Australian Capital Territory: Effectiveness of remedial works at Captains flat mining area

Seeps and previously deposited particulate material from mine workings at Captains Flat are still major sources of metal contamination in the Molonglo River. The impact of metal contamination as it entered the river is shown by the lower variety and numbers of animal taxa collected at downstream sites compared with upstream areas. Comparison with studies conducted before the remedial works shows that there has been little or no discernible change to the chemical or biological condition of the river during periods of low flow.

Australian freashwater mussel Velesunio ambiguus (Philippi) as a biological monitor for zinc, iron and manganese

The hyriid mussel V. ambiguus has been proposed as a biological monitor of zinc where there are wide environmental fluctuations. However, in the River Murray there is high variation in zinc content among individuals and between populations; part is systematic, associated with body weight and age, but a larger part remains statistically unexplained. Further, although V. ambiguus readily accumulates zinc, depuration is slow. At zinc concentrations of 20 mg I-1 and above, mussels avoid taking up zinc by significantly curtailing siphoning, movement and valve opening. Zinc levels above 20 mg l-1 are lethal, with most deaths occurring in the post-exposure periods immediately after 96-, 176- and 336-h toxicity tests. The estimated 336-h LC50 is 66 mg I-1, with 95% confidence limits 55 and 77 mg I-1. Exposure of caged mussels in the zinc-contaminated Molonglo River, N.S.W., suggests that V. ambiguus is not a suitable species to monitor variations in zinc loads between sites, and does not accurately reflect environmental fluctuations of zinc, iron or manganese, although it may have potential for materials other than heavy metals.