Supervising Scientist Division

Current and recent Ecotoxicology projects

Summaries of current (2007-10) and recent (2005-08) internal projects being undertaken by the SSD Ecotoxicology Program are presented below. Where possible, links to publications are provided.

Current projects

Recent Projects

Current projects

The toxicity of uranium to sediment biota of Magela Creek backflow billabong environments

Aim

To quantify the toxicity of uranium (U) in sediment to benthic biota of the Magela Creek catchment – specifically, the macroinvertebrate, microinvertebrate and microbial benthos of shallow, backflow billabongs.

Background

Research and monitoring of the impacts of the Ranger Uranium Mine has historically focused on water quality analysis, ecotoxicity testing and in situ monitoring of biota during mine water release, and longer-term biological monitoring of in stream macroinvertebrate and fish communities. This focus on the water column has understandably been a consequence of the fact that water is the primary transport vector for solutes released from the minesite. However, since solutes such as U have a high affinity for sediments, sediment quality assessment and derivation of protection trigger values for sediments are aspects of aquatic ecosystem protection that also need to be considered. Such trigger values will have application both for operational water management as well as the development of sediment quality closure criteria for the site. To address this knowledge gap, a field sediment U toxicity experiment is being undertaken, in collaboration with CSIRO Centre for Environmental Contaminants Research and Charles Darwin University. The experiment will involve deployment of U-spiked sediments in a natural billabong over the duration of a wet season. At the end of the exposure period, the extent of colonisation of macroinvertebrate, microinvertebrate and microbial communities will be measured in the control and test replicates.

Timeline

The project commenced in April 2009, with a baseline benthic survey of the study site. A pilot range-finding exposure study will be undertaken during the 2009-10 wet season, with the main experiment scheduled for the wet season of 2010-11.

The effect of dissolved organic matter on the bioavailability and toxicity of metals to tropical freshwater biota (PhD project)

Aim

To quantify, and develop models of, the relationship between dissolved organic matter and the bioavailability and toxicity of uranium, aluminium and arsenic to tropical freshwater biota.

Background

Dissolved organic carbon (DOC) is a key determinant of the bioavailability and therefore toxicity of many metals in aquatic systems, but has not been studied to the same degree as other physico-chemical variables such as pH, hardness and alkalinity. Quantitative relationships on the influence of DOC on metal toxicity will enable more confident estimation of ecological risks and will also guide the future development of water quality guidelines for metals. This study represents an Australian Research Council (ARC) funded PhD project being undertaken by Melanie Houston. It is a collaboration between SSD, The University of Queensland (EnTox and Centre for Mined Land Rehabilitation), The University of Hokkaido and Aquatic Solutions International.

Timeline

The project commenced in July 2007 and is scheduled for completion in July 2010.

Publications

The results of studies on the influence of DOC on uranium speciation, bioavailability and toxicity have been presented at three conferences (5th Society for Environmental Toxicology and Chemistry World Congress, Sydney, August 2008; 14th meeting of International Humic Substances Society, Moscow, September 2008; and 13th Australasian Society for Ecotoxicology Conference, Adelaide, September 2009). Some aspects of the study have been summarised in Supervising Scientist Report 200. Two journal manuscripts are currently in preparation.

The direct effects of suspended sediment on tropical freshwater biota

Aim

To quantify direct effects of suspended sediment concentration and exposure duration on local freshwater species, and derive site-specific, biological effects based trigger values.

Background

The issue of suspended sediment as an aquatic ecosystem stressor in Magela Creek downstream of the Ranger Uranium Mine will assume greater significance over the coming years, as the mine moves towards closure. The physical nature, transport and extent of suspended sediment in the creek systems around both Ranger (Magela and Gulungul Creeks) and Jabiluka (Ngarradj) have been reasonably well characterised through past and present research and monitoring by eriss. In contrast, there has as yet been no systematic attempt to characterise the potential biological impacts of increased suspended sediment in these creek systems – in the context of establishing appropriate operational water management triggers and developing closure criteria. This study is quantifying the effects of suspended sediment due to processes such as decreased light attenuation, physical abrasion and/or clogging of filtration and respiratory organs, on endpoints such as primary productivity, growth, reproduction and survival of various tropical freshwater species, under controlled conditions. It is being done in collaboration with the eriss Hydrological & Geomorphic Processes Program.

Timeline

The project commenced in late 2008 and will be completed by late 2010.

Publications

The early stages of this project were presented at the 13th Australasian Society for Ecotoxicology Conference, Adelaide, September 2009.

Toxicity of pulse-exposed magnesium to four tropical freshwater species

Aim

To assess the toxicity of magnesium (Mg) to tropical freshwater species under pulse exposure regimes corresponding to those observed in Magela Creek downstream of Ranger uranium mine.

Background

Acquisition of continuous water quality monitoring data in Magela Creek downstream of Ranger over the past three wet seasons has enabled quantification of the magnitude, duration and frequency of transient Mg concentrations resulting from mine water discharges. The mine disharge signal is tracked using Electrical Conductivity (EC) as a surrogate for Mg concentration. This is possible since a strong relationship between EC and Mg has been established in grab samples collected over many years for water quality analysis.

The monitoring data show that mine water pulses at times exceed the provisional Mg Limit of 3 mg/L, and have, on one occasion, reached a maximum Mg concentration of approximately 16 mg/L. However, the majority of these pulses occur over timescales of only minutes to hours. In contrast, the toxicity data upon which the provisional Mg Limit was derived are based on continuous exposure over three to six days (depending on the test species). Consequently it was unknown if these shorter duration exceedances were having adverse effects on aquatic biota, and an assessment of the toxicity of Mg under a pulse exposure regime was initiated.

Experiments are currently being undertaken with exposure durations for Mg that correspond with the nature of the pulses detected by the continuous monitoring data. This will include pulse magnitude and duration and may include different frequencies of multiple pulses. To date, an assessment of the effects of a single Mg pulse of 4 hours duration to five local species and a single 24 hour pulse to three local species has been undertaken.

With the potential future use of continuous chemical monitoring data for supervisory purposes, it is important that the method used to derive the Limit for Mg in Magela Creek is aligned with the data being used to monitor the mine’s discharges. The experimental work undertaken for this project will, therefore, be utilised in a review of the current method for deriving the Mg Limit.

Timeline

The project commenced in late 2008 and will be completed by mid 2010. It is likely that a subsequent study will investigate other pulse exposure aspects.

Publications

Initial results of this project were presented at the 13th Australasian Society for Ecotoxicology Conference, Adelaide, September 2009.

Toxicity of treated pond and process waters from Ranger Uranium Mine to five local freshwater species

Aim

To determine the effects of treated pond and process waters on local freshwater species, and if necessary, undertake additional investigations to understand the causes of any effects.

Background

As part of its water management system, Energy Resources of Australia Ltd (ERA) has constructed a water treatment facility at the Ranger Uranium Mine to treat both pond and process waters to a standard suitable for discharge (via wetland filters) to the off-site aquatic environment. SSD is undertaking ecotoxicological testing on both treated pond and process waters to provide additional assurance that the waters do not exhibit any unexpected or unacceptable residual toxicity.

Timeline

Assessments of treated pond water were done in December 2005 and July 2007. The assessment of treated process water was undertaken in November 2009. Follow-up experiments will be undertaken in early 2010.

Publications

The results of the two treated pond water assessments are summarised in Supervising Scientist Reports 193, 196 and 200. A full report on the July 2007 treated pond water assessment has been completed (Internal Report 534). A journal manuscript is currently in preparation.

Development of a reference toxicant test protocol and a test endpoint based on frond surface area for the Lemna aequinoctialis 96-h plant growth test

Aim

To (i) develop a standard reference toxicity testing protocol and control chart for Lemna aequinoctialis and (ii) investigate the use of an additional test endpoint based on frond surface area

Background

Reference toxicant testing (using uranium) for four of the five routine testing species at the eriss ecotoxicology laboratory is now a routine part of the research program. The development of a reference toxicity test for the fifth species, Lemna aequinoctialis, however, has been more problematic. In 2006/07, the three reference toxicity tests conducted for L. aequinoctialis failed to meet acceptability criteria due to insufficient control growth or an insufficient response to the reference toxicant. These two issues are not independent of eachother; sufficient nutrients (nitrate and phosphate) need to be added to the test solutions to ensure adequate growth of control plants, but these nutrients (esp. phosphate)interact with uranium, greatly reducing its bioavailability and toxicity.  

Further testing is planned to resolve the issues of the L. aequinoctialis reference toxicity test protocol. In addition to the reference toxicity test protocol, there is a need to develop an additional endpoint, based on plant surface area or dry weight.

Timeline

This project is expected to be undertaken during 2009-10.

Recent projects

Ecotoxicological assessment of a polyelectrolyte flocculant

Aim

To determine the toxicity of (i) flocculant block, as a whole (ie. dissolved), and (ii) the two individual ingredients, ie. polyacrylamide (PAM) and polyethylene glycol (PEG), to five local freshwater species, and derive site-specific water quality trigger values for each.

Background

Flocculant blocks are commonly used in water treatment processes to reduce suspended sediment loads of the water column.  The mining industry has been increasingly interested in the application of flocculant blocks, with the aim of improving the quality of water released into the environment. This study investigated the biological impacts of a flocculant block that contained an anionic PAM active ingredient and a PEG-based carrier. The toxicity of the whole flocculant block was assessed and the individual components of the block were also tested separately.

Timeline

The project was undertaken in 2008.

Publications

The results of this study were presented at the 5th Society for Environmental Toxicology and Chemistry World Congress, Sydney, August 2008. A journal manuscript is currently in preparation.

Preliminary assessment of the toxicity of manganese to three tropical freshwater species

Aim

To determine the toxicity of manganese (Mn) to three sensitive tropical freshwater species and to assess whether it (i) represents a significant environmental hazard downstream of Ranger Uranium Mine, and (ii) warrants a further, more detailed risk assessment

Background

Increased attention was paid to Mn as a contaminant of potential ecotoxicological concern at the Ranger mine in the early 2000s following observations of increasing concentrations in a shallow groundwater bore adjacent to Magela Creek, and ‘spikes’ in concentration in early wet season surface waters in two natural waterbodies on the mine site. Although Mn concentrations in Magela Creek downstream of the mine have remained typically two orders of magnitude lower than the Australian water quality guideline (for the protection of 99% of species) of 1200 mg/L, a preliminary assessment of the toxicity of Mn to local species under local conditions was, nonetheless, considered necessary.

Timeline

The project was undertaken in June 2008. A more comprehensive follow-up study is anticipated to be completed within the next two to three years.

Publications

The results of the preliminary study have been summarised in Supervising Scientist Report 200.

Chronic toxicity of uranium to larval purple-spotted gudgeon, Mogurnda mogurnda

Aim

To develop a 28-d larval growth toxicity test for the purple-spotted gudgeon, Mogurnda mogurnda, and use the test to assess the chronic toxicity of uranium to this species.

Background

Two of the five NOEC values currently used to derive the High reliability site-specific water quality Limit for uranium in Magela Creek represent estimates for two fish species (the purple-spotted gudgeon, Mogurnda mogurnda and the chequered rainbowfish, Melanotaenia splendida inornata,) based on mortality after only 7 d exposure (+ 7 d post-exposure for M. mogurnda)1. Although this endpoint satisfies the current WQGs criterion for a ‘chronic’ endpoint (ie >96 hour test duration), its appropriateness as an indicator of longer-term, sub-lethal chronic effects has been questioned. An Honours project, undertaken by Kim Cheng, through Charles Darwin University, addressed this issue by developing a 28-d larval growth test for M. mogurnda, and using the test to assess the chronic toxicity of uranium. The results were compared to previous studies.

1 Holdway DA 1992. Uranium toxicity to two species of Australian tropical fish. The Science of the Total Environment 125, 137–158.

Timeline

The Honours project commenced in mid 2006 and was completed in late 2007. Some supplementary testing was done in early 2008.

Publications

The Honours thesis is available as Internal Report 535. The results of the study were presented at the 5th Society for Environmental Toxicology and Chemistry World Congress, Sydney, August 2008, and 13th Australasian Society for Ecotoxicology Conference, Adelaide, September 2009. A journal manuscript was recently published in Chemosphere (2010, 79(5), 547-554)

Toxicity of Ranger mine RP2 and Pit 3 waters to native freshwater species: 2007 wet season

Aims

To determine:

Background

Following extreme rainfall at Ranger Uranium Mine in late February/early March 2007, a number of water management options were explored to reduce the volume of pond water being stored in Retention Pond 2 (RP2) and Pit 3. One possible option involved the short-term direct release of untreated Pond Water from RP2 and/or Pit 3 to Magela Creek. To provide information on the potential biological effects of such a strategy, the toxicities of RP2 water and Pit 3 water were assessed separately, using five and three native freshwater species, respectively. In addition to providing information for short-term water management options, it was intended that the data also would inform decisions about possible water management options for future wet seasons.

Timeline

The study was undertaken during March and April 2007.

Publications

A full (peer-reviewed) report is available as Supervising Scientist Report 197.

Development of a 96 hour gastropod (Amerianna cumingi) reproduction toxicity test

Aim

To develop a protocol for assessing the effects of toxicants on the reproductive ability (ie egg production) of the gastropod snail, Amerianna cumingi.

Background

The freshwater, pulmonate gastropod, Amerianna cumingi, has been used at SSD in flow-through creekside and in situ experiments to monitor waters downstream of Ranger Uranium Mine (Ranger) for almost 20 years. While preliminary laboratory experiments indicated that A. cumingi was sensitive to Ranger mine wastewater, and thus an appropriate field testing organism, this species had not been used in routine laboratory testing. The addition of a gastropod reproduction test to the suite of toxicity tests already conducted at SSD was considered important in order to increase the robustness of water quality guidelines derived by the ecotoxicology group (ie this species is from a taxanomic group that had not previously been tested). The choice of this species, in particular, was considered prudent as many of the husbandry issues associated with keeping A. cumingi in the laboratory had already been resolved during its use in creekside/in situ monitoring. The subsequent generation of toxicity data on the effects of uranium and magnesium has also enabled a greater understanding of the responses of A. cumingi during the creekside and in situ toxicity monitoring of Magela Creek.

Timeline

This method was developed and validated during 2003-2005. The final protocol was completed in 2007.

Publications

This project was presented at the Australiasian Society of Ecotoxicology Conference in Melbourne, September 2005. The protocol is available as Internal Report 525.

Toxicity of magnesium sulfate, and the influence of calcium, in very low ionic concentration waters

Aim

To (i) determine the toxicity of magnesium sulfate (MgSO4) to local freshwater species and how calcium (Ca) affects toxicity; (ii) determine whether Mg or SO4 is the toxic ion; and, (iii) where appropriate, derive appropriate water quality trigger values (TVs).

Background

The toxicity of MgSO4, and the influence of calcium (Ca) on MgSO4 toxicity, was assessed in very soft freshwater (natural Magela Creek water; NMCW) using six tropical freshwater species. The study involved five stages: i. Toxicity of MgSO4 in NMCW; ii. Determination of the toxic ion; iii. Influence of Ca on Mg toxicity; iv. Toxicity of MgSO4 at a Mg:Ca mass ratio of 9:1; and v. Derivation of water quality trigger values to protect 99% of species (PC99s).

The study found that Mg was the toxic ion, and can be toxic at concentrations in the low mg/L range to species that inhabit very low ionic strength fresh surface waters. This toxicity is likely to be due, in significant part, to its properties as a Ca channel antagonist. When elevated Mg concentrations are accompanied by elevated Ca concentrations the risks of effects are lowered for most, but not all, species. Although Mg toxicity in NMCW has the potential to be high quite, low exposure concentrations and accompanying Ca concentrations have ensured that the risks to date in Magela Creek from Mg derived from the Ranger Uranium Mine have remained low. The results of the study also have a broader global relevance, for any fresh surface waters with very low ionic concentrations, particularly where mining activities are present.

Timeline

This large study commenced in 1999 and was completed in 2007.

Publications

The results of this study have been presented at numerous conferences and summarised in Supervising Scientist Reports 189, 193 and 196. A journal paper has been published in Environmental Toxicology and Chemistry (2010, 29(2), 410-421).

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