Assessing the Toxicity of Mine-Water Mixtures and the Effectiveness of Water Quality Guideline Values in Protecting Local Aquatic Species.

Six tropical freshwater species were used to assess the toxicity of mine waters from a uranium mine adjacent to a World Heritage area in northern Australia. Key contaminants of potential concern for the mine were U, Mg, Mn, and total ammonia nitrogen (TAN). Direct toxicity assessments were carried out to assess whether the established site-specific guideline values for individual contaminants would be protective with the contaminants occurring as mixtures. Metal speciation was calculated for contaminants to determine which were the major contributors of toxicity, with 84 to 96% of Mg predicted in the free-ion form as Mg2+ , and 76 to 92% of Mn predicted as Mn2+ . Uranium, Al, and Cu were predicted to be strongly bound to fulvic acid. Uranium, Mg, Mn, and Cu were incorporated into concentration addition or independent action mixture toxicity models to compare the observed toxicity in each of the waters with predicted toxicity. For >90% of the data, mine-water toxicity was less than predicted by the concentration addition model. Instances where toxicity was greater than predicted were accompanied by exceedances of individual metal guideline values in all but one case (i.e., a Mg concentration within 10% of the guideline value). This indicates that existing individual water quality guideline values for U, Mg, Mn, and TAN would adequately protect ecosystems downstream of the mine. Environ Toxicol Chem 2021;40:2334-2346. © 2021 Commonwealth of Australia. Environmental Toxicology and Chemistry © 2021 SETAC.

Development of a Sublethal Chronic Toxicity Test for the Northern Trout Gudgeon, Mogurnda mogurnda, and Application to Uranium, Magnesium, and Manganese.

Many international guidance documents for deriving water quality guideline values recommend the use of chronic toxicity data. For the tropical fish northern trout gudgeon, Mogurnda mogurnda, 96-h acute and 28-d chronic toxicity tests have been developed, but both tests have drawbacks. The 96-h toxicity test is acute and has a lethal endpoint; hence it is not a preferred method for guideline value derivation. The 28-d method has a sublethal (growth) endpoint, but is highly resource intensive and is high risk in terms of not meeting quality control criteria. The present study aimed to determine the feasibility of a 7-d larval growth toxicity test as an alternative to the 96-h survival and 28-d growth tests. Once the method was successfully developed, derived toxicity estimates for uranium, magnesium, and manganese were compared with those for other endpoints and tests lengths within the literature. As a final validation of the 7-d method, the sensitivity of the 7-d growth endpoint was compared with those of 14-, 21-, and 28-d exposures. Fish growth rate, based on length, over 7 d was significantly more sensitive compared with existing acute toxicity endpoints for magnesium and manganese, and was similarly sensitive to existing chronic toxicity endpoints for uranium. For uranium, the sensitivity of the growth endpoint over the 4 exposure periods was similar, suggesting that 7 d as an exposure duration is sufficient to provide an indication of longer term chronic growth effects. The sensitivity of the 7-d method, across the 3 metals tested, highlights the benefit of utilizing the highly reliable short-term 7-d chronic toxicity test method in future toxicity testing using M. mogurnda. Environ Toxicol Chem 2021;40:1596-1605. © 2021 Commonwealth of Australia. Environmental Toxicology and Chemistry © 2021 SETAC.

Freshwater chronic ammonia toxicity: A tropical-to-temperate comparison.

The chronic toxicity of ammonia to tropical freshwater species is understudied, and thus data on temperate species have been used to derive water quality guideline values for tropical regions. Such practices may lead to underprotective guideline values due to differences in toxicities observed between tropical and temperate species. In addition, the presence of ammonia in low-ionic-strength waters may also result in higher toxicity, and studies on this factor are limited. The present study assessed the toxicity of ammonia to 6 tropical freshwater species in low-ionic-strength waters. Because ammonia toxicity varies depending on the pH and temperature, test water pH concentrations were maintained at approximately pH 6.0 ± 0.3 at temperatures between 27.5 and 30 °C. Low-effect chronic inhibition concentrations were derived for the following species: Chlorella sp. 66 mg L-1 ; Lemna aequinoctialis 22 mg L-1 ; Hydra viridissima 1.8 mg L-1 ; Moinodaphnia macleayi 27 mg L-1 ; Amerianna cumingi 17 mg L-1 ; and Mogurnda mogurnda 5.4 mg L-1 total ammonia nitrogen. Two of the species tested (a cnidarian and a fish species) were among the most sensitive reported anywhere within their taxonomic group. Chronic ammonia datasets representing toxicity estimates for temperate and tropical species were plotted and compared using species sensitivity distributions. The results indicate that the differences in chronic toxicity observed between tropical and temperate species were likely due to the low ionic strength of the waters to which tropical species were exposed, rather than any inherent physiological differences between species from tropical and temperate regions. This finding suggests that tropical waters of low ionic strength may be at a higher risk from ammonia compared with other freshwater ecosystems. Environ Toxicol Chem 2019;38:177-189. © 2018 Commonwealth of Australia. Published by Wiley Periodicals, Inc. on behalf of SETAC.

Increasing uranium exposure durations to the aquatic snail Amerianna cumingi does not result in lower toxicity estimates.

Reproductive inhibition (egg production) of the aquatic snail Amerianna cumingi over 4 d has been used to derive toxicity estimates for toxicants of concern in tropical Australia. Toxicity estimates from this test have been used as chronic data points in species sensitivity distributions (SSDs) for deriving site-specific guideline values. However, revised guidance for the Australian and New Zealand Water Quality Guidelines advises that test durations for adult macroinvertebrates should be ≥14 d to be considered chronic. Hence, to strengthen the data set underpinning the site-specific guideline value for uranium (U) in Magela Creek, which receives water from the Ranger Uranium Mine in northern Australia, the toxicity of U to A. cumingi was compared after 4 d, 9 d, and 14 d. Daily U concentrations were measured because of expected U loss during testing, providing extensive chemical analyses of the U exposure during the toxicity tests. Comparison of the U concentrations causing 50% reproductive inhibition (IC50) after 4 d, 9 d, and 14 d showed no difference in toxicity (4 d IC50 = 161 µg L-1 , confidence interval = 133-195; 9-d IC50 = 151 µg L-1 , confidence interval = 127-180; 14-d IC50 = 153 µg L-1 , confidence interval = 29-180). The present study provides evidence that test durations of <14 d are suitable for assessing chronic toxicity to U for this species and supports the use of the 4-d toxicity estimate in the SSD for U. Environ Toxicol Chem 2016;35:2851-2858. © 2016 Commonwealth of Australia.

Genetic variability in tolerance to copper contamination in a herbivorous marine invertebrate.

Anthropogenic stresses such as metal contamination can have profound ecological impacts in a wide range of habitats. Reduced survival of organisms in contaminated habitats has the potential to result in the evolution of genotypes tolerant to deleterious contaminants. Local adaptation to contamination requires directional selection, genetic variation in traits relating to tolerance, spatial variability in exposure to the contaminant and limited gene flow between populations. This study assesses variation in tolerance in the herbivorous marine invertebrate Peramphithoe parmerong whose algal diets in Sydney Harbour readily accumulate the metal copper. A quantitative genetics approach (a full-sib, split family design) was used to quantify variation among families in survival on the contaminated diet. A significant genotype-by-environment interaction in offspring survival between the copper contaminated and uncontaminated diet treatments revealed variation in tolerance to copper by P. parmerong. Amphipods that survived 30 days of exposure to copper contaminated diets were slightly smaller and ate less algae than those reared on uncontaminated food. This reflects an additional sub-lethal effect associated with the consumption of contaminated algae. However, there was no evidence of acclimation to contaminated diets, nor a cost of reduced feeding for those genotypes with increased tolerance. This study provides strong evidence for the potential of a marine invertebrate to evolve tolerance to contaminants found in their diet.