Advantages of model averaging of species sensitivity distributions used for regulating produced water discharges.

Produced water (PW) generated by Australian offshore oil and gas activities is typically discharged to the ocean after treatment. These complex mixtures of organic and inorganic compounds can pose significant environmental risk to receiving waters, if not managed appropriately. Oil and gas operators in Australia are required to demonstrate that environmental impacts of their activity are managed to levels that are as low as reasonably practicable, for example, through risk assessments comparing predicted no-effect concentrations (PNECs) with predicted environmental concentrations of PW. Probabilistic species sensitivity distribution (SSD) approaches are increasingly being used to derive PW PNECs and subsequently calculating dilutions of PW (termed "safe" dilutions) required to protect a nominated percentage of species in the receiving environment (e.g., 95% and 99% or PC95 and PC99, respectively). Limitations associated with SSDs include fitting a single model to small (six to eight species) data sets, resulting in large uncertainty (very wide 95% confidence limits) in the region associated with PC99 and PC95 results. Recent advances in SSD methodology, in the form of model averaging, claim to overcome some of these limitations by applying the average model fit of multiple models to a data set. We assessed the advantages and limitations of four different SSD software packages for determining PNECs for five PWs from a gas and condensate platform off the North West Shelf of Australia. Model averaging reduced occurrences of extreme uncertainty around PC95 and PC99 values compared with single model fitting and was less prone to the derivation of overly conservative PC99 and PC95 values that resulted from lack of fit to single models. Our results support the use of model averaging for improved robustness in derived PNEC and subsequent "safe" dilution values for PW discharge management and risk assessment. In addition, we present and discuss the toxicity of PW considering the paucity of such information in peer-reviewed literature. Integr Environ Assess Manag 2024;20:498-517. © 2023 Commonwealth Scientific and Industrial Research Organisation. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Applicability of Chronic Multiple Linear Regression Models for Predicting Zinc Toxicity in Australian and New Zealand Freshwaters.

Bioavailability models, for example, multiple linear regressions (MLRs) of water quality parameters, are increasingly being used to develop bioavailability-based water quality criteria for metals. However, models developed for the Northern Hemisphere cannot be adopted for Australia and New Zealand without first validating them against local species and local water chemistry characteristics. We investigated the applicability of zinc chronic bioavailability models to predict toxicity in a range of uncontaminated natural waters in Australia and New Zealand. Water chemistry data were compiled to guide a selection of waters with different zinc toxicity-modifying factors. Predicted toxicities using several bioavailability models were compared with observed chronic toxicities for the green alga Raphidocelis subcapitata and the native cladocerans Ceriodaphnia cf. dubia and Daphnia thomsoni. The most sensitive species to zinc in five New Zealand freshwaters was R. subcapitata (72-h growth rate), with toxicity ameliorated by high dissolved organic carbon (DOC) or low pH, and hardness having a minimal influence. Zinc toxicity to D. thomsoni (reproduction) was ameliorated by both high DOC and hardness in these same waters. No single trophic level-specific effect concentration, 10% (EC10) MLR was the best predictor of chronic toxicity to the cladocerans, and MLRs based on EC10 values both over- and under-predicted zinc toxicity. The EC50 MLRs better predicted toxicities to both the Australian and New Zealand cladocerans to within a factor of 2 of the observed toxicities in most waters. These findings suggest that existing MLRs may be useful for normalizing local ecotoxicity data to derive water quality criteria for Australia and New Zealand. The final choice of models will depend on their predictive ability, level of protection, and ease of use. Environ Toxicol Chem 2023;42:2614-2629. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Acute and chronic toxicity of manganese to tropical adult coral (Acropora millepora) to support the derivation of marine manganese water quality guideline values.

Adult corals are among the most sensitive marine organisms to dissolved manganese and experience tissue sloughing without bleaching (i.e., no loss of Symbiodinium spp.) but there are no chronic toxicity data for this sensitive endpoint. We exposed adult Acropora millepora to manganese in 2-d acute and 14-d chronic experiments using tissue sloughing as the toxicity endpoint. The acute tissue sloughing median effect concentration (EC50) was 2560 µg Mn/L. There was no chronic toxicity to A. millepora at concentrations up to and including the highest concentration of 1090 µg Mn/L i.e., the chronic no observed effect concentration (NOEC). A coral-specific acute-to-chronic ratio (ACR) (EC50/NOEC) of 2.3 was derived. These data were combined with chronic toxicity data for other marine organisms in a species sensitivity distribution (SSD). Marine manganese guidelines were 190, 300, 390 and 570 µg Mn/L to provide long-term protection of 99, 95, 90, and 80 % of marine species, respectively.

Adult Corals Are Uniquely More Sensitive to Manganese Than Coral Early-Life Stages.

Manganese (Mn) is an essential element and is generally considered to be one of the least toxic metals to aquatic organisms, with chronic effects rarely seen at concentrations below 1000 µg/L. Anthropogenic activities lead to elevated concentrations of Mn in tropical marine waters. Limited data suggest that Mn is more acutely toxic to adults than to early life stages of scleractinian corals in static renewal tests. However, to enable the inclusion of sufficient sensitive coral data in species sensitivity distributions to derive water quality guideline values for Mn, we determined the acute toxicity of Mn to the adult scleractinian coral, Acropora muricata, in flow-through exposures. The 48-h median effective concentration was 824 µg Mn/L (based on time-weighted average, measured, dissolved Mn). The endpoint was tissue sloughing, a lethal process by which coral tissue detaches from the coral skeleton. Tissue sloughing was unrelated to superoxidase dismutase activity in coral tissue, and occurred in the absence of bleaching, that is, toxic effects were observed for the coral host, but not for algal symbionts. We confirm that adult scleractinian corals are uniquely sensitive to Mn in acute exposures at concentrations 10-340 times lower than those reported to cause acute or chronic toxicity to coral early life stages, challenging the traditional notion that early life stages are more sensitive than mature organisms. Environ Toxicol Chem 2023;42:1359-1370. © 2023 Commonwealth Scientific and Industrial Research Organisation. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

The Influence of Oil-in-Water Preparations on the Toxicity of Crude Oil to Marine Invertebrates and Fish Following Short-Term Pulse and Continuous Exposures.

Following an oil spill, accurate assessments of the ecological risks of exposure to compounds within petroleum are required, as is knowledge regarding how those risks may change with the use of chemical dispersants. Laboratory toxicity tests are frequently used to assess these risks, but differences in the methods for preparation of oil-in-water solutions may confound interpretation, as may differences in exposure time to those solutions. In the present study, we used recently developed modifications of standardized ecotoxicity tests with copepods (Acartia sinjiensis), sea urchins (Heliocidaris tuberculata), and fish embryos (Seriola lalandi) to assess their response to crude oil solutions and assessed whether the oil-in-water preparation method changed the results. We created a water-accommodated fraction, a chemically enhanced water-accommodated fraction, and a high-energy water-accommodated fraction (HEWAF) using standard approaches using two different dispersants, Corexit 9500 and Slickgone NS. We found that toxicity was best related to total polycyclic aromatic hydrocarbon (TPAH) concentrations in solution, regardless of the preparation method used, and that the HEWAF was the most toxic because it dispersed the highest quantity of oil into solution. The TPAH composition in water did not vary appreciably with different preparation methods. For copepods and sea urchins, we also found that at least some of the toxic response could be attributed to the chemical oil dispersant. We did not observe the characteristic cardiac deformities that have been previously reported in fish embryos, most likely due to the use of unweathered oil, and, as a consequence, the high proportion of naphthalenes relative to cardiotoxic polycyclic aromatic hydrocarbon in the overall composition. The present study highlights the need to characterize both the TPAH composition and concentration in test solutions when assessing oil toxicity. Environ Toxicol Chem 2022;41:2580-2594. © 2022 SETAC.

Exposure duration and composition are important variables to predict short-term toxicity of effluents to a tropical copepod, Acartia sinjiensis.

Predicting the toxicity of effluent exposures, which vary in duration, composition, and concentration, poses a challenge for ecological risk assessments. Effluent discharges may frequently result in the exposure of aquatic organisms to high concentrations of mixed contaminants for short durations. In the receiving environment effluents will undergo dilution and physical or chemical processes that further reduce contaminant concentrations at varying rates. To date, most studies comparing toxicity risks of continuous and pulsed contaminant exposures have focused on individual contaminants. In this study, the toxicity to the tropical euryhaline copepod Acartia sinjiensis of two complex effluents was assessed, comparing 6- and 18-h pulses and 78-h continuous exposures. Observations of larval development success and population size were completed after a 78-h incubation period, to observe for latent effects after pulse exposures. The chemical compositions of the effluents were assessed over time and different contaminants (i.e., metals, ammonia or organics) declined at differing rates. These were characterized as either a minimal, steady, or rapid decline. Nauplii development and population after 78 h were more impacted by effluent exposures following an 18-h pulse, compared to a 6-h pulse. Based on pulse-exposure concentrations, the 50% effect concentrations (EC50) were similar for continuous and 18-h exposures but up to 3-fold greater (lower toxicity) for the shorter 6-h exposures. Time-weighted average concentrations did not accurately predict toxicity from pulse exposures of the effluents. Concentration-addition toxicity modelling using toxicity data from pulse exposures of single contaminants was useful for predicting the toxicity of chemical mixtures exposed for varying durations. Recommendations for modified approaches to assessing risks of short-term effluent discharges are discussed.

The influence of salinity on the chronic toxicity of shale gas flowback wastewater to freshwater organisms.

The potential environmental risk associated with flowback waters generated during hydraulic fracturing of target shale gas formations needs to be assessed to enable management decisions and actions that prevent adverse impacts on aquatic ecosystems. Using direct toxicity assessment (DTA), we determined that the shale gas flowback wastewater (FWW) from two exploration wells (Tanumbirini-1 and Kyalla 117 N2) in the Beetaloo Sub-basin, Northern Territory, Australia were chronically toxic to eight freshwater biota. Salinity in the respective FWWs contributed 16% and 55% of the chronic toxicity at the 50% effect level. The remaining toxicity was attributed to unidentified chemicals and interactive effects from the mixture of identified organics, inorganics and radionuclides. The most sensitive chronic endpoints were the snail (Physa acuta) embryo development (0.08-1.1% EC10), microalga (Chlorella sp. 12) growth rate inhibition (0.23-3.7% EC10) and water flea (Ceriodaphnia cf. dubia) reproduction (0.38-4.9% EC10). No effect and 10% effect concentrations from the DTA were used in a species sensitivity distribution to derive "safe" dilutions of 1 in 300 and 1 in 1140 for the two FWWs. These dilutions would provide site-specific long-term protection to 95% of aquatic biota in the unlikely event of an accidental spill or seepage.

Pulse-Exposure Toxicity of Ammonia and Propoxur to the Tropical Copepod Acartia sinjiensis.

Toxicity risk assessments of short-term discharges of contaminated waters to the aquatic environment have shown that receptor organisms can tolerate higher pulse-exposure than continuous-exposure concentrations of some contaminants. However, these observations are influenced by the mode of toxicity of the contaminants present and the concentration-time profile of the exposure. For common metal contaminants, the time-weighted average concentration (TAC) of the exposure has been useful for predicting risk of toxicity to multiple species, including the tropical, euryhaline copepod Acartia sinjiensis. To increase our understanding of the application and limitations of the TAC approach, the present study examined how varied pulse-exposure durations affect the toxicity of fast-acting contaminants, ammonia, and the common pesticide propoxur to this copepod species. Copepod larvae were exposed under continuous-exposure conditions (all life stages from eggs to nauplii to copepodites exposed) and as 6- and 18-h pulse exposures applied during the most sensitive life stage only (24-h-old nauplii) within 78-h tests. Larval development ratio and population size were assessed as test endpoints. Generally, increased exposure duration resulted in increased toxicity. Trends observed for ammonia and propoxur were slightly different for larval development and population size. Larvae tolerated greater concentrations of contaminants in a 6-h pulse (higher 10% effect concentration) than in an 18-h pulse, or a continuous 78-h exposure, whereas toxicity responses converged for the 18- and 78-h exposures. Continuous toxicity thresholds were always protective of pulse exposures, providing a conservative toxicity threshold for all durations of pulse exposures. Although generalizations for predictions of risk based on TACs are frequently effective for common metal contaminants, the TAC approach was not effective for ammonia and propoxur. Environ Toxicol Chem 2022;41:208-218. © 2021 SETAC.

Probabilistic risk assessment of mine-derived copper in the Ok Tedi/Fly River, Papua New Guinea.

The Ok Tedi mine discharges waste rock and tailings into the Ok Tedi River in Papua New Guinea. This has resulted in elevated copper concentrations throughout the Ok Tedi/Fly River system, which can potentially impact aquatic biota. Ten years of measured copper and toxicity monitoring data were used to assess the risk of chronic effects from the mine-derived copper. Cumulative probability plots of dissolved and labile copper were compared to a species sensitivity distribution (SSD) of published copper toxicity data for four regions of the river. The Cu-SSD was used to estimate the risk of chronic effects to aquatic organisms in the Ok Tedi/Fly River at a range of potential copper exposure scenarios. The risk to species at the median labile copper concentration for each region showed a gradient effect with distance downstream from the mine and only the most sensitive (0.2-11%) species were at risk. There were copper exceedances of the region-specific guideline values (GV) and default guideline value (DGV) 88% and 74% of the time, respectively, in the Ok Tedi region (closest to the mine) and this is considered a high risk of chronic effects. Measured copper concentrations in the middle Fly River, lower Fly River (farthest downstream of the mine) and the river at Kiunga (reference site) exceeded the region-specific GVs and DGVs less frequently to rarely and present a lower risk of chronic effects from copper. The risk was supported using toxicity tests with the local microalgal species Chlorella sp. Comparison of recent (2010-2020) and historical (1996-2004) copper monitoring data from the Ok Tedi/Fly River indicates a decrease in the labile copper concentrations (30-76%) at key sites from impacted regions and a subsequent decrease in risk. This coincides with improved mining practices aimed at reducing the copper load into the Ok Tedi/Fly River.

A Comparison of Short-Term and Continuous Exposures in Toxicity Tests of Produced Waters, Condensate, and Crude Oil to Marine Invertebrates and Fish.

Petroleum hydrocarbons can be discharged into the marine environment during offshore oil and gas production or as a result of oil spills, with potential impacts on marine organisms. Ecotoxicological assay durations (typically 24-96 h) used to characterize risks to exposed organisms may not always reflect realistic environmental exposure durations in a high-energy offshore environment where hydrocarbons are mixed and diluted rapidly in the water column. To investigate this, we adapted 3 sensitive toxicity tests to incorporate a short-term pulse exposure to 3 petroleum-based products: a produced water, the water-accommodated fraction (WAF) of a condensate, and a crude oil WAF. We measured 48-h mobility of the copepod Acartia sinjiensis, 72-h larval development of the sea urchin Heliocidaris tuberculata, and 48-h embryo survival and deformities of yellowtail kingfish Seriola lalandi, after exposure to a dilution series of each of the 3 products for 2, 4 to 12, and 24 h and for the standard duration of each toxicity test (continuous exposure). Effects on copepod survival and sea urchin larval development were significantly reduced in short-term exposures to produced water and WAFs compared to continuous exposures. Fish embryos, however, showed an increased frequency of deformities at elevated concentrations regardless of exposure duration, although there was a trend toward increased severity of deformities with continuous exposure. The results demonstrate how exposure duration alters toxic response and how incorporating relevant exposure duration to contaminants into toxicity testing may aid interpretation of more realistic effects (and hence an additional line of evidence in risk assessment) in the receiving environment. Environ Toxicol Chem 2021;40:2587-2600. © 2021 CSIRO. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

The effects of pulse exposures of metal toxicants on different life stages of the tropical copepod Acartia sinjiensis.

Effluent discharges can potentially result in high concentrations of metals entering aquatic environments for short durations, ranging from a few hours to days. The environmental risks of such exposures are challenging to accurately assess. Risk assessment tools for effluent discharges include comparison of toxicant concentrations with guideline values and the use of direct toxicity assessments, both of which were designed to assess continuous, rather than pulse, contaminant exposures. In this study, a chronic pulse-exposure toxicity test was developed using the tropical euryhaline calanoid copepod Acartia sinjiensis. This copepod has a rapid life cycle and is highly sensitive to metal contaminants, with 50% effect concentrations (chronic EC50) for larval development of 1.7, 8.6 and 0.7 µg L-1 for copper, nickel and zinc, respectively. The toxicities of copper and nickel were assessed as a continuous exposure (78 h) and as pulses (3, 6 and 18 h) initiated at varying life stages, from egg to copepodite, and measured larval development over 78 h. Generally, 24-h old nauplii were more sensitive or of similar sensitivity to copper and nickel pulses than 48-h old nauplii. The 78-h test duration enabled observations of chronic effects following pulse exposures, which frequently occurred in the absence of acute effects. The EC50 values for pulse exposures were higher than those of continuous exposure by up to approximately 16-fold and 15-fold for copper and nickel, respectively. When metal-pulse exposure concentrations were expressed using the time-weighted averaged concentration (TAC), resultant concentration response curves were similar to those in continuous exposures to the same metal, suggesting that thresholds based on continuous exposures were also protective for pulse exposures to these metals. This research improves our understanding of the toxicity of pulse contaminant exposures and assists with developing improved approaches to for the risk assessment and regulation of short-term contaminant discharges.

Development of a bioavailability-based risk assessment framework for nickel in Southeast Asia and Melanesia.

Nickel laterite ore deposits are becoming increasingly important sources of Ni for the global marketplace and are found mainly in tropical and subtropical regions, including Indonesia, the Philippines, Papua New Guinea, Cuba, and New Caledonia. There are few legislatively derived standards or guidelines for the protection of aquatic life for Ni in many of these tropical regions, and bioavailability-based environmental risk assessment (ERA) approaches for metals have mainly been developed and tested in temperate regions, such as the United States and Europe. This paper reports on a multi-institutional, 5-y testing program to evaluate Ni exposure, effects, and risk characterization in the Southeast Asia and Melanesia (SEAM) region, which includes New Caledonia, Papua New Guinea, the Philippines, and Indonesia. Further, we have developed an approach to determine if the individual components of classical ERA, including effects assessments, exposure assessments, and risk characterization methodologies (which include bioavailability normalization), are applicable in this region. A main conclusion of this research program is that although ecosystems and exposures may be different in tropical systems, ERA paradigms are constant. A large chronic ecotoxicity data set for Ni is now available for tropical species, and the data developed suggest that tropical ecosystems are not uniquely sensitive to Ni exposure; hence, scientific support exists for combining tropical and temperate data sets to develop tropical environmental quality standards (EQSs). The generic tropical database and tropical exposure scenarios generated can be used as a starting point to examine the unique biotic and abiotic characteristics of specific tropical ecosystems in the SEAM region. Integr Environ Assess Manag 2021;17:802-813. © 2021 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Use of scanning and image recognition technology to semi-automate larval development assessment in toxicity tests with a tropical copepod.

There is a high demand for the development of reliable chronic toxicity tests using tropical marine species for subsequent use in tropical risk assessment. However, many chronic test endpoints can be laborious and time-consuming to assess, particularly if the endpoints require measurements of individuals (e.g. growth, size) or advanced taxonomic expertise (e.g. differentiating between larval development stages). In this study, we used scanning and image recognition (SIR) technology to develop and validate a chronic toxicity test with larvae of the tropical euryhaline copepod, Acartia sinjiensis. Optimisation steps are described, and included egg age, and effect of algal food type and salinity on toxicity. Comparisons were made between traditional endpoints measured using microscopy and those measured using SIR. Traditional endpoints of larval development ratio (LDR) and survival achieved using microscope examination and SIR were almost identical (R2 = 0.96-0.97). Additional endpoints made possible by SIR included larval development index (LDI; based on the number of animals at different stages of development), and a range of size measurements (e.g. surface area, perimeter and length) for individual animals and for total populations (i.e. a proxy for biomass). The SIR-derived endpoints were based on measurements that had concentration-dependant responses to tested toxicants (copper, nickel, ammonia), and were a sub-set of the full range of metrics provided by the software. Toxicity values based on SIR-measurements were similar to or more sensitive than the traditional LDR endpoint. SIR technology provides a major opportunity to improve and modernise larval development tests for a range for species, but comes at a cost of increased data size and complexity. Therefore, as a research tool, SIR has significant advantages over traditional microscope methods, but for routine toxicity testing, SIR incorporation into invertebrate toxicity testing will benefit from further improvements to the associated software and data management systems.

Importance of sperm density in assessing the toxicity of metals to the fertilization of broadcast spawners.

Many marine invertebrates reproduce through broadcast spawning, where sperm and eggs are released into the water column and are vulnerable to toxicants present in the environment. The potential impacts of toxicants on spawning success are often assessed through laboratory-based fertilization tests. In most cases, these tests assess toxicant impacts at a single, pre-defined sperm density, based on a sperm:egg ratio that ensures high fertilization success (≥70-80%) in a filtered seawater control. Here we show that use of a single sperm density can considerably underestimate toxicity and that assessments over a range of sperm densities can provide more ecologically relevant, conservative and informative toxicity data. Fertilization assays were run for the polychaete Galeolaria caespitosa exposed to four heavy metals (Cu, Zn, Pb, Cd) across multiple sperm densities. There was a three-fold difference in the toxicity of copper and zinc when calculated at sperm densities of 104 and 106 sperm mL-1, both of which result in over 80% fertilization in FSW controls. By testing across multiple sperm densities, we identified that metals impact the sperm of G. caespitosa during the fertilization process. Assessing toxicity across multiple sperm densities is not always practical. This is due to the increased effort required to complete full fertilization curves, across enough concentrations of a toxicant, to establish a concentration-response relationship. In such cases, we provide recommendations for adopting aspects of fertilization assays that will improve on standard spermiotoxicity tests but which are still manageable for routine toxicity testing.

Assessing the chronic toxicity of nickel to a tropical marine gastropod and two crustaceans.

The mining and processing of nickel ores from tropical regions contributes 40% of the global supply. The potential impact of these activities on tropical marine ecosystems is poorly understood. Due to the lack of ecotoxicity data for tropical marine species, there is currently no available water quality guideline value for nickel that is specific to tropical species. In this study, we investigated the toxicity of nickel to three tropical marine invertebrates, the gastropod Nassarius dorsatus, the barnacle Amphibalanus amphitrite, and the copepod Acartia sinjiensis. All toxicity tests used chronic endpoints, namely larval growth, metamorphosis (transition from nauplii to cyprid larvae) and larval development for the snail, barnacle and copepod respectively. Toxicity tests were carried out under environmentally relevant conditions (i.e. 27-30ᵒC, salinity 34-36‰, pH 8.1-8.4). Copper was also tested for quality assurance purposes and to allow for comparisons with previous studies. The copepod was the most sensitive species to nickel, with development inhibited by 10% (EC10) at 5.5 (5.0-6.0) µg Ni/L (95% confidence limits (CL)). Based on EC10 values, the gastropod and barnacle showed similar sensitivities to nickel with growth and metamorphosis inhibited by 10% at 64 (37-91) µg Ni/L and 67 (53-80) µg Ni/L, respectively. Based on existing data available in the literature, the copepod A. sinjiensis is so far the most sensitive tropical marine species to nickel. This study has provided high quality data which will contribute to the development of a water quality guideline value for nickel in tropical marine waters. A species sensitivity distribution of chronic nickel toxicity used the data generated in this paper supplemented by available literature data, comprising 12 species representing 6 taxonomic groups. A 5% hazard concentration (HC5) was determined as 8.2 µg/L Ni.

Toxicity of nickel to tropical freshwater and sediment biota: A critical literature review and gap analysis.

More than two-thirds of the world's nickel (Ni) lateritic deposits are in tropical regions, and just less than half are within South East Asia and Melanesia (SEAM). With increasing Ni mining and processing in SEAM, environmental risk assessment tools are required to ensure sustainable development. Currently, there are no tropical-specific water or sediment quality guideline values for Ni, and the appropriateness of applying guideline values derived for temperate systems (e.g., Europe) to tropical ecosystems is unknown. Databases of Ni toxicity and toxicity tests for tropical freshwater and sediment species were compiled. Nickel toxicity data were ranked, using a quality assessment, identifying data to potentially use to derive tropical-specific Ni guideline values. There were no data for Ni toxicity in tropical freshwater sediments. For tropical freshwaters, of 163 Ni toxicity values for 40 different species, high-quality chronic data, based on measured Ni concentrations, were found for just 4 species (1 microalga, 2 macrophytes, and 1 cnidarian), all of which were relevant to SEAM. These data were insufficient to calculate tropical-specific guideline values for long-term aquatic ecosystem protection in tropical regions. For derivation of high-reliability tropical- or SEAM-specific water and sediment quality guideline values, additional research effort is required. Using gap analysis, we recommend how research gaps could be filled. Environ Toxicol Chem 2018;37:293-317. © 2017 SETAC.

A review of nickel toxicity to marine and estuarine tropical biota with particular reference to the South East Asian and Melanesian region.

The South East Asian Melanesian (SEAM) region contains the world's largest deposits of nickel lateritic ores. Environmental impacts may occur if mining operations are not adequately managed. Effects data for tropical ecosystems are required to assess risks of contaminant exposure and to derive water quality guidelines (WQG) to manage these risks. Currently, risk assessment tools and WQGs for the tropics are limited due to the sparse research on how contaminants impact tropical biota. As part of a larger project to develop appropriate risk assessment tools to ensure sustainable nickel production in SEAM, nickel effects data were required. The aim of this review was to compile data on the effects of nickel on tropical marine, estuarine, pelagic and benthic species, with a particular focus on SEAM. There were limited high quality chronic nickel toxicity data for tropical marine species, and even fewer for those relevant to SEAM. Of the data available, the most sensitive SEAM species to nickel were a sea urchin, copepod and anemone. There is a significant lack of high quality chronic data for several ecologically important taxonomic groups including cnidarians, molluscs, crustaceans, echinoderms, macroalgae and fish. No high quality chronic nickel toxicity data were available for estuarine waters or marine and estuarine sediments. The very sparse toxicity data for tropical species limits our ability to conduct robust ecological risk assessment and may require additional data generation or read-across from similar species in other databases (e.g. temperate) to fill data gaps. Recommendations on testing priorities to fill these data gaps are presented.

Ocean acidification impacts on sperm mitochondrial membrane potential bring sperm swimming behaviour near its tipping point.

Broadcast spawning marine invertebrates are susceptible to environmental stressors such as climate change, as their reproduction depends on the successful meeting and fertilization of gametes in the water column. Under near-future scenarios of ocean acidification, the swimming behaviour of marine invertebrate sperm is altered. We tested whether this was due to changes in sperm mitochondrial activity by investigating the effects of ocean acidification on sperm metabolism and swimming behaviour in the sea urchin Centrostephanus rodgersii. We used a fluorescent molecular probe (JC-1) and flow cytometry to visualize mitochondrial activity (measured as change in mitochondrial membrane potential, MMP). Sperm MMP was significantly reduced in ΔpH -0.3 (35% reduction) and ΔpH -0.5 (48% reduction) treatments, whereas sperm swimming behaviour was less sensitive with only slight changes (up to 11% decrease) observed overall. There was significant inter-individual variability in responses of sperm swimming behaviour and MMP to acidified seawater. We suggest it is likely that sperm exposed to these changes in pH are close to their tipping point in terms of physiological tolerance to acidity. Importantly, substantial inter-individual variation in responses of sperm swimming to ocean acidification may increase the scope for selection of resilient phenotypes, which, if heritable, could provide a basis for adaptation to future ocean acidification.

Geochemical and ecotoxicological assessment of iron- and steel-making slags for potential use in environmental applications.

Prior to the productive use of iron- and steel-making slags as environmental amendments, a risk assessment supported by material characterization concomitant with leaching and ecotoxicological testing is necessary. Five iron- and steel-making slags were characterized geochemically, and the leachability of their elemental constituents was assessed. The toxicity of slag leachate to microalgae (Chlorella sp.), cladocerans (Ceriodaphnia dubia), and bacteria (Vibrio fischeri) was related to elemental composition. Slag leachates with the highest concentrations of dissolved elements were the most toxic (10% effective concentration [EC10] ∼1%), whereas those with the lowest concentrations of elements were the least toxic (EC10 63-85%). It was not possible to determine which elements caused the observed toxicity; however, comparisons with contaminant guidelines and published toxicity data identified several elements of potential environmental concern. Low to moderate activities were measured for radionuclides in the U and Th decay chains in slags. Based on these data, some of the slags examined herein are potentially suitable for use as environmental amendments following ≥10 times dilution to ameliorate potential toxic effects because of leachate pH.

Environmental toxicity and radioactivity assessment of a titanium-processing residue with potential for environmental use.

Thorough examination of the physicochemical characteristics of a Ti-processing residue was undertaken, including mineralogical, geochemical, and radiochemical characterization, and an investigation of the environmental toxicity of soft-water leachate generated from the residue. Concentrations of most metals measured in the leachate were low; thus, the residue is unlikely to leach high levels of potentially toxic elements on exposure to low-ionic strength natural waters. Relative to stringent ecosystem health-based guidelines, only chromium concentrations in the leachate exceeded guideline concentrations for 95% species protection; however, sulfate was present at concentrations known to cause toxicity. It is likely that the high concentration of calcium and extreme water hardness of the leachate reduced the bioavailability of some elements. Geochemical modeling of the leachate indicated that calcium and sulfate concentrations were largely controlled by gypsum mineral dissolution. The leachate was not toxic to the microalga Chlorella sp., the cladoceran Ceriodaphnia dubia, or the estuarine bacterium Vibrio fischeri. The Ti-processing residue exhibited an absorbed dose rate of 186 nGy/h, equivalent to an annual dose of 1.63 mGy and an annual effective dose of 0.326 mGy. In summary, the results indicate that the Ti-processing residue examined is suitable for productive use as an environmental amendment following 10 to 100 times dilution to ameliorate potential toxic effects due to chromium or sulfate.