Application of a Multispecies Pulse-Exposure Microalgal Bioassay to Assess Duration and Time-of-Day Influences on the Toxicity of Chemicals.

Aquatic organisms may frequently be exposed to short-term discharges of contaminants, including those from pesticide use, stormwater runoff, or industrial effluents entering waterways. Here, a new microalgal multispecies flow cytometry-based bioassay is used to assess knowledge gaps in risk assessments posed by the short-term exposure of organisms to contaminants. The toxicities of atrazine, metolachlor, and copper were assessed using four exposure scenarios, a 72 h exposure (continuous), an 18 h pulse exposure, and two 3 h pulse exposures (light and dark conditions), that assessed chronotoxicity.

Development and Validation of Multiple Linear Regression Models for Predicting Chronic Zinc Toxicity to Freshwater Microalgae.

Multiple linear regression (MLR) models were developed for predicting chronic zinc toxicity to a freshwater microalga, Chlorella sp., using three toxicity-modifying factors (TMFs): pH, hardness, and dissolved organic carbon (DOC). The interactive effects between pH and hardness and between pH and DOC were also included.

High Sensitivity of the Antarctic Rotifer Adineta editae to Metals and Ecological Relevance in Contaminated Site Risk Assessments.

Anthropogenic activities in Antarctica have led to contamination of terrestrial sites, and soils in ice-free areas have elevated concentrations of metals, particularly around current and historic research stations. Effective management of Antarctic contaminated sites depends on the assessment of risks to a representative range of native terrestrial species. Bdelloid rotifers are an abundant and biodiverse component of Antarctic limnoterrestrial communities and play a key role in nutrient cycling in Antarctic ecosystems.

Natural organic matter source, concentration, and pH influences the toxicity of zinc to a freshwater microalga.

Zinc is a contaminant of concern in aquatic environments and is a known toxicant to many aquatic organisms. Dissolved organic matter (DOM) is a toxicity modifying factor for zinc and is an important water chemistry parameter. This study investigated the influence of DOM concentration, source, and water pH on the chronic toxicity of zinc to a freshwater microalga, Chlorella sp.

The influence of hardness at varying pH on zinc toxicity and lability to a freshwater microalga, sp.

Zinc is an essential element for aquatic organisms, however, activities such as mining and refining, as well as zinc's ubiquitous role in modern society can contribute to elevated environmental concentrations of zinc. Water hardness is widely accepted as an important toxicity modifying factor for metals in aquatic systems, though other factors such as pH are also important. This study investigated the influence of increasing water hardness, at three different pH values (6.

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.

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.

Metal lability and environmental risk in anthropogenically disturbed Antarctic melt streams.

Antarctic melt streams are important ecosystems that increasingly face contaminant pressures from anthropogenic sources. Metal contaminants are often reported in the limno-terrestrial environment but their speciation is not well characterised, making environmental risk assessments difficult. This paper characterises labile metal concentrations in five melt streams and three shallow lakes around the Casey and Wilkes research stations in East Antarctica using chemical extracts and field deployments of diffusive gradients in thin-film (DGT) samplers.

The microalga is tolerant to salinity and metal mixture toxicity interactions.

Salinity in the Antarctic nearshore marine environment is seasonally dynamic and climate change is driving greater variability through altered sea ice seasons, ocean evaporation rates, and increased terrestrial ice melt. The greatest salinity changes are likely to occur in the nearshore environment where elevated metal exposures from historical waste or wastewater discharge occur. How salinity changes affect metal toxicity has not yet been investigated.

The Influence of pH on Zinc Lability and Toxicity to a Tropical Freshwater Microalga.

Increased focus on the development and application of bioavailability-based metal water quality guideline values requires increased understanding of the influence of water chemistry on metal bioavailability and toxicity. Development of empirical models, such as multiple linear regression models, requires the assessment of the influence of individual water quality parameters as toxicity-modifying factors. The present study investigated the effect of pH on the lability and toxicity of zinc (Zn) to a tropical green microalga (Chlorella sp.

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.

Metabarcoding Reveals Changes in Benthic Eukaryote and Prokaryote Community Composition along a Tropical Marine Sediment Nickel Gradient.

The Southeast Asia and Melanesia region has extensive nickel (Ni)-rich lateritic regoliths formed from the tropical weathering of ultramafic rocks. As the global demand for Ni continues to rise, these lateritic regoliths are increasingly being exploited for their economic benefit. Mining of these regoliths contributes to the enrichment of coastal sediments in trace metals, especially Ni.

Effect of Dissolved Organic Matter Concentration and Source on the Chronic Toxicity of Copper and Nickel Mixtures to Chlorella sp.

There have been limited studies on the effects of toxicity-modifying factors, such as dissolved organic matter (DOM), on the toxicity of metal mixtures to aquatic biota. The present study investigated the effects of DOM concentration (low, 2.8 ± 0.

Assessing metal contaminants in Antarctic soils using diffusive gradients in thin-films.

Metal contaminants in Antarctic soils are typically found around research stations which are concentrated in ice-free coastal areas. The risk of these contaminants to the Antarctic environment is not well understood, given Antarctica's unique organisms and climate. This study assessed the use of diffusive gradients in thin-films (DGT), a passive sampler that measures fluxes of labile metals from soils to porewaters, in Antarctic soils.

The Diffusive Gradients in Thin Films Technique Predicts Sediment Nickel Toxicity to the Amphipod Melita plumulosa.

The geographical shift of nickel mining to small island countries of the Southeast Asia and Melanesia region has produced a need to assess the environmental risk associated with increased sediment nickel exposure to benthic estuarine/marine biota. Chemical measurements of nickel concentration and potential bioavailability, including the use of diffusive gradients in thin films (DGT), were compared to effects on 10-d reproduction of the epibenthic estuarine/marine amphipod Melita plumulosa in nickel-spiked sediments and field-contaminated sediments with different characteristics. The 10% effect concentrations (EC10s) for amphipod reproduction ranged from 280 to 690 mg/kg total recoverable nickel, from 110 to 380 mg/kg dilute acid-extractable nickel, and from 34 to 87 μg Ni/m /h DGT-labile nickel flux.

Speciation of nickel and its toxicity to Chlorella sp. in the presence of three distinct dissolved organic matter (DOM).

Nickel is often a metal of interest in regulatory settings given its increasing prevalence in disturbed freshwaters and as a known toxicant to fish and algae. Dissolved organic matter (DOM) is a toxicity modifying factor for nickel and a ubiquitous water physicochemical parameter. This study investigated the effect of DOM concentration and source on the chronic toxicity of nickel to Chlorella sp.

Amelioration of copper toxicity to a tropical freshwater microalga: Effect of natural DOM source and season.

Australian tropical freshwaters can experience extreme seasonal variability in rainfall and run off, particularly due to pulse events such as storms and cyclones. This study investigated how seasonal variability in dissolved organic matter (DOM) quality impacted the chronic toxicity of copper to a tropical green alga (Chlorella sp.) in the presence of two concentrations of DOM (low: ∼2 mg C/L; high: ∼10 mg C/L) collected from three tropical waters.

Effects of dissolved nickel and nickel-contaminated suspended sediment on the scleractinian coral, Acropora muricata.

Intensification of lateritic nickel mining in Southeast Asia and Melanesia potentially threatens coastal ecosystems from increased exposure to nickel and suspended sediment. This study investigated the response of Acropora muricata when exposed to either dissolved nickel, clean suspended sediment or nickel-contaminated suspended sediment for 7 days, followed by a 7-d recovery period. Significant bleaching and accumulation of nickel in coral tissue was observed only after exposure to high dissolved nickel concentrations and nickel-spiked suspended sediment.

Influence of Soil Phosphate on the Accumulation and Toxicity of Arsenic and Antimony in Choy Sum Cultivated in Individually and Co-contaminated Soils.

Fertilizers containing phosphate (PO ) are commonly used within the agricultural industry and are known to increase the bioavailability and mobility of metalloids like arsenic (As). This may increase plant uptake of As and hence pose a risk to human health. Arsenic and antimony (Sb) often co-occur in contaminated soils; however, little is known about the interactions between As and Sb with PO on their bioavailability, accumulation, and toxicity in plants.

Interactive effects of arsenic and antimony on Ipomoea aquatica growth and bioaccumulation in co-contaminated soil.

Antimony (Sb) is an emerging contaminant and until recently it was assumed to behave in a similar way to arsenic (As). Arsenic and Sb often co-occur in contaminated sites, yet most investigations consider their toxicity to plants singly. More research is needed to understand the interactions between As and Sb in soils and plants.

DGT and selective extractions reveal differences in arsenic and antimony uptake by the white icicle radish (Raphanus sativus).

Increasing soil contamination of arsenic (As) and antimony (Sb) is posing a serious concern to human health. Due to insufficient studies on Sb, the biogeochemical behaviour and plant uptake of Sb are assumed to be similar to that of As. As part of extensive research unravelling As and Sb biogeochemistry and plant uptake, the diffusive gradients in thin films (DGT) technique and sequential extraction procedure (SEP) were applied to evaluate As and Sb uptake by the white icicle radish (Raphanus sativus) cultivated in diluted cattle dip soils contaminated with As only and diluted mining soils contaminated with both As and Sb under agricultural conditions.

Assessing the Risk of Metals and Their Mixtures in the Antarctic Nearshore Marine Environment with Diffusive Gradients in Thin-Films.

Robust environmental assessments and contaminant monitoring in Antarctic near-shore marine environments need new techniques to overcome challenges presented by a highly dynamic environment. This study outlines an approach for contaminant monitoring and risk assessment in Antarctic marine conditions using diffusive gradients in thin-films (DGT) coupled to regionally specific ecotoxicology data and environmental quality standards. This is demonstrated in a field study where DGT samplers were deployed in the near-shore marine environment of East Antarctica around the operational Casey station and the abandoned Wilkes station to measure the time-averaged biologically available fraction of metal contaminants.

Preliminary study of cellular metal accumulation in two Antarctic marine microalgae - implications for mixture interactivity and dietary risk.

Localised sites in Antarctica are contaminated with mixtures of metals, yet the risk this contamination poses to the marine ecosystem is not well characterised. Recent research showed that two Antarctic marine microalgae have antagonistic responses to a mixture of five common metals (Koppel et al., 2018a).

Towards Sustainable Environmental Quality: Priority Research Questions for the Australasian Region of Oceania.

Environmental challenges persist across the world, including the Australasian region of Oceania, where biodiversity hotspots and unique ecosystems such as the Great Barrier Reef are common. These systems are routinely affected by multiple stressors from anthropogenic activities, and increasingly influenced by global megatrends (e.g.

The effect of dissolved nickel and copper on the adult coral Acropora muricata and its microbiome.

The potential impacts of mining activities on tropical coastal ecosystems are poorly understood. In particular, limited information is available on the effects of metals on scleractinian corals which are foundation species that form vital structural habitats supporting other biota. This study investigated the effects of dissolved nickel and copper on the coral Acropora muricata and its associated microbiota.