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

Ocean acidification alleviated nickel toxicity to a marine copepod under multigenerational scenarios but at a cost with a loss of transcriptome plasticity during recovery

Marine ecosystem has been experiencing multiple stressors caused by anthropogenic activities, including ocean acidification (OA) and nickel (Ni) pollution. Here, we examined the individual/combined effects of OA (pCO2 1000 μatm) and Ni (6 μg/L) exposure on a marine copepod Tigriopus japonicus for six generations (F1-F6), followed by one-generation recovery (F7) in clean seawater. Ni accumulation and several important phenotypic traits were measured in each generation. To explore within-generation response and transgenerational plasticity, we analyzed the transcriptome profile for the copepods of F6 and F7. The results showed that Ni exposure compromised the development, reproduction and survival of copepods during F1-F6, but its toxicity effects were alleviated by OA. Thus, under OA and Ni combined exposure, due to their antagonistic interaction, the disruption of Ca2+ homeostasis, and the inhibition of calcium signaling pathway and oxytocin signaling pathway were not found. However, as a cost of acclimatization/adaption potential to long-term OA and Ni combined exposure, there was a loss of transcriptome plasticity during recovery, which limited the resilience of copepods to previously begin environments. Overall, our work fosters a comprehensive understanding of within- and transgenerational effects of climatic stressor and metal pollution on marine biota.

Ecotoxicology of Polymetallic Nodule Seabed Mining: The Effects of Cobalt and Nickel on Phytoplankton Growth and Pigment Concentration

In order to improve the understanding of the environmental impacts of polymetallic nodule mining, ecotoxicological studies were conducted on the growth of model phytoplankton species Skeletonema costatum and Prorocentrum donghaiense using cobalt and nickel. This study evaluated various physiological and ecological indicators, such as cell proliferation, chlorophyll a, pigments, total protein, and antioxidant enzyme markers. The results show that the introduction of low amounts of cobalt or nickel increased the growth rate of phytoplankton. The phytoplankton benefited from low concentrations of cobalt and nickel stress. The increased protein levels and decreased activity of antioxidant enzymes considerably impacted physiological responses during the promotion of cell abundance. High concentrations of cobalt or nickel resulted in decreased light-absorbing pigments, increased photoprotective pigments, an inactive chlorophyll content, decreased total proteins, and maximal antioxidant enzyme activity in phytoplankton. Throughout the experiment, both the phytoplankton protein and enzyme activity declined with prolonged stress, and the cells underwent age-induced damage. Thus, seabed mining's repercussions on phytoplankton could result in both short-term growth promotion and long-term damage. These consequences depend on the impurity concentrations infiltrating the water, their duration, and the organism's physiological responses.

Synergistic effect of nickel and temperature on gene expression, multiple stress markers, and depuration: an acute toxicity in fish

Aquatic animals are prone to extinction due to metal pollution and global climate change. Even though the fish and their products are also unsafe for human consumption, their exports have been rejected due to inorganic and organic contaminants. Nickel (Ni) is a metal that induces toxicity and accumulates in the aquatic ecosystem, posing health threats to humans, animals, and fish. In light of the above, our present investigation aimed to determine the median lethal concentration (96 h-LC50) of nickel alone and concurrent with high temperature (34 °C) (Ni + T) using static non-renewable bioassay toxicity test in Pangasianodon hypophthalmus. The groups treated under exposure to Ni reared under control condition (25-28.9 °C) and Ni + T exposure group reread under 34 °C. In this study, chose the definitive dose of Ni and Ni + T as 17, 18, 19, and 20 mg L-1 after the range finding test. The median lethal concentration of Ni and Ni + T was determined as 19.38 and 18.75 mg L-1, respectively at 96 h. Oxidative stress viz. catalase (CAT), superoxide dismutase (SOD), glutathione-s-transferase (GST), and glutathione peroxidase (GPx) in the liver, gill, and kidney were noticeably elevated with Ni and Ni + T during 96 h. Whereas, the CAT, GPx, and SOD gene expressions were significantly upregulated with Ni and Ni + T. Trilox equivalent anti-oxidant capacity (TEAC), cupric reducing anti-oxidant capacity (CUPRIC), ferric reducing ability of plasma (FRAP), ethoxy resorufin-O-deethylase (EROD), and acetylcholine esterase (AChE) were reduced due to exposure to Ni and Ni + T. Cellular metabolic stress and lipid peroxidation were highly affected due to Ni and Ni + T exposure. The immunological status, as indicated by total protein, albumin, globulin, A:G ratio, and nitro blue tetrazolium chloride (NBT), was severely affected by the toxicity of Ni and Ni + T. Moreover, the gene expression of interleukin (IL), tumor necrosis factor (TNFα), toll-like receptor (TLR), and total immunoglobulin (Ig) was remarkably downregulated following exposure to Ni and Ni + T. HSP 70, iNOS expression, ATPase, Na + /K + -ATPase, cortisol, and blood glucose was significantly elevated with Ni and Ni + T in P. hypophthalmus. The bioaccumulation of Ni in fish tissues and experimental water was determined. The kidney and liver tissues were highly accumulated with Ni, whereas DNA damage was reported in gill tissue. Interestingly, depuration study revealed that at the 28th day, the Ni bioaccumulation was below the maximum residue limit (MRL) level. Therefore, the present study revealed that Ni and Ni + T led to dysfunctional gene and metabolic regulation affecting physiology and genotoxicity. The bioaccumulation and depuration results also indicate higher residual occurrence of Ni in water and aquatic organisms for longer periods.

Seawater warming intensifies nickel toxicity to a marine copepod: a multigenerational perspective

Due to human activities, marine organisms are frequently co-stressed with nickel (Ni) pollution and seawater warming; nevertheless, very scarce information is known about their interaction in marine biota under a multigenerational scenario. Here, after verifying the interaction of Ni and warming via a 48-h acute test, we conducted a multigenerational experiment (F0-F2), in which the marine copepod Tigriopus japonicus was exposed to Ni at environmentally realistic concentrations (0, 2, and 20 µg/L) under ambient (22℃) and predicted seawater warming (26℃) conditions. Ni accumulation and the important life history traits were analyzed for each generation. Results showed that Ni exposure caused Ni bioaccumulation and thus compromised the survivorship and egg production of T. japonicus. In particular, seawater warming significantly increased Ni accumulation, thus intensifying the negative effects of Ni on its survivorship and development. Overall, this study suggests that Ni multigenerational exposure even at environmentally realistic concentrations could produce a significant impact on marine copepod's health, and this impact would be intensified under the projected seawater warming, providing a mechanistic understanding of the interaction between warming and Ni pollution in marine organisms from a multigenerational perspective.

The Effects of Nickel and Copper on Tropical Marine and Freshwater Microalgae Using Single and Multispecies Tests

Microalgae are key components of aquatic food chains and are known to be sensitive to a range of contaminants. Much of the available data on metal toxicity to microalgae have been derived from temperate single-species tests with temperate data used to supplement tropical toxicity data sets to derive guideline values. In the present study, we used single-species and multispecies tests to investigate the toxicity of nickel and copper to tropical freshwater and marine microalgae, including the free-swimming stage of Symbiodinium sp., a worldwide coral endosymbiont. Based on the 10% effect concentration (EC10) for growth rate, copper was two to four times more toxic than nickel to all species tested. The temperate strain of Ceratoneis closterium was eight to 10 times more sensitive to nickel than the two tropical strains. Freshwater Monoraphidium arcuatum was less sensitive to copper and nickel in the multispecies tests compared with the single-species tests (EC10 values increasing from 0.45 to 1.4 µg Cu/L and from 62 to 330 µg Ni/L). The Symbiodinium sp. was sensitive to copper (EC10 of 3.1 µg Cu/L) and less sensitive to nickel (EC50 >1600 µg Ni/L). This is an important contribution of data on the chronic toxicity of nickel to Symbiodinium sp. A key result from the present study was that three microalgal species had EC10 values below the current copper water quality guideline value for 95% species protection in slightly to moderately disturbed systems in Australia and New Zealand, indicating that they may not be adequately protected by the current copper guideline value. By contrast, toxicity of nickel to microalgae is unlikely to occur at exposure concentrations typically found in fresh and marine waters. Environ Toxicol Chem 2023;42:901-913. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

A Molecular Mechanism to Explain the Nickel-Induced Changes in Protamine-like Proteins and Their DNA Binding Affecting Sperm Chromatin in Mytilus galloprovincialis: An In Vitro Study

Nickel is associated with reproductive toxicity, but little is known about the molecular mechanisms of nickel-induced effects on sperm chromatin and protamine-like proteins (PLs). In the present work, we analyzed PLs from Mytilus galloprovincialis by urea-acetic acid polyacrylamide gel electrophoresis (AU-PAGE) and SDS-PAGE and assessed their binding to DNA by Electrophoretic Mobility Shift Assay (EMSA) after exposing mussels to 5, 15, and 35 µM NiCl2 for 24 h. In addition, a time course of digestion with MNase and release of PLs from sperm nuclei by the NaCl gradient was performed. For all exposure doses, in AU-PAGE, there was an additional migrating band between PL-III and PL-IV, corresponding to a fraction of PLs in the form of peptides detected by SDS-PAGE. Alterations in DNA binding of PLs were observed by EMSA after exposure to 5 and 15 µM NiCl2, while, at all NiCl2 doses, increased accessibility of MNase to sperm chromatin was found. The latter was particularly relevant at 15 µM NiCl2, a dose at which increased release of PLII and PLIII from sperm nuclei and the highest value of nickel accumulated in the gonads were also found. Finally, at all exposure doses, there was also an increase in PARP expression, but especially at 5 µM NiCl2. A possible molecular mechanism for the toxic reproductive effects of nickel in Mytilus galloprovincialis is discussed.

Vulnerability and tolerance to nickel of periphytic biofilm harvested in summer and winter

Metals are naturally present in freshwater ecosystems but anthropogenic activities like mining operations represent a long-standing concern. Metals released into aquatic environments may affect microbial communities such as periphytic biofilm, which plays a key role as a primary producer in stream ecosystems. Using two 28-day microcosm studies involving two different photoperiods (light/dark cycle of 16/8 vs 8/16), the present study assessed the effects of four increasing nickel (Ni) concentrations (0-6 μM) on two natural biofilm communities collected at different seasons (summer and winter). The two communities were characterized by different structural profiles and showed significant differences in Ni accumulated content for each treatment. For instance, the biofilm metal content was four times higher in the case of summer biofilm at the highest Ni treatment and after 28 days of exposure. Biomarkers examined targeted both heterotrophic and autotrophic organisms. For heterotrophs, the β-glucosidase and β-glucosaminidase showed no marked effects of Ni exposure and were globally similar between the two communities suggesting low toxicity. However, the photosynthetic yield confirmed the toxicity of Ni on autotrophs with maximum inhibition of 81 ± 7% and 60 ± 1% respectively for the summer and winter biofilms. Furthermore, biofilms previously exposed to the highest long-term Ni concentration ([Ni²⁺] = 6 μM) revealed no acute effects in subsequent toxicity based on the PSII yield, suggesting a tolerance acquisition by the phototrophic community. Taken together, the results suggest that the biofilm response to Ni exposure was dependent of the function considered and that descriptors such as biofilm metal content could be seasonally dependent, information of great importance in a context of biomonitoring.

Ni accumulation and effects on a representative Cnidaria - Exaiptasia pallida during single element exposure and in combination with Mn

Nickel (Ni) and manganese (Mn) are well known for the production of steel and alloys and are commonly found co-occurring in Ni ores. They are metals of environmental concern and contamination in the marine environment is problematic single exposures and in combination. Several studies have documented the effects of single metal exposure on the model anemone E. pallida, but research on the effects of metal mixtures is far less common. This novel study assesses the accumulation and stress effects of Ni and Mn over a 12-d exposure period. E. pallida were exposed in two separate experiments; Ni alone and Ni in combination with Mn, to assess accumulation, along with any effect on the density of symbionts and anemone tentacle length. Anemones were transferred to ambient seawater to assess depuration and recovery over 6 d. Anemone tissue accumulated Ni at a magnitude of five times higher in a mixture of 0.5 mg Ni/L with 2.5 mg Mn/L compared to the same concentration in a single Ni exposure experiment. In both experiments, Ni and Mn preferentially accumulated in the Symbiodinium spp. compared to the anemone tissue, but Ni depuration was more rapid in the mixture than Ni alone exposure. This study reveals a significant reduction in anemone Symbiodinium spp. density after exposure to Ni and Mn mixtures, but not with Ni exposure alone. A significant dose-dependent reduction in tentacle length was observed in anemones after 12 d of the Ni exposure both with and without Mn. The estimated sublethal concentration that causes tentacle retraction in 50% of test anemones (EC50) by Ni was 0.51 (0.25-0.73) mg/L, while in combination with Mn the EC50 was 0.30 mg Ni/L (confidence limits not calculatable). The present data reveals the importance of testing metal effects in combination before establishing safe limits for marine invertebrates.

Same sensitivity with shorter exposure: behavior as an appropriate parameter to assess metal toxicity

The exposure of animals to toxicants may cause a depletion in the energy uptake, which compromises reproduction and growth. Although both parameters are ecologically relevant, they usually need long-term bioassays. This is a handicap for the availability of toxicological data for environmental risk assessment. Short-term bioassays conducted with environmental concentrations, and using relevant ecological parameters sensitive to short-term exposures, such as behavior, could be a good alternative. Therefore, to include this parameter in the risk assessment procedures, it is relevant the comparison of its sensitivity with that of growth and reproduction bioassays. The study aim was the assessment of differences between endpoints based on mortality, behaviour, reproduction, and growth for the toxicity of metals on aquatic animals. We used the ECOTOX database to gather data to construct chemical toxicity distribution (CTD) curves. The mean concentrations, the mean exposure time, and the ratio between the mean concentration and the exposure time were compared among endpoints. Our results showed that behavioral, growth, and reproduction bioassays presented similar sensitivity. The shortest exposure was found in behavioral and reproduction bioassays. In general, the amount of toxicant used per time was lower in growth and reproduction bioassays than in behavioral and mortality bioassays. We can conclude that, for metal toxicity, behavioral bioassays are less time-consuming than growth bioassays. As the sensitivity of behavior was similar to that of growth and reproduction, this endpoint could be a better alternative to longer bioassays.

Toxic effect of nickel on microalgae Phaeodactylum tricornutum (Bacillariophyceae)

Nickel acts as an essential trace nutrient or toxicant for organisms, depending on its concentration. The increased concentrations of nickel, due to anthropogenic activity, in the aquatic environment are potential threats to aquatic organisms. However, the knowledge on toxic mechanisms of nickel to microalgae remains incompletely understood. In the present study, we investigated the toxic effects of nickel in the cosmopolitan diatom Phaeodactylum tricornutum via evaluation of physiological and transcriptome responses. The results showed that the median effective concentration-72 h (EC₅₀-72 h) and EC₅₀-96 h of nickel was 2.48 ± 0.33 and 1.85 ± 0.17 mg/L, respectively. The P. tricornutum cell abundance and photosynthesis significantly decreased by 1 mg/L of nickel. Results from photosynthetic parameters including efficiency of the oxygen evolving complex (OEC) of photosystem II (PSII) (Fv/F₀), maximum photosynthetic efficiency of PS II (Fv/Fm), electron transport rate (ETR), actual photosynthetic efficiency of PS II (Y(II)), non-photochemical quenching (NPQ), and photochemical quenching (qP) indicated that OEC of PS II might be impaired by nickel. The transcriptome data also reveal that OEC apparatus coding gene PS II oxygen-evolving enhancer protein 2 (PsbP) was regulated by nickel. Moreover, induced reactive oxygen species (ROS) production and chlorophyll a content were also detected under nickel stress. Transcriptome analysis revealed that nickel affected a variety of differentially expressed genes (DEGs) that involved in redox homeostasis, nitrogen metabolisms, fatty acids, and DNA metabolism. However, thiol-disulfide redox system might play important roles in nickel-induced oxidative stress resistance. This study improved the understanding of the toxic effect of nickel on the diatom P. tricornutum.

Manganese uptake and partitioning between the tissue of the anemone host Exaiptasia pallida and Symbiodinium spp., including assessment of stress and recovery

Manganese (Mn) is essential for global steel and Mn-iron (Fe) alloy production. The human health effects of elevated Mn concentrations have been well established, but studies on its impact on marine invertebrates are limited. This study is the first to investigate Mn uptake in the sea anemone Exaiptasia pallida after chronic exposure (0.5, 1, 10, and 100 mg/L) for 24-d. Following exposure, E. pallida were transferred to ambient seawater for 6-d to assess Mn depuration. Mn accumulation and partitioning in host tissue and symbionts (Symbiodinium spp.), tentacle retraction, and symbiont cell density were measured during exposure and depuration. Mn concentrations were substantially higher in symbionts than tissue in all treatments after 24-d. No significant difference was observed for symbiont cell density after Mn exposure. Tentacle retractions were significantly higher in all Mn exposed treatments than controls at all time points. Mn depuration was observed for both tissue and symbionts but was more rapid in symbionts. This study reveals that Symbiodinium spp. can play a role in Mn uptake and depuration in anemones, but Mn loading does not affect cell density. These results help understand metal uptake and depuration in complex relationships between Symbiodinium spp. and other host taxa like corals.

Coral Ecotoxicological Data Evaluation for the Environmental Safety Assessment of Ultraviolet Filters

There is growing interest in the environmental safety of ultraviolet (UV) filters found in cosmetic and personal care products (CPCPs). The CPCP industry is assessing appropriate environmental risk assessment (ERA) methods to conduct robust environmental safety assessments for these ingredients. Relevant and reliable data are needed for ERA, particularly when the assessment is supporting regulatory decision-making. In the present study, we apply a data evaluation approach to incorporate nonstandard toxicity data into the ERA process through an expanded range of reliability scores over commonly used approaches (e.g., Klimisch scores). The method employs an upfront screening followed by a data quality assessment based largely on the Criteria for Reporting and Evaluating Ecotoxicity Data (CRED) approach. The method was applied in a coral case study in which UV filter toxicity data was evaluated to identify data points potentially suitable for higher tier and/or regulatory ERA. This is an optimal case study because there are no standard coral toxicity test methods, and UV filter bans are being enacted based on findings reported in the current peer-reviewed data set. Eight studies comprising nine assays were identified; four of the assays did not pass the initial screening assessment. None of the remaining five assays received a high enough reliability score (R_n ) to be considered of decision-making quality (i.e., R1 or R2). Four assays were suitable for a preliminary ERA (i.e., R3 or R4), and one assay was not reliable (i.e., R6). These results highlight a need for higher quality coral toxicity studies, potentially through the development of standard test protocols, to generate reliable toxicity endpoints. These data can then be used for ERA to inform environmental protection and sustainability decision-making. Environ Toxicol Chem 2021;40:3441-3464. © 2021 Personal Care Products Council. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Environmental risk of nickel in aquatic Arctic ecosystems

The Arctic faces many environmental challenges, including the continued exploitation of its mineral resources such as nickel (Ni). The responsible development of Ni mining in the Arctic requires establishing a risk assessment framework that accounts for the specificities of this unique region. We set out to conduct preliminary assessments of Ni exposure and effects in aquatic Arctic ecosystems. Our analysis of Ni source and transport processes in the Arctic suggests that fresh, estuarine, coastal, and marine waters are potential Ni-receiving environments, with both pelagic and benthic communities being at risk of exposure. Environmental concentrations of Ni show that sites with elevated Ni concentrations are located near Ni mining operations in freshwater environments, but there is a lack of data for coastal and estuarine environments near such operations. Nickel bioavailability in Arctic freshwaters seems to be mainly driven by dissolved organic carbon (DOC) concentrations with bioavailability being the highest in the High Arctic, where DOC levels are the lowest. However, this assessment is based on bioavailability models developed from non-Arctic species. At present, the lack of chronic Ni toxicity data on Arctic species constitutes the greatest hurdle toward the development of Ni quality standards in this region. Although there are some indications that polar organisms may not be more sensitive to contaminants than non-Arctic species, biological adaptations necessary for life in polar environments may have led to differences in species sensitivities, and this must be addressed in risk assessment frameworks. Finally, Ni polar risk assessment is further complicated by climate change, which affects the Arctic at a faster rate than the rest of the world. Herein we discuss the source, fate, and toxicity of Ni in Arctic aquatic environments, and discuss how climate change effects (e.g., permafrost thawing, increased precipitation, and warming) will influence risk assessments of Ni in the Arctic.

Developmental toxicity in marine medaka (Oryzias melastigma) embryos and larvae exposed to nickel

As an important trace metal, nickel (Ni) has been reported extensively in the studies on freshwater animals. However, the toxic effects of Ni on marine organisms are not clearly understood. Therefore, in order to investigate the toxic effects of Ni on the early development of marine fish, the marine medaka (Oryzias melastigma) embryos and larvae were immersed in 0.13-65.80 mg/L Ni solution. The results showed that Ni exposure changed the egg size and heart rate of the embryos, lowered the hatchability, increased the deformity rate, and shortened the total body length of newly hatched larvae. Besides, it was found that before organogenesis and post-hatching periods were the sensitive periods of embryos to Ni. The 25 d LC₅₀ value of embryos was 49.28 mg/L, and the 5 d LC₅₀ of larvae was 55.92 mg/L, indicating that the embryos were more sensitive to Ni than the larvae. Furthermore, the expressions of the metallothionein (MT) gene, the skeletal development-related gene (Cyp26b1) and the cardiac development-related genes (ATPase, smyd1, cox2 and bmp4) were determined, and the results showed that the expressions of ATPase and smyd1 were up-regulated, while MT, Cyp26b1 and cox2 were significantly down-regulated at 9 days post-fertilization (dpf). Overall, Ni exposure caused a significant toxic effect on the early development of the O. melastigma embryos and larvae. Our findings could provide an important supplement to the toxicity data of tropical Ni and provide a reference for the exploration of the molecular mechanisms of Ni toxicity.

Deriving Nickel (Ni(II)) and Chromium (Cr(III)) Based Environmentally Safe Olivine Guidelines for Coastal Enhanced Silicate Weathering

Enhanced silicate weathering (ESW) by spreading finely ground silicate rock along the coastal zone to remove atmospheric carbon dioxide (CO₂) is a proposed climate change mitigation technique. The abundant and fast-dissolving mineral olivine has received the most attention for this application. However, olivine contains nickel (Ni) and chromium (Cr), which may pose a risk to marine biota during a gigaton-scale ESW application. Herein we derive a first guideline for coastal olivine dispersal based on existing marine environmental quality standards (EQS) for Ni and Cr. Results show that benthic biota are at the highest risk when olivine and its associated trace metals are mixed in the surface sediment. Specifically, depending on local sedimentary Ni concentrations, 0.059-1.4 kg of olivine m^-2 of seabed could be supplied without posing risks for benthic biota. Accordingly, globally coastal ESW could safely sequester only 0.51-37 Gt of CO₂ in the 21st century. On the basis of current EQS, we conclude that adverse environmental impacts from Ni and Cr release could reduce the applicability of olivine in coastal ESW. Our findings call for more in-depth studies on the potential toxicity of olivine toward benthic marine biota, especially in regard to bioavailability and metal mixture toxicity.

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. The present study used high-throughput sequencing (metabarcoding) to determine changes in eukaryote (18s v7 recombinant DNA [rDNA] and diatom-specific subregion of the 18s v4 rDNA) and prokaryote (16s v4 rDNA) community compositions along a sediment Ni concentration gradient offshore from a large lateritized ultramafic regolith in New Caledonia (Vavouto Bay). Significant changes in the eukaryote, diatom, and prokaryote community compositions were found along the Ni concentration gradient. These changes correlated most with the dilute-acid extractable concentration of Ni in the sediments, which explained 26, 23, and 19% of the variation for eukaryote, diatom, and prokaryote community compositions, respectively. Univariate analyses showed that there was no consistent change in indices of biodiversity, evenness, or richness. Diatom richness and diversity did, however, decrease as sediment acid extractable-Ni concentrations increased. Threshold indicator taxa analysis was conducted separately for each of the 3 targeted genes to detect changes in taxa whose occurrences decreased or increased along the acid extractable-Ni concentration gradient. Based on these data, 46 mg acid extractable-Ni/kg was determined as a threshold value where sensitive species began to disappear. In the case of the estuarine sediments offshore from lateritized ultramafic regolith in New Caledonia, this is recommended as an interim threshold value until further lines of evidence can contribute to a region-specific Ni sediment quality guideline value. Environ Toxicol Chem 2021;40:1894-1907. © 2021 SETAC.

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).

Human health risk assessment of selected metal(loid)s via crayfish (Faxonius virilis; Procambarus acutus acutus) consumption in Missouri

Farmed crustaceans are an important component in addressing the rising animal protein demand. The present study determined the concentrations of fourteen elements (Ag, As, Be, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Sn, Pb, and Zn) in the edible abdominal muscle of cultured freshwater crayfish species (Faxonius virilis; Procambarus acutus acutus) from Missouri. Also, this paper describes the dietary intake and the human health risks from the consumption of crayfish muscle in the adult population. Overall, 172 animals were captured between February 2017 and January 2018 for assessment. Concentrations of metals (Ag, Be, Cd, Cu, Co, Cr, Fe, Mn, Ni, Pb, Sn, Mo, and Zn) and metalloid (As) in the muscle tissue were determined after microwave-assisted acid digestion by ICP - OES. Health indices (EDI/EWI: estimated daily/weekly intakes; THQ: target hazard quotient; TTHQ: total target hazard quotient; ILCR: incremental lifetime cancer risk; and ∑ILCR: cumulative lifetime cancer risk) were calculated and compared to thresholds. Of all samples, the highest concentrations (mg kg -1 wet weight) of metal(loid)s in muscle were Ag (0.11), As (3.15), Be (0.21), Cd (0.11), Co (0.32), Cr (1.22), Cu (107), Fe (23.0), Mn (8.54), Mo (0.62), Ni (2.65), Pb (1.76), Sn (5.91), and Zn (19.2). In both species, the average As, Cd, and Zn concentrations were below the legal limits. However, the levels of Cu, Pb, and As, in some samples, were in exceedance of the maximum levels. In both species, a significant correlation (p < 0.05) was observed between the carapace length (CL) and animal body weight (BW). In P. acutus, CL, BW, and animal total length were homogenous (p > 0.05) among the sexes. Non-parametric Kruskal-Wallis test results indicated significant differences (p < 0.05) in the levels of As, Be, and Zn in F. virilis, and Be and Cr in P. a. acutus among the genders. Significant inter-species differences (p < 0.05) were observed in the levels of Be, Ni, and Pb and the growth factors. The EDI/EWI values were below the permissible limits. THQ and TTHQ values, being below 1.0, indicated no probabilistic health risk. Regarding carcinogenic risk, only As and Ni indicated cancer risk (ILCR >10-5 and ∑ILCR >10-5) to the adult population. High metals/metalloid exposure from crayfish muscle consumption posed potential health hazards to the adult population.

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/m² /h DGT-labile nickel flux. Nickel bioavailability was lower in sediments with greater total organic carbon, clay content, and percentage of fine particles. Measurements of DGT-labile nickel flux at the sediment-water interface integrated exposure to nickel from porewater, overlying water, and ingested sediment exposure pathways and were found to have the strongest relationship with the biological response. At most, there was a 29% reduction in 10-d M. plumulosa reproduction relative to the control when exposed to nickel from field-contaminated sediments collected from nickel laterite mining regions of New Caledonia. The DGT technique can be used as a complementary tool to measure the bioavailability of nickel in estuarine/marine sediments, especially sediments that are in nickel laterite mining regions where there are no or few toxicity data available for determining biological effects on local species. Based on the combined data set of the 3 nickel-spiked sediments a DGT-labile nickel EC10 threshold of 50 (30-69) μg Ni/m² /h was determined. Environ Toxicol Chem 2021;40:1266-1278. © 2020 SETAC.

Complexation reduces nickel toxicity to purple sea urchin embryos (Strongylocentrotus purpuratus), a test of biotic ligand principles in seawater

The potential for Ni toxicity in seawater is of concern because of mining and processing activities in coastal regions. Determining Ni speciation is vital to understanding and predicting Ni toxicity and for bioavailability-based nickel risk assessment. The goal of this study was to characterize the complexation of Ni in relation to toxicity using embryological development of purple sea urchin (S. purpuratus). It was predicted that free ion [Ni2+] would be a better predictor of toxicity than total dissolved Ni concentrations (NiD). Synthetic ligands with known logKf values (Ethylenediaminetetraacetic acid (EDTA), Nitrilotriacetic acid (NTA), tryptophan (TRP), glutamic acid (GA), histidine (HD), and citric acid (CA)) were used to test the assumptions of the biotic ligand model (BLM) for Ni in seawater. [NiD] was measured by graphite furnace atomic absorption spectroscopy (GFAAS) and Ni2+ was first quantified using the ion-exchange technique (IET) and then concentrations were measured by GFAAS; [Ni2+] was also estimated using aquatic geochemistry modelling software (Visual Minteq). The mean EC50 values for [NiD] in unmodified artificial seawater control was 3.6 µM (95% CI 3.0-4.5) [211 µg/L 95% CI 176-264] and the addition of ligands provided protection, up to 6.5-fold higher [NiD] EC50 for EDTA. Compared to the control, measured EC50 values based on total dissolved nickel were higher in the presence of ligands. As predicted by BLM theory, [Ni2+] was a better predictor of Ni toxicity with 17% variability in EDTA and CA media while there was 72% variability in the prediction of Ni toxicity with total dissolved Ni. The results of this research provide support for the application of BLM- based prediction models for estimating Ni impacts in seawater.

Acute and chronic toxicity of nickel on freshwater and marine tropical aquatic organisms

Water quality guidelines and ecological risk assessment of chemical substances like nickel (Ni) in tropical regions such as South East Asia and Melanesia are often based on temperate information as a result of fewer Ni ecotoxicity data available for tropical species. This leaves an unknown margin of uncertainty in the risk assessment in the tropics. In order to fill this data gap, this study was designed to conduct standard toxicity tests on Ni with two freshwater species (acute tests) and three marine species (acute and chronic tests) originated from tropical Hong Kong. All tests were carried out using measured concentrations of Ni with control mortality below 15%. The median lethal concentrations (LC₅₀s) were determined as 2520 (95% confidence interval: 2210, 2860) and 426 (351, 515) μg Ni L^-1 for the freshwater gastropods Pomacea lineata (48 h) and Sulcospira hainanensis (96 h), respectively, while 96 h LC₅₀s of 4300 (3610, 5090), 18,200 (6470, 51,200), 62,400 (56,800, 68,500), and 71,700 (68,200, 75,400) μg Ni L^-1 were derived for the marine copepod Tigriopus japonicus, the gastropod Monodonta labio, juvenile and adult of the marine fish Oryzias melastigma, respectively. The chronic effect concentration of 10% (EC₁₀) based on the intrinsic rate of increase of the population of T. japonicus was 29 (12, 69) μg Ni L^-1. In terms of growth inhibition, the chronic EC₁₀ for M. labio was 34 (17, 67) μg Ni L^-1. The results also indicated that T. japonicus in maturation stage (LC₁₀: 484 (349, 919) μg Ni L^-1) was less sensitive than its nauplii stage (LC₁₀: 44 (27, 72) μg Ni L^-1). This study represents an important addition of high-quality toxicity data to the tropical Ni toxicity database which can be used for future ecological risk assessment of Ni and derivation of its water quality guidelines in tropical regions.

Deriving a Chronic Guideline Value for Nickel in Tropical and Temperate Marine Waters

The absence of chronic toxicity data for tropical marine waters has limited our ability to derive appropriate water quality guideline values for metals in tropical regions. To aid environmental management, temperate data are usually extrapolated to other climatic (e.g., tropical) regions. However, differences in climate, water chemistry, and endemic biota between temperate and tropical systems make such extrapolations uncertain. Chronic nickel (Ni) toxicity data were compiled for temperate (24 species) and tropical (16 species) marine biota and their sensitivities to Ni compared. Concentrations to cause a 10% effect for temperate biota ranged from 2.9 to 20 300 µg Ni/L, with sea urchin larval development being the most sensitive endpoint. Values for tropical data ranged from 5.5 to 3700 µg Ni/L, with copepod early-life stage development being the most sensitive test. There was little difference in temperate and tropical marine sensitivities to Ni, with 5% hazardous concentrations (95% confidence interval) of 4.4 (1.8-17), 9.6 (1.7-26), and 5.8 (2.8-15) µg Ni/L for temperate, tropical, and combined temperate and tropical species, respectively. To ensure greater taxonomic coverage and based on guidance provided in Australia and New Zealand, it is recommended that the combined data set be used as the basis to generate a jurisdiction-specific water quality guideline of 6 µg Ni/L for 95% species protection applicable to both temperate and tropical marine environments. Environ Toxicol Chem 2020;39:2540-2551. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Metal(loid)s in superficial sediments from coral reefs of French Polynesia

French Polynesia exhibits a wide diversity of islands and coral-reef habitats, from urbanized high islands to remote atolls. Here, we present a geographically extensive baseline survey that examine the concentrations of nine metals (Ag, Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn) and one metalloid (As) in superficial sediments from 28 sites spread over three islands of French Polynesia. We used Principal Component Analysis, Pearson's correlation, hierarchical cluster analysis and generalized linear mixed-effect models on Pollution Load Index to investigate site contamination and metal(loid) associations. At most sites, metal(loid) concentrations were below commonly applied sediment quality guidelines. However, a few sites located near farming activities, river discharges and urbanized areas showed concentrations above these guidelines. This study provides critical baseline values for metal(loid) contaminants in this region and in coral-reef areas in general, and spur decreased discharge of metal(loid) contaminants in the anthropogenised areas of French Polynesia.

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. No effect on A. muricata was observed from exposure to a particulate-bound nickel concentration of 60 mg/kg acid-extractable nickel at a suspended sediment concentration of 30 mg/L TSS. This study demonstrates that bioavailability of nickel associated with suspended sediment exposure plays a key role in influencing nickel toxicity to corals. These findings assist in assessments of risk posed by increasing nickel mining activities on tropical marine ecosystems.

Validation of Bioavailability-Based Toxicity Models for Metals

Regulatory jurisdictions worldwide are increasingly incorporating bioavailability-based toxicity models into development of protective values (PVALs) for freshwater and saltwater aquatic life (e.g., water quality criteria, standards, and/or guidelines) for metals. Use of such models for regulatory purposes should be contingent on their ability to meet performance criteria as specified through a model-validation process. Model validation generally involves an assessment of a model's appropriateness, relevance, and accuracy. We review existing guidance for validation of bioavailability-based toxicity models, recommend questions that should be addressed in model-validation studies, discuss model study type and design considerations, present several new ways to evaluate model performance in validation studies, and suggest a framework for use of model validation in PVAL development. We conclude that model validation should be rigorous but flexible enough to fit the user's purpose. Although a model can never be fully validated to a level of zero uncertainty, it can be sufficiently validated to fit a specific purpose. Therefore, support (or lack of support) for a model should be presented in such a way that users can choose their own level of acceptability. We recommend that models be validated using experimental designs and endpoints consistent with the data sets that were used to parameterize and calibrate the model and validated across a broad range of geographically and ecologically relevant water types. Environ Toxicol Chem 2019;39:101-117. © 2019 SETAC.

Best Practices for Derivation and Application of Thresholds for Metals Using Bioavailability-Based Approaches

The primary goal of the present study is to provide a broad view of best practices for evaluating bioavailability models for metals for use in the protection of aquatic life. We describe the state of the science regarding 1) the evaluation and selection of ecotoxicity data, 2) the selection of bioavailability models for use in normalization, and 3) subsequent application of bioavailability models. Although many examples of normalization steps exist worldwide, a scheme is proposed to evaluate and select a model that takes account of its representativeness (water chemistry and taxonomic coverage of the ecotoxicity data set) and validation performance. Important considerations for a suitable model are the quantity of inputs needed, accuracy, and ease of use, all of which are needed to set protective values for aquatic life and to use these values to evaluate potential risks to organisms in receiving waters. Although the end results of different model application approaches may be broadly similar, the differences in these application frameworks ultimately come down to a series of trade-offs between who needs to collect the data and use the bioavailability model, the different requirements of spatial scales involved (e.g., regional vs site-specific values), and model predictiveness and protectiveness. Ultimately, understanding the limits and consequences of these trade-offs allows for selection of the most appropriate model and application framework to best provide the intended levels of aquatic life protection. Environ Toxicol Chem 2019;39:118-130. © 2019 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.

Concise Review of Nickel Human Health Toxicology and Ecotoxicology

Nickel (Ni) metal and Ni compounds are widely used in applications like stainless steel, alloys, and batteries. Nickel is a naturally occurring element in water, soil, air, and living organisms, and is essential to microorganisms and plants. Thus, human and environmental nickel exposures are ubiquitous. Production and use of nickel and its compounds can, however, result in additional exposures to humans and the environment. Notable human health toxicity effects identified from human and/or animal studies include respiratory cancer, non-cancer toxicity effects following inhalation, dermatitis, and reproductive effects. These effects have thresholds, with indirect genotoxic and epigenetic events underlying the threshold mode of action for nickel carcinogenicity. Differences in human toxicity potencies/potentials of different nickel chemical forms are correlated with the bioavailability of the Ni2+ ion at target sites. Likewise, Ni2+ has been demonstrated to be the toxic chemical species in the environment, and models have been developed that account for the influence of abiotic factors on the bioavailability and toxicity of Ni2+ in different habitats. Emerging issues regarding the toxicity of nickel nanoforms and metal mixtures are briefly discussed. This review is unique in its covering of both human and environmental nickel toxicity data.

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. Corals collected from the Great Barrier Reef were exposed to dissolved nickel (45, 90, 470, 900 and 9050 μg Ni/L) or copper (4, 11, 32 and 65 μg Cu/L) in flow through chambers at the National Sea Simulator, Townsville, Qld, Australia. After a 96-h exposure DNA metabarcoding (16S rDNA and 18S rDNA) was undertaken on all samples to detect changes in the structure of the coral microbiome. The controls remained healthy throughout the study period. After 36 h, bleaching was only observed in corals exposed to 32 and 65 μg Cu/L and very high nickel concentrations (9050 μg Ni/L). At 96 h, significant discolouration of corals was only observed in 470 and 900 μg Ni/L treatments, the highest concentrations tested. While high concentrations of nickel caused bleaching, no changes in the composition of their microbiome communities were observed. In contrast, exposure to copper not only resulted in bleaching, but altered the composition of both the eukaryote and bacterial communities of the coral's microbiomes. Our findings showed that these effects were only evident at relatively high concentrations of nickel and copper, reflecting concentrations observed only in extremely polluted environments. Elevated metal concentrations have the capacity to alter the microbiomes which are inherently linked to coral health.

Comparison of the Chronic Toxicity of Nickel to Temperate and Tropical Freshwater Species

Reliable ecotoxicity data are required to derive thresholds protective for aquatic life that are scientifically defensible and practically implementable as environmental risk assessment and management tools. Much of the data that have been used to derive thresholds for environmental quality have been collected for temperate species. There are concerns that due to a lack of data for the different species present in tropical ecosystems, they may not be adequately protected by thresholds derived from temperate species. In the present study, chronic ecotoxicity data for nickel and freshwater species from different climatic regions have been collated. Comparisons were performed between tropical and temperate datasets on the basis of the threshold values and overall distributions of the ecotoxicity data, as well as between groups of species and closely related species from different climatic regions. The analysis indicated that the sensitivities of tropical and temperate species cover similar ranges. An approach based on the inclusion of as diverse a range of taxa as possible is recommended to ensure the protection of sensitive species in both temperate and tropical ecosystems. Environ Toxicol Chem 2019;38:1211-1220. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Using multi-integrated biomarker indexes approach to assess marine quality and health status of marine organism: a case study of Ruditapes philippinarum in Laizhou Bay, China

With the progress of technology and the deepening of understanding of biological monitoring, much more attention has been paid to the multiple evaluation of marine pollution monitoring. In view of this, our study aimed at establishing a multi-integrated biomarker indexes approach to evaluate marine condition systematically and comprehensively. In the current study, sampling was conducted in Laizhou Bay, China (S1, S2, and S3) in May, August, and October of 2015. And then, multi-integrated biomarker indexes approach was applied to assess marine PAHs pollution, select appropriate biomarkers, and evaluate marine environmental quality and health status of the clams of Ruditapes philippinarum. As the results showed, S2 was the most PAHs-polluted site while S1 was the least polluted site, and the levels of tPAHs in seawater and sediments ranged from 69.78 to 315.30 ng/L and 163.19 to 565.17 ng/g d.w., respectively. And all three sampling sites had different sources of PAHs. IBR represented DNA damage (F value), the expression of SOD, EROD activity, GST activity, and LPO could be served as biomarkers to monitor the PAHs pollution in Laizhou Bay. And MPI suggested the quality of all three sites: S1 was generally favorable, S2 was moderately polluted, and S3 was lightly polluted. BRI values showed that the order of health status of R. philippinarum was S1 > S3 > S2.

Unraveling sorption of nickel from aqueous solution by KMnO4 and KOH-modified peanut shell biochar: Implicit mechanism

Nickel-containing wastewater is a serious hazard to water environment, so that it is a burning issue to find an efficient and environment-friendly adsorbent. The conventional biochar could not effectively adsorb nickel (Ni(II)), so our study focuses on exploring the adsorption of chemically modified biochar to Ni(II). In this study, the biochar derived from waste peanut shell was modified by KMnO₄ and KOH (MBC). And a series of experiment were carried out to evaluate the sorption ability and explore adsorption mechanism of modified biochar to Ni(II). The results showed the adsorption ability of MBC to Ni(II) reached 87.15 mg g^-1. And the reaction process was spontaneous and endothermic chemisorption. Meanwhile, the analysis of FTIR and XPS visually revealed that the amine groups in the modified biochar could form NH₂Ni with Ni(II) by complexation, while the hydroxyl could form nickel hydroxide and complexed nickel oxide by co-precipitation and complexation. This research showed this novel MBC is a promising adsorbent and has a fantastic prospect in the application of nickel-containing wastewater.

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.

Nickel exposure alters behavioral parameters in larval and adult zebrafish

Nickel is a heavy metal that, at high concentrations, leads to environmental contamination and causes health problems. We evaluated the effects of NiCl₂ exposure on cognition and behavior in larval and adult zebrafish. Larval and adult zebrafish were exposed to NiCl₂ concentrations (0.025, 2.0, 5.0, and 15.0mg/L) or water (control) in two treatment regimens: acute and subchronic. Larvae were exposed to NiCl₂ for 2h (acute treatment: 5-day-old larvae treated for 2h, tested after treatment) or 11days (subchronic treatment: 11-day-old larvae treated since fertilization, tested at 5, 8 and 11days post-fertilization, dpf). Adults were exposed for 12h (acute treatment) or 96h (subchronic treatment) and were tested after the treatment period. In both regimens, exposed zebrafish showed concentration-dependent increases in body nickel levels compared with controls. For larvae, delayed hatching, decreased heart rate and morphological alterations were observed in subchronically treated zebrafish. Larvae from subchronic treatment tested at 5dpf decrease distance and mean speed at a low concentration (0.025mg/L) and increased at higher concentrations (5.0 and 15.0mg/L). Subchronic treated larvae decrease locomotion at 15.0mg/L at 8 and 11dpf, whereas decreased escape responses to an aversive stimulus was observed at 2.0, 5.0 and 15.0mg/L in all developmental stages. For adults, the exploratory behavior test showed that subchronic nickel exposure induced anxiogenic-like behavior and decrease aggression, whereas impaired memory was observed in both treatments. These results indicate that exposure to nickel in early life stages of zebrafish leads to morphological alterations, avoidance response impairment and locomotor deficits whereas acute and subchronic exposure in adults resulst in anxiogenic effects, impaired memory and decreased aggressive behavior. These effects may be associated to neurotoxic actions of nickel and suggest this metal may influence animals' physiology in doses that do not necessarily impact their survival.

High contribution of the particulate uptake pathway to metal bioaccumulation in the tropical marine clam Gafrarium pectinatum

The clam Gafrarium pectinatum was investigated to assess its usefulness as a bioindicator species of metal mining contamination in the New Caledonia lagoon. The uptake and depuration kinetics of Ag, Cd, Co, Cr, and Zn were determined following exposures via seawater, sediment, and food using highly sensitive radiotracer techniques (^110mAg, ¹⁰⁹Cd, ⁵¹Cr, ⁵⁷Co, and ⁶⁵Zn). When the clams were exposed to dissolved metals, Co, Zn, and Ag were readily incorporated in their tissues (concentration factors (CF) ranging from 181 to 4982 after 28 days of exposure) and all metals were strongly retained (biological half-lives always >2 months). The estimated transfer factor (TF) in clam tissues after a 35-day sediment exposure was 1 to 4 orders of magnitude lower than the estimated CF, indicating a lower bioavailability of sediment-bound metals than dissolved ones. Once incorporated, metals taken up from sediment and seawater were retained longer than metals ingested with food, indicating that the uptake pathway influences the storage processes of metals in clam tissues. Compilation of our data into a global bioaccumulation model indicated that, except for Ag that essentially originated from food (92%), sediment was the main source of metal bioaccumulation in the clam (more than 80%). These results highlight that bioaccumulation processes strongly depend from one metal to the other. The overall efficient bioaccumulation and retention capacities of the clam G. pectinatum confirm its usefulness as a bioindicator species that can provide time-integrated information about ambient contamination levels in the tropical marine coastal environment.

Toxicity of Nickel on the Selected Species of Marine Diatoms and Copepods

Toxicity values for nickel on marine diatoms and copepods were derived based on bioassay tests. The 96 h IC₅₀ of nickel on diatoms, Odontella mobiliensis and Coscinodiscus centralis were 0.31 ± 0.01 and 0.62 ± 0.02 mg/L and LC₅₀ values on copepods, Oithona similis and Acartia danae were 2.78 ± 0.14 and 2.34 ± 0.32 mg/L, respectively. The species mean chronic values of nickel were 0.016, 0.17, 0.57 and 0.42 mg/L for O. mobiliensis, C. centralis, O. similis and A. danae, respectively. A hazardous concentration was derived and evaluated using the species sensitivity distribution (SSD) method. SSD indicated that 13 µg Ni/L is the maximum allowable concentration for protection of 95% plankton species in coastal and marine ecosystem of India. Diatoms are more sensitive to nickel than copepods by almost an order of magnitude. The toxicity values derived in the present study may be useful to calculate ambient water quality criteria/standard for nickel.

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.

Inhibition in fertilisation of coral gametes following exposure to nickel and copper

The mining and production of nickel in tropical regions have the potential to impact on ecologically valuable tropical marine ecosystems. Currently, few data exist to assess the risks of nickel exposure to tropical ecosystems and to derive ecologically relevant water quality guidelines. In particular, data are lacking for keystone species such as scleractinian corals, which create the complex structural reef habitats that support many other marine species. As part of a larger study developing risk assessment tools for nickel in the tropical Asia-Pacific region, we investigated the toxicity of nickel on fertilisation success in three species of scleractinian corals: Acropora aspera, Acropora digitifera and Platygyra daedalea. In the literature, more data are available on the effects of copper on coral fertilisation, so to allow for comparisons with past studies, the toxicity of copper to A. aspera and P. daedalea was also determined. Overall, copper was more toxic than nickel to the fertilisation success of the species tested. Acropora aspera was the most sensitive species to nickel (NOEC < 280µg Ni/L), followed by A. digitifera with an EC10 of 2000µg Ni/L and P. daedalea (EC10 > 4610µg Ni/L). Acropora aspera was also the more sensitive species to copper with an EC10 of 5.8µg Cu/L. The EC10 for P. daedalea was 16µg Cu/L, similar to previous studies. This is the first time that the toxicity of nickel on fertilisation success in Acropora species has been reported, and thus provides valuable data that can contribute to the development of reliable water quality guidelines for nickel in tropical marine waters.

Mechanisms of nickel toxicity to fish and invertebrates in marine and estuarine waters

In freshwater settings the toxicity of the trace metal nickel (Ni) is relatively well understood. However, until recently, there was little knowledge regarding Ni toxicity in waters of higher salinity, where factors such as water chemistry and the physiology of estuarine and marine biota would be expected to alter toxicological impact. This review summarizes recent literature investigating Ni toxicity in marine and estuarine invertebrates and fish. As in freshwater, three main mechanisms of Ni toxicity exist: ionoregulatory impairment, inhibition of respiration, and promotion of oxidative stress. However, unlike in freshwater biota, where mechanisms of toxicity are largely Class-specific, the delineation of toxic mechanisms between different species is less defined. In general, despite changes in Ni speciation in marine waters, organism physiology appears to be the main driver of toxic impact, a fact that will need to be accounted for when adapting regulatory tools (such as bioavailability normalization) from freshwater to estuarine and marine environments.