Sensitivity of polar and temperate marine organisms to oil components

Temperate Versus Arctic: Unraveling the Effects of Temperature on Oil Toxicity in Gammarids

Shipping activities are increasing with sea ice receding in the Arctic, leading to higher risks of accidents and oil spills. Because Arctic toxicity data are limited, oil spill risk assessments for the Arctic are challenging to conduct. In the present study, we tested if acute oil toxicity metrics obtained at temperate conditions reflect those at Arctic conditions. The effects of temperature (4 °C, 12 °C, and 20 °C) on the median lethal concentration (LC50) and the critical body residue (CBR) of the temperate invertebrate Gammarus locusta exposed to water accommodated fractions of a fuel oil were determined. Both toxicity metrics decreased with increasing temperature. In addition, data for the temperate G. locusta were compared to data obtained for Arctic Gammarus species at 4 °C. The LC50 for the Arctic Gammarus sp. was a factor of 3 higher than that for the temperate G. locusta at 4 °C, but its CBR was similar, although both the exposure time and concentration were extended to reach lethality. Probably, this was a result of the larger size and higher weight and total lipid content of Arctic gammarids compared to the temperate gammarids. Taken together, the present data support the use of temperate acute oil toxicity data as a basis for assessing risks in the Arctic region, provided that the effects of temperature on oil fate and functional traits (e.g., body size and lipid content) of test species are considered. As such, using the CBR as a toxicity metric is beneficial because it is independent of functional traits, despite its temperature dependency. To the best of our knowledge, the present study is the first to report CBRs for oil. Environ Toxicol Chem 2024;43:1627-1637. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Effects of petrogenic pollutants on North Atlantic and Arctic Calanus copepods: From molecular mechanisms to population impacts

Oil and gas industries in the Northern Atlantic Ocean have gradually moved closer to the Arctic areas, a process expected to be further facilitated by sea ice withdrawal caused by global warming. Copepods of the genus Calanus hold a key position in these cold-water food webs, providing an important energetic link between primary production and higher trophic levels. Due to their ecological importance, there is a concern about how accidental oil spills and produced water discharges may impact cold-water copepods. In this review, we summarize the current knowledge of the toxicity of petroleum on North Atlantic and Arctic Calanus copepods. We also review how recent development of high-quality transcriptomes from RNA-sequencing of copepods have identified genes regulating key biological processes, like molting, diapause and reproduction in Calanus copepods, to suggest linkages between exposure, molecular mechanisms and effects on higher levels of biological organization. We found that the available ecotoxicity threshold data for these copepods provide valuable information about their sensitivity to acute petrogenic exposures; however, there is still insufficient knowledge regarding underlying mechanisms of toxicity and the potential for long-term implications of relevance for copepod ecology and phenology. Copepod transcriptomics has expanded our understanding of how key biological processes are regulated in cold-water copepods. These advances can improve our understanding of how pollutants affect biological processes, and thus provide the basis for new knowledge frameworks spanning the effect continuum from molecular initiating events to adverse effects of regulatory relevance. Such efforts, guided by concepts such as adverse outcome pathways (AOPs), enable standardized and transparent characterization and evaluation of knowledge and identifies research gaps and priorities. This review suggests enhancing mechanistic understanding of exposure-effect relationships to better understand and link biomarker responses to adverse effects to improve risk assessments assessing ecological effects of pollutant mixtures, like crude oil, in Arctic areas.

Latent Trajectories of Haematological, Hepatic, and Renal Profiles after Oil Spill Exposure: A Longitudinal Analysis

Exposure to polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs) in crude oil has carcinogenic effects on various organ systems. This longitudinal cohort study examined the effects of oil spill exposure on the haematological, hepatic, and renal profiles of Rayong oil spill clean-up workers. The sample included 869 clean-up workers from the Rayong oil spill. Latent class mixture models were used to investigate and classify the longitudinal trajectories and trends of the haematological, hepatic, and renal indices. Subgroup analysis was used to evaluate the association between the urinary metabolites of PAHs and VOCs and haematological, hepatic, and renal parameters. Most clean-up workers (97.6%) had increasing levels of white blood cells (WBCs) (0.03 × 103 cells/µL), 94.90% of the workers had a significantly increasing trend of blood urea nitrogen (0.31 mg/dL per year), and 87.20% had a significantly increasing trend of serum creatinine (0.01 mg/dL per year). A high-decreasing trend of WBCs was seen in 2.42% (-0.73 × 103 per year). Post-exposure changes in haematological, renal, and hepatic profiles are present in workers exposed to the Rayong oil spill. This indicates possible long-term health complications and worsening renal function after exposure to PAHs and VOCs in crude oil.

Toxicity to sea urchin embryos of crude and bunker oils weathered under ice alone and mixed with dispersant

A multi-index approach (larval lenghthening and malformations, developmental disruption, and genotoxicity) was applied using sea-urchin embryos as test-organisms. PAH levels measured in the under-ice weathered aqueous fraction (UIWAF) were lower than in the low-energy water accommodated fraction (LEWAF) and similar amongst UIWAFs of different oils. UIWAFs and LEWAFs caused toxic effects, more markedly in UIWAFs, that could not be attributed to measured individual PAHs or to their mixture. Conversely, UIWAF was less genotoxic than LEWAF, most likely because naphthalene concentrations were also lower. In agreement, NAN LEWAF, the most genotoxic, exhibited the highest naphthalene levels. Dispersant addition produced less consistent changes in PAH levels and embryo toxicity in UIWAFs than in LEWAFs, and did not modify LEWAF genotoxicity. Overall, under ice weathering resulted in lowered waterborne PAHs and genotoxicity but augmented embryo toxicity, not modified by dispersant application.

Oil-mediated oxidative-stress responses in a keystone zooplanktonic species, Calanus finmarchicus

The copepod Calanus finmarchicus is an ecologically important species in the North Atlantic, Norwegian and Barents seas. Accidental or continuous petroleum pollution from oil and gas production in these seas may pose a significant threat to this low trophic level keystone species. Responses related to oxidative stress, protein damage and lipid peroxidation were investigated in C. finmarchicus exposed to a water-accommodated fraction (WAF) of a naphthenic North Atlantic crude oil. The exposure concentration corresponded to 50% of the 96 h LC₅₀, and samples were obtained at 0, 24, 48, 72 and 96 h after exposure initiation. Gene expressions (superoxide dismutase, catalase, glutathione S-transferase, glutathione synthetase, heat shock protein 70 and 90, ubiquitin and cytochrome P-450 330A1), enzyme activities (superoxide dismutase, catalase, glutathione S-transferase) and concentrations of total glutathione and malondialdehyde were analyzed. Gene expression analyses showed no differences between controls and the exposed animals, however significantly higher glutathione S-transferase activity and malondialdehyde concentrations were found in the exposed group, suggests lipid peroxidation as main toxic effect.

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.

Influence of dispersant application on the toxicity to sea urchin embryos of crude and bunker oils representative of prospective oil spill threats in Arctic and Sub-Arctic seas

This study deals with the toxicity assessment of crude and bunker oils representative of prospective oil spill threats in Arctic and Sub-Arctic seas (NNA: Naphthenic North-Atlantic crude oil; MGO: Marine Gas Oil; IFO: Intermediate Fuel Oil 180), alone or in combination with a third-generation dispersant (Finasol OSR52®). Early life stages of sea urchin, Paracentrotus lividus, were selected for toxicity testing of oil low-energy water accommodated fractions. A multi-index approach, including larval size increase and malformation, and developmental disruption as endpoints, was sensitive to discriminate from slight to severe toxicity caused by the tested aqueous fractions. IFO (heavy bunker oil) was more toxic than NNA (light crude oil), with MGO (light bunker oil) in between. The dispersant was toxic and further on it enhanced oil toxicity. Toxic units revealed that identified PAHs were not the main cause for toxicity, most likely exerted by individual or combined toxic action of non-measured compounds.

A food chain-based ecological risk assessment model for oil spills in the Arctic environment

This paper investigates the linkage between the acute impacts on apex marine mammals with polar cod responses to an oil spill. It proposes a Bayesian network-based model to link these direct and indirect effects on the apex marine mammals. The model predicts a recruitment collapse (for the scenarios considered), causing a higher risk of mortality of polar bears, beluga whales, and Narwhals in the Arctic region. Whales (adult and calves) were predicted to be at higher risk when the spill was under thick ice, while adult polar bears were at higher risk when the spill occurred on thin ice. A spill over the thick ice caused the least risk to whale and adult polar bears. The spill's timing and location have a significant impact on the animals in the Arctic region due to its unique sea ice dynamics, simple food web, and short periods of food abundance.

Quantifying the consequence of applying conservative assumptions in the assessment of oil spill effects on polar cod (Boreogadus saida) populations

In order to assess the potential impact from oil spills and decide the optimal response actions, prediction of population level effects of key resources is crucial. These assessments are usually based on acute toxicity data combined with precautionary assumptions because chronic data are often lacking. To better understand the consequences of applying precautionary approaches, two approaches for assessing population level effects on the Arctic keystone species polar cod (Boreogadus saida) were compared: a precautionary approach, where all exposed individuals die when exposed above a defined threshold concentration, and a refined (full-dose-response) approach. A matrix model was used to assess the population recovery duration of scenarios with various but constant exposure concentrations, durations and temperatures. The difference between the two approaches was largest for exposures with relatively low concentrations and short durations. Here, the recovery duration for the refined approach was less than eight times that found for the precautionary approach. Quantifying these differences helps to understand the consequences of precautionary assumptions applied to environmental risk assessment used in oil spill response decision making and it can feed into the discussion about the need for more chronic toxicity testing. An elasticity analysis of our model identified embryo and larval survival as crucial processes in the life cycle of polar cod and the impact assessment of oil spills on its population.

Ecological risks of imidacloprid to aquatic species in the Netherlands: Measured and estimated concentrations compared to species sensitivity distributions

Recent declines of insects' biomass have been a major point of interest. While several causes, including use of neonicotinoids like imidacloprid, have been suggested, scientific underpinning is limited. The aim of our study was to assess the potential risk of imidacloprid for freshwater fauna in the Netherlands and to validate the SimpleBox model to allow application elsewhere. To this end, we compared imidacloprid concentrations estimated from emissions using the SimpleBox model to measurements obtained from monitoring databases and calculated the ecological risk based on measured concentrations for aquatic fauna. Imidacloprid concentration estimations were within the range measured, opening opportunities for application of SimpleBox to regions where measurements are limited. Aquatic insects were found to be most sensitive to imidacloprid while amphibians and fish are least sensitive to imidacloprid. In particular, the ecological risk of measured imidacloprid concentration in the Netherlands was 1%, implying that concentrations frequently exceed levels that are lethal in short-term experiments. Hence, based on lab toxicity data, the present study suggests that imidacloprid concentrations can be high enough to explain insect decline observed in the same areas.

The sensitivity of the deepsea species northern shrimp (Pandalus borealis) and the cold-water coral (Lophelia pertusa) to oil-associated aromatic compounds, dispersant, and Alaskan North Slope crude oil

This study investigated the sensitivity of two deepsea species using mortality of northern shrimp (Pandalus borealis) and polyp activity of stony coral (Lophelia pertusa) to dispersant, Corexit 9500 and aromatic hydrocarbons (toluene, 2-methylnaphthalene, phenanthrene) in 96-h tests. Resulting hydrocarbon toxicity data were fit to the Target Lipid Model to generate predictive models and determine species sensitivity. Toxicity of chemically enhanced water accommodated fractions of Alaskan North Slope crude oil (ANS-oil) was also investigated with shrimp using nominal loading, total petroleum hydrocarbons and biomimetic extraction (BE) as oil exposure metrics. Coral were more sensitive to dispersant than shrimp while similar sensitivity was observed for hydrocarbons. Study and literature findings indicate deepsea species exhibit acute sensitivities to dispersant, hydrocarbons and oil that are comparable to pelagic species. Results support use of passive sampling methods to quantify dissolved oil for interpreting oil toxicity tests and suggest models for predicting time-dependence of toxicity warrant re-evaluation.

Exploring inter-species sensitivity to a model hydrocarbon, 2-Methylnaphtalene, using a process-based model

We compared inter-species sensitivity to a model narcotic compound, 2-Methylnaphthalene, to test if taxonomical relatedness, feeding guilds, and trophic level govern species sensitivities on species distributed in different regions. We fitted a toxicokinetic-toxicodynamic model to survival patterns over time for 26 species using new and raw data from the literature. Species sensitivity distributions provided little insight into understanding patterns in inter-species sensitivity. The range of no-effect concentrations (NEC) obtained for 26 species showed little variation (mean 0.0081 mM; SD 0.009). Results suggest that the NEC alone does not explain the complexity of the species tolerances. The dominant rate constant and the derived time to observe an effect (t₀), a function of concentration, might provide the means for depicting patterns in sensitivity and better ecotoxicological testing. When comparing the t₀ functions, we observed that Arctic species have shorter time frames to start showing effects. Mollusks and second trophic level species took longer to build up a lethal body burden than the rest. Coupling our results with fate and transport models would allow forecasting narcotic compounds toxicity in time and thus improve risk assessment.

Current practices and knowledge supporting oil spill risk assessment in the Arctic

Oil spill response (OSR) in the Arctic marine environment conducted as part of operational planning and preparedness supporting exploration and development is most successful when knowledge of the ecosystem is readily available and applicable in an oil spill risk assessment framework. OSR strategies supporting decision-making during the critical period after a spill event should be explicit about the environmental resources potentially at risk and the efficacy of OSR countermeasures that best protect sensitive and valued resources. At present, there are 6 prominent methods for spill impact mitigation assessment (SIMA) in the Arctic aimed at supporting OSR and operational planning and preparedness; each method examines spill scenarios and identifies response strategies best suited to overcome the unique challenges posed by polar ecosystems and to minimize potential long-term environmental consequences. The different methods are grounded in classical environmental risk assessment and the net environmental benefit analysis (NEBA) approach that emerged in the 1990s after the Exxon Valdez oil spill. The different approaches share 5 primary assessment elements (oil physical and chemical properties, fate and transport, exposure, effects and consequence analysis). This paper highlights how the different Arctic methods reflect this common risk assessment framework and share a common need for oil spill science relevant to Arctic ecosystems. An online literature navigation portal, developed as part of the 5-year Arctic Oil Spill Response Technologies Joint Industry Programme, complements the different approaches currently used in the Arctic by capturing the rapidly expanding body of scientific knowledge useful to evaluating exposure, vulnerability and recovery of the Arctic ecosystem after an oil spill.

Toxicokinetics of Crude Oil Components in Arctic Copepods

The risk of accidental oil spills in the Arctic is on the rise due to increased shipping and oil exploration activities, making it essential to calibrate parameters for risk assessment of oil spills to Arctic conditions. The toxicokinetics of crude oil components were assessed by exposing one lipid-poor (CIII) and one lipid-rich (CV) stage of the Arctic copepod Calanus hyperboreus to crude oil WSF (water-soluble fraction). Water concentrations and total body residues (BR), as well as lipid volume fractions, were measured at regular intervals during exposure and recovery. Bioconcentration factors (BCFs) and elimination rates ( k_e) for 26 petrogenic oil components were estimated from one-compartment models fitted to the BR data. Our parameters were compared to estimations made by the OMEGA bioaccumulation model, which uses the octanol-water partitioning coefficient ( K_OW) in QSAR (quantitative structure-activity relationship) predictions. Our parameters for the lipid-poor CIIIs generally agreed with the OMEGA predictions, while neither the BCFs nor the k_es for the lipid-rich CVs fitted within the realistic range of the OMEGA parameters. Both the uptake and elimination rates for the CVs were in general half an order of magnitude lower than the OMEGA predictions, showing an overestimation of these parameters by the OMEGA model.

The sensitivity of a deep-sea fish species (Anoplopoma fimbria) to oil-associated aromatic compounds, dispersant, and Alaskan North Slope crude oil

A predominant concern following oil spills is toxicity to aquatic organisms. However, few data are available on effects in deep-sea cold water fishes. The present study had 3 major objectives. The first was to investigate the relative sensitivity of the deep-sea species Anoplopoma fimbria (sablefish) to acute effects of 3 aromatic compounds (toluene, 2-methylnaphthalene, and phenanthrene), dispersant alone, and chemically enhanced water accommodated fractions (CEWAFs) of Alaskan North Slope crude oil. The second was to determine the critical target lipid body burden (CTLBB) for sablefish by fitting aromatic hydrocarbon toxicity data to the target lipid model (TLM), which then allowed expression of CEWAF exposures in terms of dissolved oil toxic units. The final aim was to apply a passive sampling method that targets bioavailable, dissolved hydrocarbons as an alternative analytical technique for improved CEWAF exposure assessment. The results indicate that sablefish exhibit sensitivity to Corexit 9500 (96-h median lethal concentration [LC50] = 72.2 mg/L) within the range reported for other fish species. However, the acute CTLBB of 39.4 ± 2.1 μmol/g_octanol lies at the lower end of the sensitivity range established for aquatic species. The utility of both toxic units and passive sampling measurements for describing observed toxicity of dispersed oil is discussed. The present study is novel in that a new test species is investigated to address the uncertainty regarding the sensitivity of deep-sea fishes, while also employing modeling and measurements to improve exposure characterization in oil toxicity tests. Environ Toxicol Chem 2018;37:2210-2221. © 2018 SETAC.

Chemical characterization and toxicity of water-accommodated fraction of oil on the South American native species Hyalella curvispina

Chemical and toxicological crude oil analysis was performed on water-accommodated fraction of oil (WAF). This study characterized the chemical composition of WAF and its dissipation over a period of 192 h. Acute (96 h) and chronic (14 d) toxicity of WAF were evaluated on Hyalella curvispina from both reference (Los Barreales lake, LB) and hydrocarbon-contaminated (Durán stream, DS) sites. The total hydrocarbon (TPHs) concentration in WAF was 2.18 mg L^-1. The dissipation rates of hydrocarbons in WAF showed a first-order kinetics, with half-lives ranging between 65 h-200 h. Amphipods from LB showed acute and chronic LC50 values of 0.33 and 0.018 mg L^-1, respectively. Amphipods from DS exposed to pure WAF showed no mortality in either acute or chronic assays. Further biochemical and molecular research is required to determine the mechanisms underlying the resistance to WAF exposure on DS amphipods.

Oxidative and interactive challenge of cadmium and ocean acidification on the smooth scallop Flexopecten glaber

Ocean acidification (OA) may affect sensitivity of marine organisms to metal pollution modulating chemical bioavailability, bioaccumulation and biological responsiveness of several cellular pathways. In this study, the smooth scallop Flexopecten glaber was exposed to various combinations of reduced pH (pH/pCO₂ 7.4/∼3000 μatm) and Cd (20 μg/L). The analyses on cadmium uptake were integrated with those of a wide battery of biomarkers including metallothioneins, single antioxidant defenses and total oxyradical scavenging capacity in digestive gland and gills, lysosomal membrane stability and onset of genotoxic damage in haemocytes. Reduced pH slightly increased concentration of Cd in scallop tissues, but no effects were measured in terms of metallothioneins. Induction of some antioxidants by Cd and/or low pH in the digestive gland was not reflected in variations of the total oxyradical scavenging capacity, while the investigated stressors caused a certain inhibition of antioxidants and reduction of the scavenging capacity toward peroxyl radical in the gills. Lysosomal membrane stability and onset of genotoxic damages showed high sensitivity with possible synergistic effects of the investigated factors. The overall results suggest that indirect effects of ocean acidification on metal accumulation and toxicity are tissue-specific and modulate oxidative balance through different mechanisms.

Relative sensitivity of Arctic species to physically and chemically dispersed oil determined from three hydrocarbon measures of aquatic toxicity

The risks to Arctic species from oil releases is a global concern, but their sensitivity to chemically dispersed oil has not been assessed using a curated and standardized dataset from spiked declining tests. Species sensitivity to dispersed oil was determined by their position within species sensitivity distributions (SSDs) using three measures of hydrocarbon toxicity: total petroleum hydrocarbons (TPH), polycyclic aromatic hydrocarbon (PAHs), and naphthalenes. Comparisons of SSDs with Arctic/sub-Arctic versus non-Arctic species, and across SSDs of compositionally similar oils, showed that Arctic and non-Arctic species have comparable sensitivities even with the variability introduced by combining data across studies and oils. Regardless of hydrocarbon measure, hazard concentrations across SSDs were protective of sensitive Arctic species. While the sensitivities of Arctic species to oil exposures resemble those of commonly tested species, PAH-based toxicity data are needed for a greater species diversity including sensitive Arctic species.

Aquatic ecotoxicological models and their applicability in Arctic regions

Dose-response modeling is one of the most important steps of ecological risk assessment. It requires concentration-effects relationships for the species under consideration. There are very limited studies and experimental data available for the Arctic aquatic species. Lack of toxicity data hinders obtaining dose-response relationships for lethal (LC50 values), sub-lethal and carcinogenic effects. Gaps in toxicity data could be filled using a variety of in-silico ecotoxicological methods. This paper reviews the suitability of such methods for the Arctic scenario. Mechanistic approaches like toxicokinetic and toxicodynamic analysis are found to be better suited for interspecies extrapolation than statistical methods, such as Quantitative Structure-Activity Relationships/Quantitative Structure Activity-Activity Relationship, ICE, and other empirical models, such as Haber's law and Ostwald's equation. A novel approach is proposed where the effects of the toxicant exposure are quantified based on the probability of cellular damage and metabolites interactions. This approach recommends modeling cellular damage using a toxicodynamic model and physiology or metabolites interactions using a toxicokinetic model. Together, these models provide more reliable estimates of toxicity in the Arctic aquatic species, which will assist in conducting ecological risk assessment of Arctic environment.

Time-varying effects of aromatic oil constituents on the survival of aquatic species: Deviations between model estimates and observations

There is a need to study the time course of toxic chemical effects on organisms because there might be a time lag between the onset of chemical exposure and the corresponding adverse effects. For aquatic organisms, crude oil and oil constituents originating from either natural seeps or human activities can be relevant case studies. In the present study the authors tested a generic toxicokinetic model to quantify the time-varying effects of various oil constituents on the survival of aquatic organisms. The model is based on key parameters applicable to an array of species and compounds with baseline toxicity reflected by a generic, internal toxicity threshold or critical body burden (CBB). They compared model estimates with experimental data on the effects of 8 aromatic oil constituents on the survival of aquatic species including crustaceans and fish. The average model uncertainty, expressed as the root mean square error, was 0.25 (minimum-maximum, 0.04-0.67) on a scale between 0 and 1. The estimated survival was generally lower than the measured survival right after the onset of oil constituent exposure. In contrast, the model underestimated the maximum mortality for crustaceans and fish observed in the laboratory. Thus, the model based on the CBB concept failed to adequately predict the lethal effects of the oil constituents on crustaceans and fish. Possible explanations for the deviations between model estimates and observations may include incorrect assumptions regarding a constant lethal body burden, the absence of biotransformation products, and the steady state of aromatic hydrocarbon concentrations in organisms. Clearly, a more complex model approach than the generic model used in the present study is needed to predict toxicity dynamics of narcotic chemicals. Environ Toxicol Chem 2017;36:128-136. © 2016 SETAC.

Acute and subacute toxicity of the polycyclic aromatic hydrocarbon 1-methylnaphthalene to the shallow-water coral Porites divaricata: Application of a novel exposure protocol

Previous research evaluating hydrocarbon toxicity to corals and coral reefs has generally focused on community-level effects, and results often are not comparable between studies because of variability in hydrocarbon exposure characterization and evaluation of coral health and mortality during exposure. Toxicity of the polycyclic aromatic hydrocarbon 1-methylnaphthalene to the coral Porites divaricata was assessed in a constant exposure toxicity test utilizing a novel toxicity testing protocol uniquely applicable to shallow-water corals, which considered multiple assessment metrics and evaluated the potential for post-exposure mortality and/or recovery. Acute and subacute effects (gross morphological changes, photosynthetic efficiency, mortality, and histologic cellular changes) were evaluated during pre-exposure (4 wk), exposure (48 h), and post-exposure recovery (4 wk) periods. Coral condition scores were used to determine a 48-h median effective concentration of 7442 μg/L. Significant physical and histological changes resulted from exposure to 640 μg/L and 5427 μg/L 1-methylnaphthalene, with a 1-d to 3-d delay in photosynthetic efficiency effects (ΔF/Fm). Pigmented granular amoebocyte area was found to be a potentially useful sublethal endpoint for this species. Coral mortality was used to estimate a 48-h median lethal concentration of 12 123 μg/L. Environ Toxicol Chem 2017;36:212-219. © 2016 SETAC.

Development and application of the SSD approach in scientific case studies for ecological risk assessment

Species sensitivity distributions (SSDs) are used in ecological risk assessment for extrapolation of the results of toxicity tests with single species to a toxicity threshold considered protective of ecosystem structure and functioning. The attention to and importance of the SSD approach has increased in scientific and regulatory communities since the 1990s. Discussion and criticism have been triggered on the concept of the approach as well as its technical aspects (e.g., distribution type, number of toxicity endpoints). Various questions remain unanswered, especially with regard to different endpoints, statistical methods, and protectiveness of threshold levels, for example. In the present literature review (covering the period 2002-2013), case studies are explored in which the SSD approach was applied, as well as how endpoint types, species choice, and data availability affect SSDs. How statistical methods may be used to construct reliable SSDs and whether the lower 5th percentile hazard concentrations (HC5s) from a generic SSD can be protective for a specific local community are also investigated. It is shown that estimated protective concentrations were determined by taxonomic groups rather than the statistical method used to construct the distribution. Based on comparisons between semifield and laboratory-based SSDs, the output from a laboratory SSD was protective of semifield communities in the majority of studies. Environ Toxicol Chem 2016;35:2149-2161. © 2016 SETAC.

Acute toxicity of dispersed crude oil on the cold-water copepod Calanus finmarchicus: Elusive implications of lipid content

In this investigation, acute toxicity data were used from two previously reported studies where cold-water copepods were exposed to mechanically dispersed (MD) and chemically (CD) dispersed oil. In one of these studies, concentration-dependent mortality was observed, whereas no apparent relationship between exposure concentration and mortality was found in the other. The only marked difference between the studies is that copepods in the first experiment displayed a lower lipid sac volume (on average) than in the second one. In this study additional biometric data on lipid content were utilized and observed effects and toxicokinetics modeling applied in order to investigate whether differences in sensitivity between copepod cohorts might be explained by differences in lipid content. Results suggest that although a considerable lipid sac might retard toxicokinetics, the observed differences in lipid volume are not sufficient to explain differences in toxicity. Further, there are no apparent indications that acute toxic stress leads to lipid depletion, or that acute increased mortality rate selectively affects lipid-poor individuals. It is conceivable that other potential explanations exist, but the causal relationship between lipid content and increased mortality frequency remains elusive.

Improving environmental assessments by integrating Species Sensitivity Distributions into environmental modeling: examples with two hypothetical oil spills

A three dimensional (3D) trajectory model was used to simulate oil mass balance and environmental concentrations of two 795,000 L hypothetical oil spills modeled under physical and chemical dispersion scenarios. Species Sensitivity Distributions (SSD) for Total Hydrocarbon Concentrations (THCs) were developed, and Hazard Concentrations (HC) used as levels of concern. Potential consequences to entrained water column organisms were characterized by comparing model outputs with SSDs, and obtaining the proportion of species affected (PSA) and areas with oil concentrations exceeding HC5s (Area ⩾ HC5). Under the physically-dispersed oil scenario ⩽ 77% of the oil remains on the water surface and strands on shorelines, while with the chemically-dispersed oil scenario ⩽ 67% of the oil is entrained in the water column. For every 10% increase in chemical dispersion effectiveness, the average PSA and Area ⩾ HC5 increases (range: 0.01-0.06 and 0.50-2.9 km(2), respectively), while shoreline oiling decreases (⩽ 2919 L/km). Integrating SSDs into modeling may improve understanding of scales of potential impacts to water column organisms, while providing net environmental benefit comparison of oil spill response options.

Pollutant resilience in embryos of the Antarctic sea urchin Sterechinus neumayeri reflects maternal antioxidant status

Legacy pollutants, including polycyclic aromatic hydrocarbons (PAHs) and metals, can occur in high concentrations in some Antarctic marine environments, particularly near scientific research stations. Oxidative stress is an important unifying feature underlying the toxicity of many chemical contaminants to aquatic organisms. However, the potential impacts of pollutants on the oxidative physiology of Antarctic marine invertebrates are not well documented. Sterechinus neumayeri is a common animal in the shallow subtidal benthos surrounding Antarctica, and is considered an important keystone species. The aim of the present study was to collect baseline oxidative biomarker data for S. neumayeri and to investigate the impacts of field exposure to chemical contaminants on gamete health and parent-to-offspring transfer of oxidative stress resilience. We analysed antioxidant enzyme activities, levels of the molecular antioxidant glutathione, protein carbonylation, lipid peroxidation and levels of 8-OHdG as oxidative stress biomarkers in S. neumayeri from a contaminant-impacted site near McMurdo Station and a relatively pristine site at Cape Evans. Biomarkers were analysed in adult gamete tissue and in early stage embryos exposed to AN8 fuel oil. PAHs were quantified as a proxy for contamination and were found to be elevated in urchins from the contaminated site (up to 231.67ng/g DW). These contaminant-experienced adult urchins produced eggs with greater levels of a broad suite of antioxidants, particularly superoxide dismutase, catalase and glyoxalase-I, than those from Cape Evans. In addition, embryos that were derived from contaminant-experienced mothers were endowed with higher baseline levels of antioxidants, which conferred an enhanced capacity to minimize oxidative damage to lipids, proteins and DNA when exposed to AN8 fuel. This pattern was strongest following exposure to 900ppm AN8, where lipid and protein damage was 5-7 times greater than baseline levels in contaminant-naïve female embryos in comparison to 3-4 times greater in contaminant-experienced female embryos. Despite this inherited resilience against oxidative stress, abnormal development was as high in these embryos when exposed to AN8 as in those derived from contaminant-naïve mothers (up to 80% abnormality), implying the conferred advantage may not translate to a fitness or survival gain, at least up to the blastulae stage. Our findings document the first evidence for parent-to-offspring transfer of oxidative stress resilience in an Antarctic marine invertebrate.

Comparison of produced water toxicity to Arctic and temperate species

Produced water is the main discharge stream from oil and gas production. For offshore activities this water is usually discharged to the marine environment. Produced water contains traces of hydrocarbons such as polycyclic aromatic hydrocarbons as well as alkylphenols, which are relatively resistant to biodegradation and have been reported to cause adverse effects to marine organisms in laboratory studies. For management of produced water, risk-based tools have been developed using toxicity data for mainly non-Arctic species. Reliable risk assessment approaches for Arctic environments are requested to manage potential impacts of produced water associated with increased oil and gas activities in Arctic regions. In order to assess the applicability of existing risk tools for Arctic areas, basic knowledge on the sensitivity of Arctic species has to be developed. In the present study, acute and chronic toxicity of artificial produced water for 6 Arctic and 6 temperate species was experimentally tested and evaluated. The hazardous concentrations affecting 5% and 50% of the species were calculated from species sensitivity distribution curves. Hazardous concentrations were compared to elucidate whether temperate toxicity data used in risk assessment are sufficiently representative for Arctic species. From the study it can be concluded that hazardous concentration derived from individual species' toxicity data of temperate and Arctic species are comparable. However, the manner in which Arctic and non-Arctic populations and communities respond to exposure levels above established thresholds remains to be investigated. Hence, responses at higher levels of biological organization should be studied to reveal potential differences in sensitivities to produced water between Arctic and non-Arctic ecosystems.

Extension and validation of the target lipid model for deriving predicted no-effect concentrations for soils and sediments

Substance risk assessments require estimation of predicted no-effect concentrations (PNECs) in soil and sediment. The present study applies the target lipid model (TLM) and equilibrium partitioning (EqP) model to toxicity data to evaluate the extrapolation of the TLM-derived aquatic PNECs to these compartments. This extrapolation assumes that the sensitivity of aquatic species is similar to that of terrestrial and benthic species. The acute species sensitivity distribution, expressed in terms of species-specific critical target lipid body burdens, was computed using the TLM-EqP framework and found to span a similar range as the aquatic organism species sensitivity distribution but with a slightly lower median value (less than 2 times). The species sensitivity distribution for acute-to-chronic ratios also exhibited a similar range and distribution across species, suggesting similar mechanisms of action. This hypothesis was further tested by comparing empirical soil/sediment chronic effect levels to the calculated PNEC derived using TLM-EqP. The results showed that 95% of the compiled chronic effects data fell above the PNEC, confirming an adequate protection level. These findings support the conclusion that TLM-derived aquatic PNECs can be successfully extrapolated to derive credible PNECs for soil and sediment compartments.

Effects of an oil spill in a harbor assessed using biomarkers of exposure in eelpout

Oil spills occur commonly, and chemical compounds originating from oil spills are widespread in the aquatic environment. In order to monitor effects of a bunker oil spill on the aquatic environment, biomarker responses were measured in eelpout (Zoarces viviparus) sampled along a gradient in Göteborg harbor where the oil spill occurred and at a reference site, 2 weeks after the oil spill. Eelpout were also exposed to the bunker oil in a laboratory study to validate field data. The results show that eelpout from the Göteborg harbor are influenced by contaminants, especially polycyclic aromatic hydrocarbons (PAHs), also during "normal" conditions. The bunker oil spill strongly enhanced the biomarker responses. Results show elevated ethoxyresorufin-O-deethylase (EROD) activities in all exposed sites, but, closest to the oil spill, the EROD activity was partly inhibited, possibly by PAHs. Elevated DNA adduct levels were also observed after the bunker oil spill. Chemical analyses of bile revealed high concentrations of PAH metabolites in the eelpout exposed to the oil, and the same PAH metabolite profile was evident both in eelpout sampled in the harbor and in the eelpout exposed to the bunker oil in the laboratory study.

Development and practical application of petroleum and dispersant interspecies correlation models for aquatic species

Assessing the acute toxicity of oil has generally relied on existing toxicological data for a relatively few standard test species, which has limited the ability to estimate the impacts of spilled oil on aquatic communities. Interspecies correlation estimation (ICE) models were developed for petroleum and dispersant products to facilitate the prediction of toxicity values to a broader range of species and to better understand taxonomic differences in species sensitivity. ICE models are log linear regressions that can be used to estimate toxicity to a diversity of taxa based on the known toxicity value for a surrogate tested species. ICE models have only previously been developed for nonpetroleum chemicals. Petroleum and dispersant ICE models were statistically significant for 93 and 16 unique surrogate-predicted species pairs, respectively. These models had adjusted coefficient of determinations (adj-R(2)), square errors (MSE) and positive slope ranging from 0.29 to 0.99, 0.0002 to 0.311, and 0.187 to 2.665, respectively. Based on model cross-validation, predicted toxicity values for most ICE models (>90%) were within 5-fold of the measured values, with no influence of taxonomic relatedness on prediction accuracy. A comparison between hazard concentrations (HC) derived from empirical and ICE-based species sensitivity distributions (SSDs) showed that HC values were within the same order of magnitude of each other. These results show that ICE-based SSDs provide a statistically valid approach to estimating toxicity to a range of petroleum and dispersant products with applicability to oil spill assessment.

Issues and challenges with oil toxicity data and implications for their use in decision making: a quantitative review

Aquatic toxicity considerations are part of the net environmental benefit analysis and approval decision process on the use of dispersants in the event of an offshore oil spill. Substantial information is available on the acute toxicity of physically and chemically dispersed oil to a diverse subset of aquatic species generated under controlled laboratory conditions. However, most information has been generated following standard laboratory practices, which do not realistically represent oil spill conditions in the field. The goal of the present quantitative review is to evaluate the use of standard toxicity testing data to help inform decisions regarding dispersant use, recognizing some key issues with current practices, specifically, reporting toxicity metrics (nominal vs measured), exposure duration (standard durations vs short-term exposures), and exposure concentrations (constant vs spiked). Analytical chemistry data also were used to demonstrate the role of oil loading on acute toxicity and the influence of dispersants on chemical partitioning. The analyses presented here strongly suggest that decisions should be made, at a minimum, based on measured aqueous exposure concentrations and, ideally, using data from short-term exposure durations under spiked exposure concentrations. Available data sets are used to demonstrate how species sensitivity distribution curves can provide useful insights to the decision-making process on dispersant use. Finally, recommendations are provided, including the adoption of oil spill-appropriate toxicity testing practices.

Modelling bioaccumulation of oil constituents in aquatic species

Crude oil poses a risk to marine ecosystems due to its toxicity and tendency to accumulate in biota. The present study evaluated the applicability of the OMEGA model for estimating oil accumulation in aquatic species by comparing model predictions of kinetic rates (absorption and elimination) and bioconcentration factors (BCF) with measured values. The model was a better predictor than the means of the measurements for absorption and elimination rate constants, but did not outperform the mean measured BCF. Model estimates and measurements differed less than one order of magnitude for 91%, 80% and 61% of the absorption and elimination rates and BCFs of all oil constituents, respectively. Of the "potentially modifying" factors: exposure duration, biotransformation, molecular mass, and water temperature, the last two tended to influence the performance of the model. Inclusion of more explanatory variables in the bioaccumulation model, like the molecular mass, is expected to improve model performance.

Development of aquatic toxicity benchmarks for oil products using species sensitivity distributions

Determining the sensitivity of a diversity of species to spilled oil and chemically dispersed oil continues to be a significant challenge in spill response and impact assessment. We used standardized tests from the literature to develop species sensitivity distributions (SSDs) of acute aquatic toxicity values for several petroleum products and 2 Corexit oil dispersants. Fifth percentile hazard concentrations (HC5s) were computed from the SSDs and used to assess relative oil product toxicity and in evaluating the feasibility of establishing toxicity benchmarks for a community of species. The sensitivity of mysids (Americamysis bahia) and silversides (Menidia beryllina) were evaluated within the SSDs to determine if these common test species were appropriate surrogates for a broader range of species. In general, SSD development was limited by the availability of acute toxicity values that met standardization criteria for a diversity of species. Pooled SSDs were also developed for crude oil and Corexit dispersants because there was only small variability in the HC5s among the individual oil or dispersant products. The sensitivity of mysids and silversides varied across the oil and dispersant products, with the majority of toxicity values greater than the HC5. Application of SSDs appears to be a reasonable approach to developing oil product toxicity benchmarks, but additional toxicity data are needed for a larger range of species conducted under standardized test conditions.

The acute toxicity of chemically and physically dispersed crude oil to key Arctic species under Arctic conditions during the open water season

The acute toxicity of physically and chemically dispersed crude oil and the dispersant Corexit 9500 were evaluated for key Arctic species. The copepod Calanus glacialis, juvenile Arctic cod (Boreogadus saida), and larval sculpin (Myoxocephalus sp.) were tested under conditions representative of the Beaufort and Chukchi Seas during the ice-free season. The toxicity of 3 water-accommodated fractions (WAF) of Alaska North Slope crude oil was examined with spiked, declining exposures. A dispersant-only test was conducted with the copepod C. glacialis. Each preparation with oil (WAF, breaking wave WAF [BWWAF], and chemically enhanced WAF [CEWAF]) produced distinct suites of hydrocarbon constituents; the total concentrations of oil were lowest in WAF and highest in CEWAF preparations. The relative sensitivity for the different species and age classes was similar within each WAF type. Median lethal concentration values based on total petroleum hydrocarbons ranged from 1.6 mg/L to 4.0 mg/L for WAF and BWWAF treatments and from 22 mg/L to 62 mg/L for CEWAF. For Corexit 9500 exposures, median lethal concentration values ranged from 17 mg/L to 50 mg/L. The differences in the relative toxicity among the accommodated fractions indicated that the majority of petroleum hydrocarbons in the CEWAF are in less acutely toxic forms than the components that dominate the WAF or BWWAF. Further evaluation showed that the parent polycyclic aromatic hydrocarbon compounds, specifically naphthalene, were highly correlated to acute toxicity.

Toxicity data for modeling impacts of oil components in an Arctic ecosystem

Ecological impact assessment modeling systems are valuable support tools for managing impacts from commercial activities on marine habitats and species. The inclusion of toxic effects modeling in these systems is predicated on the availability and quality of ecotoxicology data. Here we report on a data gathering exercise to obtain toxic effects data on oil compounds for a selection of cold-water marine species of fish and plankton associated with the Barents Sea ecosystem. Effects data were collated from historical and contemporary literature resources for the endpoints mortality, development, growth, bioaccumulation and reproduction. Evaluating the utility and applicability of these data for modeling, we find that data coverage is limited to a sub-set of the required endpoints. There is a need for new experimental studies for zooplankton focused on the endpoints development and bioaccumulation and for larvae and juvenile fish focused on growth and development.

Low oxygen tolerance of different life stages of temperate freshwater fish species

Data on low dissolved oxygen (DO₂) tolerance of freshwater fish species of north-western Europe were used to create species sensitivity distributions (SSD). Lowest observed effect concentrations (LOEC) and 100% lethal concentrations (LC₁₀₀) data were collected from the scientific literature. Comparisons were made among life stages as well as between native and exotic species. In addition, lethal DO₂ concentrations were compared to oxygen concentrations corresponding to maximum tolerable water temperatures of the same species. Fish eggs and embryos were the least tolerant. Juveniles had a significantly lower mean LOEC than adults, but there was no difference in mean LC₁₀₀ between the two groups. The difference in lethal oxygen concentrations between adults and juveniles was largest for three salmonids, although it remains uncertain if this was a result of smoltification. There were no significant differences between native and exotic species; however, data on exotics are limited. DO₂ concentrations converted from maximum tolerable water temperatures were 3·9 times higher than the measured lethal DO₂ concentrations, which may reflect changes in respiration rates (Q₁₀) and may also relate to the simplicity of the model used.

Dietary exposure of Antarctic krill to p,p'-DDE: uptake kinetics and toxicological sensitivity in a key polar species

This study evaluated the dietary uptake kinetics and sublethal toxicity of p,p'-dichlorodiphenyl dichloroethylene (p,p'-DDE) in Antarctic krill. The uptake rate constant (characterised by the seawater volume stripped of contaminant sorbed to algae) of 200 ± 0.32 mL g(-1) wet weight h(-1), average absorption efficiency of 86 ± 13% and very low elimination rate constant of 5 × 10(-6) ± 0.0031 h(-1) demonstrate the importance of feeding for p,p'-DDE bioaccumulation in Antarctic krill. Faecal egestion of unabsorbed p,p'-DDE of 8.1 ± 2.7% indicates that this pathway contributes considerably to p,p'-DDE sinking fluxes. A median internal effective concentration (IEC50) of 15 mmol/kg lipid weight for complete immobility indicates baseline toxicity and that Antarctic krill exhibit comparable toxicological sensitivity as temperate species under similar 10 d exposure conditions. These findings support the critical body residue approach and provide insight to the role of Antarctic krill in the biogeochemical cycling of p,p'-DDE in the Southern Ocean.

Acute exposure of water soluble fractions of marine diesel on Arctic Calanus glacialis and boreal Calanus finmarchicus: effects on survival and biomarker response

The use of marine diesels in Arctic areas is expected to increase due to increased shipping transport, oil and gas activities, and the ban of heavy bunker oils in many areas. This project aimed at gathering information regarding the sensitivity of an Arctic copepod to marine diesel. The approach undertaken was to study the effects on survival (LC50s) and gene expression of a known detoxification gene (glutathione S-transferase [GST]) in Calanus glacialis following exposure to water soluble fractions (WSFs) of marine diesel (at 2 °C). We compared the observed LC-values of C. glacialis to the identical experimental data of the boreal Calanus finmarchicus (at 10 °C), and to the predicted LC50-values using regression models. The C. glacialis appeared more tolerant to the acute effects of marine diesel WSF compared to the "average pelagic crustacean" as predicted by regression models, and compared to C. finmarchicus. Although these results may be explained by a slower equilibration of petrogenic chemicals from the WSF at lower temperatures, C. glacialis also displayed higher GST expression following exposure than C. finmarchicus. In addition, the lipid content of the test organisms appears to be an important factor for the determination of acute toxicity, as copepods with high lipid content survived longer than copepods with low lipid content.

Modelling produced water dispersion and its direct toxic effects on the production and biomass of the marine copepod Calanus finmarchicus

Zooplankton is a key group in North Atlantic and Arctic food chains, and assessment and minimization of adverse effects from petroleum activities to this resource are important. The potential direct effects of produced water discharges on the biomass of Calanus finmarchicus were evaluated using a fully coupled, high resolution 3D hydrodynamic-ecological model system (SINMOD). Several scenarios with varying effects of produced water concentrations were considered. In order to reduce numerical dilution of the produced water effluents, a "sub grid" model component of higher resolution (80 m horizontal resolution vs 800 m for the main model grid) was developed and implemented. The results show that dilution and dispersion of produced water varies between locations. In general, realistically simulated concentrations of produced water were too low to have significant effects on the C. finmarchicus biomass and reproduction according to the toxicity-dilution profiles used, even when the toxicity of the produced water was increased 10-fold. The decrease in C. finmarchicus biomass was partially compensated by a slight increase in production.

Combined and interactive effects of global climate change and toxicants on populations and communities

Increased temperature and other environmental effects of global climate change (GCC) have documented impacts on many species (e.g., polar bears, amphibians, coral reefs) as well as on ecosystem processes and species interactions (e.g., the timing of predator-prey interactions). A challenge for ecotoxicologists is to predict how joint effects of climatic stress and toxicants measured at the individual level (e.g., reduced survival and reproduction) will be manifested at the population level (e.g., population growth rate, extinction risk) and community level (e.g., species richness, food-web structure). The authors discuss how population- and community-level responses to toxicants under GCC are likely to be influenced by various ecological mechanisms. Stress due to GCC may reduce the potential for resistance to and recovery from toxicant exposure. Long-term toxicant exposure can result in acquired tolerance to this stressor at the population or community level, but an associated cost of tolerance may be the reduced potential for tolerance to subsequent climatic stress (or vice versa). Moreover, GCC can induce large-scale shifts in community composition, which may affect the vulnerability of communities to other stressors. Ecological modeling based on species traits (representing life-history traits, population vulnerability, sensitivity to toxicants, and sensitivity to climate change) can be a promising approach for predicting combined impacts of GCC and toxicants on populations and communities.

Occurrence, bioavailability and toxic effects of trace metals and organic contaminants in mangrove ecosystems: a review

Although their ecological and socioeconomic importance has received recent attention, mangrove ecosystems are one of the most threatened tropical environments. Besides direct clearance, hydrological alterations, climatic changes or insect infestations, chemical pollution could be a significant contributor of mangrove degradation. The present paper reviews the current knowledge on the occurrence, bioavailability and toxic effects of trace contaminants in mangrove ecosystems. The literature confirmed that trace metals, Polycyclic Aromatic Hydrocarbons (PAHs), Persistent Organic Pollutants (POPs), Pharmaceuticals and Personal Care Products (PPCPs) and Endocrine Disrupters Compounds (EDCs) have been detected in various mangrove compartments (water, sediments and biota). In some cases, these chemicals have associated toxic effects on mangrove ecosystem species, with potential impact on populations and biodiversity in the field. However, nearly all studies about the bioavailability and toxic effects of contaminants in mangrove ecosystems focus on selected trace metals, PAHs or some "conventional" POPs, and virtually no data exist for other contaminant groups. The specificities of mangrove ecosystems (e.g. biology, physico-chemistry and hydrology) support the need for specific ecotoxicological tools. This review highlights the major data and methodological gaps which should be addressed to refine the risk assessment of trace pollutants in mangrove ecosystems.

Acute toxicity of crude oil water accommodated fraction on marine copepods: the relative importance of acclimatization temperature and body size

Recent oil spillage accidents around the world greatly increase harmful risks to marine ecology. This study evaluated the influences of petroleum water accommodated fraction (WAF) on 15 typical species of marine copepods collected from a subtropical bay in East China Sea at different seasons. Copepods showed impaired swimming ability, restlessness, loss of balance, anoxic coma, and even death when they were acutely exposed to the crude oil WAF under laboratory conditions. The LC(50) values (expressed in total petroleum hydrocarbon concentration) indicated that the tolerances of copepods to WAF decreased significantly (P < 0.05) with increased exposure duration and natural water temperatures (acclimatization temperature). The sensitivity of the copepods was species-specific (P < 0.01), and there was a significant (P < 0.05) positive correlation between the 48-h LC(50) and body size. Therefore, the small copepod species confront more survival challenges under oil contamination stress, especially in the warm months or regions.

Ranking ecological risks of multiple chemical stressors on amphibians

Populations of amphibians have been declining worldwide since the late 1960s. Despite global concern, no studies have quantitatively assessed the major causes of this decline. In the present study, species sensitivity distributions (SSDs) were developed to analyze the sensitivity of anurans for ammonium, nitrate, heavy metals (cadmium, copper), pesticides (18 compounds), and acidification (pH) based on laboratory toxicity data. Ecological risk (ER) was calculated as the probability that a measured environmental concentration of a particular stressor in habitats where anurans were observed would exceed the toxic effect concentrations derived from the species sensitivity distributions. The assessment of ER was used to rank the stressors according to their potential risk to anurans based on a case study of Dutch freshwater bodies. The derived ERs revealed that threats to populations of anurans decreased in the sequence of pH, copper, diazinon, ammonium, and endosulfan. Other stressors studied were of minor importance. The method of deriving ER by combining field observation data and laboratory data provides insight into potential threats to species in their habitats and can be used to prioritize stressors, which is necessary to achieve effective management in amphibian conservation.