Calibration of an acute toxicity model for the marine crustacean, Artemia franciscana, nauplii to support oil spill effect assessments

Characterization of PAHs in environmentally relevant concentrations of crude oil WAF and its effects on enzymatic biomarkers on Artemia parthenogenetica

Oil seeps and spillage events can harm the environment in various ways. In the ocean, oil may form droplets or remain in the water column, becoming ingested by exposed species and potentially contaminating humans through seafood consumption. This study aimed to characterize and evaluate the toxicity of the water accommodated fraction (WAF) obtained from a solid soil-oil mass after the Brazilian oil spill of 2019 and its effects on enzymatic biomarkers in Artemia parthenogenetica. Cysts and nauplii were exposed to 100 %, 4 % and 0.16 % WAF for 48 h, with toxicological parameters and enzymatic activities measured. GC-MS analysis of the WAF identified 15 of the 16 EPA priority PAHs in the WAF, with ∑PAHs concentrations of ∼200 μg L-1, including toxicants like naphthalene and benzo[a]pyrene. WAF exposure did not affect hatching rate or mortality in A. parthenogenetica. On the other hand, significant increases in CAT, GPx, and GSTs activities, and cholinesterase impairment were observed in nauplii exposed to 100 % WAF compared to the control group. These results indicate that while no individual changes occurred, subindividual metabolic parameters were altered in animals exposed to 100 % WAF, suggesting activation of antioxidant defenses, increased phase II metabolic activity, and neurotoxicity, potentially impacting the development of juveniles of the tested species, and possibly of other marine species and thereby affecting marine ecosystem balance.

Exposure to individual polycyclic aromatic compounds impairs the cardiac performance of American lobster (Homarus americanus) larvae

The potential for oil spills poses a threat to marine organisms, the toxicity of which has been attributed primarily to polycyclic aromatic compounds (PACs). Predictive tools such as the target lipid model (TLM) have been developed to forecast and assess these risks. The aim of the present study was to characterize the cardiotoxicity of 10 structurally diverse PACs in American lobster (Homarus americanus) larvae by assessing heart rate following a 48 h exposure in a passive dosing system, and subsequently use the TLM framework to calculate a critical target lipid body burden (CTLBB) for bradycardia. Exposure to 8 of the 10 PACs resulted in concentration-dependent bradycardia, with phenanthrene causing the greatest effect. The TLM was able to effectively characterize bradycardia in American lobsters, and the cardiotoxic CTLBB value determined in this study is among the most sensitive endpoints included in the CTLBB database. This study is one of the first to apply the TLM to a cardiac endpoint and will improve predictive models for assessing sublethal impacts of oil spills on American lobster populations.

Community ecological response to polycyclic aromatic hydrocarbons in Baiyangdian Lake based on an ecological model

The dynamic response of a single population to chemicals can be represented by a Weibull function. However, it is unclear whether the overall response can still be represented in this manner when scaled up to the community level. In this study, we investigated the responses of biological communities to polycyclic aromatic hydrocarbons by using an ecological model of Baiyangdian Lake in northern China. The community dynamics process was divided into the following three stages. In the first stage, toxicity, played a dominant role and strong, medium, and weak species responses were observed according to the toxicity sensitivity. In the second stage, the dynamic process was dominated by the interaction strength with three alternative dynamic pathways comprising of direct response, no response, or inverse response. In the third stage, the toxicity was again dominant, and the biomasses of all species decreased to extinction. The toxicological dynamics were far more complex at the community level than those at the single species level and they were also influenced by the interaction strength as well as toxicity. The toxicological dynamic process in the community was constantly driven by the competing effects of these two forces. In addition to the total biomass, the interaction strength was identified as a suitable community-level signal because it exhibited good indicator properties regarding ecosystem steady-state transitions. However, we found that food web stability indicators were not suitable for use as community-level signals because they were not sensitive to changes in the ecosystem state. Some ecological management suggestions have been proposed, including medium to long-term monitoring, and reduction of external pollution loads and bioindicators. The results obtained in this study increase our understanding of how chemicals interfere with community dynamics, and the interaction strength and total biomass were identified as useful holistic indicators.

Changes in Temperature Alter the Toxicity of Polycyclic Aromatic Compounds to American Lobster (Homarus americanus) Larvae

Polycyclic aromatic compounds (PACs) present in the water column are considered to be one of the primary contaminant groups contributing to the toxicity of a crude oil spill. Because crude oil is a complex mixture composed of thousands of different compounds, oil spill models rely on quantitative structure-activity relationships like the target lipid model to predict the effects of crude oil exposure on aquatic life. These models rely on input provided by single species toxicity studies, which remain insufficient. Although the toxicity of select PACs has been well studied, there is little data available for many, including transformation products such as oxidized hydrocarbons. In addition, the effect of environmental influencing factors such as temperature on PAC toxicity is a wide data gap. In response to these needs, in the present study, Stage I lobster larvae were exposed to six different understudied PACs (naphthalene, fluorenone, methylnaphthalene, phenanthrene, dibenzothiophene, and fluoranthene) at three different relevant temperatures (10, 15, and 20 °C) all within the biological norms for the species during summer when larval releases occur. Lobster larvae were assessed for immobilization as a sublethal effect and mortality following 3, 6, 12, 24, and 48 h of exposure. Higher temperatures increased the rate at which immobilization and mortality were observed for each of the compounds tested and also altered the predicted critical target lipid body burden, incipient median lethal concentration, and elimination rate. Our results demonstrate that temperature has an important influence on PAC toxicity for this species and provides critical data for oil spill modeling. More studies are needed so oil spill models can be appropriately calibrated and to improve their predictive ability. Environ Toxicol Chem 2023;42:2389-2399. © 2023 SETAC.