Effects of water accommodated fractions of crude oils and diesel on a suite of biomarkers in Atlantic cod (Gadus morhua).

The aim of this study was to characterize concentration- and time-dependent responses in juvenile Atlantic cod (Gadus morhua) following exposure for one and three weeks to the water-soluble fraction (WAF) of three weathered oils: Arabian Light crude oil (ALC), North Sea crude oil (NSC) and ship-diesel. The sum of polycyclic aromatic hydrocarbons (PAH) in water was highest after one week of exposure and within environmentally relevant concentrations. PAH metabolites in bile confirmed exposure to and uptake of PAHs. Hepatic cytochrome P450 1A (CYP1A) gene expression (mRNA quantification) increased dramatically following exposure to all three oil types (fold-change up to 165) and there was a time lag between gene and protein expression. Hepatic CYP1A protein concentration and ethoxyresorufin-O-deethylase (EROD) activity were more variable among individuals and treatments than gene expression. EROD activity in liver and gills increased in fish exposed to WAF from the two crude oils, but not in fish exposed to WAF from diesel. Exposure to diesel appeared to induce oxidative stress to a greater extent than exposure to crude oils. Other biomarkers (glutathione S-transferases, acetylcholine esterase, vitellogenin) did not appear to respond to the exposure and hence did not discriminate among oils. Biomarker responses in cod after exposure to weathered crude oils and diesel suggested that the CYP1A system and oxidative stress markers have the highest potential for discriminating among different oil types and to monitor the environmental consequences of spills.

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.

Acute and sub-lethal effects in juvenile Atlantic salmon exposed to low µg/L concentrations of Ag nanoparticles.

Silver nanoparticles (Ag-NP) are components in numerous commercial products and are discharged into the environment in quantities that are largely unknown. In the present study, juvenile Atlantic salmon were exposed to 1, 20, and 100 µg/L (48 h, static renewal) of a commercially available Ag-NP colloidal suspension in natural (soft) lake water. A solution of AgNO(3) containing 20 µg/L Ag(I) ions was also included to discriminate the effect of NPs from that of ionic silver. Furthermore, the commercial Ag-NP suspension was compared to an in-house synthesised colloidal NP suspension prepared from AgNO(3) and NaBH(4) in citrate buffer. The size distribution of Ag in all exposure solutions was characterised by 0.22 µm filtration and 10 kDa hollow fibre cross-flow ultrafiltration in combination with ICP-MS. All exposures were characterised by a relatively high proportion of Ag-NP in the colloidal size fraction 3-220 nm. For assessment of biological effects, acute toxicity, gill histopathology, blood plasma parameters (Na, Cl, glucose, haemoglobin), and gene expression of a selection of gill biomarkers were measured. Results showed that the gills accumulated Ag in all exposure groups apart from the fish exposed to 1 µg/L Ag-NP. Accumulated Ag caused concentration-dependent response increases in general stress markers such as plasma glucose and gill gene expression of heat shock protein 70. Furthermore, induction of the metallothionein A gene indicated that Ag had been internalized in the gills, whereas a concentration-dependant inhibition of Na/K ATPase expression indicated impaired osmoregulation at as low as 20 µg/L concentrations of Ag-NP. The commercial Ag-NP suspension caused acute gill lamellae necrosis at high concentrations (100 µg/L), potentially giving rise to the substantial (73%) fish mortality at this concentration. The two different Ag-NP preparations gave comparable results for several endpoints measured, but differed in MT-A induction and mortality, thus emphasising the variation in effects that may arise from different Ag-NP preparations.

Produced water extracts from North Sea oil production platforms result in cellular oxidative stress in a rainbow trout in vitro bioassay.

Produced water (PW) discharged from offshore oil industry contains chemicals known to contribute to different mechanisms of toxicity. The present study aimed to investigate oxidative stress and cytotoxicity in rainbow trout primary hepatocytes exposed to the water soluble and particulate organic fraction of PW from 10 different North Sea oil production platforms. The PW fractions caused a concentration-dependent increase in reactive oxygen species (ROS) after 1h exposure, as well as changes in levels of total glutathione (tGSH) and cytotoxicity after 96 h. Interestingly, the water soluble organic compounds of PW were major contributors to oxidative stress and cytotoxicity, and effects was not correlated to the content of total oil in PW. Bioassay effects were only observed at high PW concentrations (3-fold concentrated), indicating that bioaccumulation needs to occur to cause similar short term toxic effects in wild fish.

Oxidative stress responses in rainbow trout (Oncorhynchus mykiss) hepatocytes exposed to pro-oxidants and a complex environmental sample.

A wide range of pollutants in the aquatic environment have the capacity to induce toxic effects expressed as cellular oxidative stress. In the current study, the potential of an in vitro toxicity testing system was therefore investigated using rainbow trout (Oncorhynchus mykiss) hepatocytes to assess different endpoints of oxidative stress. The pro-oxidants CuSO(4) and paraquat were used as models for comparison to a complex environmental sample. Results following 6, 24, 48 and 96h exposure to different concentrations of these substances show cellular effects on intracellular ROS formation, glutathione levels and redox status, expression of the antioxidant enzymes superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, gamma-glutamyl-cysteine synthetase (GCS) and thioredoxin, as well as cytotoxicity parameters. The most consistent effects (maximum values within brackets), observed in dose and time parameters for both model compounds and environmental sample, were the depletion of total glutathione (9.4% of control), induced levels of oxidized glutathione (695% of control), and gene expression regulation depicted relative to the control gene beta-actin of GCS mRNA (239% of control) and catalase (29% of control). In conclusion, the responses on several antioxidant defence system parameters demonstrated the validity of the in vitro toxicity testing system. Not only could multiple effects be detected at sub-lethal exposure concentrations, but these effects also gave valuable insight to the toxic mechanisms at the molecular level.