Iurgi Salaberria

Effects of atrazine on hepatic metabolism and endocrine homeostasis in rainbow trout (Oncorhynchus mykiss).

The herbicide atrazine (ATZ) is one of the most widely used pesticides in the world and is now under scrutiny for its alleged capacity to disrupt the endocrine system. Exhibiting negligible interaction with the estrogen receptor (ER), ATZs mode of action remains to be elucidated. ATZ may act as an inducer of the enzyme aromatase, which converts androgens to estrogens, although other mechanisms should also be taken into consideration such as impairment of hepatic metabolism. Therefore we administered juvenile rainbow trout (Oncorhynchus mykiss) a dose of either 2 or 200 microg ATZ/kg, or of carrier control phosphate buffered saline (PBS) and we measured plasma concentrations of testosterone (T), 17beta-estradiol (E2) and vitellogenin (Vtg) 6 days after exposure. Simultaneously we analyzed hepatic gene expression of cytochrome P450 (CYP) 1A and pi-class glutathione S-transferase (GST-P), and catalase (CAT) activity. Although sex steroid levels showed no significant alterations, we found a dose-dependent increase in Vtg and a concomitant decrease in CYP1A. There was no effect of ATZ on GST-P mRNA levels but GST-P was positively correlated with CYP1A. Also, CYP1A was negatively correlated with liver CAT and E2, and varied with T concentrations in a hormetic manner. The results showed that ATZ can alter hepatic metabolism, induce estrogenic effects and oxidative stress in vivo, and that these effects are linked.

Multigenerational Exposure to Ocean Acidification during Food Limitation Reveals Consequences for Copepod Scope for Growth and Vital Rates

The copepod Calanus finmarchicus is a key component of northern Atlantic food webs, linking energy-transfer from phytoplankton to higher trophic levels. We examined the effect of different ocean acidification (OA) scenarios (i.e., ambient, 1080, 2080, and 3080 μatm CO2) over two subsequent generations under limited food availability. Determination of metabolic and feeding rates, and estimations of the scope for growth, suggests that negative effects observed on vital rates (ontogenetic development, somatic growth, fecundity) may be a consequence of energy budget constraints due to higher maintenance costs under high pCO2-environments. A significant delay in development rate among the parental generation animals exposed to 2080 μatm CO2, but not in the following F1 generation under the same conditions, suggests that C. finmarchicus may have adaptive potential to withstand the direct long-term effects of even the more pessimistic future OA scenarios but underlines the importance of transgenerational experiments. The results also indicate that in a more acidic ocean, increased energy expenditure through rising respiration could lower the energy transfer to higher trophic levels and thus hamper the productivity of the northern Atlantic ecosystem.

The impact of TiO2 nanoparticles on uptake and toxicity of benzo(a)pyrene in the blue mussel (Mytilus edulis).

Nanoparticles are emerging contaminants of concern. Knowledge on their environmental impacts is scarce, especially on their interactive effects with other contaminants. In this study we investigated effects of titanium dioxide nanoparticles (TiO2NP) on the blue mussel (Mytilus edulis) and determined their influence on the bioavailability and toxicity of benzo(a)pyrene (B(a)P), a carcinogenic polyaromatic hydrocarbon (PAH). Blue mussels were exposed to either TiO2NP (0.2 and 2.0 mg L(-1)) or B(a)P (20 μg L(-1)) and to the respective combinations of these two compounds. Aqueous contaminant concentrations, the uptake of Ti and B(a)P into mussel soft tissue, effects on oxidative stress and chromosomal damage were analyzed. The uncoated TiO2NP agglomerated rapidly in the seawater. The presence of TiO2NP significantly reduced the bioavailability of B(a)P, shown by lowered B(a)P concentrations in exposure tanks and in mussel tissue. The activities of antioxidant enzyme superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) were impacted by the various exposure regimes, indicating oxidative stress in the contaminant exposure groups. While SOD activity was increased only in the 0.2TiO2NP exposure group, CAT activity was enhanced in both combined exposure groups. The GPx activity was increased only in the groups exposed to the two single compounds. In hemocytes, increased chromosomal damage was detected in mussels exposed to the single compounds, which was further increased after exposure to the combination of compounds. In this study we show that the presence of TiO2NP in the exposure system reduced B(a)P uptake in blue mussels. However, since most biomarker responses did not decrease despite of the lower B(a)P uptake in combined exposures, the results suggest that TiO2NP can act as additional stressor, or potentially alters B(a)P toxicity by activation.

Modelling the dynamics of growth, development and lipid storage in the marine copepod Calanus finmarchicus

AbstractMechanistic models are essential tools for interpreting and predicting the consequences of a changing environment and stressors such as pollution on the life histories of marine organisms. Here, we apply the simple and generic energy-budget model DEBkiss to the life history of the marine copepod Calanus finmarchicus. Model modifications were needed to accommodate the copepod life cycle, which deviates in several respects from most other animals (e.g., a sudden stop of growth after the final moult). We identified an acceleration of growth in the early copepodite stages, which could be linked to an increase in the specific feeding rate of the animals. Lipid storage, an essential element of C. finmarchicus biology, was successfully captured with the reproduction buffer of the DEBkiss model. The resulting model was fitted to a detailed data set from the literature and was able to explain growth, development and lipid storage from egg to adult, at different temperatures and food availabilities, within a single consistent framework. The parameterised model could subsequently be used to elucidate the energetic constraints on gonad maturation and reproduction. Interestingly, the overhead costs for egg production seem to be substantially higher than the default value applied in DEB-based studies. The current model provides a solid basis for applications in stress ecology, although our model analysis also identified several knowledge gaps. Specifically, further research is needed to cover the dynamics of diapause and gonad maturation, to explain the dependence of maximum body size on food and temperature, and to verify the predicted high costs for maturity maintenance.

Oil droplet ingestion and oil fouling in the copepod Calanus finmarchicus exposed to mechanically and chemically dispersed crude oil

The rates of ingestion of oil microdroplets and oil fouling were investigated in the zooplankton filter-feeder Calanus finmarchicus (Gunnerus, 1770) at 3 concentrations of oil dispersions ranging from 0.25 mg/L to 5.6 mg/L. To compare responses to mechanically and chemically dispersed oil, the copepods were exposed to comparable dispersions of micron-sized oil droplets made with and without the use of a chemical dispersant (similar oil droplet size range and oil concentrations) together with a constant supply of microalgae for a period of 4 d. The filtration rates as well as accumulation of oil droplets decreased with increasing exposure concentration. Thus the estimated total amount of oil associated with the copepod biomass for the 2 lowest exposures in the range 11 mL/kg to 17 mL/kg was significantly higher than the approximately 6 mL/kg found in the highest exposure. For the 2 lowest concentrations the filtration rates were significantly higher in the presence of chemical dispersant. Furthermore, a significant increase in the amount of accumulated oil in the presence of dispersant was observed in the low exposure group.

Reproduction Dynamics in Copepods Following Exposure to Chemically and Mechanically Dispersed Crude Oil

Conflicting reports on the contribution of chemical dispersants on crude oil dispersion toxicity have been published. This can partly be ascribed to the influence of dispersants on the physical properties of the oil in different experimental conditions. In the present study the potential contribution of dispersants to the reproductive effects of dispersed crude oil in the marine copepod Calanus finmarchicus (Gunnerus) was isolated by keeping the oil concentrations and oil droplet size distributions comparable between parallel chemically dispersed (CD, dispersant:oil ratio 1:25) and mechanically dispersed oil (MD, no dispersant) exposures. Female copepods were exposed for 96 h to CD or MD in oil concentration range of 0.2-5.5 mg·L(-1) (THC, C5-C36) after which they were subjected to a 25-day recovery period where production of eggs and nauplii were compared between treatments. The two highest concentrations, both in the upper range of dispersed oil concentrations reported during spills, caused a lower initial production of eggs/nauplii for both MD and CD exposures. However, copepods exposed to mechanically dispersed oil exhibited compensatory reproduction during the last 10 days of the recovery period, reaching control level of cumulative egg and nauplii production whereas females exposed to a mixture of oil and dispersant did not.

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

ABSTRACT 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.

Endocrine and AhR-CYP1A pathway responses to the water-soluble fraction of oil in zebrafish (Danio rerio Hamilton).

Crude oil is a complex mixture of compounds of which the water-soluble fraction (WSF) is considered to be bioavailable and potentially toxic to aquatic biota. Containing numerous compounds, WSF becomes a source of multiple chemical stressors to wildlife when introduced into the environment. To study the combined effects of WSF components on aquatic biota, the model species zebrafish (Danio rerio Hamilton) was exposed for 24 or 72 h to 10 or 50% WSF solution of known composition, generated from artificially weathered North Sea crude oil. Hepatic expression of genes involved in the aryl hydrocarbon receptor-cytochrome P-450 1A (AhR-CYP1A) pathway (AhR2, AhRR1, CYP1A1) and steroidogenesis (StAR, CYP11A, 3β-HSD, CYP19A, CYP19B) was measured, as well as estrogen receptors ERα and ERβ1. Induction of CYP1A and particularly of AhRR1 was observed while ERα and steroidogenic enzymes CYP11A and 3β-HSD were downregulated. Regression analysis demonstrated a negative relationship between AhR-CYP1A pathway and endocrine transcript levels, although causality remains to be established. These findings indicate that exposure to WSF of oil disrupts steroidogenesis and may therefore constitute a potential risk for reproductive ability of aquatic organisms. In addition, it is proposed that hepatic gene expression of AhRR1 may serve as a novel biomarker of WSF exposure.

Maternal polycyclic aromatic hydrocarbon (PAH) transfer and effects on offspring of copepods exposed to dispersed oil with and without oil droplets

ABSTRACT Copepods of the genus Calanus have the potential for accumulating lipophilic oil components due to their high lipid content and found to filter and ingest oil droplets during exposure. As female copepods produce eggs at the expense of lipid storage, there is a concern for transfer of lipophilic contaminants to offspring. To assess the potential for maternal transfer of oil components, ovigerous female copepods (Calanus finmarchicus) were exposed to filtered and unfiltered oil dispersions for 4 days, collected and eggs maintained in clean seawater and hatching and gene expression examined in hatched nauplii. Oil droplet exposure contributed to polycyclic aromatic hydrocarbon (PAH) uptake in dispersion-treated adult copepods, as displayed through PAH body residue analyses and fluorescence microscopy. Applying the latter methodology, transfer of heavy PAH from copepod mothers to offspring were detected Subtle effects were observed in offspring as evidenced by a temporal reduction in hatching success appear to be occurring only when mothers were exposed to the unfiltered oil dispersions. Offspring reared in clean water through to late naupliar stages were collected for RNA extraction and preparation of libraries for high-throughput transcriptome sequencing. Differentially expressed genes were identified through pairwise comparisons between treatments. Among these, several expressed genes have known roles in responses to chemical stress including xenobiotic metabolism enzymes, antioxidants, chaperones, and components of the inflammatory response. While gene expression results suggest a transgenerational activation of stress responses, the increase in relatively small number of differentially expressed genes suggests a minor long-term effect on offspring following maternal exposure.