Long-term exposure to polycyclic musk tonalide - A potential threat to juvenile zebrafish (Danio rerio)?

Polycyclic musk compounds are commonly used in personal care products to replace expensive natural fragrances. Due to their huge consumption, they have become a part of the aquatic environment. In the present study, a two-month exposure effect of tonalide on juvenile zebrafish (Danio rerio) was investigated. We determined the vitellogenin concentration to define the potential endocrine-disrupting effect of tonalide and also analysed selected indices to evaluate the induction of oxidative stress. The environmentally relevant concentration of tonalide (i.e., 500 ng/l) caused a significant decrease in the catalase activity (P < 0.05) and a significant increase (P < 0.05) in the lipid peroxidation. An increasing lipid peroxidation was also recorded for the highest concentration group tested (i.e., 50 000 ng/l). On the other hand, no significant changes were recorded in vitellogenin in all the exposed groups. Thus, based on these results, we have not demonstrated the endocrine-disrupting activity of tonalide in zebrafish. The results of the oxidative stress indices showed a significant impairment of the antioxidant defence after the two-month tonalide exposure, which could indicate part of the adaptive response to the tonalide toxicity.

Multibiomarker Responses of Juvenile Stages of Zebrafish (Danio rerio) to Subchronic Exposure to Polycyclic Musk Tonalide.

Synthetic polycyclic musks, widely used as additives in personal care products, are present in both biotic and abiotic matrices of the aquatic environment at concentrations of ng/l to µg/l. Although they are determined at comparatively low concentrations, these levels are biologically relevant and pose a significant growing risk as stressors to aquatic organisms. The purpose of our study was to evaluate the effects of 28-day-long exposure to polycyclic musk tonalide in zebrafish juvenile stages (Danio rerio) using selected biomarkers. Environmentally relevant concentrations of tonalide caused significant changes in selected enzyme activities in the experimental groups exposed to the highest concentrations. The activity of glutathione S-transferase and lipid peroxidation increased significantly (p < 0.05) after exposure to the highest concentration (50,000 ng/l) compared with the control. A similar trend was observed in catalase activity; there was a significant increase (p < 0.05) after exposure to two highest concentrations of tonalide (5000 and 50,000 ng/l). In addition, a statistically significant decrease (p < 0.05) in glutathione reductase activity was found in the lowest test concentration of tonalide (50 ng/l). None of the tested concentrations resulted in histopathological changes in liver, kidney, skin, or gill. Furthermore, no effects on body weight, body length, specific growth rate, and behavior were observed. Our results showed that tonalide exposure induced profound changes in the activities of antioxidant and detoxifying enzymes, such changes representing an adaptive response of the fish organism to tonalide toxicity.

Effect of salicylic acid on early life stages of common carp (Cyprinus carpio).

Environmental concentrations of pharmaceutical residues are often low; nevertheless, they are designed to have biological effects at low doses. The aim of this study was to assess the effects of salicylic acid on the growth and development of common carp (Cyprinus carpio) early life stages with respect to antioxidant defence enzymes. An embryo-larval toxicity test lasting 34 days was performed according to OECD guidelines 210 (Fish, Early-life Stage Toxicity Test). The tested concentrations were 0.004, 0.04, 0.4, 4 and 20mg/l of salicylic acid. Hatching, early ontogeny, and both morphometric and condition characteristics were significantly influenced by subchronic exposure to salicylic acid. Also, changes in antioxidant enzyme activity and an increase in lipid peroxidation were observed. The LOEC value was found to be 0.004 mg/l salicylic acid. The results of our study confirm the suggestion that subchronic exposure to salicylic acid at environmental concentrations can have significant effects on aquatic vertebrates.

Integrated assessment of PAH contamination in the Czech Rivers using a combination of chemical and biological monitoring.

This study investigated polycyclic aromatic hydrocarbons (PAH) pollution of selected rivers in the Czech Republic. Integrated evaluation was carried out using combination of chemical and biological monitoring, in which we measured content of 1-hydroxypyrene (1-OHP) in chub bile and priority PAH in water samples obtained by exposing the semipermeable membrane devices at each location. The concentrations of 1-OHP in bile samples and sum of priority PAH in water sampler ranged from 6.8 ng mg protein(-1) to 106.6 ng mg protein(-1) and from 5.2 ng L(-1) to 173.9 ng L(-1), respectively. The highest levels of biliary metabolite and PAH in water were measured at the Odra River (the Bohumín site), which is located in relatively heavily industrialized and polluted region. Statistically significant positive correlation between biliary 1-OHP and sum of PAH in water was also obtained (P < 0.01, r s = 0.806).

Biochemical markers for the assessment of pollution of selected small streams in the Czech Republic.

OBJECTIVES: The objective of the presented study was to investigate levels of the most important biochemical markers in fish which were caught upstream and downstream from sites near waste water treatment plants situated at 3 selected small streams of the Czech Republic. Organic pollutants and mercury were determined in muscle tissue of fish for complex assessment. DESIGN: Levels of biochemical markers (cytochrome P450 (CYP450), ethoxyresorufin-O-deethylase (EROD), glutathione S-transferase (GST), vitellogenin (VTG)) were measured in selected tissues (liver, plasma, brain, gill and kidney) samples of brown trout. The concentrations of persistent organic pollutants (POPs) and mercury were determined in muscle samples. RESULTS: Significantly higher levels of biochemical markers (EROD, GST, VTG) were measured downstream from waste water treatment plant (WWTP) in Vlachovo Brezí (the small Libotýnský brook). Values of biochemical markers at the other localities Cerný brook and Moravice River were measured downstream from WWTP consistently or slightly lower with values of upstream. The values of POPs and mercury were in all monitored sites higher upstream compared with downstream from WWTP. The highest values of POPs and mercury were found on Cerný brook in Bruntál (more industrial and agricultural activity). CONCLUSION: The highest occurrence of selected POPs and mercury was generally upstream suggesting that small WWTP are able to partially remove these substances in those locations. But finding higher values of biochemical markers in downstream shows that there are many other substances endocrine disrupting chemicals (EDCs) that WWTP are unable to remove.

Oxidative stress responses in zebrafish Danio rerio after subchronic exposure to atrazine.

Atrazine is one of the most used pesticides all over the world and it is frequently detected in surface water. The aim of this study was to investigate if zebrafish exposure to atrazine could induce oxidative stress and changes in detoxifying system. Juvenile fish were exposed to sublethal concentrations of 0.3, 3, 30, or 90 µg L(-1) for 28 days. The level of oxidized lipids increased in experimental groups exposed to atrazine at 30 and 90 µg L(-1) compared to control. Activity of glutathione S-transferase decreased in group with the highest concentration compared to control. A significant decline was observed in catalase activity in all experimental groups compared to control. Activity of superoxide dismutase increased only in experimental group exposed to atrazine at 30 µg L(-1) compared to control. Activity of glutathione peroxidase and reductase (GR) increased in experimental groups exposed to atrazine at 0.3 (only for GR activity) and 90 µg L(-1) compared to control. Our results showed that atrazine exposure had profound influence on the oxidative stress markers and detoxifying enzyme of the exposed zebrafish. The changes in antioxidant enzyme activities could be an adaptive response to protect the fish from the atrazine-induced toxicity.

The effects of subchronic exposure to metribuzin on Danio rerio.

The aim of this study was to assess the impact of metribuzin in surface waters on fish under experimental conditions. The effects of subchronic exposure to metribuzin on fish growth and the development of histopathological changes in selected organs (gill, kidney, liver) and on activity of some biochemical markers (CYP450, EROD) in Danio rerio were investigated during a 28-day toxicity test. Juvenile growth tests were performed on D. rerio according to OECD method number 215. Fish at an initial age of 30 days were exposed to a range of metribuzin concentrations (1.5, 5, 16, 33, and 53 mg L⁻¹). Exposure to metribuzin at 53 mg L⁻¹ was associated with increased mortality. Negative effects with regard to total body weight, length, and the inhibition of specific growth rate were induced at concentrations of 33 and 53 mg L⁻¹. Histopathological examination revealed pathological lesions in the liver in pesticide-exposed fish only at the highest concentration of 53 mg L⁻¹ of metribuzin. Based on the results of growth rate, biochemical markers (CYP450, EROD), and histopathological examination, the lowest observed effect concentration (LOEC) value was 33 mg L⁻¹ and the no observed effect concentration (NOEC) value was 16 mg L⁻¹.