Microsomal monooxygenase activity in Tilapia (Oreochromis mossambicus) exposed to a bleached kraft mill effluent using different exposure systems

Ecophysiological responses of juvenile seabass (Dicentrarchus labrax) exposed to increased temperature and dietary methylmercury

The ecotoxicological effects of methylmercury (MeHg) exposure have been intensively described in literature. Yet, it is still unclear how marine biota will respond to the presence of MeHg under climate change, namely ocean warming. The present study aimed to investigate, for the first time, fish condition [Fulton's K index (K), hepatosomatic index (HIS) and brain-to-body mass ratio (BB-ratio)] and several stress-related responses in an ecologically and commercially important fish species (Dicentrachus labrax) exposed for 28days to dietary MeHg (8.0mg kg-1 dw) and temperature increase (+4°C). Results showed significant impairments on fish condition, i.e. up to 34% decrease on K, >100% increase on HIS and 44% decrease on BB-ratio, compared to control conditions. Significant changes on tissue biochemical responses were observed in fish exposed to both stressors, acting alone or combined, evidencing the relevance of assessing possible interactions between different environmental stressors in ecotoxicological studies. For instance, muscle showed to be the least affected tissue, only revealing significant alterations in GST activity of MeHg-enriched fish. On the other hand, liver exhibited a significant induction of GST (>100%) and CAT (up to 74%) in MeHg-enriched fish, regardless of temperature exposure, as well as decreased SOD activity (19%) and increased HSP70/HSC70 content (87%) in fish exposed to warming alone. Brain showed to be affected by temperature (69% of GST inhibition and >100% of increased CAT activity), MeHg (>100% of increased CAT activity, 47% of SOD inhibition and 55% of AChE inhibition), as well as by the combination of both (GST, SOD and AChE inhibition, 17%, 48% and 53%, respectively). Hence, our data provides evidences that the toxicological aspects of MeHg ca be potentiated by warmer temperatures, thus, evidencing the need for further research combining contaminants exposure and climate change effects, to better forecast ecological impacts in the ocean of tomorrow.

Assessment of pollution in sewage ponds using biomarker responses in wild African sharptooth catfish (Clarias gariepinus) in Tanzania

The interactive effects of mixed pollutants in sewage wastewater on biomarker responses were investigated using wild male African sharptooth catfish (Clarias gariepinus) in Morogoro, Tanzania. A total of 58 fish were used, of which 21 were from Mindu dam (reference site) and 22, 9 and 10 from Mafisa, Mazimbu and Mzumbe sewage ponds, respectively. Liver somatic index (LSI) and gonadosomatic index (GSI) were significantly greater (two- to threefold) and (five- to sixfold), respectively, in fish from all sewage ponds. Haemoglobin concentration and gill filament 7-ethoxyresurufin O-deethylase (EROD) activities were significantly higher (1.2-fold and twofold, respectively) in fish from Mzumbe sewage ponds than in fish from Mindu dam, whereas liver EROD activity was significantly higher in fish from Mzumbe and Mafisa sewage ponds (5-fold). A HPLC method for determination of enzymatically formed p-nitrophenyl-glucuronide (PNPG) was developed and applied to measure UDP-glucuronosyl transferase (UGT) activities that was significantly higher in fish from all sewage ponds (2-2.5-fold) than in fish from Mindu dam. Kinetic characteristics and assay dependence of UGT were studied with microsomal preparations. Metallothionein (MT) content was significantly lower (three- to fourfold) in fish from sewage ponds than in fish from Mindu dam, and corresponded with cumulative levels of cadmium, lead and mercury. Condition factor, vitellogenin (Vtg), acetylcholinesterase (AChE) activities in plasma, eyes and brain, haematocrit, plasma protein and cytosolic glutathione S-transferase (GST) activities were comparable in fish from sewage ponds and Mindu dam. Although specific pollutants other than the metals were not identified by chemical analysis, application of a suite of biomarkers in C. gariepinus demonstrated that all sewage ponds were contaminated by pollutants of public health concern.

Effects of ECF-Kraft pulp mill effluent treated with fungi (Rhizopus oryzae) on reproductive steroids and liver CYP1A of exposed goldfish (Carassius auratus)

The toxicity of bleached Kraft pulp mill effluents (BKME) is usually attributed to chemical compounds which are produced and released throughout various stages of pulp and paper production. The main objective of the present work was to detect sub-lethal responses of goldfish (Carassius auratus) to secondary treated BKME which was treated with Rhizopus oryzae. A total of 96 carps (C. auratus; 11 +/- 3 g) were exposed to different concentrations of the post-treated effluent (0, 1, 10, 25, 50, and 100%), in 28 days semi-static tests. Several biomarkers were then evaluated to assess the toxicological effects: induction of CYP1A (metabolic processes of organic compounds in liver), change in steroid profiles (11-Ketotestosterone, 17beta-estradiol), histopathology of liver and gonads and somatic indices (GSI, HSI) for endocrine disruption and other physiological disturbances. The most significant results show an induction of CYP1A in both sexes and a decrease of 17beta-estradiol concentrations in females. Histopathological changes such as liver tissue degeneration were observed in fish exposed to 50 and 100% of the BKME. Although the BKME was biologically treated there are some chemical compounds in the effluent that are capable to affect fish physiology, however, a clear evidence for endocrine disruption was not found.

Increased formation of carcinogenic PAH metabolites in fish promoted by nitrite

Nitrite (NO(2)(-)), a highly reactive chemical species, accumulates in coastal waters as a result of pollution with nitrogenous waste and/or an imbalance in the bacterial processes of nitrification and denitrification. The present study probed the impact of nitrite (NO(2)(-)) on the metabolism of polycyclic aromatic hydrocarbons (PAHs) in fish. In a laboratory experiment, exposure of euryhaline fish, Oreochromis mossambicus to industrial effluents containing PAHs in the presence of NO(2)(-) enhanced the cytochrome P450-dependent biotransformation activity determined as 7-ethoxyresorufin-O-deethylase (EROD), by nearly 36% compared to the value observed in the absence of NO(2)(-) (50.2 +/- 6.74 pmol resorufin min(-1) g(-1) liver). Fixed wavelength fluorescence measurements in bile revealed maximum enhancement to have occurred in the metabolites of benzo[a]pyrene, a carcinogenic PAH. Lasting, sublethal physiological deterioration was apparent in fish exposed simultaneously to an oil refinery effluent and NO(2)(-), from the unremittingly decreasing liver somatic index, even after the withdrawal of the contaminants.

Tissue levels and biomarkers of organic contaminants in feral and caged chub (Leuciscus cephalus) from rivers in the West Midlands, UK

The Birmingham conurbation (West Midlands, UK) has traditionally been a major centre of UK industry and population and consequently has a legacy of pollution, which is reflected in the water quality of local rivers. Three of these rivers, exhibiting good, intermediate and poor overall water quality, were the subject of a study in which the effects of contamination on hepatic biomarkers and tissue contaminant loads in feral and caged chub (Leuciscus cephalus) were investigated. Muscle polychlorinated biphenyls and organochlorine pesticides (PCBs and OCPs), as well as bile pyrene and benzo[a]pyrene-like metabolite levels, were variable in both caged and feral fish, but were generally higher in tissue from the more polluted sites. OCPs were, in most cases, higher in the feral fish than in the caged fish, although the opposite was true of bile PAH metabolites, possibly due to differences in relative accumulation rates. Hepatic CYP1A activity (via ethoxyresorufin-O-deethylase (EROD) activity) in both feral and caged fish was also generally higher at the more polluted sites. EROD activity in feral and caged fish was statistically associated with polycyclic aromatic hydrocarbon (PAH) contamination and specific PCB congeners. Other biomarkers measured (reduced glutathione in liver, and serum aspartate aminotransferase) showed little consistent evidence of relationships with water quality. The assessment of these parameters during different seasons also revealed relatively little evidence of temporal variation. Overall, the caged chub appeared to reflect the pattern of general water quality more accurately than did feral fish, particularly with respect to EROD activity and to some degree bile PAH metabolites, thus supporting their use as sentinel species. However, the fact that muscle OCPs were generally higher in the feral fish suggests that the use of feral fish may be more indicative of exposure to certain classes of contaminant, and so biological monitoring programs should be designed with such considerations in mind.

Toxic effects of pulp and paper-mill effluents on male reproductive organs and some systemic parameters in rats

The effect of pulp and paper-mill effluents on terrestrial animals was investigated using male albino rats as a test organism, under controlled laboratory conditions. Effluent consumption for 15 days caused a reduction in the relative weight of the testis (mg/100g body weight), compared to the control rats. The effects were not so pronounced in other regions of the male reproductive tract. Biochemical analysis revealed a drop in the activity of epididymal α-glucosidase in the effluent-treated animals. Although sperm collected from the cauda epididymis appeared morphologically normal, a decline in total sperm count and number of motile sperm was seen. The circulating level of testosterone in effluent-treated rats was slightly lower in some groups of rats given effluent treatment compared to controls. The level of progesterone and oestradiol, however, remained unaffected. Hematological and serological analyses suggest that effluents could produce anemia, liver and kidney dysfunction in rats. This inference stems from the altered blood cell counts, enhanced bilirubin and urea concentration in blood and high activity of serum GOT and GPT observed in effluent fed animals compared to controls. It is concluded that besides the general toxicity, the effluent affects the male reproductive system predominantly at the level of the testis.