Oil sands process-affected water impairs the olfactory system of rainbow trout (Oncorhynchus mykiss).

Oil sands process-affected water (OSPW), a byproduct of the extraction of bitumen in the surface mining of oil sands, is currently stored in massive on-site tailings ponds. Determining the potential effects of OSPW on aquatic ecosystems is of main concern to oil sands companies and legislators concerned about the reclamation of mining sites. In the present study, the interaction of OSPW with the chemosensory system of rainbow trout was studied. Using an electro-olfactography (EOG) technique, a 24 h inhibition curve was established and concentrations that inhibit the olfactory system by 20% and 80% (IC20 and IC80) were estimated at 3% and 22% OSPW, respectively. To study the interaction of exposure time and concentration along with the mechanism of the toxic effects, rainbow trout were exposed to 3% and 22% OSPW for 2, 24, and 96 h. An EOG investigation of olfactory sensitivity demonstrated a positive interaction between exposure time and concentration of OSPW concentration, because an increase in either or both elevated the inhibitory effect. To investigate whether or not structural damage of the olfactory epithelium could account for the observed inhibitory effects of OSPW on fish olfaction, the ultrastructure of the olfactory epithelium of exposed fish was investigated using scanning electron microscopy (SEM) and light microscopy (LM). The SEM micrographs showed no changes in the structure of the olfactory epithelium. The light micrographs revealed an increase in the number of mucous cells in 22% OSPW. The results of the present study demonstrated that exposure to OSPW impairs the olfactory system of rainbow trout and its effects increase gradually with increasing exposure time. The present study demonstrated that structural epithelial damage did not contribute to the inhibitory effects of OSPW on the olfactory system.

Effects of oil sands process-affected water on the respiratory and circulatory system of Daphnia magna Straus, 1820.

Millions of cubic meters of oil sands process-affected water (OSPW), the major by-product of oil sand surface mining, is currently stored in tailings ponds. The present study investigated the effects of OSPW on the respiratory and circulatory system of Daphnia magna Straus 1820. The effect of OSPW on the activity (i.e. total movement and active time) of D. magna was also studied, as it has been shown to interact with the respiratory and circulatory system. Daphniids were exposed to both 1 and 10% OSPW for acute (1-day) and chronic (10-day) exposure periods. At the end of the exposures, daphniid oxygen (O2) consumption, heart rate, hemoglobin (Hb) content and activity were investigated. In response to chronic exposure to 10% OSPW, O2 consumption of D. magna increased, while the hemoglobin content and activity were reduced in both 1 and 10% OSPW. None of the OSPW treatments changed the heart rate of the test organisms. The results of the present study suggest that in response to increasing metabolic rate caused by OSPW exposure, D. magna conserve their energy by reducing their activity and probably by recycling macromolecules (i.e. hemoglobin).

Investigating the chronic effects of oil sands process-affected water on growth and fitness of Daphnia magna Straus 1820.

The increasing amount of stored oil sands process-affected water (OSPW), a primary by-product of oil sands mining, is an environmental concern. In the present study, we investigated the chronic effects of OSPW on growth, reproduction, and macronutrient content in Daphnia magna. To do so, we exposed D. magna to 1 and 10% OSPW (a mixture of three OSPW samples provided by major oil sands mining operators in northern Alberta) for ten days. We measured the number of the neonates produced daily in each group throughout the exposure. At the end of the exposure, we measured the mass and length of the exposed daphniids and neonates. We also measured the carbohydrate, lipid, and protein content of exposed daphniids. In the 10% OSPW group, we observed a significant reduction in all of the measured endpoints except for body length and carbohydrate and protein content of exposed daphniids. In the 1% OSPW group, on the other hand, we found a reduction only in lipid content of exposed daphniids as compared to the control group. The results of the present study demonstrated that chronic exposure to 10% OSPW affects growth and fitness of D. magna, probably due to a reduction in energy intake that causes daphniids to deplete their energy reserves.

Interactive toxicity of Ni, Zn, Cu, and Cd on Daphnia magna at lethal and sub-lethal concentrations.

The toxicity of metal mixtures is currently of particular interest among aquatic toxicologists. To provide insight into whether the interaction of multiple metals is similar at different biological levels, the survival and feeding behavior of Daphnia magna were studied following exposure to four metals (Cd, Cu, Ni, Zn) and their binary and quaternary combinations. In terms of survival, Zn-Cu and Cu-Cd mixtures produced more-than-additive mortality, while Ni-Cd mixtures resulted in less-than-additive mortality. Regarding behavior, Zn-Cu and Zn-Cd mixtures produced a more-than-additive reduction in feeding rate. Four (i.e. Zn-Cu, Cu-Cd, Ni-Cd, and Zn-Cd) out of six binary mixtures in the present study interacted differently at the survival and behavioral levels, strengthening the emphasis on carefully selecting the toxicological endpoint when addressing metal mixture toxicity. The results of the present study demonstrated that metals are toxic to feeding behavior of D. magna at much lower concentrations (i.e. 27-63 times lower) compared to survival, suggesting that applying sub-lethal endpoints are required for producing protective regulations.

Determining the effect of oil sands process-affected water on grazing behaviour of Daphnia magna, long-term consequences, and mechanism.

Oil sands process-affected water (OSPW) is a byproduct of the extraction of bitumen in the surface-mining oil sands industry and is currently stored in on-site tailings ponds. OSPW from three oil sands companies were studied to capture some of the variability associated with OSPW characteristics. To investigate the effect and mechanism(s) of effect of OSPW on feeding behaviour, Daphnia magna were exposed to low OSPW concentrations for 24 h and monitored for their feeding rate, olfactory response and swimming activity. The Al and Si content, which are indicators of suspended particulate matter in D. magna exposed to OSPW were investigated using energy-dispersive X-ray (EDX) spectroscopy. In long-term experiments, effects of exposure to OSPW for 21 days on feeding behaviour, growth, and reproduction of D. magna were evaluated. Feeding rates were similar among the three exposure populations, yielding a 24 h IC50 of 5.3% OSPW. Results of behavioural assays suggest that OSPW impairs the chemosensory function and reduces the total activity of D. magna. In EDX spectroscopy, Al and Si were detected in the body of the exposed D. magna, suggesting that D. magna filter clay particles from the OSPW solution. Results of the long-term exposure showed that OSPW significantly inhibits feeding behaviour, suppresses growth, and reduces reproductive output of D. magna. There were no differences in the toxicity of the three samples of OSPW, which was in agreement with the fact that there were no differences in the species of dissolved organic compounds in the OSPW samples.

The effect of sublethal concentrations of the water-soluble fraction of crude oil on the chemosensory function of Caspian roach, Rutilus caspicus (YAKOVLEV, 1870).

The water-soluble fraction of crude oil is a complex and toxic mixture of hydrocarbons. Because aquatic organisms directly encounter it, the water-soluble fraction plays an important role in the toxicity of crude oil in aquatic environments. To determine whether fish are attracted to or avoid the water-soluble fraction, Caspian roaches (Rutilus caspicus) were exposed to different concentrations of the water-soluble fraction in a choice maze apparatus. The results showed that Caspian roaches can detect and avoid 2 mg/L of the water-soluble fraction. To study the effect of the water-soluble fraction on the olfactory function of fish, Caspian roaches were exposed to 3.2 mg/L and 16 mg/L of the water-soluble fraction for 96 h; afterward, exposed fish encountered food extract in a choice maze apparatus. The present study showed that the water-soluble fraction significantly impairs the olfactory function of roaches. To investigate the effect of olfactory system dysfunction on the feeding behavior of fish, Caspian roaches were exposed to 3.2 mg/L and 16 mg/L of the water-soluble fraction. After 4 d, 8 d, and 12 d of exposure, the feeding behavior toward the food extract was tested. The results showed that both 3.2 mg/L and 16 mg/L of the water-soluble fraction suppress the feeding behavior of Caspian roaches. The present study demonstrates that sublethal concentrations of crude oil's water-soluble fraction impair the olfactory function of fish and consequently suppress the feeding behavior.