Comparison of the reproductive and embyro-larval effects of commercial and extracted naphthenic acid mixtures in Fathead minnow (Pimephales promelas)

• Main Author: Mahaffey, Ashley
• Other Authors: de Boer, Dirk, Headley, John, Aitken, Alec
• Format: Thesis
• Language: unknown
• Published: University of Saskatchewan 2019
• Subjects: OSPW; naphthenic acids; commercial mixture; extracted mixture; fathead minnow; reproduction; embyro-larval development; Athabasca River; Fluka; Minnows
• Online Access: http://hdl.handle.net/10388/12223

To improve monitoring efforts and establish a guideline that is relevant to oil sands naphthenic acids, more information is needed to understand the composition of naphthenic acid components in raw OSPW and their role in determining toxicity. Commercial naphthenic acids have been used as a toxicological surrogate for naphthenic acids in raw OSPW. The primary objective of this research was to conduct a thorough source, pathway to receptor analysis for reproducing fish exposed to a commercial (Fluka) and an oil sands extracted naphthenic acid mixture. To improve the environmental relevance, reverse osmosis water was used to match water quality conditions in the Athabasca River. Steady-state naphthenic acid concentrations were achieved in the flow-through system design for both Fluka treatments. Naphthenic acid concentrations measured in the water were roughly half the nominal concentrations. The difference observed demonstrates the importance of measuring in-water concentrations in future toxicological assessments with oil sands naphthenic acids. This research is the first to apply high resolution mass spectrometry to detect and estimate the uptake of naphthenic acids in fish muscle tissue. Although the tissue estimates are semi-quantitative, the results are consistent with the current GC-MS method to analyse naphthenic acids in biological tissues. The reproductive and embryo-larval effects were more pronounced in fathead minnows exposed to the same nominal concentration (5 mg/L) of the commercial mixture relative to the oil sands extracted mixture. A significant decrease in cumulative egg production and larval survival and an increased deformity rate was observed in the commercial naphthenic acid exposure. No significant differences were observed in reproduction or embryo-larval development in the extracted naphthenic acid exposure. The results of the present study clearly demonstrate significant toxicological differences in population level endpoints between commercial and oil sands naphthenic acids. Toxicological data from commercial mixtures should not be used in the development of a water quality guideline for naphthenic acids extracted from raw OSPW. However, toxicological assessments with oil sands extracted mixtures are limited. Similar to the conclusion reported in the 1998 CEATAG review, currently there is insufficient information to recommend a water quality guideline for the protection of aquatic life for oil sands naphthenic acids.