The impact of hydraulic fracturing fluid on two key aquatic species: the water flea, Daphnia magna, and the rainbow trout, Oncorhynchus mykiss.

• Author / Creator

  Delompre, Perrine

• Wastewater produced during hydraulic fracturing activities (termed flowback and produced water; FPW), is a complex solution containing metals, organics and high concentrations of salts. The number of reported FPW spills affecting aquatic and/or terrestrial environments has increased with the rise of hydraulic fracturing activities (especially in North America), leading to concerns regarding the effects of such spills on aquatic biota.This thesis investigates the effect of FPW on two key freshwater species, Daphnia magna and Oncorhynchus mykiss. Using a salinity-matched control (SW) which replicated the major anionic and cation salt concentrations found in the raw FPW sample, specific salinity-induced effects were differentiated from other FPW component effects (i.e. metals and organics).First, the impact of FPW on the phototactic behaviour of the freshwater water flea D. magna was investigated. Overall, effects on daphnid phototactic responses were dependent on the FPW dose and the pre-exposure history of the animal. Naïve Daphnia acutely exposed to increasing FPW concentrations displayed an erratic behaviour and faster swimming speeds in response to light stimuli, defined as an accentuated positive phototactic behaviour (i.e. aversion response). A similar response was observed in SW exposed organisms, suggesting that the dose-dependence response was likely driven by the salinity of the FPW. Interestingly, pre-exposure of Daphnia to low concentrations of FPW and SW reduced positive phototactic behaviours compared to naïve, acutely exposed Daphnia, indicating acclimation to these treatments may occur. Despite the clear effect of salinity on organism behaviour, differential phototactic responses between FPW and SW exposed Daphnia were observed. FPW and SW pre-exposures resulted in a diminution of the positive phototaxis of the organisms (i.e. decrease of their swimming speed) and a loss of aversion response. However, only Daphnia pre-exposed to SW showed signs of possible acclimation in their behavioural responses. These results indicate that salt and non-salt components of FPW differentially affect the phototactic behaviour of D. magna through distinct mechanisms of action.Second, I investigated the effects of a 28-d exposure to low FPW concentrations on the ionoregulatory physiology of O. mykiss. My results suggest that low, sub-chronic exposures to 3% FPW and SW (~3.4 ppt; below the isosmotic point of O. mykiss) do not result in ionoregulatory disturbance in fish. Following these sub-chronic exposures, concentrations of plasma ions (Na+, K+, Cl-, Ca2+, Mg2+) were unchanged regardless of treatment condition, and branchial activities of Na+-K+ ATPase and H+-type ATPase (two key osmoregulatory enzymes) similarly did not change between treatment groups. However, sub-chronic FPW exposure did cause accumulation of certain trace elements (i.e. Br and Sr) in fish plasma and modified the fish gill morphology over time. Branchial remodeling following FPW exposure was observed as a function of time, but these effects were not distinct from changes that also occurred in control groups.This work contributes to the understanding of FPW toxicity on freshwater aquatic species that inhabit environments where hydraulic fracturing practices occur and where spills of FPW are most likely. By improving our knowledge on how certain behavioural and physiological traits of organisms may be affected following exposure to FPW, this study provides important insights for FPW risk assessment development, biomonitoring of FPW spills, and minimization of post-spill environmental effects.

• Subjects / Keywords

  • Hydraulic fracturing
  • toxicology
  • rainbow trout
  • osmotic effect
  • daphnia magna
  • phototactic behaviour

• Graduation date

  Spring 2019

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-kcxf-k024

• License

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