Bitumen extraction in the Athabasca oil sands in Alberta releases metals to the
region. In this study, I performed an uptake-elimination experiment with wood frog
tadpoles (Lithobates sylvaticus) to determine the bioaccumulation potential of metals
from exposure to MacKay River sediment, an area affected by oil sands contamination,
and to uncontaminated reference sediment. Wood frog tadpoles, Gosner stages 28-32,
were exposed to two sediments: (1) MacKay River sediment that is enriched in
petrogenic hydrocarbons from natural and anthropogenic sources; and (2) an
uncontaminated reference sediment. Tadpole exposures to sediments lasted 4 days,
followed by a depuration phase for an additional 4 days where tadpoles were allowed to
eliminate excess metals from their bodies. The metal concentrations at various time
points during the uptake and elimination phases were determined in order to define
toxicokinetic parameters, such as uptake and elimination first order rate constants,
accumulation by ingestion, and assimilation efficiencies for specific metals.
It was determined that tadpoles exposed to the MacKay sediment had higher
concentrations of Al, Co, Cu, Cr, Mg, Ni, Pb, V, and Zn throughout the uptake phase of
the study compared to tadpoles exposed to reference sediment. We also observed little to no decrease in concentrations of Al, Co, Cu, Cr, Mg, Ni, Pb, V, and Zn throughout the
elimination phase of the study. In addition, biota-sediment accumulation factors (BSAF)
revealed that Cu, Zn, Cr, and V had among the highest bioaccumulation potential in our
trials. The experiment was subsequently repeated by preventing direct contact of the
tadpoles to sediment with a screen, exposing tadpoles only to metals in water. By
comparing tadpole exposures to metals from ‘aqueous’ and ‘aqueous +sediment’ in separate trials, and by tracking sediment ingestion rates, I am able to show that sediment ingestion constitutes the primary source of metal bioaccumulation by tadpoles. Not only were metal concentrations higher in tadpoles that were ingesting sediment, but they also had greater metal uptake rates compared to tadpoles that were only exposed to contaminated water. It was also determined that assimilation efficiencies were higher in tadpoles exposed to reference sediment compared to ones exposed to MacKay River sediment. Using toxicokinetic parameters defined by the uptake-elimination experiment, I developed a computational model using STELLATM
system dynamics software to accurately estimate first order uptake and depuration rate constants for metals in exposed aquatic animals. The model estimated metal uptake and depuration kinetics with a mean relative error of 2.25 ± 0.93 % (±SE, n=9) for the uptake study and 2.53 ± 2.61 % (±SE, n=9) for the depuration study. With increased oil-sands production anticipated, we recommend continued monitoring of contaminants from oil-sands for the purpose of understanding the potential risks they may have on northern Alberta’s ecosystems.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/38156 |
| Date | 20 September 2018 |
| Creators | Moeun, Brian |
| Contributors | Blais, Jules |
| Publisher | Université d'Ottawa / University of Ottawa |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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