The Dixon Team

Affiliation: University of Waterloo, Department of Biology
Principal Investigator: Dr. George Dixon
Research Associate: Dr. Andrea Farwell
Current Graduate Students: None at Present

Team Role: Dixon and Farwell are supervising and coordinating stable isotope sample analysis and interpretation with respect to carbon sources and food web transfers. Waterloo students are studying disolved organic carbon (doc) and disolved inorganic carbon (dic) interactions with bioavailability, and the effects of naphthenic acids (NA)/salinity interactions (microbial metabolism of NA, phytoplankton primary production, fathead minnow reproductive capacity).





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Research Associates

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  1. Dr. Andrea Farwell
  2. Started: 2000
  3. Research role: Factors influencing stable isotope signatures of aquatic flora and fauna in oil sands reclamation strategies.
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Past Graduate Students & Postdoctoral Fellows

 

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  1. Richard Kavanagh (Ph. D.)
  2. Completed: 2012
  3. Thesis Title: The effects of oil sands process-affected waters and their associated constituents on fathead minnow (Pimephales promelas) reproductive physiology.

Thesis Abstract: As part of their wetland reclamation initiative, oils sands developers plan to transfer oil sands processed materials (OSPM), such as naphthenic acids, salts, and polyaromatic hydrocarbons to mined-out 'end pit' lakes and then cap them with either tailings pond water or a layer of natural surface water. Previous studies with fish have suggested that tailings pond water and oil sands sediment have adverse effects on reproductive endpoints including reduced plasma steroid levels and lower gonadosomatic indices (van den Heuvel et al., 1999; Tetreault et al., 2003).

Ultimately, oil sands developers plan to establish aquatic ecosystems in end pit lakes that are expected to have the same biological productivity as the natural lakes in the region. Therefore, it is important to identify the chronic effects of OSPM on native fish species. Using the fathead minnow as a model species, Richard's research utilizes reproduction assays to determine the effects that various salts and naphthenic acid has on fish reproduction.

 

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  1. Hao Chen (M.Sc.)
  2. Completed: 2011
  3. Thesis Title: The effects of nutrient and peat amendments on oil sands reclamation wetlands: a microcosm study.

Thesis Abstract:Oil sand mining operations in Alberta, Canada produce large quantities of process water and mature fine tailing (MFT) during the bitumen extraction process. Wet landscape reclamation is one of the reclamation strategies proposed to utilize process water and MFT in the creation of aquatic reclamation environments that are economically and environmentally acceptable.

In the interest of utilizing nutrient enrichment and peat amendment to improve aquatic flora and fauna colonization in new oil sands aquatic reclamation, this microcosm study was designed to assess the phytoplankton and periphyton growth (summer 2008), as well as benthic invertebrate colonization (summer 2009). Peat amendment significantly increased the growth of phytoplankton and periphyton by providing sufficient nutrients (total nitrogen, total phosphorus and dissolved organic carbon) to the system. In reference wetland, benthic invertebrate colonization was significantly increased by utilizing sand as bottom substrate and decreased by MFT/Sand mixture as bottom substrate. In OSPM-affected wetland, benthic invertebrate colonization was not affected by utilizing MFT/Sand as bottom substrate. In comparison to OSPM-affected wetlands, reference wetland had larger number of benthic invertebrate families and higher total abundance.

In this research, experimental microcosms were constructed in three reclamation wetlands with different types of reclamation materials as the bottom substrates (sand, MFT + sand) and amendments (nutrient and/or peat) added to optimize growing conditions for phytoplankton and periphyton, thus creating a biological detrital layer over unfavourable substrates to enhance benthic invertebrate colonization. The growth estimates of phytoplankton and periphyton on MFT + sand without amendment were low in comparison to the control (water only, no substrate). In comparison to sand, MFT + sand had higher growth estimates at OSPM-affected sites, but lower growth estimates at reference site. The growth estimates of phytoplankton and periphyton on MFT + sand were significantly increased with peat amendment. Nutrient (nitrogen and phosphorus) enrichment insignificantly improved the phytoplankton and periphyton growth. Peat amendments elevated the concentrations of nitrogen, phosphorus and dissolved organic carbon in the system and maintained these high concentrations throughout the experiment period. Nutrient enrichment only temporarily (less than 3 weeks) elevated nitrogen and phosphorus levels as the nutrients added were quickly utilized by the system.



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  1. Monique Boutsivongsakd (M.Sc.)
  2. Completed: 2012
  3. Thesis Title: Seasonal & spatial trends in production and stable isotope signatures of primary producers & use by primary consumers in OSPM wetlands.

Thesis Abstract: Biomass, species composition, and productivity of primary producers in oil sands reclamation wetlands may be influenced by a variety of physical (turbidity), chemical (organic and inorganic constituents) and biological (grazing) characteristics. Leung et al. (2001) and Hayes (2005) found that phytoplankton community composition was influenced by salinity and naphthenic acids. By determining estimates of community growth (chlorophyll a) and biomass for planktonic and periphytic samples, Monique is able to evaluate the differences in oil sands reclamation strategies, specifically the presence/absence of OSPM.

Using stable isotopes (carbon, nitrogen, sulphur), Monique will estimate the incorporation of oil sands carbon sources (via microbial degradation) and contrast these carbon sources with carbon from primary production. Ultimately, her study will contribute to a better understanding of the cycling of carbon sources and utilization of carbon by primary consumers in OSPM affected wetlands.


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  1. Patricia Videla (M.Sc.)
  2. Completed: 2007
  3. Thesis Title: Examining oil sands dissolved carbon and microbial degradation using stable isotope analysis.

Thesis Abstract: Oil sands mining operations in northeastern Alberta are rapidly expanding. Upgrading and extracting the bitumen from the sand requires large volumes of water generating large quantities of oil sands process water/materials (OSPM) which is high in organic content. Some of the major organic components found in OSPM include unrecovered bitumen, polycyclic aromatic compounds (PACs), naphthenic acids (NAs) and humic acids. Concerns of acute and chronic toxicity resulting from OSPM have led to provincial legislation preventing the discharge of OSPM into local water and mandating the reclamation of areas affected by oil sands mining. To date, OSPM is stored on lease in settling basins while the mining companies evaluate reclamation strategies.

One of the reclamation strategies involves the use of wetlands constructed with differing amounts of OSPM and organic amendments such as peat. Currently, numerous wetlands, both natural and constructed, are present on oil sands leases. To determine the sustainability of these wetlands for reclamation, the assimilation and flow of carbon and nitrogen within the systems need to be defined. Stable isotope analysis can enhance this understanding. To effectively use stable isotopes in the field, there is the need to determine the changes in stable isotope values occurring from the microbial degradation of organic components such as NAs which contribute a significant portion to the dissolved organic carbon (DOC) in reclamation sites.

This study examined the microbial degradation of commercial and oil sands derived NAs by oil sands derived microbial cultures. Changes in stable isotopes values in the biomass (δ13C, δ15N), DOC and dissolved inorganic carbon (DIC) (δ13C) arising from degradation of the DOC were tracked in both static and semi-continuous tests. Utilization of commercial and oil sands derived NAs resulted in minimal change of the DOC stable isotope values. The biomass was 13C enriched for both the commercial (0.3 to 2.9 per mil (‰)) and oil sands derived NAs (3.7 to 8.5 ‰) relative to the DOC stable isotope values. DIC stable isotope values showed higher variability (-5 to +5.5 ‰). The semi-continuous tests showed biomass that was 15N enriched (3.8 to 8.4 ‰) with the assimilation of ammonium. Isotope trends established in the laboratory study provide further understanding into assimilation of carbon and nitrogen compounds in the field.

DOC and DIC concentration and carbon stable isotope values were determined for water sampled from 13 oil sands aquatic reclamation sites varying in age, construction and organic material. Both DOC and DIC concentrations were elevated in OSPM affected sites, by an average of 40 mg/L for DOC and 83 mg/L for DIC concentrations. DOC concentrations were also elevated by approximately 10 mg/L at high organic sites. δ13C DOC values were slightly 13C enriched in young sites: 0.6 ‰ compared to δ13C DOC values at the mature sites. Also, from June to July 13C enrichment (0.3 to 1.9 ‰) of the DOC for all sites was seen. Corresponding with the enrichment seen in the DOC, 13C depletion (-8.8 to -0.3 ‰) of the DIC was seen for most sites from June to July. The trends seen from June to July may be a result of the release of readily degradable organics from the spring thaw stimulating the microbial community. The baseline values determined for DOC and DIC may assist future field food web studies.

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Current and Past Undergraduate Student Projects

 

 
  1. Tsu-An Tsung
  2. Completed: 2009
  3. Thesis Title: Testate amoebae colonization in nutrient and peat amended microcosms designed to simulate oil sands reclamation.


 
  1. Kristine Kirby
  2. Completed: 2008
  3. Thesis Title: Utilization of dissolved carbon in nutrient enriched oil sands reclamation wetlands.



  1. Nicole Heerkens
  2. Completed: 2007
  3. Thesis Title: The role of nutrients in reclamation strategies for Alberta's oil sands.



  1. Angela Lau
  2. Completed: 2007
  3. Thesis Title: The effects of oil sands processed material on japanese medaka (Oryzias latipes) and blackworms (Lumbriculus variegatus).



  1. Dusha Vukosavljevic
  2. Completed: 2007
  3. Thesis Title: Photodegradation and microbial degradation of oil sands PACs and the utilization of oil sands sources by primary consumers.



  1. Deborah Kuo
  2. Completed: 2006
  3. Thesis Title: Using stable isotopes to monitor the bacterial degradation of polycyclic aromatic compounds.
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