Varved sediments in meromictic Crawford Lake consist of dark–light couplets of organic matter (primarily phytoplankton and amorphous organic matter) capped by calcite crystals. The crystals precipitate in the alkaline epilimnion between spring and fall turnover, consistent with Langelier Saturation Index calculations that predict calcite precipitation when pH and temperature exceed 7.76 and ~ 15 °C, respectively. Climate, primary production, and the pH of the epilimnion control lamina thickness: acid rain primarily affects the precipitation and accumulation of calcite crystals, whereas both endogenic calcite and authigenic organic matter are affected by climate and primary production. Thin varves, often with barely perceptible light-coloured calcite laminae were deposited between the late 1940s and mid-1970s, when the pH of the epilimnion fell slightly in response to deterioration in air and water quality associated with rapid industrialization. Conditions required for precipitation of calcite laminae were absent during the sixteenth to mid-nineteenth centuries, an interval corresponding to the Little Ice Age when no human impact affected the catchment. Varves dating from 1867 CE onwards (the Canadian Zone) facilitate the candidacy of the deep basin sediments of Crawford Lake to define the Anthropocene epoch.

Abstract Varved sediments in meromictic Crawford Lake consist of dark-light couplets of organic matter (primarily phytoplankton and amorphous organic matter) capped by calcite crystals. The crystals precipitate in the alkaline epilimnion between spring and fall turnover, consistent with Langelier Saturation Index calculations that predict calcite precipitation when pH and temperature exceed 7.76 and ~ 15°C respectively. Climate, primary production, and acid precipitation control lamina thickness: acid precipitation primarily affects the precipitation and accumulation of calcite crystals, whereas both endogenic calcite and authigenic organic matter are affected by climate and primary production. Thin varves, often with barely perceptible light-coloured calcite lamina were deposited between the late 1940s and mid-1970s, when air and water quality were impacted by rapid industrialization. Conditions required for precipitation of calcite laminae were absent during the 16th to mid-19th centuries, an interval corresponding to the Little Ice Age when no human impact occurred in the catchment. Varves dating from 1867 CE onwards (the Canadian Zone) facilitate the candidacy of the deep basin sediments of Crawford Lake to define the Anthropocene epoch.

Assemblages of dinoflagellate cysts in lakebed sediments across the deep, meromictic basin of Sluice Pond (Lynn, Massachusetts) were compared with measurements of water quality and sediment geochemistry and with testate amoeba and tintinnid assemblages. Lakebed sediments below oxygenated waters (DO > 2 mg/L) contain diverse testate amoebae, but sparse Peridinium willei-dominated dinoflagellate cyst assemblages. Sediments collected under hypoxic conditions (DO < 2 mg/L) showed higher preservation of organic carbon and nitrogen, and these deep basin sediments are characterised by diverse dinoflagellate cyst assemblages, but sieved microfossil assemblages are typically dominated by the planktonic Codonella cratera and the pseudo-planktonic Cucurbitella tricuspis. Strong inverse relationships of cysts of Peridinium willei (R-2 = 0.81) and Difflugia oblonga tests (R-2 = 0.7) with water depth are attributed to variations in bottom water oxygen concentrations. Both ecological and taphonomic factors must be considered when reconstructing palaeoenvironments from microfossil assemblages.

The toxicity of oil sands process-affected waters (OSPW) from the Athabasca Oil Sands (AOS) in northern Alberta, Canada, is related to a relatively persistent group of dissolved organic acids known as naphthenic acids (NAs). Naphthenic acids are a complex mixture of carboxylic acids, with a general formula C(n)H(2n+Z)O2, where n indicates the carbon number and Z specifies the number of rings in the molecule. The present study is the first to evaluate the potential for the selective biodegradation of NAs and the associated reduction in aquatic toxicity of 2 OSPWs, maintained under 2 different hydraulic retention times and increased nutrient availability (nitrate and phosphate), using flow-through laboratory wetland microcosms over a 52-wk test period. High-performance liquid chromatography/quadrupole time of flight-mass spectrometry analysis was used to track the changes in NA mixture profiles, or "fingerprints," in each treatment over time. Based on first-order degradation kinetics, more rapid degradation was observed for NAs that had lower carbon numbers and fewer degrees of cyclization (NA congeners with carbon numbers 11-16 and Z series -2 to -4; half-lives between 19 and 28 wk). Within the NA mixture fingerprints, the 2 most persistent groups of homologues were also identified (NAs with carbon numbers 17-20 and Z series -6 to -12; half-lives between 37 and 52 wk). The persistence of this group of NAs may aid in explaining the residual chronic toxicological response as measured by the Microtox bioassay (effective concentration for 20%), after the degradation of the more labile fractions of NA mixtures in OSPW.

Oil sands process-affected waters (OSPWs) produced during the extraction of bitumen at the Athabasca Oil Sands (AOS) located in northeastern Alberta, Canada, are toxic to many aquatic organisms. Much of this toxicity is related to a group of dissolved organic acids known as naphthenic acids (NAs). Naphthenic acids are a natural component of bitumen and are released into process water during the separation of bitumen from the oil sand ore by a caustic hot water extraction process. Using laboratory microcosms as an analogue of a proposed constructed wetland reclamation strategy for OSPW, we evaluated the effectiveness of these microcosms in degrading NAs and reducing the aquatic toxicity of OSPW over a 52-week test period. Experimental manipulations included two sources of OSPW (one from Syncrude Canada Ltd. and one from Suncor Energy Inc.), two different hydraulic retention times (HRTs; 40 and 400d), and increased nutrient availability (added nitrate and phosphate). Microcosms with a longer HRT (for both OSPWs) showed higher reductions in total NAs concentrations (64–74% NAs reduction, p<0.05) over the test period, while nutrient enrichment appeared to have little effect. A 96h static acute rainbow trout (Oncorhynchus mykiss) bioassay showed that the initial acute toxicity of Syncrude OSPW (LC50=67% v/v) was reduced (LC50>100% v/v) independent of HRT. However, EC20s from separate Microtox® bioassays were relatively unchanged when comparing the input and microcosm waters at both HRTs over the 52-week study period (p>0.05), indicating that some sub-lethal toxicity persisted under these experimental conditions. The present study demonstrated that given sufficiently long HRTs, simulated wetland microcosms containing OSPW significantly reduced total NAs concentrations and acute toxicity, but left behind a persistent component of the NAs mixture that appeared to be associated with residual chronic toxicity.

Rapid and reliable toxicity assessment of oil sands process-affected waters (OSPW) is needed to support oil sands reclamation projects. Conventional toxicity tests using whole animals are relatively slow, costly, and often subjective, while at the same time requiring the sacrifice of test organisms as is the case with lethal dosage/concentration assays. A nonlethal alternative, using fish cell lines, has been developed for its potential use in supporting oil sands reclamation planning and to help predict the viability of aquatic reclamation models such as end-pit lakes. This study employed six fish cell lines (WF-2, GFSk-S1, RTL-W1, RTgill-W1, FHML, FHMT) in 24 h viability assays for rapid fluorometric assessment of cellular integrity and functionality. Forty-nine test water samples collected from the surface of oil sands developments in the Athabasca Oil Sands deposit, north of Fort McMurray, Alberta, Canada, were evaluated in blind. Small subsample volumes (8 ml) were mixed with 2 ml of 5× concentrated exposure media and used for direct cell exposures. All cell line responses in terms of viability as measured by Alamar blue assay, correlated well with the naphthenic acids (NA) content in the samples (R (2) between 0.4519 and 0.6171; p<0.0001) when data comparisons were performed after the bioassays. NA or total acid-extractable organics group has been shown to be responsible for most of the acute toxicity of OSPW and our results further corroborate this. The multifish cell line bioassay provides a strong degree of reproducibility among tested cell lines and good relative sensitivity of the cell line bioassay as compared to available in vivo data that could lead to cost effective, high-throughput screening assays.

The fate of trace metals in pore water collected from wetland sediments and organisms exposed to petroleum coke were evaluated within in situ aquatic microcosms. Oil sands operators of Fort McMurray, Alberta, Canada produced 60 million tonnes of petroleum coke by 2008, containing elevated concentrations of sulphur and several trace metals commonly seen in oil sands materials. This material may be included in the construction of reclaimed wetlands. Microcosms were filled with a surface layer of petroleum coke over mine-waste sediments and embedded in a constructed wetland for three years to determine how these materials would affect the metal concentrations in the sediment pore water, colonizing wetland plants and benthic invertebrates. Petroleum coke treatments produced significantly elevated levels of Ni. We also found unexpectedly higher concentrations of metals in "consolidated tailings" waste materials, potentially due to the use of oil sands-produced gypsum, and higher background concentration of elements in the sediment used in the controls. A trend of higher concentrations of V, Ni, La, and Y was present in the tissues of the colonizing macrophytic alga Chara spp. Aeshnid dragonflies may also be accumulating V. These results indicate that the trace metals present in some oil sands waste materials could be taken up by aquatic macro-algae and some wetland invertebrates if these materials are included in reclaimed wetlands.

Water is integral to both operational and environmental aspects of the oil sands industry. A water treatment option based on the use of petroleum coke (PC), a by-product of bitumen upgrading, was examined as an opportunity to reduce site oil sands process-affected water (OSPW) inventories and net raw water demand. Changes in OSPW quality when treated with PC included increments in pH levels and concentrations of vanadium, molybdenum, and sulphate. Constituents that decreased in concentration after PC adsorption included total acid-extractable organics (TAO), bicarbonate, calcium, barium, magnesium, and strontium. Changes in naphthenic acids (NAs) speciation were observed after PC adsorption. A battery of bioassays was used to measure the OSPW toxicity. The results indicated that untreated OSPW was toxic towards Vibrio fischeri and rainbow trout. However, OSPW treated with PC at appropriate dosages was not acutely toxic towards these test organisms. Removal of TAO was found to be an adsorption process, fitting the Langmuir and Langmuir–Freundlich isotherm models. For TAO concentrations of 60mg/L, adsorption capacities ranged between 0.1 and 0.46mg/g. This study demonstrates that freshly produced PC from fluid cokers provides an effective treatment of OSPW in terms of key constituents' removal and toxicity reduction.

Constructed wetlands and end-pit lakes will play an important role in reclamation options for fluid tailings (OSPW/M) at surface oil sands operations. Through time and with natural bioremediation viable aquatic habitats will develop, but currently few tools are available to determine the rates of remediation in produced ecosystems. A micropaleoecological environmental proxy (thecamoebians) has been demonstrated to provide a time-averaged indicator of ecosystem health. Thecamoebian communities in sediments from both impacted and non-impacted wetlands and lakes in the vicinity of oil sands operation have been compared. An index of response to stress has been compiled with the goal of using it as a predictor of the path of remediation that will produce sustainable ecosystems. This information also provides an endpoint for remediation efforts. Thecamoebian assemblages in cores and surface samples from 63 natural lakes across the region were used to establish natural ecological ranges and remediation targets. These were compared to those present in wetland sediments impacted by oil sands materials (OSPW/M). The process-affected sites had lower thecamoebian diversity and were dominated by centropyxid taxa, whereas more abundant and diverse assemblages dominated by difflugiid taxa characterized less-impacted sites. Moreover, assemblages responded quickly to changes in OSPW/M input and to various reclamation strategies, such as nutrient input. Preliminary results suggest that thecamoebians represent proxies for gauging ecosystem health, monitoring aquatic reclamation progression and developing target endpoints. INTRODUCTION The Alberta oil sands (AOS) are one of Canada’s most economically important natural resources. Assessing and remediating potential detrimental environmental impacts to aquatic habitats resulting from sands developments in the Wood Buffalo region of northern Alberta requires innovative approaches that can follow ecological, temporal and spatial distribution of possible impacts. During oil sands processing, large volumes of water are used, with most of it being recycled from tailings retention ponds. Over time, concentrations of dissolved constituents, mainly salts and dissolved organics, associated with oil sands operations become elevated in the OSPW/M. The waters released from tailings (“free” water) in surface zones or captured within the pore spaces of tailings (sands, fines) deposits have unique character and properties relative to natural nonOSPM impacted waters. In general, freshly produced OSPW will stress biota through elevated ionic content and presence of organic-acid constituents such as low-molecular-weight naphthenic acids, but the toxic character of the OSPW has been demonstrated to dissipate over time (Harris, 2007; Neville et al., 2011). Ecological Indicators Thecamoebians (testate amoebae, arcellacea) are protists (unicellular microorganisms) that comprise an important component within the microbial trophic level of the benthic community in lakes and wetlands (Patterson and Kumar, 2000; Beyens and Meisterfeld, 2001). Species and strains are characterized by a simple sac-like decay-resistant organic test of pseudochitinous material that is variably agglutinated in different species (Patterson and Kumar, 2000; Scott et al., 2001). Thecamoebians are useful in environmental research as they are characterized by rapid generation times, and sensitivity to environmental conditions at the sediment/water interface and epibenthic zone (Neville et al., 2010a). Their abundant fossilized remains preserve a record of contaminate responses and changing environmental conditions over time (McCarthy et al., 1995; Boudreau et al., 2005). Unlike most microfossil groups, thecamoebians are resistant to dissolution in lower pH environments (Swindles et al., 2007). Variation in thecamoebian community assemblages have been successfully used in investigations of paleoclimate (Boudreau et al., 2005; McCarthy et alk., 1995), sea-level change (Scott et al., 2001), and anthropogenic impact, including that of sulphide mining in acid-sensitive lakes in Ontario (Patterson et al., 1996; Reinhardt et al., 1998; Kumar and Patterson, 2000; Patterson and Kumar, 2000) and in Finland (Kauppila et al., 2006). These latter studies led us to investigate the sensitivity of thecamoebians to the by-products of oil sands production. Wetland habitats, both constructed and opportunistic, will be important components of the reclaimed oil sands impacted landscapes, and the rate of progression from OSPM-stressed to more natural systems will be an important factor for gauging reclamation success. Simple and effective methods to monitor the early stages of remediation of these wetlands need to be developed to demonstrate a trajectory towards natural processes. This study investigates the use of benthic microbiota in assessing the effectiveness of the remediation process. To further assess the applicability of thecamoebians as biomonitors of potential oil sands industrial impact, the project aims to determine reliable methods for discriminating between anthropogenic from natural sources and ecological impacts on natural areas surrounding oil sands operations. This could assist in evaluating whether OSPW/M emanating from oil sands operations is negatively impacting local aquatic habitats and whether reclaimed aquatic systems will perform as viable components in final leaseclosure landscape. Thecamoebian populations from lakes sampled as part of this program were compared to populations found at oil sands sites where there was varying levels of stress from OSPW/M. A range in degree and timing of impacts provided various test sites that were analogous to what would be expected in aquatic reclamation options including an indication of rates of progression to target endpoints. METHODS Test Pond Study Sites Thirteen surface sediment samples were collected from the Constructed Wetland Test Facility (CWTF; located at Suncor Energy Inc.; Fig. 1; Table 1) in 2007; eight of those sites were resampled in 2008. Sediment samples for both years of study were collected using an Ekman grab sampler. The test site was comprised of four areas (Suncor CT Demonstration Study Site, Sustainable Lake South, Sustainable Lake North, and Crane Lake) that differed in construction and implementation, and each contained a series of wetlands (Fig. 1; Golder Associates Ltd., 2006). Between the sample collection of Set One (2007) and Set Two (2008), modifications were made to various CWFT sites causing increased or decreased OSPW inflow and subsequent changes in their chemistry. Natural Study Sites Surface sediments were collected from 8 lakes in August 2010 and 54 lakes in August 2011 (Fig. 2), sites were chosen to create a distal and proximal radius of natural lakes around the oil sands operation. The 2010 sample set was collected using a Glew gravity corer (Glew et al., 2001). The 2011 sample set was collected using an Ekman grab sampler. Microfossil Analysis Prior to thecamoebian analysis, 2 cc of sediment were passed through a 250 μm sieve to remove coarse organic debris and then a 37 μm sieve to remove fine organic and mineral detritus. The 37– 250 μm aliquots were subdivided for quantitative analysis using a wet splitter. The wet aliquots were subsequently examined under an Olympus SZH10 dissecting binocular microscope (40 – 80X magnification) until a statistically significant number of specimens were quantified (Patterson and Fishbein, 1989). Identification of thecamoebians followed standard reference keys (e.g. Medioli and Scott, 1983; Kumar and Dalby, 1998). Scanning electron micrograph images of common species and strains were obtained using a Tescan Vega-II XMU VP scanning electron microscope at the Carleton University SEM facility (Fig. 3).

Thecamoebian (testate amoebae) assemblages in samples collected in August 2007 and June 2008 from Suncor Energy Inc. Constructed Wetlands Test Facility, Fort McMurray, Alberta were found to respond to varying levels of oil sands process-affected water/materials (OSPW/OSPM). Oil sands process affected material is characterized by elevated conductivity and naphthenic acid concentrations, and a strong relationship was found between thecamoebian assemblages and both of these impact-indicator constituents (r 2 =0.707 and r 2 =0.743, respectively). Wetlands highly impacted by OSPM contained low-diversity assemblages dominated by centropyxid thecamoebians (Centropyxis aculeataandC. constricta) andArcella vulgaris. Less-impacted sites, in contrast, had higher relative abundance and more-diverse assemblages dominated by difflugiid thecamoebians, primarilyDifflugia oblonga,D. urceolata, andCucurbitella tricuspis. Thecamoebian assemblages responded quickly to a deliberate reduction in the rate of OSPW input to some sample sites between 2007 and 2008, with increases in species diversity and relative abundance of difflugiids. At sites with little annual change in water quality, the thecamoebian assemblages were comparable, indicating reproducibility of thecamoebians as a contamination proxy. Canonical Correspondence Analysis (CCA) revealed the strong controls of Na/(Ca+Mg), Na/SO 4 , naphthenic acids, Na, alkalinity, and conductivity on the thecamoebian communities, although many of these are intercorrelated. Rmode cluster analysis emphasized the interannual similarity of the thecamoebian faunas at the same sites and the community changes at sites where the OSPW character changed. Q-mode cluster analysis showed that four main thecamoebian strains and species (Centropyxis constricta ‘‘aerophila’’,Centropyxis aculeata‘‘discoides’’,Cucurbitella tricuspis, Difflugia oblonga‘‘glans’’) significantly influence assemblage composition. The study suggests that thecamoebians are useful environmental proxies capable of gauging the impact of oil sands materials in reclaimed areas and have the potential to monitor the progression of aquatic reclamation initiatives. They also appear to be useful in gauging the success of various reclamation mitigation options, such as fertilization. The addition of nutrients resulted in higher species diversity and greater relative abundance of difflugiid thecamoebians than at a parallel site that had not been fertilized, suggesting a faster improvement in aquatic ecosystem health with nutrient loading. The rapid generation time of these protists, together with their apparent sensitivity to OSPM, make thecamoebians useful biomonitors of the progression of aquatic reclamation in oil sands operations.

Thecamoebian (testate amoeba) communities appear to respond to a variety of chemical parameters in aquatic ecosystems impacted by oil sands operations. A seasonal study, conducted over four seasons from May 2008 to March 2009 (spring, summer, fall and winter) in a constructed aquatic environment at the Mildred Lake site of Syncrude Canada Ltd. in northeastern Alberta, identified species and strain-level variation among living (i.e., Rose Bengal-stained) thecamoebians. The changes in this epibenthic community appeared to reflect seasonal and micro-environmental changes, as little change in the porewater chemistry, composition of sediments or bottom waters was observed over the study interval. The total (living + dead) thecamoebian test assemblage remained relatively constant over the course of the study, suggesting that the fossil assemblage reflects time-averaged conditions. Some variability was, however, observed among the species composing the difflugiid population. In addition, the speed at which they respond to environmental changes emphasizes their potential usefulness as environmental indicators. This has important implications for the use of thecamoebians as paleoenvironmental indicators. The difference between living and total assemblages reflects taphonomic skewing presumably resulting from variations in preservation potential and/or selective predation of species and strains.

Thecamoebians (Testate amoebae) have proven to be valuable proxies commonly used in environmental and paleoenvironmental studies. A better understanding of their geographic distribution and environmental parameters influencing this distribution is required for further thecamoebian research. Thecamoebians were analyzed from twelve lakes spanning five drainage basins and four vegetation zones, representing a variety of environmental and limnological parameters in Alberta, Canada. Species diversity is low throughout the study sites, ranging from 1.35 to 2.17, with various strains of Difflugia oblonga, Centropyxis constricta and Centropyxis aculeata dominating the fauna. Climate, as reflected in the vegetation zones, appears to be an influencing factor on species and strain distributions. Low-diversity assemblages strongly dominated by C. aculeata and C. constricta,characterize lakes in the rocky mountain region. Slightly, more diverse assemblages dominated by D. oblonga and Cucurbitella tricuspis characterize lakes in the grassland region. The highest Thecamoebian diversity was found in both the Boreal Forest and Parkland zones. The Boreal Forest is dominated by D. oblonga together with C. constricta,C. tricuspis and C. aculeata, while the Boreal Parkland is dominated by D. oblonga along with C. constricta and C. aculeata. Key words: Thecamoebians, Testate amoebae, Biogeographic, Alberta

Black spruce (Picea mariana), white spruce (Picea glauca) and jack pine (Pinus banksiana) were inoculated with Suillus tomentosus and subjected to potassium fluoride (1 mM KF and 5 mM KF) in the presence and absence of 60 mM NaCl. The NaCl and KF treatments reduced total dry weights in jack pine and black spruce seedlings, but they did not affect total dry weights in white spruce seedlings. The addition of 60 mM NaCl to KF treatment solutions alleviated fluoride-induced needle injury in ectomycorrhizal (ECM) black spruce and white spruce, but had little effect in jack pine seedlings. Both KF and 60 mM NaCl treatments reduced E values compared with non-treated control seedlings. However, with the exception of small reductions of K(r) by NaCl treatments in black spruce, the applied KF and NaCl treatments had little effect on K(r) in ECM plants. Chloride tissue concentrations in NaCl-treated plants were not affected by the presence of KF in treatment solutions. However, shoot F concentrations in ECM black spruce and white spruce treated with 5 mM KF + 60 mM NaCl were significantly reduced compared with the 5 mM KF treatment. The results point to a possible competitive inhibition of F transport by Cl. We also suggest that the possibility that aquaporins may be involved in the transmembrane transport of F should be further investigated.

The oil sands industry in Northern Alberta produces large volumes of oil sands process water (OSPW) containing high concentrations of persistent naphthenic acids (NAs; CnH2n+ZO2). Due to the growing volumes of OSPW that need to be reclaimed, it is important to understand the fate of NAs in aquatic systems. A recent laboratory study revealed several potential markers of microbial biodegradation for NAs; thus here we examined for these signatures in field-aged OSPW on the site of Syncrude Canada Ltd. (Fort McMurray, AB). NA concentrations were lower in older OSPW; however parent NA signatures were remarkably similar among all OSPW samples examined, with no discernible enrichment of the highly cyclic fraction as was observed in the laboratory. Comparison of NA signatures in fresh oil sands ore extracts to OSPW in active settling basins, however, suggested that the least cyclic fraction (i.e. Z=0 and Z=−2 homologues) may undergo relatively rapid biodegradation in active settling basins. Further evidence for biodegradation of NAs came from a significantly higher proportion of oxidized NAs (i.e. CnH2n+ZO3+CnH2n+ZO4) in the oldest OSPW from experimental reclamation ponds. Taken together, there is indirect evidence for rapid biodegradation of relatively labile Z=0 and Z=−2 NAs in active settling basins, but the remaining steady-state fraction of NAs in OSPW appear to be very recalcitrant, with half-lives on the order of 12.8–13.6years. Alternative fate mechanisms to explain the slow disappearance of parent NAs from OSPW are discussed, including adsorption and atmospheric partitioning.

Various oil sands reclamation strategies incorporate oil sands processed material (OSPM) such as mature fine tailings (MFT), engineered tailings (consolidated tailings, CT), and tailings pond water (TPW) into reclamation components that need to develop into viable aquatic ecosystems. The OSPM will contain elevated salinity and organics such as naphthenic acids (NA) and polycyclic aromatic compounds (PAC) that can be chronically toxic to aquatic organisms depending upon levels and age. Due to the complexity of the chemical mixtures, analysis of these compounds in exposed organisms can be challenging. In this study, the stable carbon and nitrogen isotope signatures of selected invertebrates from various types of oil sands reclamation sites were analyzed to determine whether stable isotopes can be used to trace the exposure of aquatic organisms to organic constituents of OSPM. In a series of experimental reclamation ponds of similar age and size, there were trends of 13C depletion and 15N enrichment for benthic invertebrates along a gradient of increased levels of MFT and/or TPW. A survey of 16 sites revealed high δ15N values for invertebrates in aquatic systems containing MFT and CT (gypsum-treated mixes of MFT and tailings sand), which was attributed to the presence of NH4 +, a process by-product in OSPM. Findings of this study indicate a potential for the use of stable nitrogen isotopes to define exposure of biota to OSPM during environmental effects monitoring programs both in surface waters and in cases where groundwater seepage containing oil sands processed water enters surface receiving environments in the region.

One strategy for reclamation of oil sands leases in northern Alberta is the construction of lakes and wetlands by capping oil sands process-affected material (OSPM) with water. To assess this approach, experimental sites containing a range of OSPM have been constructed to monitor the evolution of the resulting aquatic habitats. Stable isotopes of carbon and nitrogen were used to assess the effects of OSPM on aquatic food webs. Carbon and nitrogen isotopic signatures of sediment, dissolved inorganic and organic carbon, particulate organic matter, periphyton, plants, plankton, aquatic invertebrates, and fish were used to assess differences related to the naphthenic acid (NA) concentration in OSPM and reference sites. NAs are a principal contaminant of concern in OSPM. Sites were grouped into low (0 to 4 mg/L), medium (4 to 15 mg/L), and high (>15 mg/L) NA concentrations. There were no significant differences in food web area or length among the three NA groupings. In most cases, carbon isotope analyses of samples from low, medium, and high NA concentration sites were not significantly different, suggesting that OSPM is not a significant contributor to food web carbon sources. Significant differences were found in nitrogen isotope signatures between low, medium, and high NA sites. Ammonia from OSPM is suggested as the main contributor to delta N-15 enrichment.

In earlier studies, we established that mycorrhizal associations protect plants against salt stress. However, elevated boron levels are often present in saline soils and little is known about the effects of boron on salt resistance of mycorrhizal plants. In the present study, we inoculated jack pine (Pinus banksiana) seedlings with Hebeloma sp., Suillus tomentosus and Wilcoxina mikolae var. mikolae to study the effects of mycorrhizal associations on seedling responses to boron and salt. Seedlings were grown in the greenhouse and subjected to 60 mM NaCl, 2 mM H3BO3 or 60 mM NaCl + 2 mM H3BO3 treatments for 4 weeks. Dry weights, shoot:root ratios and chlorophyll concentrations were higher in inoculated seedlings for all treatments compared with the non-inoculated plants. When applied with NaCl, B aggravated needle necrosis while reducing Cl concentrations in shoots of non-inoculated plants. Plants treated with 2 mM H3BO3 + 60 mM NaCl had similar concentrations of Na and B to those that were treated separately with 60 mM NaCl and 2 mM H3BO3. Plants inoculated with mycorrhizal fungi had lower shoot Na concentrations compared with non-inoculated seedlings, but showed relatively little impact from elevated B concentrations.