Environmental science

Selenide is cited as a geochemically important selenium (Se) species, but it is unknown whether selenide is a stable aqueous ion in natural waters. The feasibility of using anoxic anion exchange chromatography (AEC) coupled to dynamic reaction cell-inductively coupled plasma-mass spectrometry to separate aqueous selenide was investigated with the goal of quantifying this anion to determine its importance in reducing waters.

It was possible to qualitatively identify selenide using AEC, but much of the aqueous selenide oxidises to Se0 faster than the separation procedure could be completed. AEC analyses of solutions containing polyselenides produced peaks for unidentified Se compounds, which have been assigned tentative structures Se2O22-, Se2O32-, and Se2O62- based on close matches in retention time to stable S compounds.

The results of this work show that aqueous selenide can be qualitatively observed in synthetic solutions using AEC, but it is unknown whether these conditions are relevant to natural waters.

Author Keywords: anoxic speciation, polyselenides, selenide, selenium geochemistry, selenium speciation, selenoselenate

This study presents a detailed assessment of the chemical speciation of aluminum and zinc in three streams of a small, acid-sensitive forested catchment on the southern edge of the Precambrian Shield.

Speciation analysis was achieved using an in-situ analytical technique known as Diffusive Gradient in Thin film (DGT) which measures labile metals, and a predictive computer algorithm (WHAM VI) which calculates metal species concentrations. Three types of DGT with different metal scavenging capabilities were used and a total of 11 deployments performed across four seasons. WHAM VI predictions showed that the organic fraction of aluminum was the main contributor to the dissolved concentrations in the main inflow stream (PC1) (~ 80 %) and the lake's outflow (PCO) (~ 75%); in the upland stream (PC1-08) the inorganic fraction contributed ~ 75%. For zinc the free ion was the single most important contributor to the dissolved concentration (< 90%) in all three streams. A comparative study of the DGT and WHAM methods showed an agreement between their inorganic concentrations during the spring season. Both methods indicate the greatest environmental impact for Al takes place during snow melt period in PCO and PC1-08 and in the summer for PC1. The greatest environmental impact for Zn predicted with WHAM VI, occurs during the spring in all three streams.

Author Keywords: Aluminum, DGT, Metal speciation, WHAM, Zinc

The objective of this thesis was to assess the influence of anthropogenic sulphur (S) and nitrogen (N) deposition, and harvesting on soil acidity and calcium (Ca2+), magnesium (Mg2+), potassium (K+) and N soil pools in plantation forest soils in Ireland. The response to reductions in anthropogenic S deposition was assessed using temporal trends in soil solution chemistry at two long-term monitoring plots--one on a blanket peat, the other on a peaty podzol. At the peat site, there was little evidence of a response to reductions in throughfall non marine sulphate (nmSO₄2-) and acidity; soil water acidity was determined by organic acids. In addition, temporal variation in soil water did not respond to that in throughfall. In the podzol, reductions in anthropogenic S and H+ deposition led to a significant improvement in soil water chemistry at 75 cm; pH increased and total aluminum (Al_tot) concentrations declined. The impact of harvest scenarios on exchangeable Ca2+, Mg2+ and K+ pools was assessed using input-output budgets at 40 sites (30 spruce, 10 pine). Harvest scenarios were stem-only harvest (SOH), stem plus branch harvest (SBH) and stem, branch and needle harvest (whole-tree harvesting; WTH). Average K+ and Mg2+ budgets were positive under these scenarios. However, exchangeable K+ pools were small and due to uncertainty in K+ budgets, could be depleted within one rotation. Average Ca2+ budgets for spruce were balanced under SOH, but negative under SBH and WTH. Nitrogen deposition was high, between 5 and 19 kg N ha-1 yr-1, but was balanced by N removal in SOH. However, N budgets were under SBH and WTH, indicating that these harvesting methods would lead to depletion of soil N over the long-term. Finally, monitoring of N cycling at a spruce plot indicated that N deposition was contributing to large NO₃- leaching, and as such the site was N saturated. However, N cycling did not fit the criteria of the N saturation hypothesis; instead leaching was directly related to N deposition and supported the model of kinetic N saturation.

Author Keywords: acidic deposition, base cations, input-output budgets, Ireland, nitrogen, whole-tree harvesting

The Serial Discontinuity Concept describes the downstream recovery of key biophysical variables below an impoundment. With the proliferation of hydropower dams to meet increasing societal demands, further refinement and understanding of the Serial Discontinuity Concept is needed to accurately predict downstream impacts and ensure the proper management of rivers. In this study, I examine SDC predictions on physical, chemical and biological recovery in regulated rivers providing evidence from 1) a comprehensive literature review and 2) a formal test using two regulated rivers in Northern Ontario. I specifically address how these changes are reflected in benthic invertebrate abundance, diversity, and community composition. The literature review and case studies support the predicted recovery of temperature, periphyton, substrate, and drift. In addition, the study suggests that two recovery gradients exist in regulated rivers: 1) a longer, thermal gradient taking up to hundreds of kilometres downstream; and 2) a shorter, resource subsidy gradient recovering within 1-4 km downstream of an impoundment. Total benthic invertebrate abundance varies considerably and depends on the degree of flow alteration and resource subsidies from the upstream reservoir. In contrast, benthic diversity is reduced below dams irrespective of dam location and operation with little recovery observed downstream. Contrary to SDC predictions, the longitudinal gradient in regulated rivers is not a compaction of functional changes seen over several stream orders in natural rivers but a response to dam design and reservoir conditions. Stoneflies and dragonflies are particularly sensitive to regulation while filter feeding invertebrates are enhanced. Ward and Stanford's (1983) Serial Discontinuity Concept is still a useful framework for testing hypotheses. Future studies should further expand the SDC through empirical estimation within the context of the landscape to gain a better scientific understanding of regulated river ecology.

Author Keywords: benthic invertebrates, dams, longitudinal, recovery, River Continuum Concept, Serial Discontinuity Concept

This thesis focuses on the design of a modelling framework consisting of loose-coupling of a sequence of spatial and process models and procedures necessary to predict future flood events for the years 2030 and 2050 in Tabasco Mexico. Temperature and precipitation data from the Hadley Centers Coupled Model (HadCM3), for those future years were downscaled using the Statistical Downscaling Model (SDSM4.2.9). These data were then used along with a variety of digital spatial data and models (current land use, soil characteristics, surface elevation and rivers) to parameterize the Soil Water Assessment Tool (SWAT) model and predict flows. Flow data were then input into the Hydrological Engineering Centers-River Analysis System (HEC-RAS) model. This model mapped the areas that are expected to be flooded based on the predicted flow values. Results from this modelling sequence generate images of flood extents, which are then ported to an online tool (ADAPT) for display. The results of this thesis indicate that with current prediction of climate change the city of Villahermosa, Tabasco, Mexico, and the surrounding area will experience a substantial amount of flooding. Therefore there is a need for adaptation planning to begin immediately.

Author Keywords: Adaptation Planning, Climate Change, Extreme Weather Events, Flood Planning, Simulation Modelling

The damage to Sudbury's landscape from over a century of smelter and logging activity has been severe and impacts well documented. However, despite their abundance in the region, wetlands have received little attention. Recent studies have identified that nutrient limitation is as much a problem as metal toxicity and highlighted not only the importance of wetlands but also the need for more detailed studies examining the role of wetlands in the recovery of lakes. The objective of this work is to characterize the spatial and temporal variability in the geochemistry of 18 wetlands (poor fens) surrounding Sudbury, Ontario. Peat and water chemistry in the wetlands exhibited large spatial and temporal variability. Copper and Ni concentrations in surface peat decreased with distance from the largest smelter in the area, but water chemistry was also strongly influenced by natural factors such as climate, groundwater and peat carbon content. Redox processes contribute greatly to temporal variation in pore-water chemistry: the August and October campaigns were characterized by higher SO4, lower pH and higher concentrations of metals such as Ni, Cu and Mn compared with the May campaign. Other factors contributing to the temporal variability in pore water chemistry include DOC production, senescence and water source. Despite the large variability, soil-solution partitioning can be explained by pH alone for some metals. Modeling is significantly improved with the addition of other variables representing dissolved organic matter quality and quantity, sulphate concentration and hydrology.

Author Keywords: metal contamination, metal mobility, organic matter quality, peatland geochemistry

Climate change has had numerous impacts on species' distributions by shifting suitable habitat to higher latitudes and elevations. These shifts pose new challenges to biodiversity management, in particular translocations, where suitable habitat is considered crucial for the reintroduced population. De-extinction is a new conservation tool, similar to reintroduction, except that the proposed candidates are extinct. However, this novel tool will be faced with similar problems from anthropogenic change, as are typical translocation efforts. Using ecological niche modelling, I measured suitability changes at translocation sites for several Holarctic mammal species under various climate change scenarios, and compared changes between release sites located in the southern, core, and northern regions of the species' historic range. I demonstrate that past translocations located in the southern regions of species' ranges will have a substantial decline in environmental suitability, whereas core and northern sites exhibited the reverse trend. In addition, lower percentages (< 50% in certain scenarios) of southern sites fall above the minimal suitability threshold for current and long-term species occurrence. Furthermore, I demonstrate that three popular de-extinction candidate species have experienced changes in habitat suitability in their historic range, owing to climate change and increased land conversion. Additionally, substantial increase in potentially suitable space is projected beyond the range-limits for all three species, which could raise concerns for native wildlife if de-extinct species are successfully established. In general, this thesis provides insight for how the selection of translocation sites can be more adaptable to continued climate change, and marks perhaps the first rigorous attempt to assess the potential for species de-extinction given contemporary and predicted changes in land use and climate.

Author Keywords: climate change, de-extinction, ecological niche models, MaxEnt, reintroduction, translocation

Abstract

Early Responses of Understory Vegetation After One Year of Above Canopy Nitrogen Additions in a Jack Pine Stand in Northern Alberta

Nicole Melong

Nitrogen (N) emissions are expected to increase in western Canada due to oil and gas extraction operations. An increase in N exposure could potentially impact the surrounding boreal forest, which has adapted and thrived under traditionally low N deposition. The majority of N addition studies on forest ecosystems apply N to the forest floor and often exclude the important interaction of the tree canopy. This research consisted of aerial NH₄NO₃ spray applications (5, 10, 15, 20, 25 kg N ha-1yr-1) by helicopter to a jack pine (Pinus banksiana Lamb.) stand in the Athabasca Oil Sands Region (AOSR) in northern Alberta, Canada. The main objective was to assess the impacts of elevated N after one year of treatment on the chemistry of understory vegetation, which included vascular plants, terricolous lichens, epiphytic lichens and a terricolous moss species. Changes in vegetation chemistry are expected to be early signs of stress and possible N saturation. Increased N availability is also thought to decrease plant secondary compound production because of a tradeoff that exists between growth and plant defense compounds when resources become available. Approximately 60% of applied N reached the ground vegetation in throughfall (TF) and stemflow (SF). Nitrate was the dominant form of N in TF in all treated plots and organic N (ON) was the dominant form of N in SF in all plots. The terricolous non-vascular species were the only understory vegetation that responded to the N treatments as N concentration increased with increased treatment. Foliar chemistry of the measured epiphytic lichens, vascular species, and jack pine was unaffected by the N treatments. Based on biomass measurements and N concentration increases, the non-vascular terricolous species appear to be assimilating the majority of TF N after one year. Vegetation from the high treatment plot (25 kg N ha-1yr-1) was compared to a jack pine forest receiving ambient high levels of N (21 kg N ha-1yr-1) due to its proximity to Syncrude mining activities. Nitrogen concentrations in plant tissues did not differ between the two sites; however, other elements and compounds differed significantly (Ca, Mg, Al, Fe). After one year of experimental N application, there were no environmental impacts consistent with the original N saturation hypothesis.

Author Keywords: Athabasca Oil Sands Region, Canopy Interactions, Jack Pine, Nitrogen, Secondary Chemistry, Understory Vegetation

In this study, I investigate the effects of nitrogen (N) and phosphorus (P) on the nutritional stoichiometry and growth of filamentous green algae of the family Zygnemataceae in situ and ex situ. I found a mean of Carbon (C):N:P ratio of 1308:66:1 for populations growing in the Kawartha Lakes of southern Ontario during the summer of 2012. FGA stoichiometry was variable, with much of the variation in algal P related to sediment P (p < 0.005, R2 = 0.58). Despite large variability in their cellular nutrient stoichiometry, laboratory analysis revealed that Mougeotia growth rates remained relatively consistent around 0.28 day-1. In addition, Mougeotia was found to be weakly homeostatic with respect to TDN:TDP supply (1/HNP = 0.32). These results suggest that FGA stoichiometry and growth rates are affected by sediment and water N and P. However, they will likely continue to grow slowly throughout the summer despite variable nutrient supply.

Author Keywords: Chlorophyll concentration, Filamentous algae, Growth rate, Homeostatic regulation, Nutritional stoichiometry

Theoretical work on community recovery, development, stability, and resistance to species invasions has outpaced experimental field research. There is also a need for better integration between ecological theory and the practice of ecological restoration. This thesis investigates the dynamics of community assembly following peat mining and subsequent restoration efforts at Canada's most southerly raised bog. It examines mechanisms underlying plant community changes and tests predictions arising from the Dynamic Environmental Filter Model (DEFM) and the Fluctuating Resource Hypothesis (FRH). Abiotic, biotic and dispersal filters were modified to test a conceptual model of assembly for Wainfleet Bog. Hydrology was manipulated at the plot scale across multiple nutrient gradients, and at the whole bog scale using peat dams. Trends in time series of hydrological variables were related to restoration actions and uncontrolled variables including precipitation, evapotranspiration and arrival of beaver. Impacts of a changing hydrology on the developing plant community were compared with those from cutting the invasive Betula pendula. Transplanting experiments were used to examine species interactions within primary and secondary successional communities. Seedlings of B. pendula and the native Betula papyrifera were planted together across a peat volumetric water content (VWC) gradient. Impacts of beaver dams were greater than those of peat dams and their relative importance was greatest during periods of drought. Cutting of B.pendula had little effect on the secondary successional plant community developing parallel to blocked drains. Phosphorus was the main limiting nutrient with optimum levels varying substantially between species. Primary colonisers formed a highly stable, novel plant community. Stability was due to direct and indirect facilitative interactions between all species. Reduction in frost heaving was the major mechanism behind this facilitation. Interactions within the secondary successional community were mostly competitive, driven by light and space availability. However, restricted dispersal rather than competition limited further species recruitment. Predictions based on the DEFM were partially correct. A splitting of this model's biotic filter into competition and facilitation components is proposed. There was little support for the FRH based on nutrient levels and VWC. B. pendula had higher germination and growth rates, tolerance to a wider range of peat VWCs and a greater resistance to deer browsing than native birch. Peat mining, combined with restoration actions and the arrival of beaver has moved much of the bog back to an earlier successional stage circa 350+ years BP. Evidence points to B. pendula being a "back-seat driver" in the ecosystem recovery process. Indirect facilitation of a native by an exotic congener, mediated through herbivory, has not been described previously. Shifts in relative contributions of facilitation, competition and dispersal limitations to community assembly may be useful process-oriented measures for gauging progress in restoration.

Author Keywords: Betula pendula, community assembly, competition, facilitation, peatland, restoration