Browsing by Author "Finlay, Kerri"

Now showing 1 - 20 of 20

Open Access
Abrupt changes in the physical and biological structure of endorheic upland lakes due to 8-m lake-level variation during the 20 th century
(Wiley, 2022-03-07) Bjorndahl, Judith A.; Gushulak, Cale A.C.; Mezzini, Stefano; Simpson, Gavin L.; Haig, Heather A.; Leavitt, Peter R; Finlay, Kerri
Climate-induced variation in lake level can affect physicochemical properties of endorheic lakes, but its consequences for phototrophic production and regime shifts are not well understood. Here, we quantified changes in the abundance and community composition of phototrophs in Kenosee and White Bear lakes, two endorheic basins in the parkland Moose Mountain uplands of southeastern Saskatchewan, Canada, which have experienced > 8 m declines in water level since ~ 1900. We hypothesized that lower water levels and warmer temperatures should manifest as increased abundance of phytoplankton, particularly cyanobacteria, and possibly trigger a regime shift to turbid conditions due to evaporative concentration of nutrients and solutes. High-resolution analysis of sedimentary pigments revealed an increase in total phototrophic abundance (as β-carotene) concurrent with lake-level decline beginning ~ 1930, but demonstrated little directional change in cyanobacteria. Instead, significant increases in obligately anaerobic purple sulfur bacteria (as okenone) occurred in both lakes during ~ 1930–1950, coeval with alterations to light environments and declines in lake level. The presence of okenone suggests that climate-induced increases in solute concentrations may have favored the formation of novel bacterial habitats where photic and anoxic zones overlapped. Generalized additive models showed that establishment of this unique habitat was likely preceded by increased temporal variance of sulfur bacteria, but not phytoplankton or cyanobacteria, suggesting that this abrupt change to physical lake structure was unique to deep-water environments. Such climate-induced shifts may become more frequent in the region due to hydrological stress on lake levels due to warming temperatures across the Northern Great Plains.
Open Access
Controls of Carbon Dioxide, Methane, and Nitrous Oxide Emissions in Natural and Constructed Agricultural Waterbodies on the Northern Great Plains
(2022-11-21) Jensen, Sydney; Webb, Jackie; Simpson, Gavin; Baulch, Helen Margaret; Finlay, Kerri
Inland waters are hotspots of greenhouse gas (GHG) emissions, and small water bodies are now well known to be particularly active in the production and consumption of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). High variability in physical, chemical, and environmental parameters affect the production of these GHG, but currently the mechanistic underpinnings are unclear, leading to high uncertainty in scaling up these fluxes. Here, we compare the relative magnitudes and controls of emissions of all three major GHG in twenty pairs of natural wetland ponds and constructed reservoirs in Canada’s largest agricultural region. While gaseous fluxes of CO2 and CH4 were comparable between the two waterbody types, CH4 ebullition was greater in wetland ponds. Carbon dioxide levels were associated primarily with metabolic indicators in both water body types, with primary productivity paramount in agricultural reservoirs, and heterotrophic metabolism a stronger correlate in wetland ponds. Methane emissions were positively driven by eutrophication in the reservoirs, while competitive inhibition by sulfur-reducing bacteria may have limited CH4 in both waterbody types. Contrary to expectations, N2O was undersaturated in both water body types, with wetlands a significantly stronger and more widespread N2O sink than were reservoirs. These results support the need for natural and constructed water bodies for regional GHG budgets and identification of GHG processing hotspots.
Open Access
Cretaceous Amber: A New Source of Bird Remains and of Palaeoecological Information in Dinosaur Bonebeds
(Faculty of Graduate Studies and Research, University of Regina, 2021-04) Cockx, Pierre Francois Dominique; Somers, Christopher; McKellar, Ryan; Velez, Maria; Finlay, Kerri; Hall, Britt
In order to reconstruct Cretaceous ecology and environments, this thesis investigates amber deposits in Myanmar and Western Canada, through chemical analyses of amber and study of the inclusions. As part of this work, I described a bird foot and a large series of feather inclusions from the amber of Myanmar. In the bird specimen, a series of osteological features and the morphology of the claws, support a systematic placement among Enantiornithes. I was able to describe delicate integumentary structures associated with the foot. This included scutellate scale feathers, a type of feather that has only been documented in Burmese amber specimens. Their distribution and relative size on the longest digit of the foot suggest a mechanosensory tactile function, and may allow us to draw parallels to some modern birds with tactile feathers on their feet. This finding strongly supports the longest digit acting as part of the feeding strategy of the bird, and fits well with previous interpretations of habitat use by enantiornithines. This dissertation demonstrates that even isolated vertebrate remains in amber are of high scientific interest. Through a detailed study of more than 180 Burmese amber samples preserving feathers, a diverse assemblage of Cretaceous feathers has been recovered. This provides the opportunity to document and investigate several structural types of feathers, ontogenetic stages, and pigmentation patterns. Based on recent work that associates feather types with skeletal remains, I was able to attribute many of the feathers to putative source animals. Although a few feathers may belong to non-avian dinosaur taxa, this survey confirmed earlier hypotheses that Enantiornithes were the dominant source of feathers in this ecosystem. The structure and pigmentation patterns reported added to larger-scale hypotheses regarding the groups present in the Cretaceous amber forest. One particular subset of ornamental feathers warranted detailed study because of its unusual structure. I determined that rachis-dominated feathers (RDFs) form a distinct morphotype characterized by a ventrally open rachis and a flexibility that was not documented previously. These results allow us to refine our evolutionary-developmental (evo-devo) models for integumentary structures in dinosaurs by providing additional data on structures preceding modern feathers. The structural features observed support a particular pathway for evolutionary development in feather subcomponents, addressing a major question in evo-devo models of feathers which have been based predominantly on modern material. A research deficit was addressed by focusing on Upper Cretaceous bonebed amber deposits of Western Canada. I established that amber can provide paleoecological, paleoenvironmental, paleoclimatic, and paleogeographic data, thus improving our knowledge of dinosaur habitats and their biota. Stable isotope analyses of amber refined our knowledge of the actual position and extant of the Western Interior Seaway (WIS) during the Late Cretaceous. A marine signal indicates the presence of remnants of the WIS near the deposits studied. Fourier-transform Infrared spectra showed that the dominant tree in the forests belonged to the Cupressaceae group. Feather fragments in Pipestone Creek amber, reveal the presence of aquatic birds (e.g., Hesperornithes and Ichthyornithes) 73 Ma, in Pachyrhinosaurus habitats. Insect inclusions yielded new species of Mymarommatidae wasp and Psocoptera which add to the fossil record and support the ecological interpretations based on amber chemistry. Ultimately, this line of research further supports paleoenvironmental hypotheses based on other sources of data. It also provided a new source of information on Cretaceous terrestrial habitats at high latitude, and a source for comparisons to other amber deposits during the latter part of the Cretaceous.
Open Access
Effects of experimental nitrogen fertilization on planktonic metabolism and CO2 flux in a hypereutrophic hardwater lake
(Public Library of Science, 2017-12-12) Bogard, Matthew J.; Finlay, Kerri; Waiser, Marley J.; Tumber, Vijay P.; Donald, Derek B.; Wiik, Emma; Simpson, Gavin L.; del Giorgio, Paul A.; Leavitt, Peter R.
Hardwater lakes are common in human-dominated regions of the world and often experience pollution due to agricultural and urban effluent inputs of inorganic and organic nitrogen (N). Although these lakes are landscape hotspots for CO2 exchange and food web carbon (C) cycling, the effect of N enrichment on hardwater lake food web functioning and C cycling patterns remains unclear. Specifically, it is unknown if different eutrophication scenarios (e.g., modest non point vs. extreme point sources) yield consistent effects on auto- and heterotrophic C cycling, or how biotic responses interact with the inorganic C system to shape responses of air-water CO2 exchange. To address this uncertainty, we induced large metabolic gradients in the plankton community of a hypereutrophic hardwater Canadian prairie lake by adding N as urea (the most widely applied agricultural fertilizer) at loading rates of 0, 1, 3, 8 or 18 mg N L-1 week-1 to 3240-L, in-situ mesocosms. Over three separate 21-day experiments, all treatments of N dramatically increased phytoplankton biomass and gross primary production (GPP) two- to six-fold, but the effects of N on autotrophs plateaued at ~3 mg N L-1. Conversely, heterotrophic metabolism increased linearly with N fertilization over the full treatment range. In nearly all cases, N enhanced net planktonic uptake of dissolved inorganic carbon (DIC), and increased the rate of CO2 influx, while planktonic heterotrophy and CO2 production only occurred in the highest N treatments late in each experiment, and even in these cases, enclosures continued to in-gas CO2. Chemical effects on CO2 through calcite precipitation were also observed, but similarly did not change the direction of net CO2 flux. Taken together, these results demonstrate that atmospheric exchange of CO2 in eutrophic hardwater lakes remains sensitive to increasing N loading and eutrophication, and that even modest levels of N pollution are capable of enhancing autotrophy and CO2 in-gassing in P-rich lake ecosystem
Open Access
Genomic and experimental insights into the ecology and evolution of transferable genetic elements
(Faculty of Graduate Studies and Research, University of Regina, 2022-08) Lerminiaux, Nicole Anne; Cameron, Andrew; Finlay, Kerri; Yost, Christopher; Zilles, Sandra; Hynes, Alexander
Bacteria have dynamic genomes that allow them to adapt and survive almost anywhere on Earth. This genetic flexibility is facilitated by mobile DNA elements, which can transfer within or between genomes independently of cell lineages and drive bacterial evolution. Mobile genetic elements influence many aspects of bacterial life by encoding and transferring antimicrobial resistance genes, pathogenicity factors, and toxin-antitoxin modules. Plasmids, integrons, and genomic islands are several types of mobile DNA elements that can carry beneficial genes which help host cells adapt to new environments or provide new ecological functions. However, much is still unknown about how mobile genetic elements persist in the environment, how they mediate cell survival, and how they impact interactions in bacterial communities. In this thesis, genomic and experimental techniques were used to investigate the ecology and evolution of mobile genetic elements at three different scales: genes, species, and ecosystems. At the gene level, I performed a literature review to determine how the main processes of horizontal gene transfer (conjugation, transduction, and natural transformation) impact antimicrobial resistance gene transmission in clinical environments. Conjugation of antimicrobial resistance gene-encoding plasmids does occur within clinics and patients, but there is less evidence for transduction and transformation. This may be due to low transfer rates or difficulty detecting the transfer of core genes with key mutations that provide resistance. In another project, I used comparative genomics to assess the evolutionary history of the Salmonella pathogenicity island SPI-1, which encodes a type three secretion system for invasion of mammalian intestinal cells and is remarkably conserved across the Salmonella genus. I defined the multiple genomic islands that comprise the mosaic structure of SPI-1, with some islands having arrived in the Salmonella clade earlier than others. Related pathogenicity islands possess homologs to SPI- 1 transcriptional regulator hilA, but are missing homologs to hilD and hilC; the high nucleotide identity between hilD and hilC suggests they may be paralogs. To assess how mobile genetic elements impact communities at the species level, I designed a synthetic multi-species community wherein only Escherichia coli can access a carbon source and Salmonella enterica must rely on cross-feeding to survive while simultaneously killing the E. coli with a plasmid-encoded colicin toxin. Despite relying on cross-feeding to survive, S. enterica consistently emerged as the dominant community member. Experimental results and mathematical modeling confirmed that the colicin liberates nutrients through cell lysis and benefits the colicin-producing population, which had not been previously described for this type of toxin. At the ecosystem level, I attempted to isolate all of the plasmids (“plasmidome”) from surface water of agricultural ponds (dugouts) to determine how the gene content changes over time using long-read DNA sequencing. However, ongoing technical difficulties caused by environmental contaminants resulted in limited DNA sequencing data and interference in enzymatic reactions during library preparation. Nevertheless, additional insights into these ecosystems were possible through 16S rRNA bacterial community profiling and qPCR of select antimicrobial resistance genes and mobile elements. Antimicrobial resistance genes are detectable and persist over time in dugouts, and regression modeling demonstrated that their abundance was explained by the abundance of the mobile integrin integrase intI1 and cattle presence. Altogether, these diverse projects have contributed new knowledge on the transmission, persistence, and ecological impact of mobile genetic elements at multiple scales (gene, species, ecosystem) by using experimental techniques and high-throughput sequencing technologies.
Open Access
Impacts of hydrologic management on the eutrophication of shallow lakes in an intensive agricultural landscape (Saskatchewan, Canada)
(Wiley, 2024-05-01) Gushulak, Cale A. C.; Chegoonian, Amir M.; Wolfe, Jared; Gray, Kristen; Stefano, Mezzini; Wissel, Bjoern; Hann, Brenda; Baulch, Helen M.; Finlay, Kerri; Leavitt, Peter R.
1. Hydrologic management of shallow lakes is often undertaken to prevent fluctua- tions in lake level, and to ensure sufficient water volume for economic, domestic, and recreational uses, but there is inconsistent evidence of whether lake-level sta- bilisation through hydrological management promotes or hinders eutrophication. 2. Here we used multi-proxy paleolimnological assessments of water quality (sedi- mentary carbon, nitrogen, total phosphorus, fossil pigments), and zooplankton community ecology (fossil Cladocera assemblages), combined with Landsat- derived estimates of lake surface area in two shallow eutrophic lakes, in the Prairies of southern Saskatchewan, Canada, to quantify how 8 decades of con- trasting hydrological management strategies (continuous or intermittent) affect primary production and phytoplankton composition. 3. Analysis revealed that irregular hydrological management of Pelican Lake led to sharp increases in primary production concomitant with lake-level decline. In contrast, continuously managed Buffalo Pound Lake, a drinking water reservoir for regional cities, exhibited slow, persistent eutrophication over decades despite active regulation of water levels. In both lakes, strong correlations of δ 15N val- ues with pigments from diazotrophic cyanobacteria (canthaxanthin) showed that N2-fixation increased during eutrophication irrespective of the timing of change. Finally, variation in fossil cladoceran density and composition reflected changes in pelagic and littoral habitats (e.g., reduced macrophyte cover) due to changes in both lake level and water quality. 4. Basin comparison shows that while hydrologic management can moderate water quality degradation due to lake-level change, it does not prevent eutrophication when nutrient influx remains high. 5. Given that regional water availability is forecast to decline in coming decades, we anticipate that continued hydrological management will be unavoidable and will be unable to improve water quality unless nutrient influx is also controlled.
Open Access
Influence of Temperature and Water Quality on Physiological and Behavioral Responses of Walleye at Catch and Release Angling Tournaments
(Faculty of Graduate Studies and Research, University of Regina, 2019-05) Gietzen, Kendra; Manzon, Richard G.; Somers, Christopher; Finlay, Kerri; Hart, Melanie; Hasler, Caleb
Walleye (Sander vitreus) is one of the most sought after freshwater fish for recreational angling in Canada. Physiological and behavioral measures of stress were used to determine if reduced live-well temperatures and improved water conditions can mitigate stress and facilitate recovery during catch and release angling tournaments. Fish were collected at tournament weigh-in stations to evaluate the effects of live-well water quality parameters and stress mitigation methods on recovery. Fish condition was assessed by measuring plasma cortisol and lactate levels, and observing behavioral cues. This study observed body flex, tail grab, and swim scores and these were determined valuable predictors of stress for Walleye. A commercially available live-well treatment reduced build-up of nitrogenous waste in live wells not replenished with lake water, which is useful while maintaining live-well water quality. High temperature, nitrogenous waste content, and poor weather conditions contributed to higher plasma cortisol and lactate levels, whereas higher temperatures contributed to lower blood glucose levels. Thus it may be best to avoid holding tournaments during the warm summer months or when high winds are forecasted. Additionally, this study shows water quality parameters are an important aspect of the live-well holding periods and tournament organizers should mandate mandatory conditions for live-wells to include continuous aeration and either continuous circulation or the use of live-well treatments depending on season; for instance live-well treatments and temperature control may be preferential over continuous circulation in warm conditions.
Open Access
Investigating population structure and resource use diversity in Lake Huron Lake (Coregonus clupeaformis) and Round (Prosopium cylindraceum) Whitefish using compound specific stable isotopes analysis
(Faculty of Graduate Studies and Research, University of Regina, 2024-04) Kotowich, Carmen Lianne Rose Dawn; Somers, Chris; Finlay, Kerri; Manzon, Richard
Aquatic thermal pollution from electricity generation, via once-through cooling systems, poses a potential threat to freshwater ecosystems. Research has shown that elevated temperatures can have adverse effects on whitefish reproduction and development, potentially leading to population decline. Despite these risks, there is limited understanding of whitefish population structure in areas affected by once-through cooling in Lake Huron. Population structure assessments are typically conducted with genetic methodologies but population mixing in Lake Huron complicates detection. In addition, genetic methodologies are not able to capture recent ecological aspects of population structure, necessitating the use of additional marker types. The stable isotopes of carbon (δ13C) and nitrogen (δ15N) are biochemical markers that reflect differences in prey, habitat, and trophic position within food webs making these isotopes valuable in differentiating ecological populations. Bulk stable isotope analysis (BSIA) has been used in previous research but interpretation is often confounded by various factors that contribute to isotopic variation. Compound specific stable isotope analysis (CSIA) of amino acids offers higherresolution information, allowing for the examination of baseline resource use and trophic position estimation for a sampled consumer. My research aimed to investigate the ecological population structure and baseline resource use diversity of spawning phase lake and round whitefish in Lake Huron by using CSIA. I evaluated the influence of sex, size, year, and sample site on baseline isotopic values and trophic position, examined baseline resource use by comparing isotopic niche size and overlap, and assessed the usefulness of additional amino acids for detecting population structure. I found extensive variation in δ13C phenylalanine values and moderate variation in δ15N phenylalanine for both species suggesting diversity in food web membership. While δ13C values were comparable by site to previous BSIA research, δ15N values showed differences, highlighting the advantage of CSIA in accurately assessing baseline resource use. Differences in baseline resource use among sites indicates differences in food web membership suggesting the presence of different ecological populations. Temporal factors, such as year, influenced baseline isotopic values, potentially indicating shifts in baseline resources or foraging strategies. Additionally, the biological factors such as sex and total length showed associations with baseline isotopic values, suggesting potential differences in foraging ecology and habitat use. Trophic position varied within sites for both species indicating diversity in generalist feeding strategies not connected to sample location. Lake and round whitefish separated into two areas of isotopic niche space, with δ13C values driving the differentiation. However, there was species overlap within these niche spaces suggesting the use of similar baseline resources or foraging within the same food webs. The depleted and enriched δ13C phenylalanine isotopic niche spaces may be connected to larger geographic regions of origin, and not connected to specific sample locations. Previous research using BSIA supports this, indicating broad differences in δ13C based on geographic region. The use of amino acids beyond phenylalanine and glutamine in ecological research using CSIA is uncommon despite their potential value. For δ13C, both essential and non-essential amino acids differentiated isotopically similar groups within species. Future investigations of baseline resource use may be enhanced by the inclusion of multiple amino acids to delineate ecological populations. For δ15N, the additional amino acids distinguished between the whitefish species. Overall, CSIA provided valuable insights into lake and round whitefish ecology, particularly in understanding spatial and temporal variations in baseline resource use and foraging behavior.
Open Access
Life history traits of Prussian carp (Carassius gibelio) in Saskatchewan, Canada: Age, growth, and reproduction on an advancing invasion front
(Faculty of Graduate Studies and Research, University of Regina, 2022-09) Menard, Jayme; Somers, Christopher; Finlay, Kerri; Manzon, Richard; Green, Stephanie
The Prussian carp (Carassius gibelio) is one of the most invasive fish species in Europe, and it was recently discovered in North America in Western Canada. Our knowledge of basic life history parameters, such as growth rate and mode of reproduction for Prussian carp in their new invasive range, is currently limited. In addition, Prussian carp were only recently discovered in Saskatchewan, but how long have they been in the province, and the stage of invasion is uncertain. Prussian carp can use two modes of reproduction: (1) gonochoristic, involving males and females; and (2) gynogenesis, whereby populations consist of only triploid females that steal sperm from other fish species. Newly introduced populations of Prussian carp tend to be all female and triploid, but their ploidy and mating system in Canada has not been determined. In addition, when and where spawning occurs in newly colonized waterways is completely unknown. Given these important knowledge gaps in fundamental aspects of Prussian carp biology, I focused on describing the life history traits of Prussian carp in Saskatchewan using a mixture of field and lab approaches. I found that Prussian carp in Saskatchewan are slow growing compared to other invasive populations worldwide, and take up to 2x as long to reach sexual maturity. The oldest fish I collected in Saskatchewan was 16 years old in Lake Diefenbaker, and 13 years old in Stockwell Lake, indicating that Prussian carp have been established in the province for many years and were undetected. Similar to well established populations in other parts of the world, Saskatchewan Prussian carp had mixed ploidies with diploid (2n), triploid (3n), and tetraploid (4n) individuals intermixed. In Lake Diefenbaker only female fish were detected, but males were present in Stockwell Lake in low quantities (0.14:1; M:F). Emergence of young of the year Prussian carp in Lake Diefenbaker began in early July and continued through August; however, most spawning in this area likely occurred during mid-June. The timing of spawning and habitat use by juvenile Prussian carp overlaps with that of a variety of native sucker and shiner species. My findings suggest that Prussian carp are well established in Saskatchewan and are likely in the invasive spread phase of invasion. They pose an immediate threat to native biota in Canada locally in Saskatchewan, and via dispersal and colonization of other locations.
Open Access
Magnitude and Regulating Factors of Carbon Dioxide, Methane, and Nitrous Oxide Concentration From Natural and Constructed Agricultural Waterbodies on the Northern Great Plains
(Faculty of Graduate Studies and Research, University of Regina, 2021-11) Jensen, Sydney Alexa; Finlay, Kerri; Leavitt, Peter; Hall, Britt; Tank, Suzanne
Greenhouse gases (GHGs), including carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), are increasing in concentration in the atmosphere. This poses a risk to the planet due to the radiative forcing of these gases which is ultimately leading to climate change. Inland waters across the globe, specifically lakes, rivers, and wetlands, are important sources, and occasional sinks, of GHGs to the atmosphere, due to the natural biogeochemical processes happening in these waterbodies. Understanding the contribution of these systems to the global GHG budget and the processes regulating the GHG emissions is important, as it helps to understand how these systems can contribute to climate change but also how climate change may influence the GHG emissions from these systems. However, relatively little is known about the contribution of GHGs of constructed waterbodies, particularly in agricultural regions receiving large amounts of nutrients (carbon, nitrogen, and phosphorus). This thesis investigates the magnitude and regulating factors of CO2, CH4, and N2O emissions in agricultural reservoirs on seasonal and diel timescales and compares constructed waterbodies to natural wetland ponds located on the same landscape. Applying generalized additive models in this thesis, I analyzed the controlling factors of CO2 (64-88% deviance explained), CH4 (75-86% deviance explained), and N2O (87-96% deviance explained) and the seasonal trends in the three GHGs (37-90% deviance explained) in agricultural reservoirs. In Chapter 2, I explored the concentrations of the GHGs on seasonal and diel timescales, and the regulating factors on GHG concentrations over a seasonal timescale. The GHGs exhibited significant seasonal trends, but no consistent trends on a diel timescale, and were regulated by a combination of biological, chemical, and physical parameters (Ch. 2). In Chapter 3, I contrasted the differences in concentration and regulating factors of GHGs in natural wetland ponds and agricultural reservoirs on the same landscape. Agricultural reservoirs and natural wetland ponds exhibited similar concentrations of all GHGs, however, the factors regulating the concentration of GHGs in these systems are different (Ch. 3). Together, these studies show that natural and constructed waterbodies located on the same landscape are important sources of GHGs, provide insight to how climate change may affect these systems, and potential opportunities to manage these systems to reduce GHG emissions, provided in Chapter 4.
Open Access
Oligotrophication of downwind boreal lakes caused by oil sands-derived enhanced nutrient deposition
(Faculty of Graduate Studies and Research, University of Regina, 2016-12) Wolfe, Jared Daniel; Wissel, Bjoern; Leavitt, Peter; Finlay, Kerri; Simpson, Gavin
Development of the Athabasca Oil Sands Region (AOSR) in northern Alberta, Canada has resulted in the substantial release of emissions, such as reactive nitrogen (Nr) species and base cations, which can fertilize downwind lakes in the boreal forest of Saskatchewan. However, to address the potential impacts of nutrient deposition on these algal communities, interpretations must occur in the context of ongoing regional climate change. Here, I use a factorial paleolimnological analysis to isolate the unique effects of AOSR emissions and climate change on lake geochemistry (C and N stable isotopes and elemental content) and algal assemblages (fossil pigments) over the past ~100 years. Surveyed lakes were either nitrogen (N)- or phosphorus (P)-limited and were located either within an impacted area receiving enhanced AOSR-derived deposition or within an unaffected reference region. Common trends from generalized additive models indicated that all algal groups declined after 1980 in P-limited lakes receiving deposition, coinciding with industrial intensification of the AOSR. In contrast, total algal abundance (as β-carotene and declining C/N ratios) as well as abundances of mixotrophic cryptophytes (alloxanthin) and unicellular cyanobacteria (echinenone, but not canthaxanthin) increased regionally in reference and impacted, N-limited lakes since the mid-1900s. Biomarkers from obligate autotrophs, and sedimentary δ13C and δ15N values, changed asynchronously among lakes, reiterating a fundamental restructuring of the algal community. These patterns suggest that regional climate change has intensified primary production in Saskatchewan boreal lakes and increased cyanobacteria and mixotrophic phytoplankton abundance. However, oligotrophication of impacted, P-limited sites suggests a change in nutrient export from the catchment. Specifically, increased terrestrial vegetation growth due to enhanced nutrient deposition likely resulted in subsequent diminishing of P export to these lakes. This study provides the first evidence of detrimental effects of industrial development on remote downwind lakes. Moreover, I outline a potential mechanism that incorporates a holistic view of how unique effects of the AOSR and climate change have influenced algal community composition over the last century in boreal SK. Careful evaluation of the current and future AOSR industrial footprint is required to fully understand the ramifications of development on Canada’s economy and environment.
Open Access
Phytoplankton-Specific Response to Enrichment of Phosphorus-Rich Surface Waters with Ammonium, Nitrate, and Urea
(Public Library of Science, 2013-01-17) Donald, Derek B.; Bogard, Matthew J.; Finlay, Kerri; Bunting, Lynda; Leavitt, Peter R.
Supply of anthropogenic nitrogen (N) to the biosphere has tripled since 1960; however, little is known of how in situ response to N fertilisation differs among phytoplankton, whether species response varies with the chemical form of N, or how interpretation of N effects is influenced by the method of analysis (microscopy, pigment biomarkers). To address these issues, we conducted two 21-day in situ mesocosm (3140 L) experiments to quantify the species- and genus-specific responses of phytoplankton to fertilisation of P-rich lake waters with ammonium (NH 4+), nitrate (NO 32), and urea ([NH 2 ]2 CO). Phytoplankton abundance was estimated using both microscopic enumeration of cell densities and high performance liquid chromatographic (HPLC) analysis of algal pigments. We found that total algal biomass increased 200% and 350% following fertilisation with NO 32 and chemically-reduced N (NH 4+, urea), respectively, although 144 individual taxa exhibited distinctive responses to N, including compound-specific stimulation (Planktothrix agardhii and NH 4+), increased biomass with chemically-reduced N alone (Scenedesmus spp., Coelastrum astroideum) and no response (Aphanizomenon flos-aquae, Ceratium hirundinella). Principle components analyses (PCA) captured 53.2–69.9% of variation in experimental assemblages irrespective of the degree of taxonomic resolution of analysis. PCA of species-level data revealed that congeneric taxa exhibited common responses to fertilisation regimes (e.g., Microcystis aeruginosa, M. flos-aquae, M. botrys), whereas genera within the same division had widely divergent responses to added N (e.g., Anabaena, Planktothrix, Microcystis). Least-squares regression analysis demonstrated that changes in phytoplankton biomass determined by microscopy were correlated significantly (p,0.005) with variations in HPLC-derived concentrations of biomarker pigments (r2 = 0.13–0.64) from all major algal groups, although HPLC tended to underestimate the relative abundance of cyanobacteria. Together, these findings show that while fertilisation of P-rich lakes with N can increase algal biomass, there is substantial variation in responses of genera and divisions to specific chemical forms of added N.
Open Access
Regulation of carbon dioxide and methane in small agricultural reservoirs: optimizing potential for greenhouse gas uptake
(Copernicus Publications, 2019-11-08) Webb, Jackie R.; Leavitt, Peter R.; Simpson, Gavin L.; Baulch, Helen M.; Haig, Heather A.; Hodder, Kyle R.; Finlay, Kerri
Small farm reservoirs are abundant in many agricultural regions across the globe and have the potential to be large contributing sources of carbon dioxide (CO2) and methane (CH4) to agricultural landscapes. Compared to natural ponds, these artificial waterbodies remain overlooked in both agricultural greenhouse gas (GHG) inventories and inland water global carbon (C) budgets. Improved understanding of the environmental controls of C emissions from farm reservoirs is required to address and manage their potential importance in agricultural GHG budgets. Here, we conducted a regional-scale survey (∼ 235 000 km2) to measure CO2 and CH4 surface concentrations and diffusive fluxes across 101 small farm reservoirs in Canada's largest agricultural area. A combination of abiotic, biotic, hydromorphologic, and landscape variables were modelled using generalized additive models (GAMs) to identify regulatory mechanisms. We found that CO2 concentration was estimated by a combination of internal metabolism and groundwater-derived alkalinity (66.5 % deviance explained), while multiple lines of evidence support a positive association between eutrophication and CH4 production (74.1 % deviance explained). Fluxes ranged from −21 to 466 and 0.14 to 92 mmol m−2 d−1 for CO2 and CH4, respectively, with CH4 contributing an average of 74 % of CO2-equivalent (CO2-e) emissions based on a 100-year radiative forcing. Approximately 8 % of farm reservoirs were found to be net CO2-e sinks. From our models, we show that the GHG impact of farm reservoirs can be greatly minimized with overall improvements in water quality and consideration to position and hydrology within the landscape.
Open Access
Revision of the Genus Hylaeus Fabricius (Hymenoptera: Colletidae) in Canada
(Faculty of Graduate Studies and Research, University of Regina, 2018-12) Oram, Ryan Jeffery; Stavrinides, John; Sheffield, Cory; Finlay, Kerri; McKellar, Ryan; Phillips, Iain
Hylaeus Fabricius (Hymenoptera, Colletidae) is a genus of bees that can be readily recognized by the relatively hairless black bodies with yellow maculations (markings) on the face and thorax, including the legs. However, species-level identification is difficult due to the maculations of many species being highly variable with respect to shape and size, often resulting in high degrees of similarity between and among species. I use a combination of morphological and genetic (using the 558bp COI sequence – the barcode gene) analyses to assess species richness and diversity for the Hylaeus found within Canada, and create a comprehensive checklist and key to the species. By combining these two approaches, we now have a better understanding of Canada’s bee fauna: 1) species richness is likely to be much higher in Hylaeus, with many morphologically distinct specimens representing unique molecular taxonomic units (MTOs) (corresponding to Barcode Index Numbers, or BINs) not matching previously published species descriptions; 2) H. mesillae and H. modestus, both species with many synonyms each, are likely multiple cryptic species; 3) validation of the species H. gaigei was accomplished through the discovery of the male (genetic match to female) that can be distinguished from morphologically similar species; 4) previously unknown morphological variable forms were found in several species, including H. gaigei, and H. mesillae; 5) based on specimens examined here, previous records of H. nevadensis and H. rudbeckiae in Canada may be due to misidentification; 6) the phylogenetic relationships of species and subgenera occurring in Canada are better understood, with genetic analyses supporting pre-established morphological characters used to assign species to their respective subgenus.
Open Access
A Riparian Buffer at 10 Years: The Effect of Black Plastic Mulch on Soil Variables, Nutirent Stocks and Tree Biomass
(Faculty of Graduate Studies and Research, University of Regina, 2021-03) Jones, Amy Lee; Gagnon, Daniel; Finlay, Kerri; Vanderwel, Mark; Farenick, Douglas; Laroque, Colin P.
Riparian zones are the interface between terrestrial and aquatic ecosystems. Riparian buffers are an important component of this interface environment because the vegetation of the buffer can provide many ecosystem services. Establishing riparian buffers on agricultural land can help reduce agricultural pollutants such as excessive nitrogen and phosphorus, but also provide opportunities to sequester carbon and produce biomass. Sampling was done after 10 years of growth in a riparian buffer of five tree species, hybrid poplar (Populus × canadensis), red ash (Fraxinus pennsylvanica), bur oak (Quercus macrocarpa), red oak (Quercus rubra) and white pine (Pinus strobus) to measure the long-term effects of black plastic mulch on soil variables, tree growth, tree nutrient sequestration and biomass production, as well as the species effect on these variables. Specifically, this study measured: (1) the physical, chemical and biological soil properties, and the fine root biomass of soils in the buffer to determine the long-term effects of black plastic mulch, and; (2) tree biomass production and the carbon and nutrient sequestration potential of the five tree species, as well as to determine if black plastic mulch can cause an increase or decrease in these variables. After 10 years, the use of black plastic mulch decreased soil organic matter, total soil carbon, total soil nitrogen, earthworm biomass and abundance. Soil NO3 concentration was three times greater under the mulch, despite higher tree growth in this treatment. This study shows the importance of the total pool of fine roots on the maintenance and enhancement of soil carbon and earthworm biomass. White pine growth was only slightly enhanced by the black plastic mulch, while red oak was the tree species that ii benefited the most from the mulch treatment, especially for survival. The mulch treatment produced a greater average tree height, survival and basal diameter than the control treatment. Foliage, branch and stem biomass were significantly higher in the mulch treatment, as were the sequestration of carbon, nitrogen, potassium, phosphorus, sulphur, magnesium and calcium. Hybrid poplar accumulated the greatest biomass of all species in all its compartments and had the highest quantity of carbon and all measured nutrients. Hybrid poplar was the best species to produce rapid tree biomass. Alternative mulching options that do not degrade important soil properties and other native tree species should be investigated in other studies to determine their value for future use in riparian buffers. The results from this study will help in designing agroforestry riparian buffers that will maximize nutrient capture and sequestration, and tree biomass production. Such riparian buffers will deliver more ecosystem services (reducing agricultural nitrogen and phosphorus input to watersheds; creating new habitats for flora and fauna) and produce wood biomass for timber or bioenergy.
Open Access
Space Use by Piscivorous Birds, Fish, and Humans on a Multi-Use Lake in Southern Saskatchewan
(Faculty of Graduate Studies and Research, University of Regina, 2021-10) Chupik, Michelle Ann; Somers, Christopher; Brigham, Mark; Finlay, Kerri; Fraser, Gail
On the Great Plains of North America, freshwater lakes are a critical resource in a dry landscape. Recreational development and use of lakes, as well as industrial and agricultural uses, may alter habitat and water quality. Consequently, it is important to understand how economically important fish species (walleye Sander vitreus; northern pike Esox Lucius; and burbot Lota lota) use lakes and identify key areas for protection and management efforts. Conflicts between humans and fish-eating birds over fisheries resources have also emerged and may be exacerbated by the limited availability of freshwater. In this context, the double-crested cormorant (Phalacrocorax auritus) and American white pelican (Pelecanus erythrorhynchos) have been targeted by anglers based on their diet, which is almost exclusively made up of fish. In contrast, the western grebe (Aechmophorus occidentalis) is a fish-eating bird of conservation concern and may be declining primarily due to human development of near-shore habitat. My research examined space use by three different user groups on Buffalo Pound Lake, in southern Saskatchewan, Canada: (1) sport fish; (2) fish-eating birds; and (3) humans (boats). Acoustic telemetry based on 30 fixed receivers showed that individuals of all 3 fish species (burbot, northern pike, walleye) were located in almost all portions of the lake at some point in time. In particular, northern pike occupied nearly the entire lake and also made long-distance movements throughout the study period. However, kernel density analysis identified the northwestern portion of the lake as a “hotspot” for all 3 fish species, with the majority of detections in undeveloped portions of the lake that were seldom used for recreation. These results need to be interpreted with caution, given the poor detection of fish on acoustic receivers for most of the study period. Point counts revealed that double-crested cormorants and American white pelicans had the highest relative densities in areas of Buffalo Pound Lake with undeveloped shorelines. Both of these bird species were often most abundant in the same northwestern portion of the lake used by sport fish, further highlighting this area as a “hotspot” for piscivorous species. In contrast, western grebe relative density was much more evenly spread across the entire lake, including areas with high levels of shoreline development and boating disturbance. The relative density of boats was highest in areas with developed shorelines, and few boats were ever detected in the “hotspot” area for fish and birds described above. My results suggest that the northwest portion of Buffalo Pound Lake needs to be a focal area for long-term habitat protection; more research is needed to determine how western grebes are interacting with humans.
Open Access
Sunlight-Induced Changes in Photosensitizing Properties of Dissolved Organic Carbon in Canadian Prairie Pothole Wetland Ponds
(Faculty of Graduate Studies and Research, University of Regina, 2021-12) Tran, Linh Nguyen Thao; Hall, Britt; Finlay, Kerri; Velez Caicedo, Maria; Casson, Nora
Dissolved organic carbon (DOC) is an important component of the global carbon cycle, acting in part as a potential source of carbon for microorganisms, support of flocculation of heavy metals and nutrients to sediments, as well as a protective barrier between ultraviolet radiation and aquatic organisms. In my thesis, chapter 1 is a literature review with general background information about the photodegradation process of DOC in Prairie Pothole Region (PPR). In chapter 2, I used an incubation experiment with light and depth as treatments to examine photodegradation impacts on the optical characterization of DOC in prairie wetland ponds at the St. Denis National Wildlife Area in central Saskatchewan, Canada. Surface water was collected from two ponds with seasonal average DOC concentrations of 71.1 mg L-1 (More-DOC Pond) and 32.7 mg L-1 (Less- DOC Pond) and filtered through 0.45μm GF/Fs into Teflon bottles that were transparent to UV light. Samples were then divided into dark and light treatments and incubated at three different depths (surface, 0.25m, and 0.5m) in situ and collected every 2 weeks for 4 months. Excitation emission matrix scans from 300nm to 800nm and absorbance at 254nm were collected on each sample. Absorbance at 254nm in More-DOC Pond and Less-DOC Pond waters decreased by 34% and 50%, respectively. We identified two fluorescence components in both ponds which corresponded to peak C and peak M in literature. Although bulk DOC concentrations did not show significant differences over time, fluorescence intensity of peak C decreased by 39% and 47%, and of peak M increased by 19% and 29%, in the More-DOC Pond and Less-DOC Pond, respectively. Increases in other fluorescence indicators such as fluorescence index (35% and 22%) and FRESH (29% and 30%) were observed in the More-DOC Pond and Less-DOC Pond, respectively. Overall, terrestrial DOC from our sampling ponds became less aromatic, more aliphatic, lower molecular weight, and lost absorptivity and fluorescence intensity after 12 weeks of incubation. Lastly, in chapter 3, I outlined the future research using absorbance and fluorescence to study DOC in multiple ponds at SDNWA seasonally as well the connection of DOC to mercury and methyl mercury in PPR. Results of this study will provide a better understanding at the optical characterizations, sources, and act as a foundation to further study on the role of DOC in methylation of mercury
Open Access
Thermal Tolerances of an Endemic Hot Spring Snail Physella wrighti Te and Clarke (Mollusca: Physidae)
(Faculty of Graduate Studies and Research, University of Regina, 2020-07) Helmond, Erika Kirsten; Finlay, Kerri; Sheffield, Cory; Hart, Mel; Heron, Jennifer; Leighton, Bruce
Physella wrighti (Te and Clarke, 1985) is an Endangered freshwater snail endemic to the Liard Hot Springs in northern British Columbia. It inhabits water temperatures from 23.5oC to 36oC and is active year-round. Despite its conservation status, little else is known about this species. To advance our understanding of P. wrighti in its environment, I investigated how water temperature affects aspects of its life history in a lab setting. I first investigated if P. wrighti would be more active in the scotophase versus the photophase at 30oC and observed no differences in activity level. I tested if P. wrighti had a preferred water temperature by allowing snails to explore a gradient of temperatures, and determined that the snails preferred 23oC. I reared snails in 13oC (cold), 23oC (warm), and 33oC (hot) water to examine if water temperature would affect the snail’s period of greatest activity, behaviour, survivability, number of egg masses produced, number of eggs per mass, egg volume, egg mass viability, and incubation period. I found no differences in activity level and no difference in behaviour except snails in hot water left the water more often and crawled farther away. Snails in the hot water experienced complete mortality with an average survival of 7 days; snails in warm and cold water survived an average of 84 and 240 days, respectively. Snails in warm water produced the most egg masses, with an average 348 masses compared to 39 and 5 masses in cold and warm water, respectively. The number of eggs per mass was greatest in the cold water, with an average 11 eggs compared to 5 and 6 eggs in warm and hot water, respectively. I found no difference in egg volume between water temperatures, but mass viability was highest in warm water. The incubation period was shortest in hot water and longest in cold water. These data suggest P. wrighti grows and survives better in water temperatures at the low end of the range observed in its current habitat and may only be tolerating the warmer water. This has implications for the ecology and conservation of this species.
Open Access
Variation in Tree Growth and Vascular Formation Across A Water-Limited Forest Landscape From 1951 to 2016
(Faculty of Graduate Studies and Research, University of Regina, 2019-01) Lopez, Eva Louisa; Vanderwel, Mark; Sauchyn, David; Weger, Harold; Finlay, Kerri; Laroque, Colin
Tree growth in sub-humid forests is influenced by environmental conditions that may differ across local topographic gradients. My study investigated how the growth of two conifer species (Pinus contorta var. latifolia and Picea glauca) varied across a range of habitats in a water-limited island forest landscape in western Canada. Historical precipitation from 1951-2016 had a positive overall effect on annual radial growth (as measured by tree rings), but the magnitude of this effect varied with proximity to a permanent water source and tree size. Mean annual precipitation had a greater positive influence on the growth of larger trees and on those growing far from water sources, a weaker positive effect on both species at intermediate distances from water, and the weakest influence on P. glauca trees growing close to water sources. These results indicate that tree growth rates may change if there is greater inter-annual variability of precipitation under climate change, though the magnitude and direction of these responses could be quite variable. The processes involved in tree growth and development can affect seasonal patterns of radial growth and wood density, which change across both space and time. I statistically partitioned the variation in four separate measures of growth (earlywood width, earlywood density, latewood width, and latewood density) across years, plots, and trees. Both ring width and wood density were more variable among individuals within sampling plots than they were among plots or between years. Most pairs of growth variables were positively correlated across years and individuals in the two species, but correlations between growth variables were mostly uncertain across sampling plots. An exploratory analysis revealed a number of tentative associations with environmental variables: temperature had a negative relationship with growth and latewood density; precipitation had a negative relationship with earlywood density; P. glauca growth was highest in aspen-dominated stands; P. contorta growth was negatively related to plot basal area; height and diameter had positive relationships with growth; age and slenderness had negative relationships with growth. A better understanding of variation in tree growth and wood density may lead to new insights into how wood production responds to environmental factors in a changing climate.
Open Access
Widespread nitrous oxide undersaturation in farm waterbodies creates an unexpected greenhouse gas sink
(National Academy of Sciences, 2019-05-14) Webb, Jackie R.; Hayes, Nicole M.; Simpson, Gavin L.; Leavitt, Peter R.; Baulch, Helen M.; Finlay, Kerri
Nitrogen pollution and global eutrophication are predicted to increase nitrous oxide (N2O) emissions from freshwater ecosystems. Surface waters within agricultural landscapes experience the full impact of these pressures and can contribute substantially to total landscape N2O emissions. However, N2O measurements to date have focused on flowing waters. Small artificial waterbodies remain greatly understudied in the context of agricultural N2O emissions. This study provides a regional analysis of N2O measurements in small (<0.01 km2) artificial reservoirs, of which an estimated 16 million exist globally. We show that 67% of reservoirs were N2O sinks (−12 to −2 μmol N2O⋅m−2⋅d−1) in Canada’s largest agricultural area, despite their highly eutrophic status [99 ± 289 µg⋅L−1 chlorophyll-a (Chl-a)]. Generalized additive models indicated that in situ N2O concentrations were strongly and nonlinearly related to stratification strength and dissolved inorganic nitrogen content, with the lowest N2O levels under conditions of strong water column stability and high algal biomass. Predicted fluxes from previously published models based on lakes, reservoirs, and agricultural waters overestimated measured fluxes on average by 7- to 33-fold, challenging the widely held view that eutrophic N-enriched waters are sources of N2O.