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Climate change models for continental regions of North America include reduced growing season precipitation and a “repackaging” of rainfall into fewer but larger events. Water and nutrients (NPK) have individually been proven to be a limiting resource on plant growth and determinants of competition in many grassland systems, however their interacting effects remain relatively unknown. My study will examine the effects of water and nutrient availability alone, and their combined influences on above-ground biomass production and functional group composition which could provide fundamental insight into the functioning of a mesic temperate old field meadow in southeastern Ontario. Total and graminoid above-ground biomass was significantly higher in the reduced precipitation treatment compared to the added and ambient precipitation treatments, whereas legumes and other forbs had the highest above-ground biomass in the added precipitation treatment. Below-ground processes such as microbial activity and root systems may have been enhanced under rainout shelters for graminoids, compared to legumes which were possibly able to fix nitrogen more efficiently in added water plots. Rainout shelters acting as microclimates, such as by reducing wind speed, may have created ideal conditions for the point-frame method, which could explain the highest above-ground biomass in the reduced water treatment. Soil moisture was significantly lower in the reduced precipitation treatment compared to added and ambient precipitation treatments. Nutrient addition, as well as the interacting effects of water and nutrients insignificantly affected plant above-ground biomass production and composition. Therefore, nutrient addition may not be a major limiting factor to plant productivity or composition in this community, and water addition only seems to enhance legume and other forb productivity.

A number of lakes across North America are experiencing a shift from unicellular to colonial species of scaled chrysophytes, which in some cases, is creating water-quality issues. In this study, the timing and the rate of the shift from unicellular Mallomonas taxa to colonial Synura petersenii was assessed in two lakes in the Adirondacks, NY in order to identify potential driver(s) of this shift. Lakes which have been minimally impacted by local disturbances were chosen in order to assess regional stressors such as climate change and acid deposition in driving this shift. Eagles Nest Lake displayed a single shift from unicellular Mallomonas species to colonial S. petersenii which began in the early 1960’s and intensified in the 1980’s, while Copperas Pond displayed two abrupt shifts. The first shift in Copperas Pond was from unicellular Mallomonas to colonial S. curtispina prior to the 1900’s and the second was from S. curtispina to S. petersenii which occurred in the 1990’s. The pre-1990’s shift in Copperas Pond is unusual and warrants further investigation in order to determine if a regional or local driver is at play. The shift in Eagles Nest Lake in the 1980’s and the second shift in Copperas Pond in the 1990’s corresponded with the intensification of the rise in temperatures in the Adirondack region in the 1980’s. However, as multiple regional disturbances are occurring within same time period, it was difficult to completely isolate regional drivers of change. As a result, it is also possible that both recent climate changes and/or oligotrophication resulting from long-term acid deposition played a role in causing the shift towards S. petersenii dominance in the study lakes.

Climate change is occurring most rapidly in the Arctic where warming has been twice as fast as the rest of the globe over the last few decades. Arctic soils contain a vast store of carbon and warmer arctic soils may mediate current atmospheric CO2 concentrations and global warming trends. Warmer soils could increase nutrient availability to plants, leading to increased primary production and sequestration of CO2. Presumably because of these effects of warming on shrub ecosystems, shrubs have been expanding across the arctic over the last 50 years, Arctic shrub expansion may track or cause changes in nutrient cycling and availability that favour growth of larger, denser shrubs. This study aimed at measuring gross and net nitrogen cycling rates, major soil nitrogen and carbon pool sizes, and elucidating controls on nutrient cycling and availability between a mesic birch (Betula nana) hummock tundra ecosystem and an ecosystem of dense, tall, birch (B. nana) shrubs. Nitrogen cycling and availability was enhanced at the tall shrub ecosystem compared to the birch hummock ecosystem. Net nitrogen immobilization by microbes was approximately threefold greater at the tall shrub ecosystem. This was in part because of larger microbial biomass nitrogen and carbon (interpreted as a larger microbial community) at the tall shrub ecosystem. Nitrogen inputs via litter were significantly larger at the tall shrub ecosystem and were hypothesized to be the major contributor to the higher dissolved organic and inorganic nitrogen pools in the soil at the tall shrub ecosystem. The results from this study suggest a positive feedback mechanism between litter nitrogen inputs and the enhancement of nitrogen cycling and availability as a driver of shrub expansion across the Arctic.

Climate warming will adversely affect Canadian waters and potentially predator-prey interactions in Boreal zone lakes. A series of feeding experiments were conducted at temperatures 18 - 30°C with freshwater macroinvertebrate predators, phantom midge larvae, Chaoborus punctipennis, backswimmer, Buenoa macrotibialis, and zooplankton prey from Swan Lake, Sudbury, Ontario. I wanted to determine the influence of a warming climate on predation rate and composition of predator diets. Unexpectedly, warmer water temperatures did not result in significantly higher predation from macroinvertebrate predators on zooplankton. Electivity calculations showed no general preference or avoidance trends for all species of zooplankton prey from either of the predators. This indicated that prey preference was not a factor in overall predation rate across temperature trials. Principal component analyses revealed that the zooplankton species composition in the diets of C. punctipennis and B. macrotibialis changed with temperature. A comparison of the community composition in the diet with what was available in the environment revealed a strong correlation for both predators. Findings indicate that predators were consuming zooplankton specifically present in their environment. The predators appear to be consuming prey more opportunistically rather than what may be the most energetically profitable for the energy expended to forage and consume prey. This study suggests that in light of climate warming, macroinvertebrate predators, such as the phantom midge larvae and backswimmer, will likely respond to climate-driven changes in zooplankton community composition by switching prey items.

The purpose of this study is to assess, using paleolimnological techniques, long-term (1908-2009) changes in the sedimentary assemblages of scaled-chrysophyte algae in Wolf Lake, an Adirondack ‘heritage’ lake. A ‘heritage’ lake can be defined as a lake that has experienced unusually low impact from local human activity, including: the stocking or removal of fish, extensive shoreline development, acidification, eutrophication, and the introduction of non-native species or toxic contaminants. Evaluating a ‘heritage’ lake is useful when trying to isolate the effects of climate warming from other anthropogenic influences on a lake. The scaled chrysophyte stratigraphy suggests that the relative abundance of most scaled chrysophytes have been relatively constant throughout the last century. However, Synura petersenii are one notable exception, as S. petersenii began to increase c.1980. When comparing species assemblage data to known climate data only one of the three tested variables were found to have a statistically significant effect on the species assemblage. The mean annual temperature was able to explain 19% of the variance found in the long-term (1908-2009) redundancy analysis. Increases in colonial chrysophytes, such as S. petersenii, have been known to correlate with longer periods of thermal stratification and an increase in the open-water season. Because Wolf Lake is currently considered a ‘heritage’ lake, the increase in S. petersenii is likely due to changes associated with climate warming.

The goal of this study was to determine if scaled-chrysophyte assemblages changed over the past ~1300 years and to determine if changes in scaled chrysophytes were consistent with large changes observed in diatoms from the same core. Changes in chrysophyte composition were determined through sediment analysis from a near-shore gravity core taken from a depth of ~11.5 m, and consistency with diatom changes was determined via a redundancy analysis using diatom PCA axis-1 and -2 scores as the explanatory variables. Chrysophyte composition was found to have undergone a complete shift in dominance from unicellular to colonial taxa beginning in the mid-1600s, with a sharp increase in colonials beginning in the 1850s. Changes in diatoms explained significant variation in chrysophyte assemblages, with differences likely attributable to variation in sensitivity to physical variables. These results provide evidence of increasing colonial abundance and concentration prior to that seen in previous studies, and indicate that instrumental climate records do not account for the magnitude of change observed in this lake over the past 1500 years. This study provides further evidence for the use of multi-proxy approaches for more robust interpretations of past ecological conditions.

Microalgae biodiesel provides an alternative to crude oil extraction and petroleum diesel production. However, for efficient large scale algae based biodiesel production there needs to be an increased understanding of the enzymes involved in the glycerol metabolism and triacylglycerol (TAG) synthesis. This study focuses on understanding the role of GLYCEROL 3-PHOSPHATE DEHYDROGENASE (GPDH) in TAG synthesis and glycerol metabolism from the environmentally robust oleaginous microalgae species Chlorella vulgaris. Using the known GPDH sequences in other algal species, degenerate primers were designed for amplification of C. vulgaris GPDH. The amplified region was sequenced and new gene specific primers were designed for Rapid Amplification of cDNA Ends (RACE). The amplified region was sequenced and identified to contain the GPDH open reading frame (ORF) from C. vulgaris. The ORF was then ligated into the expression vector pET-30a(+) to determine if the identified ORF encoded for GPDH through heterologous expression and protein expression in E. coli. Additionally, the ORF was then ligated into the Chlamydomonas protein expression vector pChlamy_4 so future studies could transform Chlamydomonas reinhardtii to determine if GPDH expression increases the TAG yield and enabled glycerol metabolism through heterologous expression. Restriction digests reveal successful ligation of the GPDH ORF into pET-30a(+) and pChlamy_4. Western blot analysis using His6-Tag antibodies reveals production of heterologous GPDH in transformed E. coli. Identification of C. vulgaris GPDH allows future studies to determine its role in the TAG yield and extracellular glycerol metabolism to potentially develop transgenic strains for cost effective commercial application.

There has been consistent debate since the 1970s regarding what variables control community biomass in a natural plant community. Many hypotheses have arisen to explain these controllers, including the sampling effect hypothesis, which states that the biomass of an assemblage trends to increase with species richness because of the chance of containing larger, more productive species. However, the question whether the most productive species are large and less abundant or small and more abundant is still unknown. The “size advantage” hypothesis states that larger species are better competitors and in turn should be the main predictor of community biomass. Alternatively, the “reproductive economy advantage hypothesis” states that smaller species (not larger species) should be more successful because of their increased reproductive capabilities (they have a smaller minimum reproductive threshold size). My study aimed to explain the controls on community biomass on a between-plot and between-species level: is community biomass controlled by large, less abundant species (“size advantage” hypothesis) or smaller, more abundant species (“reproductive economy advantage” hypothesis)? My project’s results do not completely support the “size advantage” hypothesis, which opens a dialogue for alternative explanations and theories, one of which being the “reproductive economy advantage” hypothesis. The “reproductive economy advantage” hypothesis is supported in both of my between-plot and between-species levels of biomass measurement and analysis. These results and conclusions suggest that traditional theory stating that “bigger is better” needs further questioning and experimentation to prove its applicability.

Climate change is expected to have profound effects on species behaviour, persistence, and distributions. Amphibians are especially sensitive to environmental change as their biphasic lifestyles rely heavily on both aquatic and terrestrial habitats and degradation of either will compromise their persistence. Anurans use temperature as an important developmental and behavioural cue, and temperature changes in the spring trigger the initiation of mating calls in many temperate species. Not all anuran species respond similarly to temperature in changing climates, and not all populations within species will respond the same way. This high variability in behavioural responses has sparked interest in monitoring anuran call phenology through time. I examine how the onset of temperate anuran vocalizations in the spring have changed between 2009 and 2021 at three marshes in eastern Ontario. Automated recording data were used to collect information on local species present and the date of first calling and peak calling for each species as a proxy to estimate the initiation of the breeding season. Contrary to my predictions, the onset of anuran calling appears to have shifted later in the year with increasing ambient spring air temperatures. Local average spring air temperatures have risen by approximately 0.2℃ between 2000 and 2021, correlating with a shift of both the initiation of vocalization and peak calling activity in spring peepers (Pseudacris crucifer) to later in the season. Northern leopard frogs (Lithobates pipiens), wood frogs (Lithobates sylvaticus), and chorus frogs (Pseudacris sp.) are also trending towards later call times under increased spring temperatures. These shifts in spring-calling anuran phenology may result in increased competition for food resources and breeding sites if the breeding season overlaps with those of late-spring- or early-summer-calling anuran species, and may place additional developmental and predation pressures on offspring.

Lithium is used in the cathode and electrolyte of rechargeable batteries in many portable electronics and electric vehicles, and is thus seen as a critical component of modern technology (Gruber et al., 2011). Electric vehicles are promoted as a way to reduce carbon emissions associated with the transportation sector, which accounts for 14.3% of anthropogenic greenhouse gas emissions (OECD International Transport Forum, 2010). However, the sustainability of lithium procurement will influence the overall environmental impact of this proposed “green” solution. It is estimated that 66% of the world’s lithium resource is contained in natural brines, 24% in pegmatites, and 8% in sedimentary rocks such as hectorite clays (Gruber et al., 2011). It has been shown that “[r]ecycling of lithium from Li-ion batteries may be a critical factor in balancing the supply of lithium with future demand” (Gruber et al., 2011). In an attempt to quantify energy and materials consumption associated with production of a unit of useful lithium compounds, industry reports and peer-reviewed scientific literature concerning lithium mining and lithium recycling were reviewed and compared. Other aspects of sustainability, such as waste or by-products produced in the production of a unit of useful lithium, were also explored. Thus, this paper will serve to further the evaluation of the comparative environmental consequences associated with lithium production via extraction versus recycling. Efficiencies must be made in both processes to maximize productivity while minimizing ecological harm.