An individual’s growth rate is a key determinant of its body size, which is in turn intrinsically linked to its fitness through reproduction and survival, and population-level processes such as recruitment. As individuals move, they experience different environmental conditions which can impact on the resources available for growth. Indeed, animals may track favourable conditions through space and time to maximise resource acquisition and thus growth. Despite the benefits, movement behaviours can vary among life stages and among individuals, with some individuals remaining resident in their natal environment. The persistence of different movement phenotypes within a population, known as partial migration, suggests that multiple phenotypes can have commensurate benefits. The degree to which movement and environmental context influence an individual fish’s growth rate at different life stages remains poorly understood. In this thesis, I use growth and movement information naturally archived in golden perch (Macquaria ambigua) otoliths (‘ear stones’) from across the Murray-Darling Basin to address key questions about the relationships between growth, movement, and variation in environmental conditions. First, does early life growth influence survival later in life? Second, does the presence and direction of movement relative to river discharge affect growth rates? Last, does knowledge of the locations inhabited by individuals throughout their lives increase the performance of fish growth models? I found that faster early-life growth (over first 30 days of life) increased the survival of stocked fish to two years of age. Wild-born individuals that moved among river reaches had faster growth over the first eight years of life compared to those that remained resident. Differences in juvenile growth rates were, however, dependent on movement direction, with increased growth of downstream dispersers, upstream dispersers, and hatchery stocked fish compared to resident individuals. The impact of environmental conditions on golden perch growth was modulated by an individual’s life stage and its movement type. Including the environmental conditions experienced by an individual throughout their life, however, did not improve the performance of growth models. Instead, environmental conditions at a fixed location (location of capture) were sufficient to explain annual growth variation in golden perch, even if they had undertaken extensive movements across their lifetime. I suggest that for highly mobile fish such as golden perch, coarser environmental conditions may be more important in governing annual growth. Growth displayed complex relationships with hydrology, that were dependent on location and life-stage. Generally, there were positive associations between increased river discharge in summer and spring and golden perch growth, although high discharge limited growth in young and vulnerable fish in early-life stages. I suggest that effects of river discharge on individual growth manifests through a combination of high velocities impacting movement energetics (upstream or downstream), feeding behaviours of young fish, and stimulating productivity pulses in the river system, increasing habitat and food availability. My thesis contributes valuable information on native fish ecology. I quantify how movement patterns and environmental conditions influence growth at multiple life stages and discuss how the presence of multiple phenotypes can bolster the resilience of populations to environmental disturbance. I expect this thesis to inform the management of freshwater fish, one of the most threatened groups of vertebrates on the planet, through improved stocking outcomes and understanding of the impacts of managed discharge regimes and the importance of connectivity.

Implantation of the blastocyst into the endometrium is a critical process for reproduction and the establishment of successful pregnancy. However, approximately 30% of natural pregnancies are lost in the peri-implantation period, and this is compounded in the 1 in 6 couples worldwide that experience infertility. Hence, failure of implantation is a major limitation of reproductive success. The success of human implantation and pregnancy is dependent on the presence of an appropriately developed blastocyst, a receptive endometrium and a dynamic dialogue between these tissues, mediated by signalling molecules of both maternal and embryonic origin. This is highlighted by the fact that both poor embryo quality, and inadequate endometrial receptivity are major contributing factors to poor implantation. Therefore, it is evidently necessary to optimise both embryo quality and viability following in vitro culture, as well as increase our understanding of the regulation of endometrial receptivity and implantation to improve pregnancy success in both natural and assisted pregnancies Using a mouse model, the effects of supplementing a defined group of maternal growth factors (GFs) and cytokines (GF5) to embryo culture media as a potential method to improve embryonic quality following in vitro culture was investigated. GF5 improved morphological indicators of embryonic development and viability, however these changes were associated with parallel alterations to the transcriptome relative to in vivo derived embryonic counterparts, thus highlighting the importance of cooperative actions between growth promoting and growth inhibiting factors within the in vivo environment to facilitate normal embryonic development and programming. The use of GFs and cytokines as clinical medium supplements to promote embryo development was further investigated through the development of a novel method by which GFs could be stabilised and subsequently delivered to the in vitro embryo, an approach that negates the breakdown of GFs associated with storage in solution. Investigations into the role of embryonic signals in facilitating implantation demonstrated a role for lactate as an embryonic signal to promote functional remodelling of the endometrium for receptivity and implantation. Lactate was found to downregulate proliferation and cell polarity within the luminal epithelium, as well altering stromal migratory capacity and promoting angiogenic induction at the implantation site. Further examination of a functional effect of lactate in other reproductive tissues failed to identify a role for lactate in the regulation of cumulus cell expansion, transcriptional regulation of a subset of genes involved in lactate transport or metabolism, or sperm motility characteristics, despite the identification of GPR81 in each of these cell types. Overall, the research presented in this thesis enhances our understanding of maternal-fetal interactions within the in vivo environment and demonstrates the capacity of both the embryo and the endometrium to modulate several cellular functions to promote optimal embryonic development and the initiation of implantation. Together, these studies contribute to our understanding and ability to improve the quality of embryos produced through in vitro culture, as well as increase our understanding of the regulation of endometrial receptivity, which together, should help to augment the success of both natural and assisted pregnancies.

Bird song has long fascinated humans with Aristotle himself postulating that it must have a function just as human communication does. Historically research has been biased toward male bird song at dawn, yet song is neither exclusive to males nor time of day. An important factor triggering song behaviour is variation in natural light levels. Morning light initiates the dawn chorus, and the end of daylight initiates the dusk chorus. Traditionally diurnal birds can be heard singing throughout the day and nocturnal birds can be heard calling at night, however, some diurnal species also sing at night. As diurnal species are adapted to bright environments, they may be particularly sensitive to changes in light at night. Light cycles driven by the sun and moon have remained relatively stable across evolutionary time, yet recently the night-time light environment has undergone a drastic change with the development of artificial light at night: a worldwide pollutant. The implications of this dramatic change for diurnal birds with nocturnal song has seldom been explored. In this dissertation, I examined the phenomenon of nocturnal bird song in the naturally diurnal willie wagtail (Rhipidura leucophrys). After providing a general introduction to the relationship between bird song and light (Chapter 1), I reviewed more broadly how light affects acoustic communication across taxa (Chapter 2). In this chapter, I reviewed current evidence documenting natural and artificial light at night effects on acoustic communication, highlighted gaps in our understanding, and suggested future opportunities for research. In my first data chapter (Chapter 3), I focussed on the relationship between moonlight and nocturnal song in the willie wagtail and examined which sex sings at night. I found that, in naturally dark locations (with no street lighting), while both male and females sing during the day, nocturnal song is sung exclusively by males and increases with brighter lunar illumination. To extrapolate the significance of these findings, I then examined the function of nocturnal bird song observationally throughout the breeding season and experimentally using playback (Chapter 4). I used automated audio recorders to monitor acoustic behaviour of a wild population of willie wagtails through the breeding season, to test whether breeding stage predicts song behaviour. My data revealed that daytime song is used for territory defence in males and females, while nocturnal song (males only) has an important role in mate attraction and territory defence. I also investigated the mating system of the willie wagtail, with genetic data revealing low to medium rates of extra-pair paternity, supporting the view that nocturnal song likely functions for mate guarding and attracting extra-pair mates. In my final data chapter (Chapter 5), I examined the effect of artificial light at night on nocturnal song behaviour. This study combined a landscape level observational approach which integrated consideration of multiple sources of light at night (moonlight, point sources and sky glow) and a population level experiment that explored the effect of adding artificial sources of light to willie wagtails’ territories in naturally dark habitats. My landscape study revealed that artificial light interacts with natural light at night leading to an overall suppression of nocturnal song behaviour. These results were confirmed at the population level when I experimentally introduced a streetlight to a previously dark area. In my concluding chapter (Chapter 6), I discuss my results in the context of the willie wagtail and more broadly in terms of the effects of artificial light at night on animal behaviour. My data highlight that nocturnal song is important for willie wagtails and further demonstrates significant impacts of light at night on song behaviour. My findings advance our understanding of the impact of light at night for bird species, suggesting artificial light at night may be harmful for urban birds and may be a driver of evolution between populations.

Lipids are important constituents of plants, performing many fundamental functions in growth and development. To study lipid structures and their biological functions robust analytical techniques are necessary. Lipidomics is a powerful tool, which can be used to measure the abundance of lipids in plant tissues and thus learn about their roles in plants, as well as to explore how plants respond to environmental perturbations and conduct an in-depth analysis of lipid biosynthetic pathways. A mass spectrometer is the predominant analytical instrument used in the field of plant lipidomics and two main approaches: the targeted and the untargeted approach are commonly followed. The untargeted approach seeks to analyse all lipids in a sample. By contrast, the targeted approach aims at identifying and quantifying a set of specific lipids. The identification of the individual chemical lipid structures represents a major limitation and challenge of the untargeted approach. Many lipids, which are structurally different, have identical molecular masses thus proving it difficult to identify them based on their molecular mass alone. As a result, biochemical pathways of specific lipid species are often difficult to decipher, which makes it challenging to interpret the data in a biological context and to integrate them with other ‘omics data. Tandem mass spectrometry allows a lipid to be assigned to a class of compounds and provides information on the total length of fatty acid chains and the number of double bonds. Although there are several in silico generated lipid mass spectral libraries for the annotation of lipids based on tandem mass spectrometric data, confident lipid identification remains challenging. This is mostly due to an over annotation of mass spectral features, and as a consequence demands manual corrections. Furthermore, plant lipids are significantly underrepresented in currently available lipid libraries. My PhD project aimed to address the above-mentioned challenges in plant lipidomics, using Arabidopsis thaliana (Arabidopsis) as the model plant. At the start of my PhD, a comprehensive untargeted lipid analysis workflow was established for the extraction, detection and identification of plant lipids. Next, this untargeted lipid analysis workflow was applied to explore the lipid profiles of different Arabidopsis tissues and developmental stages. In collaboration with the group of Prof Provart (University of Toronto) the resultant data of this study were integrated into an open-source in silico lipid map and database. In addition, a manually curated Arabidopsis specific lipid library, which represents the first plant-specific lipid library, was generated. This library can be used to confirm lipid annotations obtained through computer-generated lipid libraries and significantly reduce the number of false positives. It can also be used to annotate lipids when tandem mass spectrometric data are not available using retention time and accurate mass as identification parameters. Finally, the developed untargeted lipid analysis workflow was applied to explore the lipidomes of Arabidopsis loss-of-function mutants. Collectively, the research tools developed during my PhD and the data generated using the untargeted lipid analysis workflow will facilitate future studies into plant lipids and improve our understanding of lipids in plant functions.

Biodiversity in the anthropocene is under threat, but under current trajectories of socio-economic development it is unlikely that current targets to halt the decline of biodiversity will be met. Climate change, sea/land-use change, pollution, direct exploitation of organisms and the invasion of alien species continue to directly drive global biodiversity change, with significant adverse impacts on species and ecosys- tems. These drivers are themselves driven by global patterns in the consumption and production of economic commodities, trade, governance, human population trends, and technological innovations. To better protect biodiversity, it is necessary to reduce uncertainty around future biodiversity change and to clearly delineate how changes may manifest themselves throughout the 21st century. Accordingly, the integration biodiversity models with models from socio-economic (and other) disciplines is critical for accurate representations of linkage between human and natural systems driving biodiversity change. However, established integrated assessment models are highly complex and typi- cally not designed for biodiversity assessments. Streamlined frameworks that can be used quickly by ecologists remain very rare and new methods are sorely needed to make integrated biodiversity modelling accessible to a wide range of applications. To fill this gap, this thesis innovates a new integrated modelling framework for bio- diversity assessments, coupling macro-economic, land-use and biodiversity modelling power. Our framework capitalizes on recent advances in computable general equilib- rium (CGE) modelling, bringing unprecedented power to parametrize the impacts of various socio-economic impacts and climate change on global commodity consumption and production patterns at very high commodity and temporal resolutions. Land-use changes caused by changes in the consumption and production of agricultural com- modities are spatially downscaled and resulting predicted land-use maps serve as input for biodiversity models. Chapter 2 provides the initial roll-out of our integrated assessment framework to quantify the relative influence of direct biophysical and indirect socio-economic (via commodity demand and land-use change) climate change impacts on bird species in Vietnam and Australia. In this chapter, we spatially downscale projected changes in commodity demand, using an existing categorical land-use model with limited appli- cability. Chapter 3 introduces and validates a new land-use model to interface global com- modity demand projections and biodiversity change. The model enables the fine-scale mapping of future land-use change under alternative scenarios of commodity demand change. It represents land-use as fractional cover within grid cells, thus providing higher information content than discrete categories of land-use, without the need to de- crease the spatial resolution. The model allows us to upscale the modelling framework to the global extent and to better align land-use predictions with the requirements of global-scale biodiversity modelling. Chapter 4 presents a first global implementation of our framework to predict global biodiversity under shared socio-economic scenarios. We use the land-use model devel- oped in Chapter 3 to spatially downscale commodity demand change expected under two socio-economic scenarios also commonly applied in other disciplines, and compare predictions made using our streamlined framework against predictions made using a highly complex integrated assessment model. We contribute an open and streamlined method to model socio-economic impacts on biodiversity, bringing integrated assessments of biodiversity change within reach of ecologists. The work presented here demonstrates that we are now capable of success- ful applications under a wide range of scenarios and highlights where developments are necessary to further improve our framework’s relevance to support global biodiversity policy.

Dermaptera (earwigs) are a cosmopolitan order of insects that have recently come to the attention of the Australian grain industry. Researchers have been sampling Dermapteran diversity and abundance across the southern Australian grain belt, but resolution of the sample is stifled by taxonomic impediment, particularly for specimens of the morphologically uniform Anisolabididae family. Molecular methods can provide much needed resolution to the study of Australian Dermaptera. I barcoded known Dermaptera species from across the southern Australian states to assess the utility of barcoding for Dermapteran biodiversity research. I also assessed the diversity of the Anisolabididae by combining morphological identification and DNA barcodes. I then estimated their phylogeny with a larger molecular dataset comprised of two mitochondrial and two nuclear gene fragments under a maximum-likelihood framework. Anisolabididae males were divided into seven morphospecies based on the shape of the forceps and parameres (a male genital structure), and these morphospecies were corroborated by barcodes (low within versus between-species genetic distance). Paramere shape distinguished two putative genera, Anisolabis Fieber and Gonolabis Burr. The molecular phylogeny did not support the monophyly of the genera, rather forming clades distinguished by the shape of the forceps. The evolutionary significance of paramere versus forceps morphology in Dermapteran taxonomy is discussed. Anisolabididae were only found in Western and South Australia and showed apparent endemism. Extending the study of Australian Anisolabididae beyond grains-producing regions may reveal a diverse endemic fauna, almost entirely unexplored heretofore.

Although it is commonly argued that local adaptation is central to invasion success, previous theoretical work has shown that adaptation is not always required for species establishment, even where there are significant hurdles imposed by Allee effects arising from self-incompatible breeding system and low population size. We have shown that the dynamics of closely related invading plant species – and pairs of compatible species in general - can be governed by the interactions between their pollinators and the plants’ breeding systems through hybridisation. Hybridisation may aid in the establishment of an invasive species through the transfer of genes between related species, or it can lead to the extinction of species via demographic or genetic swamping. Investigating the interactions between two closely related plant species - Cakile edentula and Cakile maritima - with their shared pollinators can provide a good model for examining the effects of pollinator-mediated hybridisation on invasion outcomes. Through the quantification of pollinators movements between plants, microscopic assessment of in situ pollen tube competition and siring determination through genotyping-by-sequencing, we estimated how pollinator behaviour as pre pollination reproductive barrier and pollen competition as post pollination reproductive barrier are likely to influence the composition of the next generation. Our results suggest that pre pollination reproductive barriers are stronger than post pollination barriers in the mixed population of Cakile species and pollinator behaviour are the main driver of hybridisation outcome in this system. These findings allowed us to fill some of the knowledge gaps with respect to the key steps driving hybridisation and its potential impact on invasion.

Aquaculture production of finfish continues to grow. Despite the billions of individual fish produced annually, there is still much to learn about farmed fish behaviour. Knowledge of animal behaviour is to improve animal welfare in production systems. Basic farming practices can become less stressful when natural behaviours or an animal’s learning capacity are incorporated into animal husbandry. Yet behaviour is challenging to monitor in commercial aquaculture, where hundreds of unique species are produced globally, and are stocked at high densities underwater. However, some farmed species are well studied and provide test cases for how to learn about fish behaviour and apply that knowledge to improve production and welfare outcomes. Atlantic salmon (Salmo salar) is the species farmed in the highest abundance in a marine setting. A major hurdle to industry growth is infestations of a persistent ectoparasite, the salmon louse (Lepeophtheirus salmonis). Lice create health and welfare issues for farmed salmon, have negative consequences for wild salmonid populations, and cost farmers billions annually. Novel depth-modified sea-cages have been designed to inhibit contact between the infective lice at the water’s surface and caged salmon that refill their swim bladder at the surface. These cages modify surface access and force salmon to swim deep, potentially compromising their buoyancy regulation, which has fundamental consequences for salmon behaviour and welfare. Therefore, the needs of farmed fish will change as production technologies evolve and create new and diverse environments for fish to adapt to. In this thesis, I first conducted a systematic review to assess the evidence for whether innate and learned behaviours could be feasibly applied in commercial aquaculture to facilitate animal husbandry. My findings reveal that there are several barriers to scaling-up experimental use of behaviour to industrial settings. However, several promising examples demonstrate that providing farmed fish with an opportunity to learn increases behavioural flexibility, which has positive welfare outcomes. The depth that salmon can remain neutrally buoyant was previously unknown. Yet, this is expected to be an important factor in their swimming depth behaviour. By first determining the basic limits salmon have relating to buoyancy, behaviour can be consequently investigated as a strategy to ensure salmon welfare in depth-modified cages. In laboratory experiments, I found that the maximum depth that salmon can achieve neutral buoyancy was approximately 22 metres across a range of sizes. These results have significant implications for how deep farmers can hold salmon in the sea without having welfare consequences. To reduce the impact of cages that force deep swimming on salmon buoyancy, an underwater air dome can be included in cages to allow salmon to refill their swim bladder and maintain buoyancy without entering the lice-infested surface waters. In a field trial, I explored whether salmon could be habituated to surface-based air domes in tanks before being transferred to submerged air dome cages at sea. I found that salmon with previous experience of domes in tanks refilled their swim bladders in the air domes at sea 2.5 times more often and had a higher swim bladder volume compared to salmon that did not undergo habituation. These results show farmed salmon can learn to adapt a fundamental behaviour via human-mediated training and apply this behaviour in a different production environment to the one they learned in. Finally, I investigated the use and effects of tagging fish, which is a promising technique for collecting behavioural data on individual farmed fish. I conducted a meta-analysis to assess the state of knowledge on tagging fish in aquaculture and what factors affect tagged fish mortality. I discovered mortality of tagged fish was 10 times greater in studies conducted in sea-cage environments compared to studies conducted in tanks, suggesting the results of tagging studies in tanks must be then tested in the field to have any commercial relevance for mariculture. Basic information, like how many tagged and untagged fish died throughout experiments, was often unreported making it impossible to determine the true impact of tags on survival or welfare.

Patterning along the apical-basal (A-B) axis is a crucial step during the early stages of plant embryogenesis and leads to the establishment of two poles of which each will develop their own stem cell niches. The activity of these meristems is responsible for post-embryonic growth, with the shoot apical meristem (SAM) generating the above-ground organs and the root apical meristem (RAM) producing the subterranean structures of the plant. While several transcriptional regulators governing A-B patterning have been identified, precisely how their regulatory function is orchestrated remains elusive. This study focuses on transcriptional co-regulators LEUNIG (LUG) and closely related LEUNIG_HOMOLOG (LUH) and their role in the formation of A-B patterning during embryogenesis as well as their post-embryonic maintenance. A link between the LUG regulatory complex and SAM formation and maintenance comes from the observation that lug mutants heterozygous for the luh allele (lug luh+/-) often have enlarged SAMs resulting from misregulated cell divisions. A more severe phenotype is observed in lug luh double mutants which are embryonically lethal. In this study, a detailed characterisation of lug luh embryo phenotype reveals that these mutants display aberrant cell divisions along the A-B axis, which correlates with defects in auxin distribution, complete loss of apical identity, and altered expression of transcription factors determining basal fate. Like other co-regulators, LUG and LUH lack intrinsic DNA-binding domains and instead must interact with DNA-binding cofactors to ensure recruitment to regulatory elements of target genes. This either involves direct contact between the co-regulators and transcription factors (TFs) or the formation of higher-order complexes with adaptor proteins such as SEUSS (SEU) or related SEUSS-LIKEs (SLKs), which facilitate binding to specific TFs. Results presented in this study provide insight into the molecular framework for the LUG regulatory complex activity during embryogenesis. Both yeast and in planta assays showed that LUG/LUH and SEU/SLKs physically associate with a variety of WUSCHEL-RELATED HOMEOBOX (WOX) TFs including members of the WOX2-module. Furthermore, genetic interactions between members of the WOX2-module and the LUG regulatory complex, support their mutual action during embryogenesis. Based on the reduced activity of HOMEODOMAIN LEUCINE-ZIPPER CLASS III (HD-ZIPIII) promoters in lug luh embryos, a model is proposed in which the LUG regulatory complex functions together with WOX2-module to promote apical identity and subsequent SAM initiation through regulation of the HD-ZIPIIIs. The activity of the LUG complex in promoting basal embryo identity through positive regulation of microRNA165/166 suggests that this complex also has functions that are independent of the WOX2-module. Preliminary work reported in this study further uncovered the role of the LUG regulatory complex in post-embryonic development. While the fasciated inflorescence meristems of lug luh+/- plants displayed defects in auxin transport and altered activity of stem cell markers, embryonically rescued lug luh mutants formed flat and differentiated SAMs. In addition, rescued lug luh mutants exhibited severely disorganised RAM and defects in quiescent center (QC) specification, supporting the involvement of the LUG complex in post-embryonic RAM maintenance.

Nicotinic acetylcholine receptors (nAChRs) are essential neuronal receptors that mediate fast synaptic neurotransmission influencing many aspects of behaviour. The insecticide imidacloprid (IMI) bind to nAChRs, disrupting their function and causing insect death. The widespread use of IMI has led to the evolution of resistance in a number of pest species. In most cases resistance has been attributed to elevated levels of cytochrome P450 enzymes that detoxify the insecticide. That target site resistances are rarer suggests that resistant mutations may incur fitness costs. Published studies using mutagenesis in the model insect, the vinegar fly Drosophila melanogaster, have proven to be fruitful in identifying some of the nAChR subunits that may co assemble to form IMI targets. This thesis builds on and extends those studies. This study systematically investigated the targets of IMI in D. melanogaster. The first aim of this study was to identify all of the nAChR subunits that contribute to IMI toxicity. Given the relatively small number of nAChR subunit genes in this species, the capacity for individual subunits to contribute to the IMI targets was tested using mutant generated for each of the genes using CRISPR-Cas9 gene editing. Toxicological assays were performed and identified the Dalpha1, Dalpha2, Dbeta1 and Dbeta2 subunits as the primary targets of IMI in this species. The second aim investigated the fitness costs associated with IMI resistance. Given the potential for functional redundancy among the nAChR genes, this research included an investigation of strains with knockout alleles for more than one gene. Two of the IMI targeted nAChR genes, Dalpha1 and Dbeta2, were selected for this study, given their IMI resistance levels and apparent fitness deficits. Single and double knockout mutant strains were generated for Dalpha1 and Dbeta2, which were tested using toxicological and a range of phenotypic assays to investigate the functional contribution that Dalpha1 and Dbeta2 make as the IMI targets and to the capacity to survive and reproduce. This research provided insights into the function of these subunits and the potential for resistance to evolve via mutations in them. The third aim examined the expression patterns of the IMI targets in the D. melanogaster larval brain. This was achieved by using GAL4 and split GAL4 strains combined with a UAS controlled fluorescent reporter. A 3rd instar larval brain single cell transcriptome atlas was also used to help identify the brain cell types that express combinations of the IMI targeted subunits to provide further insights into the functions that the receptors formed might perform. Given that nAChR genes are highly conserved among insects, the results from this study are likely to be applicable to other insect species and facilitate the rational use and rotation of insecticides targeting members of the nAChR family.

Cellulose is the most abundant biopolymer on Earth and cell wall (CW) synthesis is one of the major carbon consumers in the plant cell. Structure and several interaction partners of plasma membrane (PM)-bound cellulose synthase (CESA) complexes, CSCs, have been studied extensively, but much less is understood about the signals that activate and translocate CESAs to the PM and how exactly cellulose synthesis is being regulated during the diel cycle. The literature describes CSC regulation possibilities through interactions with accessory proteins upon stress conditions (e.g. CC1), post-translational modifications that regulate CSC speed and their possible anchoring in the PM (e.g. with phosphorylation and S-acylation, respectively). In this thesis, 13CO2 labeling and imaging techniques were employed in the same Arabidopsis seedling growth system to elucidate how and when new carbon is incorporated into cell wall (CW) sugars and UDP-glucose, and to follow CSC behavior during the diel cycle. Additionally, an ubiquitination analysis was performed to investigate a possible mechanism to affect CSC trafficking to and/or from the PM. Carbon is being incorporated into CW glucose at a 3-fold higher rate during the light period in comparison to the night in wild-type seedlings. Furthermore, CSC density at the PM, as an indication of active cellulose synthesizing machinery, is increasing in the light and falling during the night, showing that CW biosynthesis is more active in the light. Therefore, CW synthesis might be regulated by the carbon status of the cell. This regulation is broken in the starchless pgm mutant where light and dark carbon incorporation rates into CW glucose are similar, possibly due to the high soluble sugar content in pgm during the first part of the night. Strikingly, pgm CSC abundance at the PM is constantly low during the whole diel cycle, indicating little or no cellulose synthesis, but can be restored with exogenous sucrose or a longer photoperiod. Ubiquitination was explored as a possible regulating mechanism for translocation of primary CW CSCs from the PM and several potential ubiquitination sites have been identified. The approach in this thesis enabled to study cellulose/CW synthesis from different angles but in the same growth system, allowing direct comparison of those methodologies, which could help understand the relationship between the amount of available carbon in a plant cell and the cells capacity to synthesize cellulose/CW. Understanding which factors contribute to cellulose synthesis regulation and addressing those fundamental questions can provide essential knowledge to manage the need for increased crop production.

Anthropogenic activities associated with urbanisation have increased the presence of a diverse range of pollutants in waterways. Often these pollutants are delivered to receiving waterways via stormwater runoff. Among the variety of pollutants present in stormwater, metals continue to be identified as a priority due to their ubiquity, legacy, and ability to bioaccumulate and cause impacts in aquatic organisms. Monitoring of stormwater has revealed that discharges into receiving waterbodies tend to occur over short-term (2-48 h) ‘pulses’. As a consequence, organisms that access these environments tend to be subject to intermittent, short term exposures rather than a continuous exposure. The water quality guidelines (WQGs) currently set by Australian and New Zealand regulatory bodies to protect these ecosystems are typically derived from continuous toxicity tests. This is an issue as these guidelines may not be protective of episodic, short-term exposures typical of stormwater runoff. The key aim of this research was to investigate the forms of metal contaminants over a pulse storm event, and the resulting impact these short-term exposures have on representative aquatic organisms. Field investigations aimed to provide detailed information on the changes to metal partitioning across a storm hydrograph, with a focus on the fraction of metals that are potentially bioavailable to aquatic organisms. Water samples in a representative system were collected and diffusive gradients in thin films (DGTs) were deployed to measure the DGT-labile metal concentrations. Results indicated that dissolved metal concentrations exhibited narrow pollutographs over the storm, with the concentration of six key metals exceeding WQGs. However, the portion of labile metal as measured by DGTs indicated that a substantial fraction of metals in the system are complexed during the storm and pose minimal risk to aquatic organisms. Following on from the field investigation, a series of laboratory studies examined the response of local aquatic organisms to metal contaminants following short-term aqueous and dietary exposures. These studies intended to assess the bioaccumulation kinetics and organ distribution of two common stormwater metal contaminants through the use of gamma-emitting radioisotope tracers. Whole-body metal concentrations determined by gamma spectrometry indicated the uptake of metals in an invertebrate over the pulsed exposure period. The fish species preferentially accumulated metals via diet. Finally, a systematic review of the current literature focused on the experimental design and statistical analysis of aquatic live animal radiotracing studies. The review was able to provide clear guidance on the analysis and interpretation of data collected from a range of experimental designs common to radiotracing studies and highly relevant to the broader field of ecotoxicology. Together, the data presented in this thesis provides an insight into the composition and dynamics of metals in urban stormwater runoff, and how these contaminants impact local biota. This research improves the understanding of metal contaminants in a dynamic urban environment and assists with the development of improved approaches for the assessment and management of short-term, intermittent discharge events.