1,721,018 research outputs found
The Public Perception of Urban Stormwater Ponds as Environmental Amenities
No full textIntegrating green or blue space into cities can provide environmental and public health benefits which maximize urban sustainability. One type of green/blue infrastructure that has been understudied is urban stormwater ponds, which are used to manage stormwater runoff. Their performance is typically only evaluated in terms of hydrological functions, with little focus on their capacity to provide ancillary benefits to communities. In this exploratory study, an online survey was distributed to six neighbourhoods in the City of Ottawa, ON to gain insight into the social value of urban stormwater ponds. The results revealed that despite some disadvantages, most respondents visited their neighbourhood stormwater ponds regularly and largely appreciated the cultural ecosystem services provided by these ponds, such as opportunities for experiencing nature, especially wildlife, and outdoor recreation. These findings can be used to improve the multifunctionality of stormwater ponds and optimize both environmental and social sustainability outcomes
Effects of Glyphosate on Flower Production in Three Entomophilous Herbaceous Plant Species (Rudbeckia hirta L., Centaurea cyanus L. and Trifolium pratense L.)
No full textReproductive endpoints are generally not considered in regulatory risk assessments used to inform registration decisions for pesticides, and relatively few studies have examined effects of herbicides on reproduction in non-target plants. In two sets of greenhouse experiments using three wild species (Rudbeckia hirta L., Centaurea cyanus L. and Trifolium pratense L), effects on flowering phenology and inflorescence characteristics were investigated following low, drift-equivalent glyphosate exposure at an early bud stage. Weekly post-spray observations included the number of inflorescences, aborted buds and malformed inflorescences. In the experiment focusing on inflorescence characteristics (C. cyanus and T. pratense only), inflorescences and pollen were collected at five weeks post-spray to measure inflorescence dry weight, count the number of reproductive florets, estimate the amount of pollen per floret, and assess pollen germination in vitro. Flower production was adversely affected in all three species, including delays in flowering, significant increases in the number of aborted buds and malformed inflorescences, an overall reduction in the number of inflorescences produced, as well as a reduction in the duration of individual inflorescence bloom time (R. hirta and T. pratense assessed only). Inflorescence dry weight and in vitro pollen germination were significantly reduced for C. cyanus exposed to glyphosate, but not for T. pratense. However, both species experienced a significant reduction in the number of reproductive florets produced per inflorescence in response to glyphosate exposure. Neither species was observed to have significant reductions in the amount of pollen produced per reproductive floret. These results have important implications for risk assessment, demonstrating that current glyphosate use in Canada and elsewhere could be adversely affecting non-target flowering plants in field margins, as well as other taxa that rely on them, particularly pollinators.
Les effets sur la reproduction des plantes ne sont généralement pas pris en ligne de compte dans les évaluations réglementaires sur les risques des pesticides lors de leur homologation. De plus, relativement peu d'études ont examiné les effets des herbicides sur la reproduction des plantes non ciblées. Dans deux séries d'expériences en serres avec trois espèces sauvages (Rudbeckia hirta L., Centaurea cyanus L. et Trifolium pratense L), les effets sur la phénologie florale et les caractéristiques des inflorescences ont été étudiés après une faible exposition au glyphosate équivalente à la dérive durant la pulvérisation lorsque les plantes sont au début des boutons floraux. Des observations hebdomadaires post-pulvérisation ont été effectuées sur le nombre d'inflorescences, de bourgeons avortés et d’inflorescences malformées. Dans l'expérience portant sur les caractéristiques des inflorescences (C. cyanus et T. pratense seulement), les inflorescences et le pollen ont été recueillis cinq semaines après la pulvérisation pour mesurer le poids sec des inflorescences, compter le nombre de fleurons reproducteurs, estimer la quantité de pollen par fleur et évaluer la germination du pollen in vitro. La production de fleurs a été affectée chez les trois espèces, y compris des retards de floraison, des augmentations significatives du nombre de bourgeons avortés et d’inflorescences malformées, une réduction globale du nombre d'inflorescences produites et une diminution de la durée de floraison par inflorescence. (R. hirta et T. pratense évalués seulement). Le poids sec des inflorescences et la germination in vitro du pollen ont été significativement réduits chez C. cyanus exposé au glyphosate, mais pas chez T. pratense. Cependant, les deux espèces ont subi une réduction significative du nombre de fleurons reproducteurs produits par inflorescence en réponse à l'exposition au glyphosate. Aucune des deux espèces n'a montré de réduction significative de la quantité de pollen produit par fleuron. Ces résultats ont des implications importantes pour l'évaluation de risques, démontrant que le glyphosate, tel qu’utilisé présentement au Canada et ailleurs, pourrait nuire aux plantes à fleurs non ciblées retrouvées en bordure de champs, ainsi qu'à d'autres taxons qui en dépendent, particulièrement les pollinisateurs
The diversity and community composition of aquatic macrophytes in relation to physical and chemical environmental variables in the Rideau River, Ontario.
No full textLike many rivers around the world, the Rideau River is under pressure from a number of human induced activities resulting in a loss of species and habitat. In order to prioritise conservation efforts, it is necessary to understand what type of habitats will support the widest range of species. This study examines which physical and chemical factors exert the strongest influence on the diversity and community composition of aquatic macrophytes in the Rideau River. Macrophyte species were surveyed at 33 sites on the Rideau River, Ontario, in six 1 m2 quadrats aligned in a belt transect perpendicular to shore along a depth gradient of 0.5 m to 2.0 m. Regression analysis showed species richness and Shannon diversity were significantly related to water velocity, transect length, slope, and organic content. Multiple regression provided a model whereby 70% of species richness was explained by organic content, transect length, water velocity and chlorophyll a, and 77% of Shannon diversity was explained by organic content and water velocity. Mantel tests showed only chlorophyll a was weakly correlated with species composition. Canonical correlation analysis showed floating and floating-leaved species to favour habitats with low water velocity. No other significant patterns were found. It appears that while species diversity can be predicted from physical environmental variables, species composition cannot
Floating algal mats in the Rideau River and their relationship to nutrient concentrations and sources
No full textMetaphyton is a poorly studied algal community that can develop into large floating mats in rivers, wetlands and lakes. In this thesis, I examined the role of nutrients in determining differences in metaphyton biomass both seasonally and spatially within a lowland temperate river, the Rideau River, Ontario. The source of nutrients was also examined by analyzing the stable isotope signature of the mats in relation to adjacent land-use.
Metaphyton in the river was restricted to slow-flowing areas of the littoral zone and was mainly comprised of filamentous green algae (Spirogyra and Cladophora).
From the results of this study, conditions for the presence of large metaphyton communities in rivers include: (1) shallow littoral zones with minimal current, (2) the presence of macrophytes (as a substratum), and (3) moderate to high nutrient concentrations (particularly dissolved inorganic nitrogen). To control metaphyton in the Rideau River, the nitrogen loading to the system must be considered as well as phosphorus. (Abstract shortened by UMI.
Temporal and Spatial Trends in Toxic Cyanobacteria as Identified Through Lake Sediment DNA
No full textCyanobacterial and algal blooms can negatively affect water quality particularly when producing toxins that affect human health and wildlife. While reports of blooms are on the rise globally, their underlying causes remain unclear. The goal of this thesis was to determine temporal changes in cyanobacterial abundance and composition through sediment cores in relation to (1) altered land-use leading to cultural eutrophication and (2) warmer air temperatures that have been recorded in the past few decades. This involved evaluating the use of DNA extracted from lake sediments to quantify cyanobacterial abundance and composition.
Lake sediments preserved under appropriate storage conditions showed the potential to yield high quality DNA for downstream molecular applications. Cyanobacteria, quantified using the 16S rRNA gene, were found to have increased over the last three decades in comparison to historical averages (since the 1850s) both inside and outside a protected area in western Quebec, Canada, in concert with recent regional warming. Copy numbers of 16S rRNA genes specific to cyanobacteria largely correlated to temporal trends in cyanobacterial pigments. Larger percent increases were seen in cyanobacterial genes in recent times compared to changes in the eubacterial glutamine synthetase (glnA) gene. The mcyD gene was quantified as a proxy for microcystin production through sediment cores from two lakes of western Canada. Copy numbers of both mcyD and Microcystis 16S rRNA correlated with chemical analyses of microcystin through time in cores. Cyanobacteria in the more eutrophic of these lakes shifted toward less diverse assemblages and more toxigenic taxa in recent years. Lastly, temporal and spatial changes in cyanobacterial diversity were analyzed through pyrosequencing of cyanobacterial 16S rRNA along a latitudinal transect representative of northern Canada. Significant shifts towards less diverse assemblages were found, composed of potentially toxigenic strains, suggestive of climate warming in northern latitudes. These results support recent reports of increased abundance and geographic expansion of cyanobacteria and point to increases in cyanotoxins in some cases. Using DNA archived in sediments to determine the historical state of cyanobacterial abundance and diversity could help inform lake management policies
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The Role of Iron and Anthropogenic Activities in Eutrophication: A Contemporary and Paleolimnological Study
No full textIn this study, I examined water chemistry of 31 Canadian Shield lakes in relation to catchment characteristics to test the hypothesis that Shield lakes with more marble may exhibit iron (Fe) deficiency and, hence, be more vulnerable to eutrophication. I performed a diatom-based paleolimnological reconstruction of one of these lakes (Heney Lake), which was subjected to anthropogenic stresses including a fish farm. Results suggest that the presence of marble influenced lake chemistry, including lowering the ratio of Fe: P. The reconstruction of historical P concentrations was not statistically possible but past Fe could be inferred, which no previous study has attempted. Certain eutrophication-associated diatom species suggest that logging and European settlement beginning in the early XXth century led to a slight increase in nutrient concentrations. However, a more important diatom species shift was likely related to climate change, as observed in other temperate lakes worldwide
Metal concentrations in benthic invertebrates in peatlands.
No full textIn order to assess the influence of various abiotic and biotic factors on metal accumulation in peatlands, insects were collected from bogs, mineral poor fens and circumneutral fens located in Central Ontario. The peatlands represented a gradient in alkalinity from 0 (acid bogs) to 200 eqL\sp{-1} (circumneutral fens). Further, the peatlands had important hydrological differences with no obvious inflows in the bogs and inflow/outflow streams in the fens. Given these contrasting environments, it was hypothesized that there would also be differences in metal accumulation in the associated biota. The results of this study indicate that the acidification of peatlands, whether natural or anthropogenic, will not lead to greater availability of metals such as Zn, Cu, Al, and Mn. High organic matter levels may serve to mitigate the effects of acidification on metal availability in such peatlands. (Abstract shortened by UMI.
Metabolic Variation in the Toxigenic Cyanobacterium Microcystis Aeruginosa
No full textCyanobacteria are notorious for their potential to produce toxins with human health effects, particularly the hepatotoxic microcystins (MCs), but cyanobacteria also produce other bioactive compounds. A wide variety of oligopeptides including aeruginosins, cyanopeptolins and cyanobactins may be as toxic as MCs. To investigate the production of these compounds, an UPLC QTOF-MS/MS method was developed to compare the metabolomic profiles of various strains of a common bloom-forming and toxigenic species, Microcystis aeruginosa, as well as those obtained from lakes with mixed cyanobacterial assemblages. Although many compounds could not be confirmed, MCs were rarely the dominant secondary metabolite in any sample. Since the biological role of MCs remains unknown, I tested the hypothesis that MCs provide protection against oxidative stress as induced through exposure to the herbicide atrazine and UV radiation in pure cultures of toxic vs non-toxic strains. Results were inconclusive and varied between strains suggesting other mechanisms exist to counter oxidative stress
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