Dissertations / Theses: 'Freshwater systems'

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Klein, Sascha. "Microplastics in Freshwater Systems." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-200861.

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Synthetic polymers are one of the most significant pollutants in the aquatic environment, because of abilities such as buoyancy and extreme persistency. Serious effects are expected from so-called microplastics (particle size <5 mm) that are reported in rivers, lakes as well as the ocean and that accumulate in sediments worldwide. In this thesis the abundance of microplastics in river shore sediments in the Rhine-Main area of Germany was studied. Therefore, a new method was developed that is based on a sodium chloride density separation with subsequent destruction of natural debris, and identification of the plastic particles by microscopy or Fourier transform infrared spectroscopy (FTIR). Using the improved density separation, microplastics were separated from river shore sediments of 12 sites originating from the river Rhine, the river Main, and the stream Schwarzbach. Large amounts of microplastic particles of up to 1 g kg-1 or up to 4000 particles kg-1 were detected in the shore sediments. The identification by FTIR showed that polyethylene, polypropylene, and polystyrene were the most abundant polymer types in the sediments, covering over 75% of all plastics identified. Transport of microplastics from tributaries to main streams was indicated by the detection of identical pellets in the River Rhine and in the Main mouth. Comparable concentrations detected by sampling one site over a period of two years suggest a constant pollution of the river shore sediments with microplastics. For deeper insights into the sorption process of organic contaminants to synthetic polymers in freshwater systems, batch experiments in synthetic freshwater were conducted to determine sorption kinetics and sorption isotherms for four selected glass state polymers (polycarbonate, poly(methyl methacrylate), polystyrene, and polyvinyl chloride) and six different model substances (carbamazepine, hexachlorocyclohexane (β/γ), 17α-ethynilestradiol, chlorpyrifos, and o,p-dichlorodiphenyltrichlorethane). Sorption to the polymer particles was observed for all contaminants increasing with the KOW values of the contaminants. Because of losses of contaminants in control samples, sorption reaction models could be applied to four out of six contaminants, and isotherms were calculated for three contaminants. Furthermore, influences of the different polymer types used were observed in the experiments. Finally, microplastics separated from sediments were extracted and analyzed by GC/MS and LC-MS/MS using target screening methods and non-target approaches. Different pesticides were identified in the polymer particles, suggesting that microplastics can act as a sink for hydrophobic contaminants. Moreover, several plastic additives such as phthalates or chlorinated flame retardants were identified. For this reason, it is very likely that microplastics act as a direct source for these chemicals in aquatic systems. The results of this thesis stress the urgency for the mitigation of the plastic particles in the aquatic environment.

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Manolopoulos, Helen. "Metal sulfides in oxidizing freshwater systems /." *McMaster only, 2001.

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Rodrigues, Mariana Oliveira. "Impacts of microplastics in freshwater systems." Master's thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/21469.

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Mestrado em Toxicologia e Ecotoxicologia Plastics, in particular microplastics (particles with dimensions < 5 mm), are a widespread and persistent pollutant constituting an emerging scientific and societal issue. Its characteristics allied to an inadequate management contributes to their accumulation in aquatic systems, reaching high densities. Moreover, they can also interact with environment affecting economy, human health and aesthetics. However, most of scientific studies have been focused in marine environment while scarce knowledge exists regarding freshwater systems, including in Portugal. Hence, this study aimed to contribute to fill this gap of information both in uniformization of methodologies of isolation of microplastics (MPs) in water samples as well as on the MPs’ characterization in a Portuguese freshwater system. Thus, the first part of this study aimed to assess the effectiveness of distinct separation methods including density separation methods (sucrose, olive oil and zinc chloride) as well as organic matter degradation methods (hydrogen peroxide and multienzymatic detergent). For that, artificial samples containing the eleven most common types of plastics were prepared, subjected to the different methods and then polymers were detected, quantified and identified using a stereoscope microscope and Fourier transform infrared spectroscopy (FTIR). Among the several tested methods, the most cost-effective was the method of wet peroxide oxidation with addition of zinc chloride. Hence, this study highlights the importance of the use of zinc chloride both in the processing of sediment and water samples. In a following step, the abundance and distribution of MPs in the water and sediment of Antuã river were determined by applying the separation method identified as the most effective previously. The abundance of MPs in water varied from 5 – 8.3 mg m-3 or 58 – 193 items m-3 in March and from 5.8 – 51.7 mg m-3 or 71 – 1265 items m-3 in October. In sediments, the abundance of MPs varied from 13.5 – 52.7 mg kg-1 or 100 – 629 items kg-1 in March and from 2.6 – 71.4 mg kg-1 or 18 – 514 items kg-1 in October. It shows that this river is severely impacted by MPs, in orders similar to that found in marine/coastal environments. A spatial and temporal variation was observed dependent on seasonal conditions, flow velocity and anthropogenic pressure. Thus, this study emphasizes the importance of rivers as carriage systems of MPs, and highlight the potential impacts of MPs as emerging contaminants on freshwater systems. Os plásticos, em particular os microplásticos (partículas com dimensões <5 mm), são poluentes ubíquos e persistentes que constituem uma preocupação científica e social emergente. As suas características, aliadas a uma gestão inadequada, contribuíram para a sua acumulação nos sistemas aquáticos, podendo atingir elevadas densidades. Estas partículas podem interagir com o ambiente, afetando a economia, a saúde humana e a estética. No entanto, a maioria dos estudos científicos tem-se focado no ambiente marinho, sendo o conhecimento sobre os sistemas de água doce escasso, incluindo em Portugal. Deste modo, este trabalho pretende contribuir para esta lacuna de informação, tanto ao nível da uniformização de metodologias de isolamento de microplásticos (MPs) em amostras de água como na caracterização de MPs num sistema de água doce português. Assim, numa primeira fase este estudo pretendeu avaliar a eficácia de diferentes métodos de separação, incluindo métodos de separação por densidade (açúcar, azeite e cloreto de zinco), bem como métodos de degradação de matéria orgânica (peróxido de hidrogénio e detergente multienzimático). Neste sentido, amostras artificiais contendo onze tipos de plásticos pertencentes aos polímeros mais comuns foram preparadas e submetidas aos diferentes métodos, procedendo-se posteriormente à quantificação e identificação dos polímeros usando um microscópio estereoscópico e um espectroscópio de infravermelhos com transformada de Fourier (FTIR). De entre os vários métodos testados, aquele que revelou o melhor custo-eficácia foi o método da oxidação com peróxido de hidrogénio e adição de cloreto de zinco. Este estudo enfatiza a importância do uso do cloreto de zinco tanto no processamento de amostras de sedimento como de água. Numa fase seguinte do estudo, determinou-se a abundância e distribuição de MPs na água e sedimento do rio Antuã, aplicando o método de separação identificado como o mais eficaz anteriormente. A abundância de MPs nas amostras de água variou entre 5 – 8.3 mg m-3 ou 58 – 193 items m-3 em Março e entre 5.8 – 51.7 mg m-3 ou 71 – 1265 items m-3 em Outubro. No sedimento, a abundância de MPs variou entre 13.5 – 52.7 mg kg-1 ou 100 – 629 items kg-1 em Março e entre 2.6 – 71.4 mg kg-1 ou 18 – 514 items kg-1 em Outubro. Estes resultados demonstram que este rio está severamente impactado por MPs, com valores semelhantes aos encontrados em sistemas marinhos/costeiros. Foi ainda observada uma variação espacial e temporal, dependente da estação do ano, do caudal do rio e da pressão antropogénica. Deste modo, este estudo vem enfatizar a importância dos rios como sistemas de transporte de MPs e realçar os potenciais impactos dos MPs como contaminantes emergentes nos ecossistemas aquáticos dulçaquícolas.

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Palmer-Felgate, Elizabeth Jane. "Biogeochemical controls on phosphorus dynamics in freshwater systems." Thesis, University of Leeds, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.536096.

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Peters, Michael Steven. "Temporal impacts of volcanic ash in freshwater systems." Thesis, University of Canterbury. Geological Sciences, 2012. http://hdl.handle.net/10092/7639.

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Volcanic ash can cause acidification and metal contamination of freshwater systems. Shmt-te1m chemical and pH fluxes in water have been attributed to dissolution of the ash surface film while dissolution of the glassy matrix has been linked to metal input over longer time periods. The rate at which ash surface film and glassy matrix dissolution occurs and the associated impact of ash to freshwater pH and chemistry over time has not previously been established. The influence of volcanic ash BET surface area on initial pH fluxes and metal dissolution rates in freshwater systems was investigated using pristine basaltic-andesite volcanic ashes from Mt. Ruapehu (New Zealand), Mt. Sakurajima (Japan) and Soufriere Hills (Montserrat). The aim of this study was to investigate the bi-temporal hazard of volcanic ash in freshwater systems including freshwater drinking-water supplies. All ashes provided an immediate pH decrease to water that was directly related to sulphur concentrations released from ash surface film (p < 0.02). The maximum pH decrease was observed after 2.5 minutes. The rate of change was independent of ash surface area due to the high solubility of the surface film. Initial pH decreases for all ashes were transient with the degree of acidification lessening following surface film removal via water rinse(s) and time in solution. The rapid rate of dissolution means in 'real-world' settings the surface film will be removed within the upper layer of a water body and will only provide a shmt-te1m source of acidification and chemical contamination. Release rates for (Al, Mn and As) from the glassy matrix of ashes over longer-time periods (0-1 00 hours) were dependent on BET surface area and ash to water ratios for each ash. The influence of differing physical and chemical characteristics between the three ashes, however, prevented surface area being used as a proxy for all dissolution rates. The metal release rates were used to calculate the time needed for the drinking water quality guidelines to be exceeded under three different ashfall scenarios. Using the derived metal release rates for the Mt Ruapehu Ash, Al was the element most likely to exceed the drinking water standards. This exceedance can be attributed to the relatively fast release rate (Al 10.4 flg h -I m-2 ) and high concentration within the ash (14% by weight). An ashfall of 1 Omm would result in exceedances of the drinking water standards for AI in the Waitakere and Hays Creek Reservoirs (Auckland city water supply) after ~8 hours.

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Sanchez, Montelongo Jessica Lynn. "The Adaptive Evolution of Herbivory in Freshwater Systems." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3813.

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Herbivory is thought to be nutritionally inefficient relative to carnivory and omnivory. But, herbivory evolved from carnivory in many lineages, suggesting that there are advantages to eating plants. To understand the adaptive significance of the transition from carnivory to herbivory, I proposed five hypotheses for the adaptive evolution of herbivory and reviewed the current freshwater literature to identify conditions where eating plants might be adaptive over eating animals. I tested three of these ideas (Suboptimal Habitat, Heterotroph Facilitation, and Lipid Allocation) using the herbivorous Sailfin Molly (Poecilia latipinna)and identified each as a potential mechanism for the evolution of herbivory. To understand the origins of herbivory in Sailfin Mollies, I reconstructed ancestral habitats and dietsacross a phylogeny of the genus Poeciliaand then used phylogenetically independent contrasts to identify patterns of diet evolution. I found that the degree of herbivory increases with increasing salinity affiliation, suggesting that in this genus, herbivory evolved as an adaptation for invading less productive saline habitats from freshwaters. This result is consistent with the Suboptimal Habitat hypothesis, which states that herbivory allows organisms to invade and persist in ‘suboptimal’ habitats. To understand how herbivory is maintained in extant populations, I raised juvenile Sailfin Mollies in mesocosms and enclosure cages placed in the Everglades to document that dietary autotrophic lipids play a role in early life history by supporting rapid growth (Lipid Allocation). However, dietary bacterial fatty acids promoted fish survival, consistent with the Heterotroph Facilitation hypothesis, which states that indirect detritivory supplements the herbivorous diet. Finally, I quantified periphyton quality/availability and consumer density across the Everglades landscape to examine the correlates of trophic dynamics in nature. Results revealed that herbivores can persist in diverse habitats and survive on varying resources when habitats are unfavorable, supporting the Suboptimal Habitat hypothesis.

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She, Nian. "Chaos in aquatic systems /." Thesis, Connect to this title online; UW restricted, 1995. http://hdl.handle.net/1773/6370.

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Wagner, Sasha. "Black Carbon: Sources, Mobility and Fate in Freshwater Systems." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2213.

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Black carbon (BC) is a complex mixture of polycondensed aromatic compounds produced by the incomplete combustion of biomass during events such as wildfires and the burning of fossil fuels. Black carbon was initially considered to be a refractory form of organic matter. However, recent studies have shown that BC can be quite mobile and reactive in the terrestrial environment. Black carbon can be translocated from soils and sediments in the form of dissolved BC (DBC). A global correlation between DBC and bulk dissolved organic carbon (DOC) has been established for fluvial systems where DBC comprises approximately 10% of the total DOC pool, which suggests that DBC may be a significant contributor to the global carbon cycle. The primary objective of this thesis was to further characterize DBC and elucidate some of the specific physical and chemical processes that promote its transfer to the aqueous phase and drive the DBC-DOC relationship. The molecular composition and qualitative distribution of DBC was assessed using Fourier transform ion cyclotron resonance mass spectrometry. Black carbon in both dissolved and particulate (PBC) phases was quantified by the benzenepolycarboxylic acid method. Dissolved BC was found to contain considerable amounts of nitrogen and the export of this dissolved black nitrogen was linked to watershed land use in global rivers. The riverine flux of PBC, a previously unstudied BC removal mechanism, was significantly increased by local wildfire activity. However in-stream DBC did not appear to be affected by short-term fire events. Once translocated to surface waters, DBC is susceptible to photodegradative processes. Dissolved BC in high molecular weight DOC fractions was more photoreactive than DBC associated with lower molecular weight fractions. In the coming decades, wildfire frequency is expected to increase with climate change and natural lands will continue to be altered for anthropogenic use. These processes have already been shown to significantly impact the composition of DOC and associated DBC exported to inland waters. The quality of DBC influences its stability in soil and resistance to degradation. Therefore, it is essential that we aim to fully understand DBC dynamics in natural systems in order to assess its contribution to global carbon cycling.

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Martin, Grant Douglas. "Drivers of macrophyte assemblages in South African freshwater systems." Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1004127.

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Potentially damaging submerged invasive freshwater macrophytes have been identified in South African freshwater systems, but have received less attention than their floating counterparts. To ascertain the changes and effects that these species may have on macrophyte ecology, an understanding of the drivers of macrophyte assemblages is essential. The aims of this thesis were to investigate select abiotic and biotic factors driving introduction, establishment and spread of submerged macrophytes in South Africa. Surveys on the status of submerged plant species in South Africa were conducted to find out the distribution and diversity of the species present, imported to, and traded in South Africa. Numerous submerged indigenous and invasive macrophyte locality records were collected during field surveys, of which many were first time records. Pet stores and aquarist trading activities were identified as potential vectors for the spread of submerged macrophytes through online surveys and personal interviews. These results highlighted the potential these species have for continuing to enter, and spread within South African water bodies. Maximum Entropy (MAXENT) is a general-purpose method used to predict or infer distributions from incomplete information, and was used here to predict areas suitable for the establishment of five of these invasive macrophytes. Many systems throughout South Africa, particularly those in the subtropical coastal regions, were found to be climatically suitable for the establishment of Elodea canadensis Michx., Egeria densa Planch., Hydrilla verticillata (L.f.) Royle (all Hydrocharitaceae), Myriophyllum spicatum L. (Haloragaceae), and Cabomba caroliniana Gray (Cabombaceae). Despite the high probability of invasion, facilitated by vectors and suitable climate, South Africa’s rich indigenous submerged aquatic flora may be preventing the establishment of these submerged invasive species. Studies on the competitive interactions between a common indigenous submerged macrophytes, Lagarosiphon major (Roxb.) (Hydrocharitaceae) and M.spicatum, an invasive native to Eurasia, were conducted to ascertain which conditions influence competitive superiority. High sediment nutrient conditions significantly increased the growth rate and competitive ability of both species, while clay sediments significantly increased the competitive ability of L. major over M. spicatum, but sandy sediments improved the competitive ability of M. spicatum. These results highlighted the dynamic changes in competition between submerged species driven by abiotic factors, but did not take into consideration the effect that herbivory, a biotic factor, could have on competition between the two species. The effect of herbivory by phytophagous insects of submerged plant species has been regarded as negligible. To find out what this effect is, multiple field surveys were undertaken throughout South Africa to find natural enemies of indigenous Lagarosiphon species with the aim of identifying such species, and quantifying their influence on plant growth dynamics. Several new phytophagous species were recorded for the first time. An ephydrid fly, Hydrellia lagarosiphon Deeming (Diptera: Ephydridae) was ascertained to be the most ubiquitous and abundant species associated with L. major in South Africa. The influence of herbivory by this fly on the competitive ability of L. major in the presence of M. spicatum was investigated using an inverse linear model, which showed that herbivory by H. lagarosiphon reduced the competitive ability of L. major by approximately five times in favour of M. spicatum. This study served to highlight the importance of herbivory as a driver of submerged aquatic plant dynamics. Current ecological theory emphasises the importance of investigating beyond plant-herbivore interactions, by including multitrophic interactions in community dynamics. Therefore, the potential of parasitism by a parasitoid wasp, Chaenusa luteostigma sp. n. Achterberg (Hymenoptera: Braconidae: Alysiinae) on H. lagarosiphon to shift the competitive interactions between the two plant species was also examined. The addition of the parasitoid reduced the effect of herbivory by the fly on L. major by half, thereby shifting the competitive balance in favour of L. major over M. spicatum. This study provides valuable insight into a selection of drivers of submerged macrophyte assemblages of South Africa. It highlights the precarious position of South African freshwater systems with regard to the potential invasion by damaging submerged invasive species. It also provides interesting insights into the effect of competition, herbivory and parasitism on the establishment and spread of species within submerged freshwater systems. Understanding the different influences could assist managers and policy makers to make validated decisions ensuring the integrity of South African freshwater systems.

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Knights, Deon Hanley. "The Fate of Nutrients in Two Coastal Freshwater Systems." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu159494472722077.

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Pattinson, Sarah N. "Denitrification within riverine systems of north-east England." Thesis, Durham University, 1999. http://etheses.dur.ac.uk/4558/.

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This study was undertaken to investigate denitrification and nitrous oxide production in sediments and the key environmental factors influencing these within selected river systems of the LOIS (Land-Ocean Interaction Study) area in North-East England and southern Scotland. Seasonal and spatial trends were evident in both environmental and denitrification data measured monthly for 1.5 years along the Swale-Ouse system from source to tidal limits. Denitrification, measured in sediment cores using acetylene inhibition and expressed by unit area of sediment, increased with distance from source down to freshwater tidal limits. Results from a supplementary survey of the freshwater tidal reaches of the Yorkshire Ouse showed a decrease from the tidal limits. Denitrification activity showed a spring (March to May) peak, particularly in the lowland sites. The highest rate (883±134 µmol N m(^-2) h(^-1)) was measured on the River Wiske, a highly eutrophic lowland tributary to the Swale. A high degree of colinearity was evident between environmental variables, although a significant relationship between denitrification, nitrate and temperature was found through multiple regression. For comparison, measurements were made in the less populated Tweed river system. The seasonal and spatial trends evident in both the environmental and denitrification data from the River Tweed, under a more limited sampling programme, were generally consistent with those observed in the Swale-Ouse system. An intensive field investigation of 50 river sites showed that both potential denitrification rate and N(_2)O production in sediment slurries were positively correlated with nitrate water concentration, sediment water content and percentage of fine (<100 µm) sediment particles. An experimental study investigating the kinetic parameters for denitrification, found that sediment cores taken along the Swale-Ouse exhibited a saturation type curve with added nitrate. Apparent affinity and estimates of apparent maximum velocity for mixed populations of denitrifying bacteria showed an increase on moving downstream and were highest on the Wiske.

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Amin, M. K. A. "The ecology and genetics of Pseudomonas bacteriophage in freshwater systems." Thesis, Cardiff University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381224.

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Wu, Dayong. "Bioassessing lotic systems using benthic insect communities in southeast Wyoming." Laramie, Wyo. : University of Wyoming, 2006. http://proquest.umi.com/pqdweb?did=1296087911&sid=2&Fmt=2&clientId=18949&RQT=309&VName=PQD.

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Steinsen, Ragnar. "Form Processing Program for the Institute of Freshwater Fisheries in Iceland." Thesis, University of Skövde, Department of Computer Science, 1998. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-231.

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Instituten för Färskvatten Fiske på Island administrerar och styr fiske i över 80 av Islands floder. Detta görs genom att för varje fisk som fångas registreras fiskens längd, tyngd, kön plus några andra attribut i en bok, som kallas för “fiskebok”. Dessa böcker skickas sedan till Institutet varje år där informationen ur böckerna manuellt registreras i en databas. Den manuella inmatningen är mycket tidskrävande och dyr för Instituten. Önskemål finns om automatisering av denna process. Lösningen som föreslås här är att skanna in fiskeböckerna, översätta den inskannade bilden till datorhanterbara symboler som sedan lagras i en databas. Detta projekt fokuserar endast på överföringsprocessen, det vill säga överföringen av bilder till symboler. I stort fanns det tre problem som behövde lösas, dels att ändra böckerna så att de skulle bli lämpliga för att överföra automatiskt, dels att hitta de fält som skulle överföras samt att överföra fälten. Det fanns två typer av fält som skulle överföras; isolerade siffror och kryss. Att se om en kryssruta är ikryssad eller inte, är kanske inte så svårt men överföring av bild av siffra till en symbol var det stora problemet i detta projekt. För att lösa detta används teknik som kallas för ”Artificiella Neurala Nätverk” eller ”ANN”. Till slut fungerade lösningen någorlunda, fälten kunde enkelt hittas och överföringen av kryssymbolerna blev helt korrekt. Överföringen av siffror blev tyvärr inte lika bra. I en undersökning visade det sig att på varje isolerad siffra så översatte det framtagna Neurala Nätverket 87% av siffrorna korrekt, och med innehållskontroll (t.ex. att det finns bara 31 dagar i månad) kunde denna siffran bli 96%. Om programmet någon gång skall sättas i bruk måste vissa delar av det förbättras, men i och med att bristerna är kända kan man säga att prototypapplikationen som gjordes kan fungera bra som bas till fortsätt arbete.

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Kazanjian, Garabet. "Primary production in shallow freshwater systems amid a rapidly changing world." Doctoral thesis, Humboldt-Universität zu Berlin, 2019. http://dx.doi.org/10.18452/20561.

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Kleine, flache Gewässer gelten als sogenannte „hotspots“ der Primärproduktion und Kohlenstoffbindung. Diese Doktorarbeit zielt darauf ab, die Primärproduktion verschiedener kleiner Gewässer zu quantifizieren sowie die Mechanismen, die den Kohlenstoffkreislauf dieser Systeme beeinflussen, zu analysieren. Der Fokus liegt dabei auf dem Einfluss globaler Veränderungen, die diese Mechanismen verändern können Im ersten Abschnitt wurde die Primärproduktion (PP) in kleinen, temporären Söllen untersucht, die sehr anfällig für Störungen sind. Ich konnte zeigen, dass die PP der Sölle im Sommer außergewöhnlich hoch ist, was hauptsächlich auf eine hohe Makrophytenproduktion zurückzuführen ist Im zweiten Teil analysiere ich die Ergebnisse eines Experiments zum Einfluss erhöhter Temperaturen auf die benthische PP kleiner Gewässer im Frühjahr. Acht Mesokosmen wurden bei normalen und um 4°C erhöhten Wassertemperaturen gemäßigter Breiten betrieben. In der ersten Hälfte des Experiments konnte ich eine erhöhte benthische PP in den erwärmten Mesokosmen feststellen, die auf direkte Temperatureffekte und indirekte Auswirkungen einer höheren Nährstoffverfügbarkeit zurückzuführen war. Anfang Juni stieg jedoch der Einfluss der Makroinvertebraten auf das Periphyton in den erwärmten Mesokosmen, so dass keine Unterschiede in der PP mehr auftraten. Schließlich, untersuche ich die Resilienz eines Sees gegenüber einem plötzlichen Eintrag gelösten organischen Kohlenstoffs (DOC) aus dem terrestrischen Umland, der zu einer starken Braunfärbung des Wassers führte. Der Fokus liegt dabei auf Veränderungen der Wasserqualität und der aquatischen PP des Sees, nachdem sich die DOC-Konzentration verfünffacht hatte. Drei Jahren nach Erreichen der maximalen DOC- und Gesamt-Phosphor im See sanken diese signifikant, lagen jedoch noch immer 1,5- bzw. 2-fach oberhalb der Ausgangskonzentrationen vor dem DOC-Eintrag. Die benthische PP zeigte eine teilweise Erholung, erreichte jedoch ebenfalls nicht die Ausgangswerte. Small, shallow freshwater ecosystems are now considered hotspots of primary production & carbon sequestration. Yet till recently they’ve been mostly neglected. This thesis aims at explaining the underlying mechanisms affecting carbon cycling in these systems, particularly focusing on how contemporary global changes alter ecological equilibria. In the first section, using a compartmental approach, I study primary production in small, temporary ponds (kettle holes) within agricultural fields that are highly susceptible to environmental & anthropogenic disturbances. I show that summertime gross primary production (GPP) in kettle holes is exceptionally high, mostly driven by a strong macrophyte production. In winter, periphyton contributes to the majority of the systems’ GPP. High summertime deposition, correlated to GPP, and low sediment mineralization rates, signified a high potential for carbon burial. In the second experiment, I test the impact of increased temperatures on periphyton production during spring. I use eight mesocosms running at normal & +4°C temperatures. Initially, I recorded elevated periphyton GPP in the warmed treatment driven by direct temperature effects & indirect effects of higher nutrient availability. By late spring, the trend is reversed due to increased grazing pressure in the warm treatment. In the third study, I investigate a lake’s resilience to a sudden brownification event: A 5-fold increase in dissolved organic carbon (DOC) concentrations. Within three years after peak brownification, the lake DOC & total phosphorous concentrations dropped significantly but seem to have plateaued at 1.5 & 2-fold their pre-brownification levels, respectively. Consequently, benthic GPP, which had collapsed due to light limitation at peak brownification, marked only a partial recovery, while phytoplankton (& whole-lake) GPP remained higher than pre-brownification levels. Phytoplankton & periphyton exhibited an inverse response to DOC & TP concentrations.

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NAVA, VERONICA. "Microplastics in freshwater systems: characterization, quantification and interaction with aquatic organisms." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/363436.

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Gli ecosistemi acquatici risentono di differenti impatti antropici. Tra questi, la presenza di plastiche e microplastiche rappresenta una problematica ambientale diffusa. La maggior parte delle ricerche svolte fino ad ora si è concentrata specialmente sull’ambiente marino e le informazioni riguardanti la presenza e gli effetti di questi contaminanti nei sistemi di acqua dolce sono limitate. Inoltre, non esiste ancora nella comunità scientifica un’armonizzazione delle procedure di campionamento e dei protocolli analitici per la caratterizzazione e quantificazione delle plastiche in ambiente acquatico. Questo rende il confronto dei dati ottenuti da ricerche differenti complesso. Oltre a questi aspetti, sono necessari ulteriori studi per comprendere l’influenza che le (micro)plastiche possono esercitare sugli organismi e sul funzionamento degli ecosistemi acquatici. In particolare, le informazioni relative agli effetti sugli organismi dei più bassi livelli trofici sono molto limitate. Dato questo contesto, nella presente tesi di dottorato sono illustrati quattro lavori che hanno contribuito ad aumentare le informazioni disponibili sulle (micro)plastiche in ambienti di acqua dolce. Il primo lavoro si è concentrato sull’utilizzo della micro-spettroscopia Raman per l’identificazione della composizione polimerica dei materiali plastici, la cui determinazione è fondamentale per una corretta e adeguata caratterizzazione di questi inquinanti. Al fine di aumentare le conoscenze relativamente a questa tecnica, è stato sviluppato e descritto un database, liberamente fruibile, di spettri di diversi polimeri plastici ed additivi che possono essere comunemente individuati in ambiente. Inoltre, è stato anche sviluppato un nuovo pacchetto in R che fornisce diversi strumenti per l’analisi e l’identificazione di spettri. I vantaggi e gli svantaggi della spettroscopia Raman sono stati evidenziati e sono state fornite utili indicazioni per studi futuri. Il secondo lavoro si è invece concentrato sulla determinazione e caratterizzazione di plastiche e microplastiche nelle acque superficiali di laghi di diverse regioni del mondo. Infatti, sono stati analizzati campioni provenienti da 38 laghi (distribuiti in 28 Stati), selezionati in modo da essere rappresentativi di diverse condizioni limnologiche e differente grado di impatto antropico. I campioni sono stati prelevati seguendo una procedura standardizzata che ha permesso di ottenere in questo modo dati realmente confrontabili. Con questo dataset globale sono state valutate non solo le concentrazioni ma anche le caratteristiche delle particelle plastiche. Inoltre, l’analisi dei dati ha permesso di evidenziare la presenza di una relazione positiva tra la concentrazione di (micro)plastiche e attributi del bacino idrografico, espressione di impatto antropico. Oltre a ciò, è stato evidenziato come laghi profondi, con estesa area superficiale ed elevato tempo di ritenzione delle acque tendano ad accumulare un numero maggiore di microplastiche. Nell’ultima parte della tesi, è stata invece investigata la relazione tra microplastiche e microalghe. Questo argomento è stato approfondito attraverso un duplice approccio: dapprima è stata svolta un’estesa ricerca bibliografica e successivamente è stata condotta una sperimentazione in mesocosmi per valutare la colonizzazione di diversi polimeri plastici in ambienti con differenti caratteristiche chimico-fisiche e ambientali. Questo esperimento ha permesso di evidenziare come le microplastiche siano in grado di supportare la crescita di molte e diverse specie microalgali. Non è stata però evidenziata una specificità nella colonizzazione di polimeri differenti. Infatti, è stato mostrato come, non la composizione polimerica del substrato, ma le specie esistenti nei diversi mesocosmi e le differenti condizioni ambientali rappresentino i principali fattori che determinano ed influenzano la composizione specifica del biofilm algale. Among the multiple stressors that affect aquatic ecosystems, plastic pollution is deemed a widespread and pervasive environmental issue. The majority of the research has been conducted in marine environments and information about the occurrence and effects of these pollutants in freshwater systems is scattered. Moreover, there is a lack of consensus on sampling and analytical procedures for their characterization and quantification, which makes comparison among studies difficult. Besides, more research is needed to assess the influences of plastics and microplastics on ecosystem functions and aquatic organisms, especially focusing on lower trophic levels. Given these gaps, the present project describes four pieces of work that contribute to enhancing our knowledge about plastics and microplastics in freshwater ecosystems. Firstly, since polymer identification constitutes a fundamental step in plastic analysis, the suitability of Raman spectroscopy for polymeric characterization was examined, and a free database with Raman spectra of plastics complemented by a new R package with tools for their processing were developed and described. Advantages and drawbacks of this technique were discussed, with a particular emphasis on plastic additives, which are contained in the majority of polymers but are still poorly investigated, and a catalog with detailed information about peaks of most common plastic polymers was reported to provide guidance for further studies. Secondly, microplastic occurrence in surface water of different freshwater systems was assessed. Indeed, water samples of 38 lakes from 28 different countries covering an assortment of limnologically diverse freshwater ecosystems under varying levels of anthropogenic stress were collected, following a common protocol. This global investigation allowed obtaining comparable data about plastic concentration and features. Moreover, the results suggested the existence of a relationship between urban-related attributes of lakes/watersheds and the plastic concentration but also highlighted as large and deep lakes with high retention times accumulated plastic debris at higher concentrations. Lastly, the relationship between microplastics and microalgae was investigated. This was pursued by combining a critical review of the literature with an experimental approach aimed at analyzing the phytobenthos establishment on two different plastic polymers using a multi-site mesocosm system. This experiment highlighted that microplastics supported the growth of a rich and diversified community of microalgae, showing that many species could coexist on the surface of relatively small plastic items. Species-specificity in the colonization of the different plastic polymers was not observed. Indeed, local species pool and nutrient concentration rather than polymeric composition seemed to be the determinant factors defying the community diversity.

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Chakona, Albert. "Comparative biogeography and ecology of freshwater fishes in the Breede and associated river systems, South Africa." Thesis, Rhodes University, 2012. http://hdl.handle.net/10962/d1015694.

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Distribution patterns and levels of genetic diversity in extant taxa are a product of complex palaeogeographic processes and climatic oscillations as well as the species’ intrinsic ecological adaptations. The Cape Floristic Region of South Africa presents a unique system for studying the processes that promote species diversification and distribution patterns. This region has a high degree of endemism of both terrestrial and aquatic biota and is clearly isolated from neighbouring areas by the Cape Fold Mountains and the Great Escarpment. The objective of this study was to firstly examine the ecology of freshwater fishes belonging to the genera Galaxias, Pseudobarbus and Sandelia in the south-western CFR. This was followed by an assessment of the genetic diversity of these taxa. Unique lineages were identified and their distribution was mapped. The work aimed to explore the role of the region’s complex palaeogeographic and climatic history as well as the role of the species’ ecological adaptations in driving lineage diversification and shaping contemporary distribution patterns. The four main components of the study can be summarised as follows: 1. Habitat associations of three widely distributed lineages of Galaxias zebratus Pseudobarbus burchelli and Sandelia capensis were evaluated at multiple localities in minimally disturbed mountain tributaries of the Breede, Duiwenhoks and Goukou River systems. The lineages have distinct habitat associations which were related to differences in their morphological traits. The slender-bodied Galaxias ‘nebula’ and the fusiform-shaped Pseudobarbus ‘Breede’ are capable of exploiting upper reaches with faster water velocity. By contrast, the laterally compressed Sandelia ‘eastern’ is restricted to lower reaches, making this lineage more susceptible to a wide array of impacts. 2. A recently discovered lineage of Galaxias zebratus, (Galaxias ‘nebula’), was found to be capable of tolerating emersion for a prolonged period of time. This is the first time that such capabilities have been documented in an African galaxiid. These adaptations have implications for the interpretation of Galaxias ‘nebula’s wide distribution range. 3. The phylogeography of Galaxias ‘nebula’ across its entire distribution range was investigated using two mitochondrial genes (cytochrome c oxidase subunit I (COI) and cytochrome b (cyt b)). This lineage has a complex evolutionary history that was influenced by both intrinsic and extrinsic factors. Rare events such as episodic drainage connections during Pleistocene and Holocene pluvial periods, possibly augmented by river confluences during periods of lower sea-levels and river capture events seem to be the most credible explanation for the extensive contemporary distribution and the relatively shallow genetic divergence between different river systems. 4. Mitochondrial cyt b sequences were used (i) to assess genetic diversity in G. zebratus, P. burchelli and S. capensis from the south-western CFR and (ii) to determine the roles of intrinsic ecological adaptations and extrinsic landscape and climatic changes in promoting genetic diversification and shaping present day distribution patterns of lineages in the three taxa. Marine incursions during periods of major sea-level transgressions are proposed to have isolated populations in upland refugia, thereby driving allopatric divergence in these species. Subsequent connections of rivers during wetter periods and lower sea-levels are proposed to have facilitated post-speciation dispersal of lineages to attain present day distribution patterns. While detailed morphological studies and further genetic analysis are needed to substantiate the taxonomic status of the newly discovered lineages of Galaxias zebratus, Pseudobarbus burchelli and Sandelia capensis, results of the present study indicate that the south-western CFR represents a previously unrecognised centre of freshwater fish diversity and microendemism in the broader Cape Floristic Region. Accurate identification of lineages and comprehensive mapping of their distribution is a fundamental pre-requisite for ecological studies, assessing conservation status and implementation of appropriate conservation measures.

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Witton, K. E. "The degradation of a synthetic 2-stroke lubricating oil in freshwater systems." Thesis, University of Kent, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383093.

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19

Baudoin, Lucie Madeleine. "Testing the waters: dealing with freshwater systems in organization and management studies." Doctoral thesis, Universitat Ramon Llull, 2020. http://hdl.handle.net/10803/669985.

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Els sistemes d’aigua dolça, com ara rius, llacs o zones humides, proporcionen una infinitat de béns i serveis ecosistèmics a les societats humanes. Tot i això, la gestió d’aquests sistemes és complexa, interorganitzativa i sovint insostenible des d’una perspectiva ecològica. La investigació en estudis d’organització i gestió, tot i que pot ser fructífera, no pot contribuir a resoldre aquest problema, si no inclou aspectes conceptualment ecològics dels sistemes d’aigua dolça o no té una perspectiva del sistema. Aquestes recomanacions conceptuals i metodològiques són més fàcils a dir que a fer. Com poden els estudis d’organització i gestió integrar la gestió interorganitzativa d’un sistema d’aigua dolça amb les condicions ecològiques d’aquest sistema? Aquesta tesi doctoral intenta aprendre fent i estudia la relació entre la gestió interorganitzativa dels sistemes d’aigua dolça i l’estat ecològic d’aquests sistemes de diverses maneres, amb un enfocament interdisciplinari. Es desenvolupen tres assajos i tres enfocaments metodològics: una revisió sistemàtica de la literatura de gestió existent sobre la gestió de l’aigua dolça, un estudi qualitatiu de la inserció ecològica i una prova quantitativa dels resultats ecològics de les diferents formes de participació dels actors. Los sistemas de agua dulce, como ríos, lagos o humedales, proporcionan una gran variedad de bienes y servicios de los ecosistemas a las sociedades humanas. No obstante, la gestión de esos sistemas es compleja, interorganizacional y, a menudo, insostenible desde una perspectiva ecológica. La investigación en estudios de organización y gestión, aunque potencialmente fructífera, no puede contribuir a resolver este problema mientras no incluya aspectos conceptualmente ecológicos de los sistemas de agua dulce o no adopte una perspectiva de sistema. Tales recomendaciones conceptuales y metodológicas son más fáciles de decir que de hacer. ¿Cómo pueden los estudios de organización y gestión integrar la gestión interorganizacional de un sistema de agua dulce con las condiciones ecológicas de ese sistema? Esta tesis doctoral busca aprender haciendo y estudia la relación entre la gestión interorganizacional de los sistemas de agua dulce y la condición ecológica de esos sistemas de diversas formas, con un enfoque interdisciplinario. Se desarrollan tres ensayos y tres enfoques metodológicos: una revisión sistemática de la literatura de gestión existente sobre la gestión del agua dulce, un estudio cualitativo de la integración ecológica y una prueba cuantitativa de los resultados ecológicos de las diferentes formas de participación de los actores. Freshwater systems - such as rivers, lakes or wetlands - provide a myriad of ecosystem goods and services to human societies. Nonetheless, the management of those systems is complex, inter-organizational and often unsustainable from an ecological perspective. Research in organization and management studies, although potentially fruitful, cannot contribute to solving this issue as long as it does not include conceptually ecological aspects of freshwater systems, or does not take a system perspective. Such conceptual and methodological recommendations are easier said than done. How can organization and management studies integrate the inter-organizational management of a freshwater system with the ecological conditions of that system? This PhD thesis endeavors to learn by doing and studies the relationship between the inter-organizational management of freshwater systems and the ecological condition of those systems in various ways, with an interdisciplinary approach. Three essays and three methodological approaches are developed - a systematic review of the existing management literature on freshwater management, a qualitative study of ecological embeddedness, and a quantitative test of the ecological outcomes of different forms of actors' participation.

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Conway, Carol Leza, and n/a. "Oxic and anoxic transformations of leaf derived organic matter in freshwater systems." University of Canberra. Resource, Environmental & Heritage Sciences, 2005. http://erl.canberra.edu.au./public/adt-AUC20060519.105559.

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In Australia, significant effort goes into reducing the amount of nitrogen and phosphorus entering inland waters from point sources. However, little is known of the extent to which riparian organic matter may act as a source of these nutrients. Also, whilst the relationships between the nitrogen, phosphorus and carbon cycles are broadly known, there is little quantitative data regarding the release of these elements from Australian riparian organic matter and their subsequent microbial mineralisation within aquatic environments. In particular, comparatively little is known of their comparative role in nutrient and organic matter cycling within anoxic zones, and the influence that different riparian organic matter may have on stream water quality. This lack of such data presently hampers the ability of water managers to make educated decisions regarding the management of riparian zones in Australia. In order to improve understanding in this area, a combination of laboratory and in situ experiments were carried out in order to compare the abiotic release and aerobic/ anaerobic mineralisation of leaf derived dissolved organic carbon (DOC), dissolved nitrate/nitrite (NOx) and soluble reactive phosphorus (SRP) under different environmental conditions. Four plants common to Australian riparian zones were investigated: two native species, Eucalyptus camaldulensis (gum) and Phragmites australis (common reed), and two exotic species, Salix babylonica (willow) and Lolium multiflorum (rye grass). After 30 days, formaldehyde inhibited 1g willow and rye grass extracts contained the most SRP (0.7 mg/L), whilst gum extracts contained 0.3 mg/L and common reed 0.1 mg/L of SRP.Willow and rye grass abiotically released twice as much NOx than gum and common reed, although concentrations were only between 0.05-0.1 mg/L. Gum and common reed released the most DOC per gram of leaf matter (14 and 12 mmol/g of leaf matter respectively), but based on the initial carbon content of each leaf type, the largest percentage contributor of DOC under abiotic conditions was common reed and rye grass (both 38% mass/mass), with gum (33% mass/mass) and willow (30% mass/mass) being smaller contributors. The most bioavailable DOC was released by rye grass and common reed, with between 83 and 94% of this DOC microbially mineralised after 30 days in oxic conditions. When conditions were not inhibited, microbial growth was evident almost immediately in willow, rye grass and common reed leaf extracts. However, microbial growth was suppressed for the first 48 hours in gum leaf extracts. After this suppression period, the rate of DOC mineralisation was equal in willow and gum leaf extracts (0.1 day-1). Under anoxic conditions, the rate and extent of DOC mineralisation of willow and gum leaves depended on the type of electron acceptor provided. Added nitrate and iron III enhanced the mineralisation of both willow and gum leaves relative to no terminal electron acceptors (from zero to 0.01-0.04 and 0.002- 0.004 moles/day respectively), but added sulphate only enhanced the mineralisation of gum leaves (0.04 moles/day). When no additional electron acceptors were provided, particulate leaf mineralisation was more extensive under oxic than anoxic conditions. However, the mineralisation of leaf derived DOC were the same regardless of oxygen availability, and after 35 days in either condition the percentage of leaf DOC mineralised for each leaf type was of the order common reed > rye grass > willow > gum. All the leaf types tested were able to sustain the caddis fly larvae Triplectides australis under controlled laboratory conditions, and survival rates were high using all four leaf types as a food source. Triplectides australis did not significantly increase the amount of DOC released from each type of leaf matter, but they did consistently increase the proportion of simple carbohydrates present within the DOC fraction. The results of these experiments suggest that changes to riparian vegetation, particularly from the native to exotic species used in this study, will inherently alter in-stream concentrations of dissolved carbon and nutrients (particularly SRP). This potentially will affect in-stream, hyporheic and subsurface processes, particularly in areas where surface water flow is low and riparian leaf inputs are high.

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21

Droppo, Ian Gerald. "Characteristics of suspended and bottom sediment in natural and engineered freshwater systems." Thesis, University of Exeter, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302556.

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22

Motitsoe, Samuel Nkopane. "Mapping Nitrogen Loading in Freshwater Systems: Using Aquatic Biota to Trace Nutrients." Thesis, Rhodes University, 2016. http://hdl.handle.net/10962/d1020819.

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The majority of river systems in developing countries like South Africa, are found in catchments areas that are densely human populated, therefore are subjected to intense land-use and developmental pressures. Anthropogenic nutrient pollution or the excessive addition of nutrients is one important type of stressors that river systems often experience through intense land-use, which includes poor waste management and agricultural practices. Such events are referred to as the “urban syndrome”, were human populations and developmental demands outpace ecosystem services. Traditional measurements of water quality (e.g. physicochemical and micro-nutrient assessments) and biological monitoring (e.g. South African Scoring System 5, SASS5) techniques for assessing ecosystem health have being widely used to reflect the ecological health and status of river systems. However these techniques have a number of challenges associated with their application. SASS5 which is used most prevalently in southern Africa for example, can only be applied in lotic systems, it is habitat dependent and finally (but arguably most importantly) it cannot identify the source of pollution inputs. Recent laboratory studies using stable isotopic ratios (δ15N and δ13C) of aquatic macrophytes (duckweed: Spirodela sp.) have shown successful differentiation between different N-sources and the mapping of temporal and spatial nitrogen dynamics in freshwater systems. Furthermore δ15N isotopic values of Spirodela sp. showed the capability to act as an early warning indicator of eutrophication, before the onset of aquatic ecosystem degradation. Therefore, this study aimed to field test the potential of sewage plume mapping using the stable isotopic values of Spirodela sp. and aquatic macroinvertebrates at nine study sites on the Bloukrans-Kowie River and ten study sites on the Bushman-New Year’s River systems in the Eastern Cape, South Africa. And more...

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23

Yamane, Hideyuki. "Reproductive strategies and interspecific interactions in nest-association systems of freshwater fishes." 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/142416.

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24

AMALFITANO, STEFANO. "Structure and function of benthic microbial community in highly variable freshwater systems." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2008. http://hdl.handle.net/2108/576.

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In the semi-arid Mediterranean regions, extended reaches of rivers and streams show a recurrent dry phases of varying duration and spatial extent. It is important to study the effects of water stress on riverine ecological processes since freshwater systems are crucial in linking terrestrial and marine environments, My Doctorate thesis research, supported by the European TempQsim project (EVK1-CT2002-00112), was aimed to investigate the dynamics of microbial communities associated to sediments in temporary rivers. In particular, I have been investigating the effects of water stress on the structure and function of benthic bacterial communities and their role in the carbon cycle of rivers characterized by a seasonal hydrologic regime. Bacterial abundance and phylogenetic composition were assessed by molecular techniques, while bacterial activity was estimated by measuring the incorporation rates of radioactive tracers and by immunofluorescence. From a methodological point of view, all applied techniques required a specific optimization phase in order to increase their analytical efficiency. In particular, a detachment procedure to extract and purify bacterial cells from freshwater sediments was optimized by the combined use of different chemical and physical treatments, followed by high-speed density gradient centrifugation using the medium Nycodenz. This procedure was initially applied to analyze the benthic bacterial communities in rivers with stable water flow conditions (Rivers Albegna, Ente, Fiora – Tuscany, Italy; River Cremera – Lazio, Italy). In addition, the efficiency of specific in situ hybridization techniques (Fluorescence In Situ Hybridization with fluorescently monolabeled probes – FISH; Fluorescence In Situ Hybridization with signal amplification by Catalyzed Reporter Deposition – CARD-FISH) was tested with regards to the different physicochemical characteristics of selected sediments (i.e. sediment organic matter and moisture content). In this respect, CARD-FISH protocol was improved to better estimate the occurrence of specific phylogenetic clusters in dry sediments. For the field study, sediments were regularly collected at the river outlet section of the River Mulargia (Sardinia, Italy). A seasonal in-depth study was performed for benthic bacterial composition and activity analyses. Additional tests were performed in artificial microcosms to experimentally describe benthic bacterial responses to drying and rewetting processes, by simulating desiccation and re-inundation of sediments collected from four European temporary rivers (River Mulargia and Tagliamento - Italy; River Krathis - Greece; River Pardiela - Portugal). In a further laboratory experiment, the composition and activity of the bacterial community that primary colonized the water phase was followed in microcosms set up with Mulargia sediments. This study could contribute to better understand the ecological role of those benthic microbes that reside in a state of low-activity in dry sediments and promptly colonize the new incoming water at the end of the dry period. In synthesis, my Doctorate research contributed to a better understanding of the functional role of bacterial community in river sediments. The results could help to elucidate the mechanisms involved in the sediment transformation processes during drought periods, which are attended to increase in length and frequency as a possible effect of climatic changes.

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Ferronato, Chiara <1984&gt. "Water, sediment and soil physicochemical interactions in freshwater, brackish and saline systems." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/6881/1/Ferronato_PHD.pdf.

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The physicochemical interactions between water, sediment and soil deeply influence the formation and development of the ecosystem. In this research, different freshwater, brackish and saline subaqueous environments of Northern Italy were chosen as study area to investigate the physicochemical processes which occur at the interface between water and sediments, as well as the effects of soil submergence on ecosystem development. In the freshwater system of the Reno river basin, the main purpose was to define the heavy metals hazard in water and sediments of natural and artificial water courses. Heavy metals partitioning and speciation allowed to assess the environmental risk linked to the critical action of dredging canal sediments, for the maintenance of the hydraulic safety of plain lands. In addition, some bioremediation techniques were experimented for protecting sediments from heavy metals contamination, and for giving an answer to the problem of sediments management. In the brackish system of S. Vitale park, the development of hydromorphic and subaqueous soils was investigated. The study of soil profiles highlighted the presence of a soil continuum among pedons subjected to different saturation degrees. This investigation allowed to the identification of both morphological and physicochemical indicators, which characterize the formation of subaqueous soils and describe the soil hydromorphism in transitional soil systems. In the saline system of Grado lagoon, an ecosystem approach was used to define the role of water oscillation in soil characterization and plants colonization. This study highlighted the close relationship and the mutual influence of soil submergence and aeration, tide oscillation and vegetation cover, on the soil development. In view of climate change, this study contribute to understand and suppose how soil and landscape could evolve. However, a complete evaluation of hydromorphic soil functionality will be achieved only involving physiological and biochemical expertise in these kind of studies.

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26

Ferronato, Chiara <1984&gt. "Water, sediment and soil physicochemical interactions in freshwater, brackish and saline systems." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/6881/.

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The physicochemical interactions between water, sediment and soil deeply influence the formation and development of the ecosystem. In this research, different freshwater, brackish and saline subaqueous environments of Northern Italy were chosen as study area to investigate the physicochemical processes which occur at the interface between water and sediments, as well as the effects of soil submergence on ecosystem development. In the freshwater system of the Reno river basin, the main purpose was to define the heavy metals hazard in water and sediments of natural and artificial water courses. Heavy metals partitioning and speciation allowed to assess the environmental risk linked to the critical action of dredging canal sediments, for the maintenance of the hydraulic safety of plain lands. In addition, some bioremediation techniques were experimented for protecting sediments from heavy metals contamination, and for giving an answer to the problem of sediments management. In the brackish system of S. Vitale park, the development of hydromorphic and subaqueous soils was investigated. The study of soil profiles highlighted the presence of a soil continuum among pedons subjected to different saturation degrees. This investigation allowed to the identification of both morphological and physicochemical indicators, which characterize the formation of subaqueous soils and describe the soil hydromorphism in transitional soil systems. In the saline system of Grado lagoon, an ecosystem approach was used to define the role of water oscillation in soil characterization and plants colonization. This study highlighted the close relationship and the mutual influence of soil submergence and aeration, tide oscillation and vegetation cover, on the soil development. In view of climate change, this study contribute to understand and suppose how soil and landscape could evolve. However, a complete evaluation of hydromorphic soil functionality will be achieved only involving physiological and biochemical expertise in these kind of studies.

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27

Decker, Emilia. "Ecoacoustics as a sustainable tool to characterize, investigate and monitor freshwater streams." Thesis, Griffith University, 2021. http://hdl.handle.net/10072/405193.

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Freshwater systems are dramatically transformed by human activities and are in need of effective monitoring to halt the decline of ecosystem health. Ecoacoustics presents a new cost effective way to monitor changes in ecosystems by investigating sounds and their relationships with the environment. However, while ecoacoustics has been explored as a monitoring tool in terrestrial and marine realms, it only gained traction in recent years in freshwater systems. In this thesis, I investigate ecoacoustics as a monitoring tool for freshwater systems. By investigating spatial-temporal variation in soundscapes of this realm (Chapter 2), examining the main biological drivers of these soundscapes (Chapter 3) and relating acoustic properties to environmental parameters (Chapter 4), I provide comprehensive studies on how freshwater soundscapes change and how ecoacoustics can be used as a monitoring tool. In the first study (Chapter 2), I characterize soundscapes across multiple freshwater streams, classify these streams according to their soundscape and use acoustic indices to describe spatial-temporal variation of freshwater soundscapes. The results demonstrate that soundscapes in 12 freshwater streams can be highly variable in both space and time. Even among similar streams in the same region, soundscapes differ greatly. Further all 12 streams used in this thesis have a unique soundscape with most differences between soundscapes being observed during the daytime. For the second study, I manually annotated biological sounds from the 12 freshwater streams analysed in the previous study. Results demonstrate high level of spatial and temporal variation in sound composition between streams with each stream containing a unique sound composition. The sound composition in each stream exhibits a daily cycle with site-specific sequences of sonic activity. Further, sound types are partitioned into temporal, frequency and spatial niches which aligns with the acoustic niche hypothesis. In my last study I relate acoustic properties of 12 freshwater streams to their environmental parameters. In particular, I explore the relationship between acoustic indices from Chapter 2, annotated biological sounds from Chapter 3 and environmental parameters of each stream. Further I investigate 1) the capacity of acoustic indices to detect biological sounds and 2) biological sounds and acoustic indices as potential monitoring tool for environmental parameters in freshwater streams. Results demonstrate that flow, depth and macrophyte cover are the key drivers of sound composition and that acoustic indices can be used to detect biological sounds and reflect environmental parameters in freshwater streams. Very few studies have explored soundscapes of freshwater bodies over a broad spatial and temporal scale. Overall, my thesis represents an important first step towards monitoring and analysing freshwater soundscapes. Soundscapes of freshwater streams exhibit spatial-temporal variation and are unique in their sound composition. This suggests that there is a great potential for ecoacoustics to provide a monitoring tool for freshwater systems, especially through easy and efficient use of acoustic indices. However, more research should investigate automated process to extract more acoustic information by using machine learning. My research expands our knowledge of freshwater acoustics and ecoacoustics as a cost effective long-term monitoring tool. Thesis (PhD Doctorate) Doctor of Philosophy (PhD) School of Environment and Sc Science, Environment, Engineering and Technology Full Text

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28

Storer, Timothy. "Ethology and production of freshwater crayfish in aquatic polysystems in Western Australia." Thesis, Curtin University, 2005. http://hdl.handle.net/20.500.11937/2442.

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Aquatic polyculture has been recognised as a potential way of increasing the costeffectiveness of farming marron (Cherax tenuimanus), as it can lower average costs of production, increase system yields, and reduce economic risks associated with monoculture operations. Polyculture also increases ecological stability and assists recycling processes, which can result in synergistic benefits to participating species. In aquaculture, this synergism can result in increased profitability through advanced growth rates and/or reduced feed input. However, many of the inherent advantages of aquatic polyculture rely on cohabitants occupying distinct ecological niches within the system. In Western Australia, opportunities to multi-crop aquatic species are limited by species choice due to low natural diversity and strict translocation policies. This creates a situation where available aquaculture species exhibit overlaps in occupied niches. Effects of this overlap can include direct predation, increased intraspecific conflict, and competition for resources such as shelter and food. Prior to this study, silver perch (Bidyanus bidyanus) were identified as a prime candidate for duoculture with marron, based on favourable schooling and feeding characteristics, and preliminary trials demonstrated commercial benefits, including synergistic growth advantages to marron. However, investigations also showed that silver perch will predate on both small and moulting crayfish under certain conditions, and that growth of silver perch was inhibited when held in cages to prevent predation. The work reported in this thesis was undertaken to address the niche overlap existing between marron and silver perch, and therefore assist the marron industry in Western Australia in implementing appropriate management strategies for diversification.Research focussed on investigating the ecological issues underlying interspecific interactions in marron polysystems, with the eventual aim of presenting information that could assist system managers in determining optimal conditions required to reduce antagonistic relationships and maximise synergism, ultimately leading to higher yields. Seven trials were conducted in three culture systems (54L aquaria, 250L aquaria and 720m2 experimental ponds) examining the ability of marron to detect, recognise and respond to a range of information cues (chemical, visual, tactile) from two potential predators (silver perch and Murray cod), with and without competition from conspecific and heterospecific crayfish (Cherax albidus). The ability of marron to interpret and respond appropriately to these variables was tested under a range of system-specific conditions, including stocking density, stocking size, shelter/habitat complexity, food availability, light intensity and life stage. Cage culture conditions were also examined to determine if the addition of shelter would mediate growth inhibition previously recorded, and to determine the desired stocking regime to return market sized fish in one growth season (8 months). Results from laboratory research and field-based trials did not support the free-range culture of marron and silver perch, even where turbidity and habitat complexity is high. Although both male and female marron (various sizes) demonstrated an ability to detect and differentiate between chemical and visual cues from potential predators, avoidance responses were only displayed upon attack from predators, or following predation of conspecifics; and avoidance strategies employed by marron were relatively ineffective.Although marron showed some capacity to recognise an impending predatory threat, high initial mortalities and growth inhibition due to reduced foraging, would greatly reduce system yields. In addition, intraspecific competition between marron is likely to increase as avoidance responses would lead to high relative densities within shelters. The lack of avoidance behaviour displayed by marron when only visual and chemical cues from predators are present strongly supports cage culture of silver perch in marron ponds. As marron did not appear to alter their general behaviour (e.g. foraging) based on cues associated with silver perch held in cages they stand to benefit from cohabitation. Field-trials examining the pond culture of marron and caged silver perch demonstrated synergistic growth advantages to marron, compared to monoculture, and also identified several system variables that appear to improve polyculture production. The addition of bank shelters (within 1m of waters edge) was suggested to give marron a competitive advantage when moulting, expressed through growth and survival. Survival of marron was also increased in caged polyculture ponds, compared to monoculture, most likely due to increased health status (due to improved recycling) and/ or increased habitat complexity owing to the presence of fish cages. Growth inhibition previously reported when silver perch are held in cages was mediated to some degree by cage shelters, which appeared to increase feeding behaviour, reduce general anxiety and resulted in increased growth. The introduction of advanced silver perch fingerlings in order to produce market-sized fish in one growth season was also supported. However, it is recommended that cage culture dynamics require further elucidation if silver perch are to be commercially successful as a stand-alone crop using this growout strategy.Significantly, the synergistic growth advantages experienced by marron when grown with fish demonstrate value from polyculture even if fish are not depended on as a secondary income. In this case, other species may also provide similar advantages, and a native candidate such as freshwater cobbler (Tandanus bostocki) would also redress problems associated with translocation laws restricting the use of silver perch in some areas of Western Australia. As no density effects were recorded in any of the trials conducted for either species, further investigation into increased system loads is required. In addition, as nutrient loads, and thus phytoplankton density, usually increases proportionately with pond biomass it is recommended that an additional herbivorous species, for example white eye mullet (Mugil cephalus), be examined in conjunction with increased density trials. Field research reported in this thesis was carried out in earthen ponds utilising remediated water from a acidified mine lake. Over a three-year period water quality parameters were maintained within optimal ranges for marron and silver perch, and survival and growth of both species was comparable to industry levels. These results validate the effectiveness of mine-water treatment technology; and accordingly, results support commercial viability of crayfish polyculture utilising remediated acid mine water. The large water resources offered by the numerous artificial lakes created from open cut mining has the potential to sustain a large successful aquaculture industry for Collie (Western Australia), and in other areas with extension of water treatment technology.The incorporation of caged silver perch into marron ponds not only takes advantage of the inherent economic and risk-spreading benefits from a diversified management strategy, but also incorporates a number of within-system benefits due to synergism between species. The ecological approach to aquatic polyculture research reported in this thesis has elucidated key communication factors underlying interactions within crayfish polysystems, which is critical to a knowledge-based approach to system management.

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29

Harford, Andrew James, and andrew harford@rmit edu au. "The characterisation of Australian freshwater fish immune systems and their response to immunomodulators." RMIT University. School of Medical Science, 2005. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20060307.171411.

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The Murray-Darling basin is the largest river system in Australia with significant economic, social, recreational and cultural value. It supplies water for drinking and agriculture to a large inland area of the eastern and southern states of Australia. It is also the ultimate sink for many environmental contaminants that result from human activities within the catchment. Aquatic organisms live intimately with their environment and may be continuously exposed to these contaminants through the water column or the food chain. Some chemicals are bioaccumulated and biomagnified in tissue to reach high body burdens. Populations of native fish species within the Murray-Darling basin have been in decline since human settlement, yet little is known about the lethal and sublethal effects of environmental pollutants on native freshwater fish and many of the Australian water quality guidelines are based on data from exotic fish species. Researchers have correlated levels of pollution with immune dysfunction and an increased incidence of disease amongst wildlife populations. Many of the pollutants of the Murray-Darling basin have known immunotoxicity in both mammals and exotic fish species. The immune system is a sensitive target organ because, in order to maintain integrity, it requires constant renewal through the rapid proliferation and differentiation of cells. Efforts to increase numbers of native fish in the wild have led to an aquaculture industry that produces fingerlings for the restocking of waterways. In more recent years, this industry has matured and now produces table-size native freshwater fish for local and international markets. Although the industry has researched areas of reproduction, nutrition and stocking, there is little understanding of the immunology or immunotoxicology of Australian freshwater fish. This research project investigated the immunology of three large native fish species (i.e. 2 Murray cod, golden perch and silver perch), which are the basis of the native freshwater aquaculture industry. Additionally, a small fish species native to the basin (i.e. crimsonspotted rainbowfish) was studied as an alternative to the use of large fish. Of the four species, Murray cod possessed characteristics that made it an excellent candidate for ecoimmunotoxicity testing.

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30

Yates, Christopher Alan. "Characterising dissolved organic matter flux in UK freshwater systems : sources, transport and delivery." Thesis, University of Reading, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.631698.

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Dissolved organic matter (DOM) is a significant component of carbon (C), nitrogen (N) and phosphorus (P) flux from source to sea. This thesis presents the results of an investigation into the seasonal and spatial variability of DOM character, and flux of DOM relative to inorganic N and P, in two contrasting lowland UK catchments: the chalk-dominated River Wylye and peat-dominated Millersford Brook. Each catchment was sampled weekly at a total of 14 sampling locations, with daily sampling at three sites in each catchment. Dissolved organic carbon (DOC), all N species, P fractions, and both chromophoric and fluorescent dissolved organic matter were measured over a two year period (2010-2012). Contributing nutrient source areas varied between catchments. In the Wylye catchment nutrient fluxes were strongly influenced by groundwater and diffuse agricultural inputs. Point source discharges from sewage treatment facilities contributed significantly to instream loading in the lower reaches with inorganic fractions dominating the nutrient chemistry across the catchment. Chromophoric dissolved organic matter (CDOM) measurements related to aromaticity and molecular weight were low across the Wylye catchment, but significantly elevated during periods of high flow indicating the flushing of material with a greater aromatic content from the surrounding catchment. In contrast, Nand P data from Millersford Brook was dominated by organic Nand P respectively with DOC significantly elevated compared to the Wylye catchment. As a result of catchment geology and varying nutrient source areas CDOM measurements suggested both waters to differ significantly in their DOM aromatic content. No obvious temporal variation instream was observed during the monitoring period however, data from storm event sampling found high flow events responsible for the delivery of material with a low aromatic content when compared to CDOM under baseflow conditions. Results presented here give further insight into the compositional variations in the bulk chemistry within and between two contrasting lowland catchments, suggesting significant differences in DOM composition across study areas

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31

Filizadeh, Yousef. "The management ecology of aquatic weeds which cause problems in Iranian freshwater systems." Thesis, University of Glasgow, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318119.

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32

Cabello, Yeves Pedro José. "Novel microbial lineages from freshwater systems revealed by genomics and genome-resolved metagenomics." Doctoral thesis, Universidad de Alicante, 2018. http://hdl.handle.net/10045/87431.

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Few genomic and metagenomic studies have focused on freshwater systems in the last years. Most of the studies carried out on these particular environments so far rely on microscopy, physiology, phenotypic observations, individual genes and 16S rRNA sequencing. Here, we shed light on microbial communities from oligotrophic and mesotrophic freshwater systems using high-throughput deep sequencing metagenomics and genome-resolved metagenomics. We have focused on the study of ubiquitous and cosmopolitan microbial groups from two temperate Spanish reservoirs (Tous, Amadorio). Among these, we studied freshwater picocyanobacteria from Synechococcus and Cyanobium genera, which so far have not been well characterized at the genomic level, compared to the marine representatives. In particular, we were able to isolate two of the most abundant picocyanobacteria from Tous reservoir, which were previously studied via metagenomics. These picocyanobacteria are not only abundant in this reservoir but are widely distributed in different freshwater and brackish systems. In this work we also shed light on some of the first freshwater representatives of the phylum Verrucomicrobia, that are ecologically uncharacterized in freshwater systems about which relatively little is known. We discovered a wide range of metabolisms in these microbes, ranging from nitrogen fixation and photoheterotrophy via rhodopsin pumps to important contributions in the degradation of recalcitrant matter and polysaccharides. We also include the first metagenomic study of the microbial communities under the ice waters of the largest (by volume) ultraoligotrophic lake in the world, Lake Baikal. This study has provided a first glimpse and a particular microbial composition on the sub-ice, having found an unusual fraction of Verrucomicrobia and new microbial lineages from many typical freshwater phyla, including the first freshwater representative of the groups I/II of SAR11 lineage and novel genomes of Proteobacteria, Thaumarchaeaota, Gemmatimonadetes, Cyanobacteria, Planctomycetes, Bacteroidetes, Acidobacteria, Nitrospirae, Verrucomicrobia or Actinobacteria.

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33

Wilkes, Austin. "Phosphorus Mobility and Speciation Under Dynamic Redox Conditions in Shallow Eutrophic Freshwater Systems." ScholarWorks @ UVM, 2019. https://scholarworks.uvm.edu/graddis/1145.

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Internal loading of phosphorus (P) from lake sediments can delay the recovery of lakes from eutrophication for years to decades following decreases in external nutrient inputs. While internal P loading is a pervasive problem in freshwater systems, molecular speciation of P in benthic sediments of these systems remains poorly characterized. As different P species will exhibit different responses to changing sediment-water interface (SWI) geochemistry, quantifying P speciation in sediments is a critical step in understanding P dynamics in sediment-water systems. Here, various synchrotron-based techniques were employed to directly probe the bonding environments of P and iron (Fe) in natural and experimentally manipulated lake sediments in order to link chemical speciation to chemical behavior and to identify the geochemical drivers that mediate this linkage. We manipulated SWI redox conditions in mesocosm experiments to investigate the impacts of prolonged anoxia and redox oscillations on P mobility and speciation in sediments. Mesocosm experiments demonstrate that oscillating redox conditions near the SWI may drive accelerated P release from sediments relative to uninterrupted reducing conditions. Sediment P is found to be predominantly associated with Fe oxyhydroxides, calcium carbonate, and apatite minerals in three shallow hyper/eutrophic lakes in northern Vermont. In Missisquoi Bay and Lake Carmi, Fe redox cycling controls P mobility via precipitation and dissolution of Fe oxyhydroxides. In the hypereutrophic Shelburne Pond, the presence of Fe sulfides precludes redox-driven P cycling and P mobility is instead dominated by organic matter mineralization. Our results demonstrate that internal P loading can manifest differently in similar shallow lake systems due to differences in lake configuration, sediment P and Fe speciation, and organic content of sediments. This work demonstrates the potential utility, as well as the limitations, of P K- edge X-ray absorption near edge structure spectroscopy in determining sediment P speciation in freshwater lakes.

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34

Scott, Lucy Elizabeth Powell. "The development of a geographic information systems based atlas of southern African freshwater fish, and its application to biogeographic analysis." Thesis, Rhodes University, 2000. http://hdl.handle.net/10962/d1005099.

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A Geographic Information Systems (GIS) atlas of southern African freshwater fish was developed for the SADC countries from natural history collection specimens, hydrological, topographical and climatological data. The primary purpose of the development of the atlas of freshwater fish was the construction of a practical framework to transform vast amounts of existing biological data for use in research and management of aquatic resources. The database of freshwater fish collection specimens that was incorporated into the atlas, was developed in association with ALCOM (Aquatic Resources Management for Local Community Development Programme). The development of advanced computing and GIS technology has increased the scope of biological atlas projects by facilitating the integration of large amounts of spatial data to produce derived databases for specific applications. The atlas of freshwater fish was constructed using TNTmips GIS software as the most practical system available for managing and analysing biological data with a spatial component. The atlas contains 35 180 comprehensive distribution records of 735 species of fish. It has many applications as an inventory of ichthyofaunal spatial biodiversity, including those of conservation planning, environmental assessment and biogeographic research. Biogeographic studies have traditionally been subjective due to the logistical problems of working with large amounts of distribution data, although some small-scale quantitative research has been carried out in the past. The content of the atlas of freshwater fish is tested with respect to these previous studies, on known patterns of freshwater fish distributions, and the analytical capability of the atlas is tested and demonstrated with some new preliminary approaches to the analysis of freshwater fish distributions in southern Africa.

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35

Thrush, Mariah A. "Analyzing Algal Diversity in Aquatic Systems Using Next Generation Sequencing." Ohio University Honors Tutorial College / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1366807717.

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36

Storer, Timothy. "Ethology and production of freshwater crayfish in aquatic polysystems in Western Australia." Curtin University of Technology, Department of Applied Biosciences, 2005. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=16749.

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Aquatic polyculture has been recognised as a potential way of increasing the costeffectiveness of farming marron (Cherax tenuimanus), as it can lower average costs of production, increase system yields, and reduce economic risks associated with monoculture operations. Polyculture also increases ecological stability and assists recycling processes, which can result in synergistic benefits to participating species. In aquaculture, this synergism can result in increased profitability through advanced growth rates and/or reduced feed input. However, many of the inherent advantages of aquatic polyculture rely on cohabitants occupying distinct ecological niches within the system. In Western Australia, opportunities to multi-crop aquatic species are limited by species choice due to low natural diversity and strict translocation policies. This creates a situation where available aquaculture species exhibit overlaps in occupied niches. Effects of this overlap can include direct predation, increased intraspecific conflict, and competition for resources such as shelter and food. Prior to this study, silver perch (Bidyanus bidyanus) were identified as a prime candidate for duoculture with marron, based on favourable schooling and feeding characteristics, and preliminary trials demonstrated commercial benefits, including synergistic growth advantages to marron. However, investigations also showed that silver perch will predate on both small and moulting crayfish under certain conditions, and that growth of silver perch was inhibited when held in cages to prevent predation. The work reported in this thesis was undertaken to address the niche overlap existing between marron and silver perch, and therefore assist the marron industry in Western Australia in implementing appropriate management strategies for diversification. Research focussed on investigating the ecological issues underlying interspecific interactions in marron polysystems, with the eventual aim of presenting information that could assist system managers in determining optimal conditions required to reduce antagonistic relationships and maximise synergism, ultimately leading to higher yields. Seven trials were conducted in three culture systems (54L aquaria, 250L aquaria and 720m2 experimental ponds) examining the ability of marron to detect, recognise and respond to a range of information cues (chemical, visual, tactile) from two potential predators (silver perch and Murray cod), with and without competition from conspecific and heterospecific crayfish (Cherax albidus). The ability of marron to interpret and respond appropriately to these variables was tested under a range of system-specific conditions, including stocking density, stocking size, shelter/habitat complexity, food availability, light intensity and life stage. Cage culture conditions were also examined to determine if the addition of shelter would mediate growth inhibition previously recorded, and to determine the desired stocking regime to return market sized fish in one growth season (8 months). Results from laboratory research and field-based trials did not support the free-range culture of marron and silver perch, even where turbidity and habitat complexity is high. Although both male and female marron (various sizes) demonstrated an ability to detect and differentiate between chemical and visual cues from potential predators, avoidance responses were only displayed upon attack from predators, or following predation of conspecifics; and avoidance strategies employed by marron were relatively ineffective. Although marron showed some capacity to recognise an impending predatory threat, high initial mortalities and growth inhibition due to reduced foraging, would greatly reduce system yields. In addition, intraspecific competition between marron is likely to increase as avoidance responses would lead to high relative densities within shelters. The lack of avoidance behaviour displayed by marron when only visual and chemical cues from predators are present strongly supports cage culture of silver perch in marron ponds. As marron did not appear to alter their general behaviour (e.g. foraging) based on cues associated with silver perch held in cages they stand to benefit from cohabitation. Field-trials examining the pond culture of marron and caged silver perch demonstrated synergistic growth advantages to marron, compared to monoculture, and also identified several system variables that appear to improve polyculture production. The addition of bank shelters (within 1m of waters edge) was suggested to give marron a competitive advantage when moulting, expressed through growth and survival. Survival of marron was also increased in caged polyculture ponds, compared to monoculture, most likely due to increased health status (due to improved recycling) and/ or increased habitat complexity owing to the presence of fish cages. Growth inhibition previously reported when silver perch are held in cages was mediated to some degree by cage shelters, which appeared to increase feeding behaviour, reduce general anxiety and resulted in increased growth. The introduction of advanced silver perch fingerlings in order to produce market-sized fish in one growth season was also supported. However, it is recommended that cage culture dynamics require further elucidation if silver perch are to be commercially successful as a stand-alone crop using this growout strategy. Significantly, the synergistic growth advantages experienced by marron when grown with fish demonstrate value from polyculture even if fish are not depended on as a secondary income. In this case, other species may also provide similar advantages, and a native candidate such as freshwater cobbler (Tandanus bostocki) would also redress problems associated with translocation laws restricting the use of silver perch in some areas of Western Australia. As no density effects were recorded in any of the trials conducted for either species, further investigation into increased system loads is required. In addition, as nutrient loads, and thus phytoplankton density, usually increases proportionately with pond biomass it is recommended that an additional herbivorous species, for example white eye mullet (Mugil cephalus), be examined in conjunction with increased density trials. Field research reported in this thesis was carried out in earthen ponds utilising remediated water from a acidified mine lake. Over a three-year period water quality parameters were maintained within optimal ranges for marron and silver perch, and survival and growth of both species was comparable to industry levels. These results validate the effectiveness of mine-water treatment technology; and accordingly, results support commercial viability of crayfish polyculture utilising remediated acid mine water. The large water resources offered by the numerous artificial lakes created from open cut mining has the potential to sustain a large successful aquaculture industry for Collie (Western Australia), and in other areas with extension of water treatment technology. The incorporation of caged silver perch into marron ponds not only takes advantage of the inherent economic and risk-spreading benefits from a diversified management strategy, but also incorporates a number of within-system benefits due to synergism between species. The ecological approach to aquatic polyculture research reported in this thesis has elucidated key communication factors underlying interactions within crayfish polysystems, which is critical to a knowledge-based approach to system management.

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37

Jones, Susan Elizabeth. "Extracellular enzyme activity in aquatic systems with particular emphasis on attached freshwater microbial communities." Thesis, Bangor University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278143.

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38

Holding, Kathleen Louise Marie. "Epithilic periphyton as a potential biomonitor of trace metals contamination in freshwater aquatic systems." Thesis, University of Derby, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416563.

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39

Albanese, Katie. "Photochemistry and Toxicity of Triclosan, Triclocarban, and their Photoproducts and Mixtures in Freshwater Systems." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1468967416.

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40

Berggren, Martin. "Bacterial use of allochthonous organic carbon for respiration and growth in boreal freshwater systems." Doctoral thesis, Umeå : Department of Ecology and Environmental Science, Umeå University, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-30051.

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41

Clarke, Neil. "Seasonal effects of treated sewage effluents upon the reproduction and development of European freshwater molluscs." Thesis, Brunel University, 2009. http://bura.brunel.ac.uk/handle/2438/4458.

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The most widespread evidence of environmental endocrine disruption in aquatic wildlife is from the feminising effects of oestrogenic endocrine disrupting compounds. However, very little is known of the effects of these chemicals (and others) upon freshwater molluscs found in our river and lakes. This thesis aimed at evaluating the effects of treated sewage effluent upon the reproductive and developmental cycle of a range of commonly found European freshwater gastropod molluscs. Initial mesocosm experiments were undertaken to test a range of mollusc species for their the suitability to the experimental system, and to test adult snails for their reproductive and developmental responses during spring to summer time. With suitable species chosen, P.corneus, a pulmonate species (sequential hermaphrodite), and V. Viviparus a prosobranch species (dioeious; separate sexes), full reproductive output was assessed over summertime and into autumn, along with developmental responses amongst the F1 generation of snails. My results suggest that the affects of effluent upon the reproductive and developmental cycle of P. corneus are strongly mitigated by both day length and water temperature (day length is most important with V. viviparus); results are sensitive to seasonal effects. However, at the peak of reproduction mid summer, P. corneus produced significantly more egg masses in effluent (100% effluent particularly), and more than one parameter of reproduction was affected. Egg masses were significantly smaller in effluent and contained significantly fewer eggs per mass. Further, there were indications that total reproductive output was increased (100% effluent significantly) in effluent compared to the river water control. In the prosobranch species V. viviparus results were less convincing, however, in 100% effluent a second reproductive peak occurred that was not seen in river water. Further, in both species there was a failure of certain reproductive parameters to observe the normal seasonal decline towards winter. In P. corneus there was a failure to stop producing egg masses in effluent, in V. viviparus the second reproductive peak in effluent could also threaten their survival with winter approaching. Developmental effects in the F1 generation were the subject of preliminary investigations, however, F1 V. viviparus demonstrated a higher than normal incidence of intersex (male and female developmental features) in effluent, and P. corneus appeared to have disturbed reproductive function (disturbance of both male and female reproductive function in the ovotestis). Therefore, both of these species of molluscs demonstrated that they are sensitive to the effects of effluent in mesocosm studies. However, we need to understand much more about their responses to effluent; in particular whether these effects could have repercussions for wild mollusc populations, and whether these effects could occur over more than one generation of snail threatening the survival of wild populations of molluscs.

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42

Joyner, Jennifer Jendro Alperin Marc J. "Molecular identity and nutrient limitation of Lyngbya wollei mat communities in north Florida freshwater systems." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,1121.

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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2007. Title from electronic title page (viewed Mar. 27, 2008). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Marine Sciences." Discipline: Marine Sciences; Department/School: Marine Sciences.

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43

Eaton, Philip. "The biochemical ecology of freshwater modular systems : the role of amino acids and humic substances." Thesis, University of Sussex, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295954.

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1. Free amino acid (faa) and humic substance (HS) concentrations were measured seasonally using high performance liquid chromatography (HPLC) in two contrasting freshwater ecosystems. FAA concentrations were generally higher in the eutrophic Lewes Brooks than in the oligotrophic Isle of Thorns lake, whereas the converse was the case with HS concentration. 2 Faa and HS accumulation patterns were measured in media conditioned by Ceratophyllum demersum alone, Biompha/aria g/abrata alone, and media conditioned by the snail and plant together. It was hypothesised that nutrient exchange may benefit the modular components and that HS may also provide benefits by acting as a growth factor or as a protective shield. 3 Total faa (tfaa) and HS accumulated at a significantly higher rate in axenic compared to non-axenic Lemna cultures. This seems to be the first clear report of HS formation without bacterial involvement. Tfaa concentrations accumulated at a significantly higher rate in the axenic Lemna system, most probably due to the absence of bacteria. 4 The rate of accumulation of exogenous faa in snail conditioned media (SCM) decreased with temperature and oxygen availability, and displayed saturable kinetics. 5 B. g/abrata tissue faa were shown to act as osmolytes. Thus their cellular faa concentrations increased proportionately with rises in environmental osmolarity. 6 The exogenous faa medleys that accumulated in SCM were shown by statistical methods to be species specific. These medleys may therefore serve as sources of information and could have a role in chemotaxonomy. 7 B. g/abrata was capable of inward net accumulation of exogenous amino acids, including a non-metabolisable amino acid analogue - aminoisobutyric acid (AlB). 8 The experimental evidence suggested that AlB was accumulated by B. g/abrata via an active amino acid transport system. The transport system had a low Vmax (15.4 nmol/g/hr) and a Km of 20.6 f.lM, a concentration similar in magnitude to that measured in natural sediments (chapter 2). Inward transport of exogenous faa was calculated to meet 0.24 % of basal metabolism, and thus has a limited nutritional role.

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44

Enwright, Nicholas. "Using Geographic Information Systems for the Functional Assessment of Texas Coastal Prairie Freshwater Wetlands Around Galveston Bay." Thesis, University of North Texas, 2010. https://digital.library.unt.edu/ark:/67531/metadc28416/.

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The objective of this study was to deploy a conceptual framework developed by M. Forbes using a geographic information system (GIS) approach to assess the functionality of wetlands in the Galveston Bay Area of Texas. This study utilized geospatial datasets which included National Wetland Inventory maps (NWI), LiDAR data, National Agriculture Imagery Program (NAIP) imagery and USGS National Land Cover data to assess the capacity of wetlands to store surface water and remove pollutants, including nitrogen, phosphorus, heavy metals, and organic compounds. The use of LiDAR to characterize the hydrogeomorphic characteristics of wetlands is a key contribution of this study to the science of wetland functional assessment. LiDAR data was used to estimate volumes for the 7,370 wetlands and delineate catchments for over 4,000 wetlands, located outside the 100-yr floodplain, within a 2,075 square mile area around Galveston Bay. Results from this study suggest that coastal prairie freshwater wetlands typically have a moderate capacity to store surface water from precipitation events, remove ammonium, and retain phosphorus and heavy metals and tend to have a high capacity for removing nitrate and retainremove organic compounds. The results serve as a valuable survey instrument for increasing the understanding of coastal prairie freshwater wetlands and support a cumulative estimate of the water quality and water storage functions on a regional scale.

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45

Mpherwane, Salome Kedibone. "An investigation into the allozyme genetic variation patterns among populations of freshwater fish from different river systems of Southern Africa." Thesis, University of Limpopo (Turfloop Campus), 2011. http://hdl.handle.net/10386/910.

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46

Caulkett, Andrew Paul. "Studies of dissolved species and suspended particulate matter in the freshwater systems of Signy Island, maritime Antarctic." Thesis, Open University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311860.

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47

Stoyanovich, Sawyer. "The Fate and Behaviour of Diluted Bitumen and Its Chemical Constituents In Freshwater Systems Following Simulated Spills." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/42576.

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As conventional oil reserves deplete and more efficient refining technologies emerge, the use and transportation of heavy fuel oils such as dilbit is rising. Despite the risk of accidental dilbit spills, the fate and behaviour in aquatic systems is largely unknown. The objective of this thesis was to develop new approaches and insights to directly address knowledge gaps surrounding the fate and behaviour of diluted bitumen (dilbit) in freshwater systems. During the summers of 2017 and 2018, a large-scale collaborative field study was conducted at the International Institute for sustainable Development’s – Experimental Lakes Area (IISD-ELA), a world-renowned freshwater research station located in Northwestern Ontario, Canada. First, two tank-based dilbit spill simulations were carried out at oil:water ratios of 1:8000 and 1:800 v/v (Chapter 2). Here I examined the physical fate and behaviour of dilbit spilled onto the water’s surface for 11 days. In this chapter I provide, for the first time, experimental evidence of dilbit physically sinking after 8 days of environmental weathering in land-based tanks containing natural lake water. Building on the findings of chapter 2, the remaining four chapters focus on a series of 70-d long experimental dilbit spills carried out in limnocorrals (10 m diameter x 1.5 m depth) installed directly in a freshwater lake. Chapter 3 provides, to our knowledge, the most detailed temporal account to date of dilbit submergence in freshwater at multiple oil:water ratios. In Chapter 4 I provide the rates at which over 100 individual hydrocarbons are depleted over time from the dilbit slicks and apply diagnostic ratios to postulate which weathering processes are responsible for the observed depletions. As predicted, evaporation, dissolution, and photooxidation are prominent weathering processes whereas biodegradation is not. I then describe both the short- and long-term behaviour of these compounds as they partition from the dilbit slick to the air, water, and sediments of the limnocorrals in Chapter 5. While the concentrations of polycyclic aromatic hydrocarbons (PAHs) were elevated in the water columns of each treatment, they were orders of magnitude lower than concentrations that pose a toxicological risk. The same was true for all sediment samples except those that were in direct contact with sunken dilbit. This suggests that the major threat of dilbit spills from an ecotoxicological point of view is the dilbit-laden sediments produced by submergence. Finally, I demonstrated the successful application of a mass transfer model to predict the dissolution trends of the highly toxic benzene, toluene, ethylbenzene, and o,m,p-xylene (BTEX) compounds following the dilbit spills. In Chapter 7 I detail the implications and conclusions for each chapter and the thesis as a whole. I also describe areas where future research is needed. In the end, the conclusions of this thesis were: 1) dilbit has the propensity to sink following spills in freshwater, 2) prominent weathering processes include evaporation, dissolution, and photooxidation, 3) our regression design allowed for important relationships between contamination and spill size to be realized, 4) sunken dilbit poses a toxicological threat to aquatic biota, and 5) mass transfer models can accurately predict BTEX dynamics in the water column following a dilbit spill.

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West, Rae Ann. "Trialling small-scale passive systems for treatment of acidmine drainage: A case study from Bellvue Mine, WestCoast, New Zealand." Thesis, University of Canterbury. School of Geological Sciences, 2014. http://hdl.handle.net/10092/10907.

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Bellvue Mine is an abandoned coal mine on the West Coast of the South Island which discharges severe acid mine drainage (AMD) into the nearby Cannel Creek. This site is unique in that iron is in a ferrous or reduced form at the mouth of the mine, but due to the slope of the site, the AMD becomes aerated and subsequently the iron oxidises into ferric form as it moves downstream. Research was conducted to examine the geochemistry of the AMD at the site and investigate the performance of selected passive treatment systems at this site, with a view to informing decisions for passive treatment at other comparable mines on the West Coast. A range of small-scale trial passive remediation systems were installed, including an anoxic limestone drain (ALD), a bioreactor, and two mussel shell reactors. Results from the trials showed that the mussel shell reactor treating oxidised water was the most effective at reducing the concentration of dissolved metals in the AMD. A range of factors including hydraulic residence time, geochemistry of the Bellvue Mine discharge, and unexpected equipment issues all contributed to the results of the trials, and are important factors that need to be taken into consideration when designing a full-scale system for this site and others.

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Stewart-Koster, Ben Donald. "Modelling Multiscale Relationships in Riverine Landscapes: Putting the "Riverscape" into Statistical Models for River Ecology and Management." Thesis, Griffith University, 2011. http://hdl.handle.net/10072/367114.

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Many questions in ecology involve exploring the environmental processes that influence species’ distributions and abundances in both space and time. Such environmental processes are rarely independent, and generally operate across many scales. This is particularly relevant to riverine systems, where the nested hierarchical structure of the riverscape means fine-scale processes are strongly influenced by processes operating across larger scales. Recent research has identified some key advantages in applying Bayesian hierarchical models to hierarchical ecological problems such as identifying relationships between species’ abundances and environmental predictor variables across multiple scales. This thesis focuses on applying Bayesian hierarchical models to multiscale datasets for freshwater fishes and aquatic macrophyte cover in South-East Queensland, Australia, to address two key aspects of applied river ecology and management. Firstly, it examines multiscale species-environment relationships for freshwater fishes. This involves developing Bayesian hierarchical models that reflect the structure of a conceptual model of fish species’ distribution and abundance. Secondly, this thesis examines methods to integrate such multiscale relationships into models for river management and restoration using Bayesian networks with an emphasis on the management of aquatic macrophytes (BNs). Novel statistical methods such as Bayesian hierarchical models and BNs have the potential to advance our understanding of multiscale abiotic drivers of ecosystem structure and function across the riverscape. Thesis (PhD Doctorate) Doctor of Philosophy (PhD) Griffith School of Environment Science, Environment, Engineering and Technology Full Text

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Bergström, Ulf. "Spatial heterogeneity and biotic interactions : scaling from experiments to natural systems." Doctoral thesis, Umeå University, Ecology and Environmental Science, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-249.

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Much of current ecological theory stems from experimental studies. These studies have often been conducted in closed systems, at spatial scales that are much smaller than the systems of interest. It is known that the outcome of these experiments may be seriously affected by artefacts associated with the caging procedures, as well as by the actual difference in spatial scale between experimental and target system. Yet, quantitative methods for estimating and removing artefacts of enclosure and for extrapolating experimental results to the scales of natural systems are largely lacking.The aim of this thesis was to confront some of the problems encountered when scaling from experiments to nature in studies on predator-prey systems, with focus on effects of changes in spatial heterogeneity. Specifically, I examined mechanisms that may cause consumption rate estimates to depend on the size of the experimental arena. I also studied methods for scaling up these process rate estimates to natural predator-prey systems. The studies were performed on invertebrate predator-prey systems found in the northern Baltic Sea. Initially, a descriptive study of small-scale distribution patterns was performed, in order to get background information on how the behaviour of the organisms was manifested in the spatial structure of the community. Experimental studies of two predator-prey systems exposed an artefact that may be widespread in experiments aiming at quantifying biotic interactions. It is caused by predator and prey aggregating along the walls of the experimental containers. This behaviour affects the encounter rate between predator and prey, thereby causing consumption rates to be scale-dependent. Opposing the common belief that larger arenas always produce less biased results, this scale effect may instead be reduced by decreasing arena size. An alternative method for estimating the magnitude of, and subsequently removing, the artefact caused by aggregation along the arena wall was presented.Once unbiased estimates of process functions have been derived, the next step is to scale up the functions to natural systems. This extrapolation entails a considerable increase in spatial heterogeneity, which may have important implications for the dynamics of the system. Moment approximation provides a method of taking the heterogeneity of natural populations into account in the extrapolation process. In the last study of the thesis, the concepts of moment approximation and how to estimate relevant heterogeneity were explained, and it was shown how the method may be used for adding space as a component to a dynamic predator-prey model. It was concluded that moment approximation provides a simple and useful technique for dealing with effects of spatial variation, and that a major benefit of the method is that it provides a way of visualising how heterogeneity affects ecological processes.

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Dissertations / Theses on the topic 'Freshwater systems'

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