Dissertations / Theses on the topic 'Freshwater'

Most people don’t actually think about the supply of water. Water is easy to ignore, you can just turn on a tap and water comes out! We still have the same amount of water in our ecosystem but the supply of freshwater faces a three-pronged attack from population growth, climate change and industrialisation. As it currently stands, there’s not enough water to go around. Of the World’s total water supply 97% is seawater and of the remaining only 0.3% is usable unpolluted clean waterthat is readily available to us for our daily water supply.

Includes abstract.
Includes bibliographical references.
Freshwater ecosystems and biota are among the most endangered in the world. This current situation is even more disturbing when future threats of escalating human demand and global climate change are considered. Urgent measures are therefore needed to conserve freshwater ecosystems and sustain the services they provide. These may take the form of formal protection but also need to include less restrictive mechanisms, such as implementing integrated catchment management and environmental water requirements. Systematic conservation planning provides a strategic and scientifically defensible framework for doing this. Pioneered in the terrestrial realm, uptake of systematic conservation planning for freshwater ecosystems has been slow. While broad principles are applicable, approaches need to be freshwaterspecific. The lack of freshwater-specific frameworks and tools is a key factor hampering the application of systematic conservation planning in the freshwater realm. The aim of this thesis was to address this need by developing a suite of frameworks and practical applications for planning in freshwater settings. The development of a framework for the rapid assessment of river ecosystem endangerment and protection levels provided a common currency for comparing the state of biodiversity across terrestrial and aquatic realms. It showed, for the first time, that the state of river ecosystems in South Africa is dire, far worse than that of terrestrial ecosystems. In addition, river ecosystems have very low levels of representation in protected areas, with many not represented at all. A more optimistic finding was that river systems in protected areas appear to be in a better overall condition than those outside of protected areas, emphasizing the potential of protected areas in conserving freshwater ecosystems. Currently, however, protected area systems worldwide show significant gaps in their conservation of freshwater biodiversity. A framework was therefore developed for locating and designing protected area systems for the benefit of river biodiversity. Conservation objectives were established for improving river biodiversity pattern and processes in both new and existing protected areas. These included representation of river ecosystems and freshwater fish species, representation of large-scale biodiversity processes associated with free-flowing rivers and catchment-estuarine linkages, and improving the persistence of river reaches already contained within protected areas. Data were collated in a Geographic Information System (GIS) and a conservation planning algorithm was used as a means of integrating the multiple objectives in a spatially efficient manner. Realistically, protected areas can only play a partial role in overall efforts to conserve freshwater biodiversity and need to be supplemented with other off-reserve conservation strategies. In addition, conservation strategies that focus only on representation of biodiversity in isolated areas are conceptually flawed, especially given the inherent connectivity of freshwater ecosystems. Such conservation strategies need to be augmented with approaches that address the persistence of freshwater biodiversity. A framework for planning for the persistence of freshwater biodiversity was therefore developed, synthesizing concepts from freshwater ecology and terrestrial conservation planning. When considering issues of persistence, making use of a multiple-use zoning strategy is a practical option because it helps to emphasize that different levels of protection, and hence utilization, can be afforded to different conservation areas. This helps to strengthen the linkages between people and conservation, and aligns more closely with planning categories used by water resource managers and land use planners. Planning for both representation and persistence should be achieved simultaneously to maximize spatial efficiency. Several methods of planning for representation and persistence were explored. An existing conservation planning algorithm (MARXAN) was adapted for use in freshwater settings through the incorporation of directional connectivity considerations. When using a conservation planning algorithm, the manner in which spatial efficiency between persistence and representation is achieved depends on whether or not a multiple-use zoning strategy will be applied during design. Given the practicalities of multiple-use zoning at local levels of planning, it is recommended that zones should be used in the design phase, rather than merely allocated at the end once the design is complete. In summary, research and practice in conservation has tended to focus on terrestrial biodiversity; while water resources management has tended to have a more utilitarian focus. It is high time to elevate freshwater biodiversity concerns on the agendas of both these sectors. By developing common conservation frameworks around which the water and conservation sector can engage and debate, this thesis attempts to enhance the integration of freshwater biodiversity concerns into both these sectors.

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.

Biology
Ph.D.
Environmental heterogeneity in both space and time has significant repercussions for community structure and ecosystem processes. Dimictic lakes provide examples of vertically structured ecosystems that oscillate between stable and mixed thermal layers on a seasonal basis. Vertical patterns in abiotic conditions vary during both states, but with differing degrees of variation. For example, during summer thermal stratification there is high spatial heterogeneity in temperature, nutrients, dissolved oxygen and photosynthetically active radiation. The breakdown of stratification and subsequent mixing of the water column in fall greatly reduces the stability of the water column to a vertical gradient in light. Nutrients and biomass that were otherwise constrained to the depths are also suspended, leading to a boom in productivity. Freshwater lakes are teeming with microbial diversity that responds to the dynamic environment in a seemingly predictable manner. Although such patterns have been well studied for nanoplanktonic phototrophic and heterotrophic populations, less work has been done to integrate the influence of mixotrophic nutrition to the protistan assemblage. Phagotrophy by phytoplankton increases the complexity of nutrient and energy flow due to their dual functioning as producers and consumers. The role of mixotrophs in freshwater planktonic communities also varies depending on the relative balance between taxon-specific utilization of carbon and energy sources that ranges widely between phototrophy and heterotrophy. Therefore, the role of mixotrophy in the microbial food web is difficult to predict because functional types of mixotrophs along a gradient of nutritional strategies contribute differently to nutrient cycling and carbon sequestration. The overall objective of this work was to advance existing knowledge of the abundance and activity of phagotrophy phytoplankton in lacustrine systems. The incorporation of mixotrophy into the microbial food web requires the complement of physiological studies in culture (as described in chapter 2) and quantification of activity (including abundance and bacterivory) in relation to strict phototrophs and heterotrophs in situ (as described in chapter 3 and 4). Information on the physiological ecology of mixotrophic protists is crucial to understanding their role in planktonic food webs and influence on the dynamic microbial community structure in lake ecosystems. An understanding of the ecological functioning of lakes has ultimate consequences for management of water resources, particularly in the face of global climate change.
Temple University--Theses

Mestrado em Biologia Aplicada - Ecologia, Biodiversidade e Gestão de Ecossistemas
Os dinoflagelados são um grupo de protistas com características intra- e extracelulares invulgares, encontrados tanto em habitats marinhos como de água doce. Estes organismos são tradicionalmente classificados como tecados ou atecados tendo em conta a constituição da sua região externa, conhecida como anfiesma. Esta região compreende uma camada única de vesículas achatadas subjacentes ao plasmalema, as quais podem ser preenchidas com placas celulósicas mais ou menos espessas nos dinoflagelados tecados, ou com placas celulósicas muito finas, ou mesmo não possuírem placas, nos dinoflagelados atecados. Durante o século XX, contudo, foi demonstrado que algumas espécies atecadas do género Gymnodinium tinham um anfiesma constituído por numerosas placas celulósicas finas. Tais espécies foram transferidas para um novo género, Woloszynskia, o qual foi posteriormente objeto de controvérsia, principalmente associada com o estabelecimento da espécie tipo e a possibilidade de compreender outros grupos taxonómicos, sendo portanto polifilético. Recentemente, uma série de estudos confirmaram a última ideia, e vários géneros foram criados para receber espécies de Woloszynskia, conhecidas como woloszynskióides. Esses géneros foram distribuídos por diferentes famílias: Tovellia, Jadwigia, Esoptrodinium e Opisthoaulax na nova família Tovelliaceae; Borghiella e Baldinia na nova família Borghiellaceae; Biecheleria e Biecheleriopsis incluídos na família Suessiaceae. Estas mudanças taxonómicas foram suportadas por dados moleculares e diferenças morfológicas na estrutura do estigma, organização do apex da célula e tipo de quisto de resistência. O conhecimento taxonómico sobre a diversidade e distribuição de dinoflagelados de água doce em Portugal Continental foi reunido pela primeira vez numa "checklist" e aqui apresentado (Capítulo 2). As entradas na lista foram definidas tendo em conta pesquisa filogenética recente, em particular mudanças taxonómicas que afetam os limites a nível genérico dos taxa. Registos publicados de espécies de dinoflagelados de água doce, retirados de 37 referências, formam a base do inventário, aos quais foi adicionada documentação para 12 taxa ainda não referenciados para Portugal (11 espécies e uma forma). Duas novas espécies de woloszynskióides para a ciência, não incluídas nesta "checklist", são aqui apresentadas (Capítulos 3, 4). A morfologia das células e quistos é descrita, bem como a ultraestrutura das células móveis e aspetos particulares do ciclo de vida. Filogenias baseadas em sequências de LSU rDNA confirmam as novas espécies. A primeira espécie pertence à família Tovelliaceae, género Tovellia (Capítulo 3). O epíteto específico escolhido foi aveirensis, o qual constitui uma referência ao nome da universidade, bem como da cidade onde foi encontrada: Campus da Universidade de Aveiro, Aveiro, Portugal. Tovellia aveirensis possui a característica peculiar de produzir um quisto de resistência com paracíngulo e ornamentado com numerosos processos ramificados, que não só difere do quisto bipolar e quase não ornamentado do género, mas também de todos os outros descritos para woloszynskióides. Morfologicamente esta difere de outras espécies de Tovellia principalmente por ter uma linha de pontos posicionada ao nível do limite posterior do cíngulo, rodeando a célula, e por não possuir uma placa antapical distinta, à volta da qual as séries de placas do hipocone poderiam estar dispostas. A segunda espécie de woloszynskióide foi encontrada na área alagada do Ribeiro da Palha, Nariz, Aveiro, Portugal, e num lago de água doce na Escócia (Capítulo 4). Esta pertence à família Borghiellaceae, género Borghiella, e foi nomeada B. andersenii em honra do Prof. Robert A. Andersen, que primeiro estabeleceu cultura da mesma a partir de material colhido na Escócia. Morfologicamente é idêntica à B. dodgei, divergindo desta principalmente por ter um epicone arredondado e um par de vesículas anfiesmais alongadas (PEV) mais curto, com menos pontos e delineado por duas a três placas apicais. B. andersenii é capaz de se reproduzir assexuadamente tanto no estado móvel, por fissão, como no estado imóvel, com produção de quistos de divisão, algo que nunca foi referenciado para Borghiellaceae. Além disso, evidências mais fortes de reprodução sexuada para esta família foram ainda observadas em culturas de B. andersenii, nomeadamente planozigotos e aparentes quistos de resistência. Dois outros woloszynskióides, designados MSP1 e MSP12, são aqui brevemente descritos (Capítulo 5). Estes foram colhidos respetivamente num lago da Gafanha da Boavista, próxima da Vista Alegre, Ílhavo, Aveiro, e no mesmo local, em Portugal, onde B. andersenii foi encontrada. Tanto os resultados morfológicos como filogenéticos sugerem que são duas novas espécies de Tovellia, evolucionariamente próximas de T. aveirensis.
Dinoflagellates are a group of protists with intra- and extracellular unusual features, found in both marine and freshwater habitats. These organisms are traditionally classified as armoured or thecate, and unarmoured or athecate taking into account the constitution of their outer region, known as amphiesma. This region comprises a single layer of flat vesicles underlying the plasmalemma, which can be filled with more or less thick cellulosic plates in the thecate dinoflagellates, or with very thin cellulosic plates or no plates at all in the athecate ones. During the 20th century, however, it was demonstrated that some athecate species of the genus Gymnodinium had an amphiesma constituted by numerous thin cellulosic plates. Such species were transferred to a new genus, Woloszynskia, which has been later object of controversy, mainly associated with the establishment of the type species and the possibility to comprise other taxonomic groups, thus being polyphyletic. Recently, a series of studies have confirmed the latter idea, and several genera have been created to receive Woloszynskia species, known as woloszynskioids. Those genera have been distributed over different families: Tovellia, Jadwigia, Esoptrodinium and Opisthoaulax in the new family Tovelliaceae; Borghiella and Baldinia in the new family Borghiellaceae; Biecheleria and Biecheleriopsis ranged with the family Suessiaceae. These taxonomic changes have been supported by molecular data and by morphological differences in eyespot structure, organization of the cell apex and type of resting cyst. Taxonomic knowledge about the diversity and geographic distribution of freshwater dinoflagellates in continental Portugal were assembled in a checklist for the first time and here presented (Chapter 2). Entries in the list were defined taking into account recent phylogenetic research, particularly the resulting taxonomic changes that affect genus-level limits of taxa. Published reports of freshwater dinoflagellate species, taken from 37 references, form the basis of the inventory, to which it was added documentation for 12 previously unreported taxa (11 species and one form). Two new woloszynskioid species for science, not included in this checklist, are presented here (Chapter 3, 4). The morphology of cells and cysts is described as well as the ultrastructure of motile cells and particular aspects of the life cycle. LSU rDNA-based phylogenies confirm the new species. The first one belongs to the family Tovelliaceae, genus Tovellia (Chapter 3). The species epithet chosen was aveirensis, which constitutes a reference to the name of the university as well as the city where it has been found: University of Aveiro Campus, Aveiro, Portugal. Tovellia aveirensis has the peculiar feature of producing a resting cyst with paracingulum and ornamented by numerous branched processes, which not only differs from the bipolar and almost not ornamented Tovellia cyst, but also from all others described for woloszynskioids. Morphologically, it differs from other species of the genus mainly by having a line of knobs placed at the posterior edge of the cingulum, surrounding the cell, and lacking a distinct antapical plate around which the series of plates on the hypocone could be arranged. The second new woloszynskioid has been found in a flooded area in Ribeiro da Palha stream, Nariz, Aveiro, Portugal, and in a freshwater pond in Scotland (Chapter 4). It belongs to the family Borghiellaceae, genus Borghiella, and was named B. andersenii in honor of Prof. Robert A. Andersen, who first established a culture of this species from material collected in Scotland. Morphologically, it is identical to B. dodgei, diverging from this mainly by having a rounded epicone and a shorter pair of elongate amphiesmal vesicles (PEV) with fewer knobs and lined on each side by two to three apical plates. B. andersenii is able to reproduce asexually both in the motile stage, by fission, and non-motile stage, with production of division cysts, something that has never been reported within Borghiellaceae so far. Furthermore, stronger evidences of sexual reproduction for this family have yet been observed in B. andersenii cultures, namely planozygotes and apparent resting cysts. Two other woloszynskioids, designated as MSP1 and MSP12, are here briefly described (Chapter 5). These have been collected respectively in a farm pond at Gafanha da Boavista, near Vista Alegre, Ílhavo, Aveiro, and in the same place where B. andersenni was found. Both morphologic and phylogenetic results suggest that they are two new Tovellia species, evolutionarily close to T. aveirensis.

This study researches the potential for using hyperspectral remote sensing to identify the phytoplanktonic composition of a freshwater bloom. Six novel analytical techniques were developed to identify phytoplankton class from reflectance spectra. These techniques offer the water manager a variety of means to identify the dominant phytoplankton class in a target water body. Identification of phytoplankton class is possible because certain photosynthetic pigments contained within phytoplankton cells are taxonomically significant, being indicative of a particular class. The detection of these pigments can be used to identify the presence of a particular phytoplanktonic class in an aquatic system. It is possible to identify these pigments using optical methods because they exhibit unique spectral absorption signatures. Such pigment absorption features are manifest in the composite reflectance signature from water bodies as measured by remote sensing instruments. However, due to the presence of the spectral features from other photosynthetic pigments and the other optically active components of water bodies, extracting from reflectance spectra the spectral information pertaining to individual class marker pigments can be difficult. The phytoplankton class identification techniques presented in this study were developed using absorption and reflectance spectra from pure cultures of phytoplankton. The reflectance spectra were measured in the controlled environment of a laboratory based experimental tank designed for this study. The class identification techniques were tested on field and airborne reflectance spectra measured from a eutrophic inland lake.

The proliferation of undesirable cyanobacteria within eutrophic freshwaters is now reported on a global scale, however the factors triggering cyanobacteria bloom formation were found to be especially complex. Even within a single water body, physical, chemical and biological factors all influence the assemblage of phytoplankton found. Notwithstanding the body of research conducted over the past 50 years, where concerted efforts have been applied to observing bloom patterns and the drivers of cyanobacteria blooms, substantial knowledge gaps were identified. An examination of field methods, the factors promoting the growth of cyanobacteria blooms in modified inland aquatic ecosystems, modelling to predict the onset of a bloom using a 7 day positive model, and consideration of the likely effects increasing atmospheric CO2 could have on the development of surface dwelling species were key themes addressed. The thesis represents a combination of field based and controlled experimental laboratory research. A three-year case study was undertaken at an inland freshwater impoundment where cyanobacteria blooms had become a burgeoning issue. Standard surface monitoring and in situ multi-parameter instruments were used to determine environmental stressors. Importantly the water body was characterised as a well-mixed system. A hypertrophic classification was attributed to the water body due to nutrient super saturation, high water temperatures and suspended sediment measured in all years. A discrepancy between the available analysis methods was found, as the molecular method detected a diversity of microorganisms including several cyanobacteria species, whereas microscopy detected only one species. Notably harmful colonies of picocyanobacteria were not observed using standard microscopy. The molecular data also showed cyanobacteria represented 30% of the total bacterial community yet; molecular analyses may be limited when cell counts are required for a comparison with the alert level framework. The case study found the adoption of multi-monitoring and analysis methods constitutes best practice, and should therefore be integral to early detection, risk mitigation and system characterisation. A controlled laboratory study was undertaken to measure the efficacy of emerging technology as a water quality-monitoring stratagem, with emphasis placed on the accuracy of fluorometry in turbid waters above 50 nephelometric turbidity units (NTUs). The results found in vivo fluorometry using a Manta 2 probe was useful for detecting Microcystis aeruginosa at concentrations consistent with the National Health and Medical Research Council’s alert framework (Green, Amber and Red). Phycocyanin was found to be a more reliable measure of cyanobacteria than chlorophyll a, and by using a calibrated instrument it was possible to accurately detect cyanobacteria in turbid waters up to 220 NTUs. Cyanobacteria are highly effective at CO2 assimilation, with a remarkable capacity to adapt to different CO2 conditions, however scant research had previously focused on understanding how freshwater species may respond to increasing atmospheric CO2. Controlled laboratory experiments were performed and diazotrophic and non-diazotrophic cultures were exposed to past and projected atmospheric CO2 concentrations. Both experimental species adapted to the ambient low and high CO2 conditions, however, significantly higher bio volume was measured in the elevated CO2 chambers. The ability of freshwater ecosystems to maintain steady state water chemistry or base-neutralizing capacity if atmospheric CO2 concentrations reach levels projected for the latter part of this century is questionable, and furthermore, the study provided empirical evidence to support the theoretical position that increasing CO2 may lead to changes in water chemistry, particularly a decrease in pH values.

In dieser Dissertation wurden das Auftreten und die ökologische Bedeutung Vivianits in Süßwassersedimenten erforscht. Vivianit ist das am weitensten verbreitete reduzierte Eisenphosphatmineral, das sich in Gewässersedimenten bildet. Über die Mechanismen der Vivianitbildung in Sedimenten und die quantitative Rolle des Minerals für die Speicherung von Phosphor ist bisher wenig bekannt. Die neuen Erkenntnisse dieser Arbeit basieren auf der Entwicklung einer neuartigen Methode, die eine direkte Identifikation Vivianits mittels Röntgendiffraktometrie in Sedimenten erlaubte. Es gelang erstmalig, Vivianit in Oberflächensedimenten zu quantifizieren. Die vorliegende Arbeit zeigt, dass Vivianit signifikant, mit 10-40 %, zur Phosphorretention in Süßwassersedimenten beitragen kann. Die Untersuchung der Bildungsbedingungen Vivianits in unterschiedlichen Gewässersedimenten Norddeutschlands zeigte, dass das molare Schwefel zu Eisen Verhältnis des Sediments als ein wichtiger Indikator für die Bedingungen identifiziert, welche die Triebkräfte für die An- und Abwesenheit Vivianits darstellen. Eine Eutrophierung von Gewässern und der damit verbundene Anstieg der Sulfidproduktion kann dabei die Bildung Vivianits beeinträchtigen, und eine Abnahme des Phosphorbindungsvermögens des Sediments zur Folge haben. Die vorliegende Arbeit macht deutlich, dass eine artifizielle Erhöhung des Eisengehaltes des Sediments im Rahmen einer Seenrestaurierung eine Vivianitbildung induzieren kann und so langfristig zu einem erhöhten Phosphorrückhalt führt. Sättigungsberechnungen ergaben, dass ein hinsichtlich Vivianits übersättigtes Porenwasser kein sicheres Indiz für die Anwesenheit des Minerals ist. Die Berechnungen sind nicht in der Lage die kleinskaligen chemischen Bedingungen im Porenraum des Sediments abzubilden. Die Untersuchungen zeigen, dass die Bildung von Vivianit einen wichtigen Prozess der Phosphorbindung in Gewässersedimenten darstellt, der bislang jedoch weitestgehend vernachlässigt wurde.
In this thesis, the occurrence and environmental relevance of vivianite in freshwater sediments were explored. Vivianite is the most common reduced iron phosphate mineral which forms in sedimentary environments. Not much is known about the mechanisms which lead to vivianite formation in surface sediments, and about the quantitative role of vivianite in phosphorus sequestration. The development of a novel sediment preparation technique allowed the direct identification of vivianite by powder X-ray diffraction. Notably, for the first time, vivianite was quantified in surface freshwater sediments. The study examplifies that vivianite can significantly contribute to the phosphorus retention in surface freshwater sediments, accounting for 10-40 % of total sedimentary phosphorus. The exploration of vivianite in different surface freshwater sediments located in northern Germany revealed that the sedimentary sulphur to iron ratio is a valuable indicator for the conditions that are important drivers behind the formation or absence of vivianite. It has been demonstrated that eutrophication and the accompanied increase in sulphide production hampers vivianite formation, leading to a decreased phosphorus binding capacity of sediments through increased sediment sulphidization. The present study also revealed, that an iron addition as a measure of lake restoration can trigger vivianite formation, and significantly increases the long-term phosphorus retention of sediments. Pore water equilibrium calculations demonstrated that supersaturated pore water is not sufficient to predict the occurrence of the mineral in situ. Those calculations often fail to predict the occurrence of vivianite because they do not adequately represent chemical conditions within sediment microenvironments. In summary, the formation of vivianite in aquatic sediments constitutes an important process in phosphorus sequestration which has so far largely been ignored.

Thesis (M.Sc. (Hons.)) -- University of Western Sydney, 2000.
"A thesis submitted in part-fulfilment of the requirements for the degree of Master of Science (Honours)" Bibliography : leaves 131-152.

This study aimed to describe the key consequences of three invasive species within freshwater systems, namely Lagarosiphon major, Squalius cephalus and Hemimysis anomala. I utilised a combination of tried and tested traditional methods such as age, growth and diet analyses alongside modern methods such as stable isotope analysis (SIA) and assessment of functional responses. Research questions or hypotheses were examined to assess the impacts (if any) an invader was having on ecosystem function within freshwater systems. The research methods applied and developed in this study will help ecologists quantify the direction of ecological change after an invasion has taken place. It may also help ecologists to forecast the effects an invader is likely to have in an ecosystem. In Lough Corrib the potential impacts of a L. major invasion were assessed. The findings showed that macroinvertebrate assemblage structure differed between L. major dominated habitats and native macrophyte habitats. Fish captured in invaded and native habitats differed in key, characteristics. SIA revealed that L. major made little contribution to the food-web. In the River Inny, the non native fish Squalius cephalus was discovered in 2005. This study assesses the potential for this species to have an ecological impact. 1 concluded that the population size was low. SIA revealed that the diet of this species overlapped that of several species of conservation concern. This study contributed to the probable eradication of this species from Ireland. 1 also describe the most recent distribution of the Ponto-Caspian invader Hemimysis anomala in Ireland including its spread to the River Erne catchment. In addition, functional response experiments showed the potential for this species to be a voracious predator when compared to its closest native ecological equivalent.

The main aims of this thesis were to develop an integrative approach (i.e. one that included physiological as well as traditional morphological events) that allowed the construction of "timelines" of event sequences during development for pulmonate gastropods and to investigate how these sequences varied between (heterochrony) and within (heterokairy) species. Detailed descriptions of development in twelve species from three families (Lymaeidae, Planorbidae and Physidae) highlighted several heterochronies that were confirmed by a phylogenetically explicit analysis (PARSIMOV). These heterochronies involved physiological events (i.e. the first heart beat, appearance of the eye, body flexing, mantle muscle activity, attachment to egg capsule and crawling) and were associated with basal and terminal branches within the phylogeny. The same sequence-based approach also demonstrated altered relative times of onset of developmental events (i.e. heterokairy) and durations of key developmental stages in three pulmonate species (Physella acuta, Radix balthica and R. auricularia) exposed to predator cues. Species varied in their degree of response and in the events showing alterations but there were no obvious overall effects on development. A further study of the developmental sequences in three pulmonate species with a simple conical shell form revealed additional evidence for heterochrony, including the early occurrence of hatching in a possible ancestral lineage (the family Acroloxidae). Together these findings suggest that sequence heterochrony may have played an important role in the evolution of freshwater pulmonate gastropods and that this group of invertebrate could offer the opportunity to address the potential link between heterochrony (the pattern) and heterokairy (the – potential – process).

Invasions of non-native species cause problems in ecosystems worldwide, and despite the extensive effort that has been put into research about invasions, we still lack a good understanding for why some, but not other, communities resist these invasions. In this doctoral thesis I test hypotheses on biotic resistance using a large dataset of more than 1000 both failed and successful introductions of freshwater fish into Swedish lakes. We have found that the classic species richness hypothesis is a poor descriptor of introduction success because it fails to acknowledge that resident species contribute to the resistance in different ways. We developed a new measure of biotic resistance, the weighted species richness, which takes into account that the resident species contributes to the resistance with different strength and sign. Further, we correlated performance traits of species in their role as an invader and as a resident species to predict how the biotic resistance of these communities would develop over time. We found a positive correlation between performance traits: Some species have high introduction success, they make a large contribution to the resistance, and they cause extinctions when introduced but do not go extinct themselves when other species establishes, whereas other species are weak performers in these respects. Thus, the biotic resistance of these communities should grow stronger as non-native species accumulates. These results give us clues about what type of communities that should be most sensitive to further invasions, i.e., communities harboring species weak performers.  My results show that the biotic resistance of communities is an important factor in determining invasibility of a community. They also show that methods for quantifying resistance must take into account how interactions are structured in nature. What determine the biotic resistance of a community is the type of interactions that the resident species have with the invader and not the species richness of the community.

Biodiversity is declining worldwide with detrimental effects on ecosystems functions and services that it sustains. The relationship between biodiversity and freshwater purification remains unclear. Freshwater purification is of paramount importance for humankind as eighty percent of the world’s population is exposed to high levels of threat in terms of water security. Bacteria are the most diverse and abundant organisms on Earth and they play, directly or indirectly, a key role in the majority of ecosystem services including water purification. The current work aimed, in freshwater systems, to unravel the relationships between microbial diversity and: (a) biodegradation of toxic compounds (i.e. specialised function); (b) respiration (i.e. broad function) and; (c) stability of broad functioning. Firstly, preliminary experiments were carried out to establish freshwater sample size to representatively evaluate bacterial communities’ diversity and also suitable natural and man-made toxic compounds for freshwater incubation experiments. Then, the microbial communities’ ability to degrade microcystin-LR was explored in the context of previous exposures and nutrient availability. Finally, we focused on the relationships between diversity and functioning. A decrease in microbial diversity caused a decrease in both broad and specialised ecosystem functions tested. Stability of broad functioning was also negatively affected by a decrease in microbial diversity. Both lakes (Scotland) and rivers (Australia) microcosms experiments resulted in comparable findings suggesting consistent relationships across different freshwater systems. These results highlight that, similarly to macro-organisms (plant and animals), declining diversity of the microbial communities has direct consequences for important ecosystem functioning and services and therefore, microbial diversity should be explicitly considered in all biodiversity conservation debates.

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.

The main goal of this thesis was to improve the knowledge on the mechanisms involved on Human dispersal of freshwater invasive fauna, contributing for the management of these problematic species. Several vectors were investigated, both accidental and intentional, from a freshwater invaders list that included some of the worse species. It was found that the red swamp crayfish and the signal crayfish presented desiccation survival capacities compatible with long-distance human-mediated dispersal. Off-road vehicles constituted a viable accidental vector for invasive macroinvertebrates, like the red swamp crayfish and the bladder snail. Live bait capture using dip nets and crayfish trapping constitute viable vectors for invasive freshwater macrofauna dispersal. The former is more related with accidental transport of small invasive organisms, and the latter is mostly related with intentional transport of invasive fish species. The importance of the angling web forums as a useful tool to help detection of non-native fish species was demonstrated with the first record of European Perch, a non-native fish in continental Portugal. Freshwater anglers from Portugal and Spain presented preference for invasive fish species, similar mobility, low incidence of live bait use and similar perception of biological freshwater invasions processes and impacts. Differences among countries were found for angler's activity patterns throughout the year and motivations for introductions. Zebra mussel larvae desiccation survival is compatible with long-distance overland dispersal. Its transport by natural vectors, like ducks, or human vectors like fishing tackle, such as waders and keep nets is viable. Yet, when comparing both types of vectors, fishing tackle presented a higher propensity to spread zebra mussel larvae than ducks; Dispersão de fauna invasiva dulçaquícola pelo Homem Resumo: O principal objetivo desta tese foi melhorar o conhecimento dos mecanismos envolvidos na dispersão de fauna dulçaquícola invasiva pelo homem, contribuindo assim para a gestão destas espécies problemáticas. Investigaram-se vários vetores, quer acidentais quer intencionais de uma lista de invasores dulçaquícolas que incluem algumas das piores espécies. Verificou-se que o lagostim vermelho e o lagostim sinal possuem uma capacidade de sobrevivência à dessecação compatível com a sua dispersão a longa distância pelo Homem. Os veículos todo-o-terreno constituem um vetor viável para macroinvertebrados invasivos como o lagostim vermelho e o caracol aquático. A captura de isco vivo com recurso a camaroeiro e o uso de armadilhas para a captura de lagostim constituem vetores viáveis de dispersão para a macrofauna dulçaquícola, sendo que o primeiro está relacionado com o transporte acidental de pequenos organismos invasores e o segundo com transporte intencional de peixes invasores. Através do primeiro registo em Portugal Continental de Perca-europeia, uma espécie não-nativa, demostrou-se a importância de fóruns on-line de pesca desportiva como uma ferramenta útil para a deteção de peixes não-nativos. Os pescadores dulçaquícolas de Portugal e Espanha apresentam preferência por espécies de peixes invasores, similar mobilidade, baixa incidência no uso de isco vivo e similar perceção dos processos e impactos das invasões biológicas dulçaquícolas. Detetaram-se diferenças entre países nos padrões de atividade dos pescadores durante o ano e na motivação para as introduções. A sobrevivência à dessecação de larvas de mexilhão-zebra é compatível com o seu transporte a longas distâncias fora de água, sendo viável o seu transporte quer por vetores naturais, como patos, quer humanos como equipamento de pesca, como botas altas e redes de retenção. No entanto, quando se comparam ambos os tipos de vetores, o equipamento de pesca apresenta maior propensão que os patos para dispersar larvas de mexilhão-zebra.

Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1988.
Includes bibliographical references (leaves 163-172).
A freshwater plume often forms when a river or an estuary discharges water onto the continental shelf. Freshwater plumes are ubiquitous features of the coastal ocean and usually leave a striking signature in the coastal hydrography. The present study combines both hydrographic data and idealized numerical simulations to examine how ambient currents and winds influence the transport and mixing of plume waters. The first portion of the thesis considers the alongshore transport of freshwater using idealized numerical simulations. In the absence of any ambient current, the downstream coastal current only carries a fraction of the discharged fresh water; the remaining fraction recirculates in a continually growing "bulge" of fresh water in the vicinity of the river mouth. The fraction of fresh water transported in the coastal current is dependent on the source conditions at the river mouth. The presence of an ambient current augments the transport in the plume so that its freshwater transport matches the freshwater source. For any ambient current in the same direction as the geostrophic coastal current, the plume will evolve to a steady-state width. A key result is that an external forcing agent is required in order for the entire freshwater volume discharged by a river to be transported as a coastal current. The next section of the thesis addresses the wind-induced advection of a river plume, using hydrographic data collected in the western Gulf of Maine. The observations suggest that the plume's cross-shore structure varies markedly as a function of fluctuations in alongshore wind forcing. Consistent with Ekman dynamics, upwelling favorable winds spread the plume offshore, at times widening it to over 50 km in offshore extent, while downwelling favorable winds narrow the plume width to a few Rossby radii. Near-surface current meters show significant correlations between cross-shore currents and alongshore wind stress, consistent with Ekman theory. Estimates of the terms in the alongshore momentum equation calculated from moored current meter arrays also indicate an approximate Ekman balance within the plume. A significant correlation between alongshore currents and alongshore wind stress suggests that interfacial drag may be important. The final section of the thesis is an investigation of the advection and mixing of a surface-trapped river plume in the presence of an upwelling favorable wind stress, using a three-dimensional model in a simple, rectangular domain. Model simulations demonstrate that the plume thins and is advected offshore by the cross shore Ekman transport. The thinned plume is susceptible to significant mixing due to the vertically sheared horizontal currents. The first order plume response is explained by Ekman dynamics and a Richardson number mixing criterion.
by Derek Allen Fong.
Ph.D.

The overall aim of this thesis was to determine the relative importance of heterotrophy and autotrophy in lake plankton. Empirical analyses using extensive surveys of literature data revealed three specific patterns in metabolism and biomass structure in freshwater plankton. First, the ratio of phytoplankton production to plankton respiration (P/R ratio) tends to be low in unproductive lakes ($<$1), and increases along gradients of enrichment. Second, the contribution of planktonic heterotrophs (bacteria and zooplankton) to community respiration is highest in oligotrophic lakes. Third, planktonic heterotrophs dominate community biomass in oligotrophic lakes, whereas phytoplankton increasingly dominate plankton biomass along gradients of enrichment. These three distinct patterns were then tested simultaneously in a set of lakes that span a wide trophic gradient. Results indicated that the plankton of oligotrophic and mesotrophic lakes were characterized by P/R ratios well below unity, and a high contribution of heterotrophs to both community respiration and biomass. These trends are completely the opposite in the most productive lakes. The plankton communities of oligotrophic temperate lakes are predominantly heterotrophic and extensively utilize external inputs of carbon, and therefore only the plankton of eutrophic lakes conformed to the classical phytoplankton-based food web. In most lakes, excess heterotrophic activity could be supported by inputs of organic matter from the drainage basin. Excess plankton respiration, fueled by allochthonous organic carbon, could represent an important source of CO$ sb2$ to lakes.

The researcher investigated a number of closed catchment lakes in western Victoria that have been stocked with exotic fish. Exotic-native fish interactions were studied and the potential of the exotic species to affect the lake ecosystem structure was explored.
Doctor of Philosophy

The number of species extinctions is increasing at an alarming rate. Long-lived freshwater mussels of the order Unionoida, which include a parasitic stage on a host fish, are highly threatened. Habitat degradation by turbidity and sedimentation is thought to be one major reason for their decline. The objective of this thesis was to examine recruitment patterns and identify the causes of the lack of recruitment in the threatened unionoid freshwater pearl mussel (Margaritifera margaritifera). In addition, I investigated the effects of turbidity on non-endangered dreissenid mussels, where turbidity was manipulated through use of bioturbating mayflies.

In a survey of 107 Swedish streams, mussel population size and trout density were both positively correlated to recruitment probability of M. margaritifera. A more in-depth study of the age-structure of nine populations revealed that four of these populations showed no signs of recruitment over the last ten years. Within-stream variation in recruitment was high as both mussels and trout had patchy distribution, and may be important for population regulation. Moreover, examination of different life stages revealed no differences in the gravid mussel stage or the stage when mussels infect salmonid fish. Instead, differences were observed for the juvenile, benthic stage, presumably related to differences in turbidity and sedimentation. High turbidity may affect filter-feeding efficiency of mussels and high sedimentation may reduce survival by clogging sediments, thereby altering, for example, oxygen and food conditions. In the study of the effects of turbidity, bioturbating mayflies increased turbidity and filter-feeding dreissenid mussels reduced turbidity. Mussel growth both decreased and increased with increasing turbidity, depending on sediment type.

Turbidity and sedimentation often impact entire stream systems, and a holistic, catchment-based management strategy may be needed to reduce the effects of sedimentation on freshwater pearl mussels. The effects of restoration take a long time and must start soon if recruitment of mussels is to be re-established. Restoration may also be more urgent in some streams than in others, as the maximum age of M. margaritifera populations in my study differed by as much as 60 years. As mussel and trout densities seem to be important for recruitment success, one conservation method may be to concentrate mussels into sites where trout density is high.

Storage of freshwater in saline aquifers has a strategic importance in water deficit countries. The freshwater stored in these aquifers may be the only source of water available during times of crisis. Coupled simulation and optimization type groundwater management models have been developed that will achieve the optimal control of the storage of freshwater in a stagnant manner for constant density and variable density flows in hypothetical single- and multi-layered saline aquifers. The study is carried out in two stages. In the first stage, a transient model of five years is simulated that allows sufficient time for the freshwater mound to be created. In the second stage, an optimization model is formulated which minimizes the pumping/injection rates of a set of hydraulic gradient control wells subject to a set of constraints consisting of systems response equations, demand requirements, hydraulic gradient controls, pumping and injection limitations. The optimization models select which wells to be pumped and which ones to be injected and decide on their pumping/injection schedules to maintain the freshwater mound from migration. The results of the optimization models showed that the mound is successfully contained in its original location by controlling the hydraulic gradient via pumping/injection wells.