Rozprawy doktorskie na temat „Eutrophication – Control”

A good ecological status of streams and rivers is crucial for maintaining ecological functionality of running waters. Worldwide eutrophication threatens to change structure and function of freshwater ecosystems (Dodds et al., 2008). To reduce the symptoms of eutrophication in streams and rivers an additional approach, besides the reduction of external nutrient inputs from catchment areas, is needed. Therefore the goal has been set to transfer the approach of biomanipulation, which is widely accepted as tool in water quality management in lakes and reservoirs, to streams. The objective of this study was accordingly to analyse and evaluate some crucial preconditions for top-down control of stream food webs. For that purpose the present thesis examined effects of fish predation (stone loach and gudgeon) on grazer-periphyton interaction in small streams by assessing predator avoidance by benthic grazers, effects of benthic grazers on periphyton community composition during fish presence/absence and the possibility of top-down control on algal biomass by benthivorous fish.

Thesis (MSc. Agriculture (Soil Science)) -- University of Limpopo, 2014
Phosphorus (P) runoff from agricultural sites and the subsequent loading into surface water bodies contribute to eutrophication. Environmental concerns associated with P loading in soil have motivated the need for the development of a proper tool that will allow farmers to identify agricultural areas or management practices that have the greatest potential to accelerate eutrophication. The objective of the study was to determine the spatial variability of soil test P, soil loss potential of the farm, P application rate and methods, and map P runoff risk across the field. This study was conducted in Vierfontein Boerdery in Kriel, Mpumalanga province, South Africa (longitude 29.11258833 and latitude -26.27104340). The field was under dryland cultivation and planted to yellow maize that was rotated with soybeans. Soil samples were taken at georeferenced locations in a 100 x 100 m grid for soil analysis. Spatial layers of soil P distribution, soil loss potential as well as application rate and method were created in ArcGIS software. These layers were used as input factors in a P index model to identify areas in the farm that are vulnerable to P runoff. Results indicated a variation in soil test P. Although soil test P variation was not statistically different at P≤0.05, variation had both agronomic and environmental implications. This variation could be attributed to differences in site-specific conditions and management practices. Furthermore, soil loss potential across the study site predicted by the Revised Universal Soil Loss Equation (RUSLE) showed variation with a range of 3-15 tons/ha/yr. This variation was attributed to differences in topographic variations in the study site. There is a need for best management practices that control soil erosion to minimize P runoff into water bodies. KEYWORDS: Eutrophication, Geographic Information System, Phosphorus best management practises, Phosphorus runoff index, Soil erosion, Site-specific management.

This dissertation evaluates the role and effectiveness of law in the transboundary environmental governance of the Baltic Sea with regard to eutrophication. To this end, it reviews the applicable international agreements with their related instruments, as well as the EU legal frameworks, for the protection of the Baltic Sea environment on the basis of theories on resilience in social-ecological systems. The scientific discourse on resilience in social-ecological systems provides theories on effective governance of complex environmental problems with nonlinear causal connections. The governance features identified in resilience governance also show significant similarities with characteristic features of the concept of ecosystem approach. The resilience features can thus provide guidance to the operationalization of this concept, which lacks a distinct meaning in the legal context. Eutrophication is one of the main environmental problems in the Baltic Sea. Despite the fact that this problem has been acknowledged since the 1970s, only little progress has been visible in the attempts to limit the problem. Environmental governance in the form of cooperation and common action has, however, been established by the coastal states of the Baltic Sea to reduce the discharges to their common resource. This was originally coordinated through the Helsinki Convention and its administrative organization HELCOM in the 1970s. Since the year 2000 a new set of legal instruments and approaches have developed, emphasizing also the ecosystem approach. These instruments have a basis both in HELCOM and in EU environmental law, most significantly represented by the Water Framework Directive and the Marine Strategy Framework Directive. They establish a unique regulatory structure, with new approaches to regulation, which also give rise to questions regarding interpretation and effectiveness that have not previously been analyzed. It is concluded that applicable law in the Baltic Sea area reflects resilience features such as adaptability, flexibility and redundancy within the legal structure. The legal structure for the Baltic Sea is dynamic and stretches over many levels of governance. The applicable legal instruments are constructed so as to be adaptable and flexible. The legal instruments moreover include significant elements that provide for participation at different levels and in different forms, which contribute to enabling the mentioned resilience features. However, the Baltic Sea legal structure – as law in general – has different core functions than just providing for effective environmental governance. Law is based in a number of general principles connected to the rule of law and the function of law as a foundation for stability in the society and in human interactions. These principles are also important since they are directly linked to enforcement, monitoring and control. While the legal structure in the Baltic Sea may provide for effective governance and social-ecological resilience, the resilience features reflected in law do not always appear as far-reaching as suggested by resilience theories, much due to the legal principles. It is however because of these principles and the base for binding requirements they enable, that law can push for governance measures and features that might not have been accomplished otherwise. This, in the larger perspective, includes creating requirements that steer human activities away from critical thresholds.
Baltic Ecosystem Adaptive Management, BEAM

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
The phytoplankton growth is dependent of several abiotic (nutrients, temperature) and biotic (predation by zooplankton) variables. In this work, a mathematical model was developed in Stella software to understand the planktonic dynamics of Extremoz Lagoon (RN) and to simulate scenarios of different environmental conditions. Data were collected monthly at two points of the lagoon. The state variables are phytoplankton and zooplankton and forcing variables are nitrogen, phosphorus and temperature. The results show that: a) the model are well coupled, especially when some constants assume different values; b) simulated nutrient concentrations reduction decreases phytoplankton biomass, but the increase of nutrients does not stimulate the growth; c) changes in the temperature does not change the phytoplankton biomass; d) changes in zooplankton biomass affect directly and reduces the phytoplankton, indicating a topdown control mechanism; e) changes in the nutrient concentration modified the biomass of zooplankton suggesting a rapid flow of energy between nutrients, phytoplankton and zooplankton and a ecosystem likely arranged in an inverted pyramid (higher concentration of zooplankton than phytoplankton)
O crescimento fitoplanct?nico ? dependente de uma s?rie de vari?veis abi?ticas (nutrientes, temperatura, luz) e bi?ticas (preda??o por zoopl?ncton e outros fitoplanct?fagos, bact?rias que provocam lise celular no fitopl?ncton). Neste trabalho, um modelo de compartimentos foi desenvolvido no software Stella para entender a din?mica planct?nica da Lagoa de Extremoz (RN) e simular diferentes cen?rios de altera??es em importantes vari?veis ambientais como fitopl?ncton e zoopl?ncton. As medi??es foram realizadas mensalmente em dois pontos da lagoa. As vari?veis de estado s?o fitopl?ncton e zoopl?ncton e as for?antes s?o nitrog?nio, f?sforo e temperatura. Os resultados mostram que: a) o modelo se ajusta bem aos dados, especialmente quando algumas constantes assumem diferentes valores; b) simula??es de redu??es das concentra??es de nutrientes diminuem a biomassa fitoplanct?nica, mas o aumento dos nutrientes n?o favorece o crescimento; c) altera??es na temperatura n?o modificam a biomassa fitoplanct?nica; d) modifica??es na biomassa de zoopl?ncton afetam diretamente e consideravelmente o fitopl?ncton, indicando um mecanismo de controle top-down; e) altera??es nas concentra??es de nutrientes modificam a biomassa do zoopl?ncton sugerindo um r?pido fluxo de energia entre nutrientes, fito e zoopl?ncton e um prov?vel ecossistema arranjado em pir?mide invertida (maior biomassa de zoopl?ncton do que fitopl?ncton)

El incremento de disponibilidad de nutrientes produce cambios en la estructura y funcionamiento de los ecosistemas litorales. La eutrofización en los ecosistemas litorales mediterráneos favorece el predominio de algas epifitas de crecimiento rápido que compiten por la luz y los nutrientes con Posidonia oceanica. La herbivoría sobre los epifitos suministra la mayor parte del carbono que asimilan los consumidores primarios y secundarios asociados a la pradera. Esta tesis evalúa la importancia del consumo ejercido por la epifauna asociada a las praderas de P. oceanica en revertir los efectos de la eutrofización sobre la biomasa de algas epifitas. Los resultados muestran un incremento de las tasas de consumo en respuesta a una mayor disponibilidad de biomasa epifita si bien el consumo no es capaz de revertir los efectos del aumento de nutrientes sobre la biomasa epifita. La comunidad íctica tiene un papel marginal en la regulación de la biomasa epifita en la Bahía de Palma.

The ocean is the most extended biome present on our planet. Recent decades have seen a dramatic increase in the number and gravity of threats impacting the ocean, including discharge of pollutants, cultural eutrophication and spread of alien species. It is essential therefore to understand how different impacts may affect the marine realm, its life forms and biogeochemical cycles. The marine nitrogen cycle is of particular importance because nitrogen is the limiting factor in the ocean and a better understanding of its reaction mechanisms and regulation is indispensable. Furthermore, new nitrogen pathways have continuously been described. The scope of this project was to better constrain cause-effect mechanisms of microbially mediated nitrogen pathways, and how these can be affected by biotic and abiotic factors. This thesis demonstrates that meiofauna, the most abundant animal group inhabiting the world’s seafloors, considerably alters nitrogen cycling by enhancing nitrogen loss from the system. In contrast, larger fauna such as the polychaete Marenzelleria spp. enhance nitrogen retention, when they invade eutrophic Baltic Sea sediments. Sediment anoxia, caused by nutrient excess, has negative consequences for ecosystem processes such as nitrogen removal because it stops nitrification, which in turn limits both denitrification and anammox. This was the case of Himmerfjärden and Byfjord, two estuarine systems affected by anthropogenic activities, such as treated sewage discharges. When Byfjord was artificially oxygenated, nitrate reduction mechanisms started just one month after pumping. However, the balance between denitrification and nitrate ammonification did not favor either nitrogen removal or its retention. Anoxia is also present in aggregates of the filamentous cyanobacteria Nodularia spumigena. This thesis shows that even in fully oxic waters, millimetric aggregates can host anaerobic nitrogen processes, with clear implications for the pelagic compartment. While the thesis contributed to our knowledge on marine nitrogen cycling, more data need to be collected and experiments performed in order to understand key processes and regulation mechanisms of element cycles in the ocean. In this way, stakeholders may follow and take decisions in order to limit the continuous flow of human metabolites and impacts on the marine environment.

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 2: Manuscript.

Thesis (MScEng)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: The study of climate change and its effect on the eutrophication of surface waters is a current and critically important study for the well-being of the entire planet. Within the same emission scenario various probable climate change models outcomes are possible that affect the water quality of a body of water. Voëlvlei is an off-channel dam that supplies water to the city of Cape Town in the Western Cape Province of South Africa. Historically, it is a eutrophic dam and with climate change, its water quality is expected to worsen. Four statistically downscaled climate models are used to produce meteorological outputs that drive the hydrodynamic and water quality model. The times simulated were the present day (1971-1990), the intermediate future (2046-2065) and the distant future (2081-2100). The operating procedure was not expected to change for the dam and inflows and withdrawals were kept the same for each of the simulation periods. The water quality model CE-QUAL-W2 version 3.6 was used. The bathymetry was validated with measured data. The model was calibrated for temperature, phosphorus loading, ammonium, nitrite-nitrates and chlorophyll-a concentration. The model was used to predict a present day situation in the dam, which was the basis from which future changes would be assessed. The main driver for algal growth other than nutrients and light was water temperature, which was linked to air temperature. With climate change, the air temperature will raise and enhance algal growth. The limiting nutrient was phosphorus during the winter and the rest of the year nitrogen limits algal growth. In the present day, the dominant algal group was the green algae. With climate change an increase in the surface water temperature will increase evaporation and cause a decrease in the yield of the dam and further concentrates the algal nutrients. The surface phosphates concentration show increases in all months but especially in autumn. The total algal growth was increased annually and especially during autumn, signalling a seasonal shift and lengthening of the bloom season. The dominant algae however are still the green algae. There will be an increase in the annual concentration of diatoms. The green algae are present in the highest concentrations when compared to diatoms and cyanobacteria. The increase in its nutrients throughout the year as well as the increased water temperature allowed for unabated growth the entire year with peaks earlier in the year during autumn. Cyanobacteria are present at the surface for the entire year at significant concentrations but with intermediate and future climate change their concentrations does not change significantly. The result for cyanobacteria was inconclusive as the inter-variability between the climate models has the greatest variability for cyanobacteria, with 2 models showing an increased concentration and 2 a decreased concentration for intermediate and future time-period. For climate change, the water quality worsens especially during winter. With climate change water quality will worsen earlier in the year confirming a seasonal shift. The modelling of dissolved oxygen proved daunting as the results indicated supersaturation. The concentration of dissolved oxygen does not vary much as would be expected due to the warmer waters.
AFRIKAANSE OPSOMMING: Die studie van klimaatsverandering en die uitwerking daarvan op die eutrofiseering van die oppervlaktewater is 'n huidige en krities belangrike studie vir die welsyn van die hele planeet. Binne dieselfde emissie scenario, is verskeie moontlike uitkomste van klimaat modelle moontlik en die invloed op die kwaliteit van die oppervlakwater. Voëlvlei is 'n buite-bedding dam wat water verskaf aan die stad van Kaapstad in die Westelike Provinsie van Suid-Afrika. Histories is dit is 'n eutrofiese dam en met die verandering van die klimaat sal die kwaliteit van die water na verwagting verswak. Vier statisties afgeskaal klimaat modelle word gebruik om meterologiese toesttande te skep en hiedie word dan gebruik as invoer vir die hidrologiese and water kwaliteits model vir die huidige situasie (1971-1990), die intermediêre toekoms (2046-2065) en die verre toekoms (2081-2100). Die bedruifs-proses vir die dam was nie verwag om te verander nie en die invloei en onttrekkings was dieselfde gehou vir elk van die simulasie periodes. Die watergehalte model CE-QUAL-W2 3.6 was gebruik. Die bathymetrie was bevestig met gemete data. Die model was gekalibreer vir temperatuur, fosfor, ammonium, nitriet-nitrate en chlorofil-a konsentrasie. Die model was gebruik om 'n huidige situasie in die dam te simuleer, wat die basis vir klimaatsveranderinge sou wees. Die vernaamste aandrywer vir die alge groei anders as voedingstowwe en lig, was water temperatuur, wat met lugtemperatuur gekoppel was. Met klimaatsverandering word die lugtemperatuur verhoog en alge groei. Die beperkende voedingstof was fosfor gedurende die winter en die res van die jaar was die dam stikstof beperk. Die dominante alge-groep in die huidige situasie was die groen alge. Met klimaatsverandering stuig die temperatuur van die oppervlakwater, verhoog verdamping, veroorsaak afname in die vlak van die dam en verhoog die konsentrasie van die alge voedingstowwe. Die oppervlak fosfate konsentrasie verhoog in al die maande veral in die herfs. Die totale alge groei jaarliks en veral gedurende die herfs, 'n teken van 'n seisoenale verskuiwing en verlenging van die blom seisoen. Die dominante alge was nog steeds groen alge. Daar sal 'n toename in die jaarlikse konsentrasie van diatome wees. Die groen alge is in die hoogste konsentrasies vergelyk met diatome en sianobakterieë. Die toename in die voedingstowwe deur die loop van die jaar, sowel as die verhoogde watertemperatuur kan vir 'n onverpoos groei vir die hele jaar, veral in die herfs. Sianobakterieë is teenwoordig vir die hele jaar op beduidende konsentrasies, maar met intermediêre en toekomstige klimaat verander die konsentrasies nie veel nie. Die resultaat vir sianobakterieë was onoortuigend as gevolg van die inter-veranderlikheid tussen die klimaats modelle, met 2 modelle wat 'n toename in konsentrasie voorspel en 2 'n afname in konsentrasie voorspel. Vir klimaatsverandering, die kwaliteit van die water vererger veral in die winter. Met klimaatsverandering skyf hierdie verswakking van water kwaliteit na vroeër in die jaar, wat bevestig 'n seisoenale skui vir verergering. Die modellering van opgeloste suurstof was uitdagende en die resultate was super-versadig. Die konsentrasie van opgeloste suurstof wissel nie veel as wat verwag sou word as gevolg van die warmer water.

Du fait des activités humaines, en particulier agricoles, les systèmes lacustres sont soumis à d'importants entrants de nutriments. Ce phénomène, appelé eutrophisation, conduit à une prolifération de cyanobactéries. Cette prolifération est un enjeu écologique, puisque l'écosystème sevoit alors déséquilibré, mais également sanitaire, puisque certaines espèces de cyanobactéries parmiles plus répandues sont capables de produire des toxines. Enfin, l'eutrophisation est également un enjeu économique, puisque l'exploitation des lacs concernés est impossible. Comprendre les phénomènes régissant les mécanismes liés à l'eutrophisation est alors indispensable, d'une part pour en anticiper les conséquences, et d'autre part pour mettre en place des politiques de gestion des systèmes lacustres eutrophes. Dans cette thèse, nous analysons ces phénomènes via les modèles dynamiques. L'étude de l'eutrophisation passe par l'étude mathématique de ces modèles. En introduction, nous présentons les différents critères étudiés permettant d'évaluer l'état générale d'un milieu lacustre. Nous présentons également les différents modèles existants. Cette analyse nous conduit à sélectionner une approche de modélisation qui consiste à agréger les variables et phénomènes existants à travers des lois mathématiques abstraites. L'intérêt de tels modèles est qu'ils réduisent considérablement la dimension du système étudié et nécessitent donc d'un nombre réduit de données pour être calibrés. De plus, de tels modèles sont abordables à une étude analytique de leurs propriétés mathématiques.Notre étude se compose en trois principaux axes. Le premier présente l'analyse des populations toxiques et non toxiques cyanobactériennes. En effet, la toxicité des proliférations cyanobactériennes est le principal enjeu sanitaire de l'eutrophisation des lacs. Or il n'existe pas actuellement d'outils permettant d'anticiper cette toxicité. En effet, si certaines espèces parmi les plus répandues sont bien capables de produire de telles toxines, tous les individus au sein d'une même espèce n'en sont pas capables: cela dépend du patrimoine génétique de chaque individu. Ainsi, deux sous-populations au sein d'une même espèce doivent être considérées: l'une toxique, capable de produire ces toxines, et l'une non toxique. L'étude de la dynamique des populations toxiques est donc indispensable pour anticiper la toxicité des proliférations cyanobactériennes. Or l'analyse de cas réels montre que les épisodes de prolifération des populations toxiques et non toxiques ne se produisent pas aux mêmes moments, ce qui implique que leurs dynamiques sont régies par des lois différentes. Afin de décrire la dynamique de ces sous populations toxiques et non toxiques, nous nous concentrons sur l'impact de la température, dont il est admis qu'il s'agit de l'un des paramètres régissant la toxicité des proliférations cyanobactériennes. A travers un modèle mettant en oeuvre les phénomènes de compétition entre les populations toxiques et non toxiques, et liant leurs dynamiques à la température, nous montrons que les variations saisonnières de température fournissent une explication à la répartition temporelle constatée des populations toxiques et non toxiques. Nous validons ces résultats théoriques via la mise en place d'une expérience en milieu contrôlé, et via l'analyse de cas réels.Cette première analyse nous fournit donc des éléments de compréhension des phénomènes régissantla toxicité des proliférations cynanobactériennes. La seconde partie de cette thèse s'intéresse aux stratégies d'endiguement de l'eutrophisation des lacs. Il ne s'agit plus de se focaliser sur la seule toxicité des proliférations cyanobactériennes, mais de s'intéresser à la dynamique des nutriments, en particulier du phosphore. (...)
As a consequence of human activities, particularly agricultural activities, lake systems are subject tosignificant nutrient inputs. This phenomenon, called eutrophication, leads to a proliferation of cyanobacteria. This proliferation is an ecological issue, since it causes an imbalance in the lake ecosystem, but also a health issue, since some of the most common species of cyanobacteria can produce toxins. Finally, eutrophication is also an economic issue, since the lakes concerned cannot be exploited. Understanding the phenomena governing the mechanisms linked to eutrophication is therefore essential, on the one hand to anticipate the consequences, and on the other hand to set up policies for the management of eutrophic lake systems. In this thesis, we analyse these phenomena via dynamic models. The study of eutrophication then requires the mathematical study of these models. As an introduction, we present the different criteria studied to evaluate the general state of alake environment. We also present the various existing models. This analysis allows us to select a modeling approach which consists in aggregating the existing variables and phenomena through abstract mathematical laws. The interest of such models is that they considerably reduce the dimension of the studied system and thus require a reduced number of data to be calibrated. Moreover, such models can be analysed with an analytical study of their mathematical properties.Our study consists of three main axes. The first presents the analysis of toxic and non-toxic cyanobacterial populations. Indeed, the toxicity of cyanobacterial blooms is the main health issue oflake eutrophication. However, there are currently no tools to anticipate this toxicity. Although some of the most common species may produce such toxins, not all individuals of the same species are capable of doing so: it depends on the genetic properties of each individual. Thus, two sub-populations within a species must be considered: one toxic, able to produce such toxins, and one non-toxic. The study of the dynamics of toxic populations is therefore essential to anticipate the toxicity of cyanobacterial proliferation. However, analysis of real cases shows that the proliferationsof toxic and non-toxic populations do not occur at the same time, which implies that their dynamics are governed by different laws. In order to describe the dynamics of these toxic and non-toxic subpopulations, we focus on the impact of temperature on their dynamics, which is assumed as one of the parameters governing the toxicity of cyanobacterial blooms. Analysing a model that uses competition between toxic and non-toxic populations and links their dynamics to temperature, we show that seasonal variations in temperature provide an explanation for the observed temporal distribution of toxic and non-toxic populations. We validate these theoretical results through the implementation of an experiment in a controlled environment, and through the analysis of real cases.This first analysis thus provides us with elements of understanding of the phenomena governing the toxicity of cynanobacterial proliferation. The second part of this thesis focuses on strategies for the mitigation of eutrophication in lakes. We no longer focuse on the toxicity of cyanobacterial blooms, but on the dynamics of nutrients, particularly phosphorus. The first way to reduce this phosphorus concentration is to change agricultural policies upstream of the lakes. In addition to these phosphorus emission reductions, some lakes have retention structures. These structures are between the lake and its watershed, and their role is to retain some of the incoming nutrients. Currently, thesestructures are evaluated on their retention capacity alone, and their effects on downstream lake dynamics are not analyzed. This is the subject of this second chapter of the thesis. (...)

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Florações de cianobactérias são consequência principalmente da eutrofização de ambientes aquáticos que afeta a qualidade e compromete o uso da água para diversas finalidades. A restauração de sistemas aquáticos eutrofizados é um dos principais desafios da limnologia atual. Nosso objetivo foi identificar as principais causas do processo de eutrofização e ocorrência de florações de cianobactérias e testar a eficácia e aplicabilidade do uso combinado de coagulantes e adsorventes de P em fase sólida no controle da eutrofização e florações em um lago tropical raso. O estudo foi conduzido no lago do Museu Mariano Procópio, localizado em Juiz de Fora – MG e dividido em quatro fases. As duas primeiras fases compreendem uma análise sistêmica do lago. Na primeira, buscou-se conhecer a dinâmica da comunidade fitoplanctônica a fim de entender a dominância de cianobactéria deste sistema. Na segunda, foram avaliados os aportes de fósforo (P) para o sistema. Na terceira fase foram realizados experimentos em laboratório, para verificar a eficácia de diferentes coagulantes e lastros para remoção de cianobactérias. E na quarta fase foram realizados experimentos em mesocosmos no lago, para testar o controle da eutrofização e florações de cianobactérias. A análise sistêmica mostrou dominância de diferentes espécies de cianobactérias e que as altas concentrações de nutrientes presentes do sistema vêm principalmente de contribuição externa. O uso combinado de coagulantes e lastros foi eficiente para a remoção de biomassa de cianobactérias, porém foi dependente da espécie. Nos experimentos com mesocosmos, foi observada uma forte redução de Clorofila a (Chl a 85%) e fósforo total (TP 78%) (p <0,0010) em todos os tratamentos, porém estas reduções não se mantiveram ao longo do tempo. Para mitigar as florações de cianobactérias deste sistema, será necessário o controle das fontes externas de nutrientes e um ajuste na técnica de coagulante-lastro para manter a clorofila e o fósforo total em concentrações reduzidas por mais tempo.
Cyanobacterial Blooms are mainly a consequence of eutrophication of aquatic environments that affect the water quality and compromise the use of water for various purposes. The restoration of eutrophic aquatic systems is one of the main challenges of today's limnology. Our objective was to identify the main causes of the eutrophication process and the occurrence of cyanobacterial blooms in a shallow tropical lake, and to test the efficacy and applicability of the combined use of coagulants and adsorbents of P in solid phase for the control of eutrophication and cyanobacteria blooms in a tropical shallow system. The study was conducted in the lake of the Mariano Procópio Museum, located in Juiz de Fora - MG and divided into four phases. The first two phases comprised a systemic analysis of the lake. The first one sought to know the dynamics of the phytoplankton community and to understand the causes of the cyanobacteria dominance in this system. In the second one, the main contributions of phosphorus to the system and the general balance of P were evaluated. In the third phase, laboratory experiments were carried out to evaluate the efficacy of different coagulants and ballasts for the removal of cyanobacteria. Last, in the fourth phase experiments were carried out in mesocosmos in the lake to test the control of eutrophication and cyanobacterial blooms. The systemic analysis showed the dominance of different species of cyanobacteria and that the high concentrations of nutrients present in the system come mainly from external contribution. The combined use of coagulants and ballasts was efficient for the removal of cyanobacteria biomass, but it is dependent on the species pool. In the experiments with mesocosms, a strong reductions of chloropyll a (Chl a) 85% and total phosphorus (TP) 78% (p < 0.001) were observed in all treatments, however these reductions were not lasting. To mitigate the cyanobacterial blooms of this system, it will be necessary to control the external sources of nutrients and also an adjustment in the coagulant-ballast technique to keep Chl a l and TP in reduced concentrations for longer time.

[Truncated abstract] The use of constructed wetlands for tertiary purification of municipal wastewater has received increasing attention around the world because direct discharge of secondary-treated municipal wastewater to water bodies has caused eutrophication. Plant species selection and vegetation management may enhance nutrient removal efficiency in constructed wetlands. However, there is a lack of knowledge on the relations between plant growth and nutrient removal efficiency in constructed wetlands. The objective of this study is to better understand how plant growth and resource allocation are influenced by nutrients in wastewater and how nutrient removal efficiencies are affected by plant species and vegetation management. The preliminary experiment was conducted to select macrophytes, especially ornamental species, to grow in the wastewater in the wetland microcosms. Ten plant species, comprising six ornamental species: Alocasia macrorrhiza, Canna indica, Iris louisiana, Lythrum sp., Zantedeschia aethiopica, Zantedeschia sp., and four sedge species: Baumea articulate, Baumea juncea, Carex tereticaulis and Schoenoplectus validus, were planted in the wetland microcosms and fed a simulated wastewater solution in the concentrations similar to the secondary-treated municipal wastewater. C. indica has shown vigorous and healthy growth, and a relatively high potential of rooting-zone aeration and nutrient removal efficiency. B. articulata and S. validus also showed relatively high nutrient removal efficiency. ... The high nutrient availability and optimum N/P ratio were required for stimulating plant growth, resulting in allocation of more resources to above-ground tissues compared to below-ground parts, and enhancing nutrient removal efficiency. Nutrient removal efficiencies were significantly influenced by growth of C. indica and S. validus, nutrient loading rates and N/P ratios in the wastewater. The nutrient uptake kinetics of C. indica and S. validus were investigated to elucidate the differences in nutrient uptake between species. Wetland plant species have shown differential nutrient uptake efficiency and different preferences for inorganic N source, with C. indica preferring NO3-N and S. validus preferring NH4-N. C. indica had greater capacity than S. validus to take up PO4-P when the concentration of PO4-P in the solution was relatively low, whereas S. validus was more capable than C. indica to take up NO3-N when the concentration of NO3-N in the solution was relatively low. The PO4-P uptake capacity was higher in younger than older plants. Overall, the study has suggested that different plant species have differential capacity to take up nutrients. In addition to nutrient uptake, plants have significant other roles in terms of nutrient removal from the wastewater (such as leaking oxygen into the rhizosphere in which oxidation of substances like ammonia can occur). The properly high nutrient availability and optimum N/P ratio are required to stimulate the plant growth, resulting in enhancing the treatment performance in the wetlands. These findings have important implications for improving our ability to engineer ecological solutions to the problems associated with nutrient-rich wastewater.

Bacteria, nanoflagellates and ciliates constitute the microbial loop and it is a model of the pathways of carbon and nutrient cycling through microbial components of pelagic aquatic communities. The current study comprised of a comparative study of the microbial food web community along north to south latitudinal gradient using space for time susbtitute, monitoring and mesocosms experiments with contrasting nutrient and predation states. We investigated effect of fish predation through different zooplankton taxa on microbial loop community with in situ food web experiments in 14 lakes along north to south latitudinal gradient. The effect of seasonality was also determined by monitoring in Lakes Eymir and Mogan between 2010 and 2011. Effects of hydrology and fish through microbial community was studied in mesocosms in Lake Eymir. An implication of global warming along with eutrophication on microbial community was further explored in warmed and nutrient enriched artificial ponds during 4 months in Silkeborg, Denmark. Our results revealed that temperature, hydrology, fish, macrophytes and seasonality affected the top down control of zooplankton and bottom up control of nutrients on microbial loop and interactions between controls and increase in these controls had a strong negative impact on the contribution and biomass of microbial loop and change the interactions within microbial community. Global warming may also effect the impact of top down and bottom up controls through increasing eutrophication, temperature, change in hydrology and zooplankton composition and in a consequence of that efficiency of microbial loop may decrease in the future warmer, drier and eutrophic conditions.

Phytoplankton blooms compromise the quality of freshwater ecosystems and the efficient processing of water by treatment works worldwide. This research aims to determine whether in-situ filamentous biofiltration processes mediated by living roots and synthetic filters as media can reduce or remove the phytoplankton loading (micro-algae and cyanobacteria) prior to a potable water treatment works intake. The underlying biofiltration mechanisms were investigated using field and laboratory studies. A novel macroscale biofilter with three plant species, named the "Living-Filter", installed in Farmoor II reservoir, UK, was surveyed weekly for physicochemical and biological variables under continuous flow conditions during 17 weeks. The efficiency of a mesoscale biofilter using the aquatic plant Phalaris arundinacea and synthetic filters, was tested with Microcystis aeruginosa under continuous flow conditions and in batch experiments. The 'simultaneous allelochemical method' was developed for quantifying allelochemicals from Phalaris in aqueous samples. Microscale studies were used to investigate biofilter allelochemical release in response to environmental stressors and Microcystis growth inhibition in filtered and unfiltered aqueous root exudate. Results demonstrate that the removal of phytoplankton biomass by physical mechanisms has a removal efficiency of ≤45% in the "Living-Filter" (filamentous biofilter plus synthetic fabric) and that the removal of Microcystis biomass using only biofilters was 25%. Chemical mechanisms that reduce Microcystis cell numbers are mediated by allelochemicals released from biofilter roots. Root exudate treatments on Microcystis revealed that Microcystis growth is inhibited by allelochemicals, not by nutrient competition, and that protists and invertebrates play a role in removing Microcystis. Filamentous biofilters can remove phytoplankton biomass by physical, chemical and biological mechanisms. Biofilters and synthetic filters in combination improve removal efficiency. Application of macroscale biofilters prior to potable water treatment works benefits the ecosystem. Plant properties, biofilter size to surface water ratio, and retention time must be considered to maximise the benefits of biofiltration processes.

Ce travail se situe dans le cadre d’un projet global visant à développer un procédé innovant pour un traitement ciblé de plantes aquatiques invasives dans une masse d’eau lentique. L’un des enjeux est d’optimiser la concentration de substance active nécessaire pour éliminer les plantes ciblées sans créer de potentiels dommages écologiques. Une méthodologie basée sur une approche de modélisation ascendante a été appliquée en utilisant la Mécanique des Fluides Numérique (MFN) afin de pouvoir définir des conditions optimales pour un traitement efficace. Cette approche de modélisation a été appliquée pour la simulation de l’écoulement et la dispersion des substances actives de l’échelle d’un pilote de 1m3 à celle de plans d’eau alimentés en surface et par le fond. Cinq modèles de turbulence ont été présélectionnés afin d’évaluer leur influence sur les résultats de simulation. Le modèle RNG k-ε a été choisi définitivement après sa validation par des traçages expérimentaux à l’échelle du pilote mimant le fonctionnement hydrodynamique d’un plan d’eau réel. Des mesures expérimentales sur pilote et des simulations numériques réalisées à l’échelle de celui-ci et sur quatre configurations de plans d’eau ont permis d’évaluer l’impact de plusieurs paramètres hydrodynamiques (débit, nombre d’entrées et sorties, type d’alimentation en eau, …) et des forçages extérieurs (vent, température) sur le maintien de la concentration algicide au cours du traitement. Le vent joue principalement le rôle d'un diffuseur naturel provoquant 95% de la dilution de la concentration algicide. La prise en compte de la vitesse de réaction chimique de la substance active dans l’eau indique également une diminution de la concentration locale de substance active. Le traitement optimal ne serait donc pas seulement lié à la maîtrise de la concentration à injecter mais à une bonne compréhension de l’écoulement local
This work is part of an overall project to develop an innovative process for targeted treatment of invasive aquatic plants in a lentic water body. One of the challenges is to optimize the concentration of active substance required to remove the target plants without creating potential ecological damage. A methodology based on a bottom-up modeling approach was applied using Computational Fluid Dynamics (CFD) in order to define optimal conditions for effective treatment. This modeling approach was used for the flow and the dispersion of active substance simulations from a 1 m3 pilot to lentic water bodies fed by surface water or groundwater. Five turbulence models were preselected in order to assess their influence on the simulation results. The RNG k-ε model was selected after final validation by tracer experiments at pilot scale mimicking the hydrodynamics of a real lentic water bodies. Experimental measurements on pilot and numerical simulations carried out on scale thereof with four configurations of lentic water bodies have allowed to evaluate the impact of several hydrodynamic parameters (water flow, number of inlets and outlets, type of water supply, …) and external forcing (wind, temperature) on maintaining of algaecide concentration during the treatment. The wind mainly acts as a natural diffuser causing 95% of diluting the algaecide concentration. Taking account of the rate of chemical reaction of the active substance in water also indicates a decrease of the local concentration of active substance. The optimal treatment is not only based to the control of injected concentration but it is also related to a good understanding of the local water flow

碩士
國立東華大學
海洋生物多樣性及演化研究所
102
Excessive levels of nutrients and trace contaminants in seawater can lead to algal blooms, including red tides. Algal blooms and red tides in particular are detrimental to marine ecosystems and fisheries, and can additionally generate human health concerns. Herein seawater quality parameters, including chlorophyll a (chl-a) concentration and nutrient levels, were measured at Tapong Bay, Southern Taiwan. Additionally, experiments were designed in order to determine the effects of elevated nitrogen and phosphorus levels on algal growth. Some of these laboratory incubations were conducted with oysters of varying densities in order to determine how these bivalves influence seawater quality. Briefly, it was hypothesized that certain oyster densities may prevent algal blooms due to their ability to sequester nutrients from the seawater, and thus serve as environmental bioremediators. The results of these studies show that land-based pollution, coupled with early spring rains, can indeed lead to red tide formation in Tapong Bay. There was a negative associations between chl-a concentration and dissolved inorganic nitrogen (DIN) concentration in situ, though a positive correlation between chl-a concentration and dissolved inorganic phosphorus (DIP); these observations may be due to nitrogen absorption by phytoplankton. During the winter, vertical mixing brings benthos-entrenched nutrients to the surface, yet no red tides occurred at this time. This suggests that additional biolimiting factors must act in concert with nutrient levels to control such algal blooms. Collectively, our results show that nitrogen is the main nutrient associated with algae blooms, meaning that nitrogen levels must be better controlled. At a mean mariculture density of 75 individuals/m3, oysters were able to remove 23.4 % nitrogen and 8.6 % phosphate daily to minimize blooms occurrence. According to this culture condition, it is estimated that the annual removal from lagoon is about 267.9t for nitrogen and 38.6t for phosphorus.

碩士
國立臺灣大學
環境工程學研究所
96
The high concentration of algae in water body is the most significant symptom of eutrophication and often perplexes the users of the water. With the approach of biomanipulation, we built several artificial refuges made of plastic net for zooplankton in an artificial pond. We wanted to reduce the quantity of algae in the water by the enhanced consumption of zooplankton due to their increased population. These refuges could offer safe habitats for zooplankton to hide and increase the space heterogeneity in the pond. The results of our research indicate that the species diversity of zooplankton in the refuges has increased due to the appearance of rotifers and protozoa. But the amount of zooplankton was still low in open water outside the refuges. Without large body-sized zooplankton in the water in this case, the concentration of algae in the pond remained high after the installation of the refuges.

Tese de doutoramento em Engenharia Química e Biológica
Eutrophication is the most common reason for lake management and results mainly from anthropogenic activities occurring in their watersheds. Nowadays, eutrophication is also due to internal inputs of phosphorus (P), as is the case of Azoreans lakes. P tends to accumulate in lake sediments leading to an excess of P in the water column and the concomitant proliferation of planktonic algae. In Azores, despite the considerable effort made to describe the phytoplankton growing on the water column, the lack of information regarding the microbial processes in sediments is still high. In that regard, the present work aims to assess the sediment reference conditions (e.g. biogeochemical composition of sediments) of Azorean lakes in order to incorporate sediment issues and knowledge into management strategies enhancing the efficacy of the remediation activities that should be taken to achieve the good ecological status until 2015. Sediment samples were collected and biogeochemical profiles, organic matter (OM), total nitrogen, TP and total iron (TFe), were determined. Lake Azul profiles were quite homogeneous for all parameters, while in lake Furnas TFe profile presented a peak below the aerobic layer. For lake Verde, the concentration of all studied elements (20±2 % OM; 2.10±0.08 mg/g TP; 1.31±0.50 mg/g TN; 8.06±0.13 mg/g TFe) in the uppermost sediment layer was approximately two times higher than the ones in sediments from other lakes, decreasing with sediment depth. The higher amounts of P and OM in lake Verde suggested a higher internal contribution of P to eutrophication. Dominant members were mostly affiliated to Proteobacteria phylum (Alpha-, Delta-, and Gamma-subclasses), group Bacteroidetes/Chlorobi and phylum Chloroflexi. The Cyanobacteria phylum was solely detected in sediments from lake Verde and lake Furnas that presented the highest amounts of N and P both in the water column and sediments, while the other phyla were detected in sediments from the three studied lakes. The combination of quantitative PCR and activity tests suggested that bacteria performing ammonium oxidation (aerobic and anaerobic), nitrite oxidation, heterotrophic nitrate reduction, iron reduction and biological P storage/release were present and active in sediments. Bacteria performing anaerobic ammonium oxidation were the most abundant in sediments from the eutrophic lakes Verde, Azul and Furnas (4.5 % to 16.6 %), followed by nitrifying bacteria (0.8 % to 13.0 %), denitrifying bacteria (0.5 to 6.8 %), iron-reducing bacteria of the Geobacteraceae family (0.2 % to 1.4 %), and phosphorus-accumulating organisms affiliated to Candidatus Accumulibacter (less than 0.3 %). In opposition, denitrifying bacteria dominated in sediments from the oligo-mesotrophic lake Fogo (8.8 %). Lake Furnas sediments presented bacterial stratification (aerobes in upper layers and anaerobes downward) due to the presence oxygen in the hypolimnion all year round. The present work also suggested that biological phosphorus storage/release by denitrifying bacteria in sediments might as well contribute to the release of P from sediments. Moreover, lake Furnas sediment bacterial community was electroactive as demonstrated both by cyclic voltammetry and power generation in a simulated benthic microbial fuel cell.Martins G. 2010 sediments from the eutrophic lakes Verde, Azul and Furnas (4.5 % to 16.6 %), followed by nitrifying bacteria (0.8 % to 13.0 %), denitrifying bacteria (0.5 to 6.8 %), iron-reducing bacteria of the Geobacteraceae family (0.2 % to 1.4 %), and phosphorus-accumulating organisms affiliated to Candidatus Accumulibacter (less than 0.3 %). In opposition, denitrifying bacteria dominated in sediments from the oligo-mesotrophic lake Fogo (8.8 %). Lake Furnas sediments presented bacterial stratification (aerobes in upper layers and anaerobes downward) due to the presence oxygen in the hypolimnion all year round. The present work also suggested that biological phosphorus storage/release by denitrifying bacteria in sediments might as well contribute to the release of P from sediments. Moreover, lake Furnas sediment bacterial community was electroactive as demonstrated both by cyclic voltammetry and power generation in a simulated benthic microbial fuel cell. Finally, a mathematical model for lake Verde water quality was developed and calibrated in order to support the decision making processes in aquatic restoration programmes. Prospective scenarios showed that external measures are not enough to improve water quality in lake Verde (an average concentration of TP of 26 g/L and phytoplankton biomass of 1.4 mg/L could be reached in a 10 years horizon) and that an integrated approach (external and internal measures) need to be designed. In conclusion, the present work suggested that sediment bacteria were active and performed diverse roles on carbon, nutrients and iron cycling. The variability of sediment geochemical profiles as well as the structure and activity of sediment bacterial community indicates that individual lake sediment characterization and site-specific assessments of the efficacy of remediation approaches are required. In this regard, the designing of re-qualification strategies towards the good ecological status prescribed by the Water Framework Directive should include, in addition to the classical procedure, an evaluation of the contribution of biological processes in sediments to the eutrophication problem.
A eutrofização é o motivo mais comum para a necessidade de gestão de lagos e, resulta principalmente de actividades antropogénicas que ocorrem nas bacias hidrográficas. Actualmente, a eutrofização é também devida a entradas internas de fósforo (P). O P tende a acumular-se nos sedimentos, levando a um excesso de P na coluna de água e à consequente proliferação de algas planctónicas. Nos Açores, apesar dos consideráveis esforços para descrever o crescimento do fitoplâncton na coluna de água, a falta de informação relativa aos processos microbianos nos sedimentos é ainda muito elevada. Nesse sentido, o presente trabalho teve como objectivo avaliar as condições de referência dos sedimentos (e.g., a composição biogeoquímica dos sedimentos) dos lagos dos Açores, a fim de incorporar as questões e conhecimento sobre sedimentos nas estratégias de gestão, bem como reforçar a eficácia das actividades de remediação que devem ser tomadas para alcançar o bom estado ecológico até 2015. Nesse sentido, foram recolhidas amostras de sedimentos e os perfis biogeoquímicos, matéria orgânica (OM), azoto total (TN), P total (TP) e ferro total (TFe), foram determinados. Os perfis biogeoquímicos para a lagoa Azul revelaram-se bastante homogéneos para todos os parâmetros determinados, enquanto na lagoa das Furnas, o perfil de TFe apresentou um pico abaixo da camada aeróbia. As maiores quantidades de P e OM na lagoa Verde sugeriram uma maior contribuição interna de P para a eutrofização. Relativamente aos membros dominantes da comunidade bacteriana presente nos sedimentos das lagoas Verde, Azul e Furnas, a sua maioria estava afiliada ao filo Proteobacteria, grupo Bacteroidetes/Chlorobi e filo Chloroflexi. O filo Cyanobacteria foi apenas detectado nos sedimentos das lagoas Verde e Furnas, que correspondem às lagoas com maiores teores de N e P, tanto na coluna de água como nos sedimentos. A combinação do PCR quantitativo com os testes de actividade sugeriu que as bactérias que realizam a oxidação do amónio (aeróbia e anaeróbia), a oxidação do nitrito, a redução heterotrófica de nitrato, a redução de ferro e o armazenamento/libertação biológica de fósforo estavam presentes e activas nos sedimentos. As bactérias anaeróbias oxidantes de amónio foram as mais abundantes nos sedimentos das lagoas eutróficas Verde, Azul e Furnas (4.5 % a 16.6 %), seguidas pelas bactérias nitrificantes (0.8 % a 13.0 %), desnitrificantes (0.5 a 6.8 %), redutoras de ferro da família Geobacteraceae (0.2 % a 1.4 %) e organismos acumuladores de fósforo filiados a “Candidatus Accumulibacter” (<0.3 %). Em oposição, as bacterias desnitrificantes dominaram os sedimentos da lagoa oligo-mesotrófica do Fogo (8.8 %). Os sedimentos da lagoa das Furnas apresentaram estratificação bacteriana (os grupos aeróbios dominaram as camadas superiores e os anaeróbios as camadas mais profundas) devido à presença de oxigénio no hipolímnio durante todo o ano. O presente trabalho também sugeriu que a acumulação/libertação biológica de P pelas bactérias desnitrificantes pode contribuir para a liberação de P dos sedimentos. Além disso, a comunidade bacteriana presente nos sedimentos da lagoa das Furnas apresentou electroactividade como demonstrado tanto por voltametria cíclica como pela produção de energia numa célula de combustível microbiana bêntica.Finalmente, um modelo matemático de qualidade da água da lagoa Verde foi desenvolvido e calibrado de forma a apoiar os processos de decisão em programas de recuperação aquáticos. Os cenários prospectivos mostraram que medidas externas não são suficientes para melhorar a qualidade da água na lagoa Verde (uma concentração média de TP, 26 g/L P e fitoplâncton, 1.4 mg/L, podem ser alcançadas num horizonte de 10 anos) e que uma abordagem integrada (medidas internas e externas) deve ser desenhada. Em conclusão, o presente trabalho sugeriu que as bactérias presentes nos sedimentos desempenham um papel activo no ciclo do carbono, nutrientes e ferro. A variabilidade dos perfis biogeoquímicos nos sedimentos, bem como a estrutura e a actividade da comunidade bacteriana indicaram que uma caracterização individual dos sedimentos dos diferentes lagos e que avaliações específicas da eficácia das medidas de remediação são necessárias. Neste sentido, a concepção de estratégias de requalificação para o bom estado ecológico prescrito pela Directiva Quadro da Água deve incluir, para além do procedimento clássico, uma avaliação da contribuição dos processos biológicos nos sedimentos para o problema da eutrofização.
Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/25639/2005

碩士
弘光科技大學
環境工程研究所
102
In this study, 21 major reservoirs in Taiwan were investigated, including water quality parameters (transparency (SD), water temperature (WT), pH value , dissolved oxygen (DO), chlorophyll a (Chl-a), total phosphorus (TP), total organic carbon (TOC) and total nitrogen (TN)), eutrophic index (Carlson Trophic State Index, CTSI), and multiple regression analysis, whereby the province to identify the main causes of eutrophication of reservoirs. The results showed that low transparency southern reservoirs , high water temperature, low dissolved oxygen , chlorophyll a higher nutrient ( phosphorus , carbon, nitrogen ) were the highest , resulting in the highest value of CTSI Reservoir in southern province , also cause eutrophication of reservoirs in southern main reason. According to the study of methods to control eutrophication that found to reduce phosphorus discharged into the reservoir is the best control strategy, this method would be reduced the reproduction rate of algae , to avoid the deterioration of water quality. Moreover, the situation in Southern Taiwan reservoirs, some reservoirs in nearly a decade of statistics showing a slowing trend in Lantan reservoir and reservoir Agongdian more significant, mainly because of the nutrient phosphorus, carbon and nitrogen are reduced year by year due to , and by the transparency (SD) data discovery reservoir gradually becomes clear, and chlorophyll a (Chl-a) significantly dropped significantly, which is to reduce the concentration of algae. Emerald another reservoir in northern CTSI value increased in recent years, the phenomenon has a tendency, judged mainly due to an increase in water and nutrient phosphorus trend. The results of this study may suggest eutrophication province have advised against the tendency of the reservoir of nutrients into the conduct of the watershed control, including the planting of crops should be counseling their correct fertilization or fallow, especially for the small amount of phosphorus control, must also there are elaborate plans to avoid drinking water suffer algal blooms, and even lead to safety concerns public water algae poison. Keywords: reservoir, eutrophication, Carlson trophic state index, algae, chlorophyll a, nutrients

碩士
國立臺灣大學
土木工程學系研究所
86
The purpose of this thesis is to develop an optimization model for reservoir eutrophication control, using DDP ( Dynamic Differential Programming)as the optimization method to solve the problem, and taking Feitsui Reservoir as our example. The objective function of this model is the minimum needed pollution reorganization scale. The constraints of water quality model is an equality, along with a physical inequality constraint. This research employs the zero- dimensional water quality model, considering six water quality variables. The biochemical reaction equation is nonlinear. When considering time-variant factors, the model is dynamic and unsteady. The results of the optimization enables us to find the necessary efficiency to deal with the pollution sources, in order to keep the "chlorophyll-a" consistency within the lake under a certain level. Since the model is time-variant, the resulting control project is a function of time, and is adaptable and able to make economical as well as effective arrangements. This research adopts the DDP method to solve optimization problems of dynamic eutrophication control. The results show the feasibility of this optimization method as a way to solve dynamic reservoir eutrophication control problems.

碩士
國立臺灣大學
環境工程學研究所
94
Hsin shan reservoir is located in Keelung, Taiwan. By sampling during last year, we collected the water quality data of this reservoir, including algae phase and nutrient such as ammonia nitrogen, nitrate and phosphate. These data were used in developing an algae dynamic model which is zero dimension. From surface to ten meters down to the water, we divided three levels to simulate the growth situation of different kinds of algae. The measured data showed that there was a phenomenon about algae succession happened in this reservoir. The physical characteristics of different kind algae and the environmental condition controlled which kind of algae would be the widely distributed species. Take Hsin Shan reservoir for example, Cyanophyta had a wide distribution in summer, but in fall, Bacillariophyta and Chrysophyta replaced it. After calculating all parameters of this model, other data were needed to verify the model. This model can also be used for environmental management, and to predict when bloom will happen in reservoirs. Eutrophication is a serious problem in reservoirs, and Hsin shan reservoir was examined beyond standard in 2003 with Carlson Index. In order to correct this, we established a pilot in this reservoir. In the pilot, mixing was thought to destratify the stable condition of water. In the end of the experiment, the goal species, Microcystis, didn’t leave the water body. The possible reason was that the environment below the surface water was also suitable for it, and there might be enough light and nutrient for its growth. More powerful mixing or other artificial methods are needed to alleviate the bloom happened in Hsin shan reservoir.

Thesis (M.A.)--York University, 2007. Graduate Programme in Geography.
Typescript. Includes bibliographical references (leaves 112-121). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR38799

A good ecological status of streams and rivers is crucial for maintaining ecological functionality of running waters. Worldwide eutrophication threatens to change structure and function of freshwater ecosystems (Dodds et al., 2008). To reduce the symptoms of eutrophication in streams and rivers an additional approach, besides the reduction of external nutrient inputs from catchment areas, is needed. Therefore the goal has been set to transfer the approach of biomanipulation, which is widely accepted as tool in water quality management in lakes and reservoirs, to streams. The objective of this study was accordingly to analyse and evaluate some crucial preconditions for top-down control of stream food webs. For that purpose the present thesis examined effects of fish predation (stone loach and gudgeon) on grazer-periphyton interaction in small streams by assessing predator avoidance by benthic grazers, effects of benthic grazers on periphyton community composition during fish presence/absence and the possibility of top-down control on algal biomass by benthivorous fish.

South Africa has some of the most eutrophic aquatic systems in the world, as a result of the adoption of an unnecessarily high 1 mg l-1 phosphorus (P) standard for all water treatment works in the 1970 s. The floating aquatic macrophyte, water hyacinth (Eichhornia crassipes (Mart.) Solms (Pontederiaceae), has taken advantage of these nutrient rich systems, becoming highly invasive and damaging. Despite the implementation of a biological control programme in South Africa, water hyacinth remains the worst aquatic weed. A meta-analysis of published and unpublished laboratory studies that investigated the combined effect of P and nitrogen (N) water nutrient concentration and control agent herbivory showed that water nutrient status was more important than herbivory in water hyacinth growth. Analysis of long-term field data collected monthly from 14 sites around South Africa between 2004 and 2005 supported these findings. Therefore, the first step in any water hyacinth control programme should be to reduce the nutrient status of the water body.

Phosphorus load reduction and dreissenid invasion are the two most important factors that influence europhication dynamics in the Great Lakes. The 1978 amendments to the Great Lakes Water Quality Agreement (GLWQA) between the United States and Canada established target phosphorus loads for the lakes, leading to reductions in external phosphorus loading to the Great Lakes. With diminished phosphorus levels, further nutrient management was a minor concern until the proliferation of invasive dreissenid mussels. Dreissenid mussels were first documented in the Laurentian Great Lakes in the late 1980s. Zebra mussels (Dreissena polymorpha) spread quickly into shallow, hard-substrate areas; quagga mussels (Dreissena rostriformis bugensis) spread more slowly and are currently colonizing deep, offshore areas. These mussels have the potential to modify biogeochemical processes and food web structure, altering nutrient cycling and availability. Following the mussel invasion, cyanobacterial blooms and nuisance benthic algal growth have reappeared in many nearshore areas of the Great Lakes.

This dissertation characterizes long-term patterns of phosphorus loading and mussel populations for Saginaw Bay, and estimates the effects of load reductions and dreissenid invasion on several aspects of pelagic water quality, focusing on phosphorus flux and cycling in Saginaw Bay. Bayesian approaches were used to quantify the impacts of load reduction and mussel invasion, while at the same time addressing model parameter uncertainty and prediction uncertainty associated with long-term observational data. Annual total phosphorus load estimates suggest a decreasing trend until the late 1970s to early 1980s, reflecting the effectiveness of point source controls implemented pursuant to GLWQA. Despite the decrease, however, the annual loads have not likely met the 440 tonne yr-1 target established for Saginaw Bay. In 1990 zebra mussels were discovered in the bay and by 1992 they were widespread and peaked with densities of >30,000 m-2. Following the peak, mean densities dropped and modeling results predict that the density will reach equilibria at ~600 m-2. When mussels appeared, the proportion of tributary phosphorus retained in Saginaw Bay increased from ~0.5 to ~0.7, reducing phosphorus export to the main body of Lake Huron. The combined effects of increased phosphorus retention and decreased phosphorus loading have caused an ~60% decrease in phosphorus export from Saginaw Bay to Lake Huron. The analysis of long-term patterns of pelagic water quality highlights the sustained effects of mussel invasion on altering water quality parameters in Saginaw Bay; there was a consistent decrease in chlorophyll concentrations by ~46%, and total phosphorus concentrations by ~25%, and an increase in secchi depths by ~15% over ~20 year invasion of mussels. A comparison of chlorophyll-phospohrus relationship between pre- and post-invasion periods suggest the reduced chlorophyll yield for a given phosphorus concentration after the mussel invasion. Further, decreases in both total phosphorus and chlorophyll concentrations were found in the majority of 24 mussel-invaded US lakes in addition to Saginaw Bay, and modeling results predict less chlorophyll yields per unit phosphorus level that ranges from oligo- to mesotrophic conditions. All lines of evidence presented in the dissertation point to the important roles of load reductions and invasive mussels affecting eutrophication dynamics in lake ecosystems.

Dissertation

碩士
國立臺灣大學
環境工程學研究所
104
Jin-sha Reservoir and Rong-hu Reservoir in Kinmen County suffer from the problems of high concentration of dissolved organic carbon (DOC) and eutrophication. High DOC in raw water will lower the efficiency of water treatment, cause the production of disinfection byproducts (DBP) in tap water, increase the treating cost and pose risk of cancer to the public. Eutrophication also leads to problems such as high turbidity, low dissolved oxygen, bad odors, etc. Cylindrospermopsis raciborskii, which was thought as a tolerator of high salinity in previous researches, was the dominating species in Jin-sha Reservoir and Rong-hu Reservoir most of the time, This study aimed to find out the correlations between the abundance of Cylindrospermopsis raciborskii and several water quality parameters in the reservoirs as well as the reason for high DOC by investigating physical and chemical characteristics of reservoirs, nutrient loadings from the watersheds , and the algal composition. Sources of saline water that resulted in high salinity and conductivity in these two reservoirs were sought. In addition, this study devoted to develop a new method for estimating the nutrient loadings of the reservoirs, and constructed a model for simulating the concentration of DIN (dissolved inorganic nitrogen ) and DIP (dissolved inorganic phosphorus) in the two reservoirs. In order to control the growth of algae, a device as light-shading board was developed and its performance was evaluated by field test. The results of investigation shows that dominance of Cylindrospermopsis raciborskii does have correlation with the high salinity in the water. Saline water entered through inflow channels of these two reservoirs. Large proportion of dissolved organic carbon in the reservoirs was produced by algae, and the environment with low dissolved inorganic nitrogen (DIN) to dissolved inorganic phosphorus (DIP) ratio and low temperature favored the dominance of Cylindrospermopsis raciborskii. Simulated nutrient concentrations fall in the ranges the same as the real concentrations. Finally, we found that light-shading device would not be effective when shading only 50% of the water surface, and more tests are needed. With all these results, controlling strategies for eutrophication ( Cylindrospermopsis raciborskii ) were figured out: 1. Keeping the water level high to avoid saline water entering Rong-hu Reservoir from the bottom, and using saline groundwater for irrigation should be avoided. 2. building retention pond at the inflow channels of the reservoirs to retain eroded soil as much as possible.

Benthic filter feeders (BFF) can reduce phytoplankton concentration (abundance) thereby controlling eutrophication in several ecosystems, including rivers. However, experiments suggest warming can alter the relationship between BFF grazing rate and the growth rate of (heterotrophic) planktonic prey. To investigate how eutrophication control by grazers is altered with temperature under the influence of other important abiotic (water depth, and speed, light, and turbidity) and biotic factors (initial phytoplankton concentration [hereafter: Pin value], BFF density and spatial BFF distribution), we developed a spatially-explicit computer simulation model. This model simulates the dynamics of a phytoplankton population traveling through a simplified river channel while being grazed by BFF. Our model includes the thermal responses of BFF grazing and phytoplankton growth. The results show that BFF grazing can qualitatively alter and, in some circumstances, even reverse the response of phytoplankton to warming. Moreover, the response of grazer-controlled phytoplankton to warming, water depth and Pin value is non-linear and phytoplankton can increase steeply with slight changes within some ranges of these variables. In addition, these variables can interact causing their combined effects on eutrophication to differ from what is expected considering their isolated effects. Generally, the effect of most variables, including temperature, Pin value and BFF density and spatial distribution, is larger at shallow waters. Moreover, our study shows that phytoplankton control can be substantially improved by heterogeneous BFF distributions where the BFF are located at the extremes of the river either upstream or downstream instead of homogenously distributed along the whole river. However, warming can cause a switch between these two optimal distributions or even can cause differences among the spatial distributions to disappear. In general, the homogeneous BFF distribution can be used as conservative estimate of eutrophication control. In conclusion, this work shows that trophic control can qualitatively alter the response of eutrophication to warming, supporting previous studies suggesting that the prediction of global warming effects requires considering not only the thermal responses of organisms but also their trophic interactions. In addition to these biotic variables, this thesis reveals that considering the interactions between abiotic and biotic variables and including their spatial distribution are important for eutrophication control. Especially, the detection of thresholds in the response of grazer-controlled phytoplankton to temperature, water depth, Pin value, and spatial BFF distribution indicates that one should be careful with predictions because of potential abrupt changes. Although further studies are needed to make specific recommendations for water quality management, our work provides preliminary suggestions on the conditions where grazers or Pin reductions can be more efficient to control eutrophication.

Indiana University-Purdue University Indianapolis (IUPUI)
The transfer of nutrients from US Midwest croplands into surface waters causes eutrophication and a decline in water quality. Temporary retention of nutrient-rich runoff in constructed wetlands can help mitigate these negative impacts through physical entrapment and biological transformation of nitrogen (N) and phosphorus (P). However, with the expectation that wet-dry periods will be more frequent in the region, there is a need to better understand the mechanisms that control nutrient retention and release in US Midwest wetlands constructed on former croplands. In this study, soil cores (30 cm long, 20 cm diam) were collected from two constructed wetlands (4 and 8-yr old), and the surface (0-20 cm) and subsurface (40-60 cm) layers of a cropland where a constructed wetland will be constructed in the future. Soil cores were subjected to either a moist or a dry treatment for 5 weeks, and then flooded with stream water (water depth 6 cm). The flux of nutrients, N2O, cations, and variation in floodwater chemistry (pH and ORP) were monitored for another 5 week period. Porewater was tested during the final 3 weeks of the experiment. Nitrate (0.1-130 mg N m-2 d-1) and inorganic P (Pi) fluxes (0.09-2.9 mg P m-2 d-1) were significantly higher in the dry treatment cores. Regardless of site, the dry treatment also resulted in higher floodwater NO3- concentrations suggesting organic matter mineralization and mineral N build up during the drying phase. However, this initial NO3- release was rapidly denitrified as indicated by the sharp increase in N2O production during that period. In contrast to N, the release of Pi was significantly higher in cores from the cropland. Soil at these sites had higher water extractable Pi and total P. Contrary to the study hypothesis and the results of previous studies, Pi concentration in floodwater and porewater was not correlated with dissolved Fe suggesting that reductive dissolution was not the dominant process controlling P release in US Midwest mineral soils developed from calcareous glacial till. Rather, variation in Ca2+ concentration and its relationship with Pi suggest that dissolution of Ca-containing minerals may be more important and should be the focus of future studies examining the geochemistry of P in these constructed wetlands.

Darvill Wastewater Works (DWWW) receives and treats both domestic and industrial wastewater from the city of Pietermaritzburg, in KwaZulu-Natal. Sludge from the wastewater treatment is sprayed onto surrounding lands, causing odour and fly problems. The plant also discharges treated effluent into the Msunduzi River, compromising water quality. This study uses several economic valuation techniques to estimate the value of the benefits of improving air and water quality to overcome these problems caused by DWWW. The benefits. are then compared with the costs of upgrading DWWW to see whether or not upgrading DWWW to improve air and water quality would be worthwhile. The Contingent Valuation Method (CVM) was used to elicit people's willingness to pay (WTP) for improvements in air quality due to the elimination of odours and flies caused by sludge deposited by DWWW. The WTP estimates reflect individual's preferences for improvements in air quality. The stated WTP amounts were positively related to household income, but negatively related to the age and gender of the respondent and the number of dependants in the household. The mean monthly WTP for the surveyed households is higher for those that are closer to the pollution source (R23.00 and R29.00 for Zones land 2) and less for those further away (RI4.00 for Zone 3). Sobantu residential area had the lowest mean monthly WTP (R18.00), followed by Lincoln Meade (R27.00) and Hayfields (R54.00). This is expected, as Sobantu has relatively high levels of unemployment and lower household incomes. Strategic, hypothetical and free rider bias may have led to the unexpected signs of some estimated regression coefficients in linear regression models used to estimate WTP. The mean WTP was estimated as R307.20 per annum per household, and when this is aggregated over the total population in the residential areas impacted by odours and flies (37192 households), the benefits of eliminating odours and flies are estimated as R11 425 382.00 per annum. A hedonic price method was used to quantify the decline in property values as a result of odours and flies caused by sludge deposited by DWWW. Properties experienced a R6650.08 decline in selling price if the distance from them to DWWW is decreased by one kilometre. Properties that are closer to DWWW were worth RI5 953.90 less than those further away from DWWW. Aggregating these values over all estimated impacted households in the study, gives an estimated benefit of improving air quality of R28 480 518.00 per annum. The impact of water pollution was quantified by estimating the revenue (R3 744 975.00) that would be lost by Pietermaritzburg if the Duzi Canoe Marathon were to be cancelled due to incidences of diarrheoa reported during the race. A cost of illness procedure was adopted to quantify the effect of water pollution on the health of communities that use the Msunduzi River as a source of potable water supply. A value of R1 243 372.50 was estimated as the annual cost of water-related illnesses in these rural areas. This value represents the costs of the river pollution to those communities. Both of these exercises indicated that improving water quality of the Msunduzi River would be beneficial to society. The effect of nutrient enrichment of the Msunduzi River was quantified by estimating the cost of removing water hyacinth from the Inanda Dam, treatment cost at Wiggins water treatment works and the value of recreation at Mahlabathini Park (Inanda Dam). The annual cost of removing water hyacinth was estimated from the direct costs of chemicals and labour as R47 202.15. The increased treatment costs at Wiggins attributable to DWWW were estimated as R1 104 999.20 and R956 924.15 per annum for removal of algae, and tastes and odours, respectively. The value of R706.90 per annum was estimated as the consumer surplus accruing to recreationists, and, therefore, the value of recreation at Mahlabathini Park to an individual. These annual benefits, when aggregated over the total study population (296 590) were over two hundred million rands (R209 659 470.00). The estimated total benefits (R256 662 840.00) of eliminating odours and flies and effluent problems were compared to the actual costs of two alternative methods of upgrading DWWW using cost-benefit analysis. These alternatives were co-disposal option (R170 473 320) and a land disposal option (R168 809377). Benefit-cost ratios of 1.51 and 1.52 suggest that from society's standpoint, it would be beneficial to upgrade the plant in order to eliminate its adverse environmental impacts. The study results have important implications for policy makers, both the DWWW management and the Pietermaritzburg-TLC municipality. At present DWWW is operating beyond its design capacity, and this problem, together with the poor status of Pietermaritzburg's reticulation system, causes overflow of untreated or compromised final effluent into the Msunduzi River during rainy seasons. These problems also impact on the efficient operation of the plant as the sludge is not properly digested before being sprayed onto surrounding land. Thus to prevent further environmental degradation, a fundamental basis of the National Environmental Management Act, DWWW would need to address these issues. Upgrading DWWW would be a short-term solution if the problems with the storm-runoff into the plant is not addressed.
Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2002.