Made available in DSpace on 2014-12-17T14:33:11Z (GMT). No. of bitstreams: 1 MariaCS_DISSERT.pdf: 580924 bytes, checksum: a3954782366f82820809d4c2d8582d75 (MD5) Previous issue date: 2014-03-07 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The Brazilian Northeast is the most vulnerable region to climatic variability risks. For the Brazilian semi-arid is expected a reduction in the overall rates of precipitation and an increase in the number of dry days. These changes predicted by the IPCC (2007) will intensify the rainfall and droughts period that could promote the dominance of cyanobacteria, thus affecting the water quality of reservoirs, that are most used for water supply, in the semi-arid. The aim of this study was to evaluate the effects of increasing temperature combined with nutrient enrichment on the functional structure of the phytoplankton community of a mesotrophic reservoir in the semi-arid, in the worst case scenario of climate change predicted by the IPCC (2007). Two experiments were performed, one in a rainy season and another in the dry season. In the water sampled, nutrients (nitrate and orthophosphate) were added in different concentrations. The microcosms were submitted to two different temperatures, five-year average of air temperature in the reservoir (control) and 4?C above the control temperature (warming). The results of this study showed that warming and nutrient enrichment benefited mainly the functional groups of cyanobacteria. During the rainy season it was verified the increasing biomass of small functional groups of unicellular and opportunists algae such as F (colonial green algae with mucilage) and X1 (nanoplanktonic algae of eutrophic lake systems). It was also observed an increasing in total biomass, in the richness and diversity of the community. In the dry season experiment there was a greater contribution in the relative biomass of filamentous algae, with a replacement of the group S1 (non-filamentous cyanobacteria with heterocytes) for H1 (filamentous cyanobacteria with heterocytes) in nutrient- enriched treatments. Moreover, there was also loss in total biomass, species richness and diversity of the community. The effects of temperature and nutrients manipulation on phytoplankton community of reservoir Ministro Jo?o Alves provoked changes in species richness, the diversity of the community and its functional composition, being the dry period which showed the highest susceptibility to the increase in the contribution of potentially toxic cyanobacteria with heterocytes / O Nordeste ? a regi?o do Brasil mais vulner?vel aos riscos da variabilidade clim?tica. Para o semi?rido brasileiro ? esperada uma redu??o nos ?ndices totais de precipita??o e um aumento no n?mero de dias secos. Tais mudan?as previstas pelo IPCC (2007) afetar?o a intensidade e dura??o de chuvas e secas que poder?o promover a domin?ncia de cianobact?rias, afetando assim, a qualidade da ?gua dos reservat?rios no semi?rido. O objetivo deste trabalho foi avaliar os efeitos do aumento de temperatura combinado ao enriquecimento de nutrientes sobre a estrutura funcional da comunidade fitoplanct?nica de um reservat?rio mesotr?fico no semi?rido, no cen?rio mais pessimista de mudan?as clim?ticas previstas pelo IPCC (2007). Foram realizados dois experimentos um no per?odo chuvoso e outro no seco. A ?gua coletada no reservat?rio foi enriquecida com nutrientes (nitrato e f?sforo sol?vel reativo) em diferentes concentra??es. Os microcosmos foram submetidos a duas temperaturas diferentes, controle (m?dia de cinco anos da temperatura do ar no reservat?rio) e aquecimento (4 ?C acima da temperatura controle). Os resultados deste trabalham mostraram que o aquecimento e o enriquecimento nutricional beneficiaram principalmente os grupos funcionais de cianobact?rias, mas tamb?m alguns grupos compostos por clorof?ceas. No per?odo chuvoso foi verificado o aumento da biomassa de grupos funcionais de algas oportunistas, como o F (algas verdes coloniais com mucilagem) e X1 (algas nanoplanct?nicas de sistemas eutrofizados). No experimento do per?odo chuvoso tamb?m foi averiguado um aumento na biomassa total, na riqueza e diversidade da comunidade. No per?odo seco houve uma maior contribui??o na biomassa relativa de algas filamentosas, com uma substitui??o do grupo S1 (cianobact?rias filamentosas n?o-heterocitadas) pelo H1 (cianobact?rias filamentosas heterocitadas) nos tratamentos enriquecidos. Al?m disso, ocorreu tamb?m perda na biomassa total, riqueza de esp?cies e diversidade da comunidade. Assim, efeitos da manipula??o da temperatura e/ou nutrientes sobre a comunidade fitoplanct?nica do reservat?rio Ministro Jo?o Alves provocaram mudan?as na riqueza de esp?cies, na diversidade da comunidade e na sua composi??o funcional, sendo o per?odo seco o que apresentou maior suscetibilidade ao aumento na contribui??o de cianobact?rias heterocitadas potencialmente t?xicas

Estuarine systems are of crucial importance to the provision of goods and services on a global scale. High human population densities in coastal systems have caused an increasing input of pollutants, of which nutrient pollution is of major concern. Increasingly, these areas are also impacted by physical disturbance, which can originate from anthropogenic sources (e.g. bait digging, shipping) or climate change causing increasingly frequent and intense storms. The individual impacts of such stressors on ecosystems have been investigated however their combined impacts have received less attention. Cumulative impacts of multiple stressors are unpredictable and will likely result in non-additive effects. Further, the effect of local environmental context on multiple stressors is a relatively understudied topic. Work in this thesis compared the combined impact of nutrient enrichment and physical disturbance in Scotland and Australia, using a series of manipulative field experiments. Results demonstrate that response to stressors is highly context dependent, varying between and within geographic locations. While the background levels of stress may vary, by comparing these two locations it is possible to comment on the adaptations and response that communities within different parts of the world display when subjected to additional stress. This study demonstrates that environmental context must be considered when implementing future management practices. Further work demonstrated that the impact of multiple stressors varies depending on how the stress is applied –whether stressors are applied simultaneously or whether there is a delay between two stressors. This study was among the first of its kind, assessing the implications of how multiple stressors react with each other given the order and intensity in which stressors were applied. Results demonstrated that systems can become sensitised to stress making them increasingly vulnerable to additional stress. Future research should be focussed on incorporating ecologically relevant scenarios of how stressors will impact estuaries while considering how environmental context will mediate impacts.

Humans have transformed much of the earth’s surface through a wide range of activities of varying intensities and scales, shaping the landscape we see today. The combination of time and complex human-environment interactions within the Hakai Lúxvbálís Conservancy on the Central Coast of British Columbia has resulted in a landscape with many anthropogenically-generated modifications, such as shell middens which can be found at sites with histories of long-term habitation. Globally, shell middens (and in general, habitation sites) have been found to be factors in shaping site ecology. This thesis seeks to investigate this relationship between human activity and occupation and the landscape. The goal of this project is to examine the legacies from past land use, and subsidies from shell middens, within the present-day plant communities. I conducted an observational study to determine if species richness and overall plant communities on these habitation sites differed from sites without a history of intense occupation. To do this I selected ten habitation sites with known extensive shell middens and paired them with ten control sites with similar site conditions (but without the same site history or shell middens). I measured species abundances within 540 1 m x 1 m quadrats. I also surveyed a select group of culturally significant plant species and culturally modified trees within belt transects at each site. Data regarding the water table level and soil and foliar samples were also collected. A variety of environmental factors, along with the site history were evaluated as explanatory variables. Principal component analyses were used to describe how the gradients within the vegetation communities at three vegetation layers (ground, herb, shrub) to see if they respond differently to long-term site use. The habitation sites were found to be characterized by N-rich plant communities, which were significantly different from the plant communities on the control sites at the ground layer, herb layer, and with all layers combined, at both transect distances analysed, but the shrub layer was only significantly different when the entire transect was considered. The results show plant community composition is most strongly influenced by a combination of factors including site type, canopy cover, slope, topography, and distance from shore, with the weight of their importance depending on what vegetation layer is considered. The habitation sites had a lower average species richness at all layers, compared to the control sites, and their plant communities were shown to change differently with distance from the marine shoreline. Habitation sites also differed by having higher soil nutrient content, lower water table levels, and contained culturally important plant species that were absent on the control sites. This research highlights the influence that humans have had on landscapes in this region. This study shows how the patterns within the plant communities at the habitation sites differ from what is expected within the Coastal Western Hemlock zone. The research improves our understanding of the factors influencing vegetation patterns on the Central Coast of British Columbia with this examination of the complex intersection of historical practices and environmental changes. / Graduate

No description available.

<p> Nutrient enrichment through pollution causes intense aquatic growth in many of our lakes, which results in their deterioration for man's use. Phosphorus is suspected as possibly the most important element in this problem since it often is the limiting nutrient for growth. Condensed phosphates from detergents in wastewater are a major supply of phosphorus to surface waters. They hydrolyze to orthophosphate, the form most readily available to plants and organisms. The removal of phosphorus in treatment plants has therefore been suggested. </p> <p> The chemical industry has carried our many studies on the rate of hydrolysis of condensed phosphate in distilled water. However few investigations have been made on this effect in natural water and wastewater. This work concentrates on studies on the rate of hydrolysis of condensed phosphates in wastewater and lake water under conditions of temperature, pH and concentration levels actually occurring in the environment. </p> / Thesis / Doctor of Philosophy (PhD)

Annex 2 of the Great Lakes Water Quality Protocol calls for the collaborative development of a ‘nearshore framework’, but does not provide guidance with respect to nearshore governance. This thesis bridges this gap with a series of studies on the determinants for adaptive governance that will inform implementation of the Great Lakes Water Quality Protocol 2012. The principal focus of this work is on eutrophication, which is essentially a nearshore issue. The methodology includes a comprehensive literature review and 35 key informant interviews using a standardized questionnaire. The results assess Great Lakes governance, examine the strengths of the Great Lakes Water Quality Agreement Protocol 2012 and evaluate the effectiveness of the International Joint Commission. A major product of the research is the development of a framework for assessing adaptive capacity based on six determinants: public participation, science, networks, leadership, flexibility and resources. The framework is validated in the case study of eutrophication in Lake Erie and used to identify gaps in adaptive capacity for current eutrophication governance of Lake Erie. The framework was then tested on two additional case studies, the Chesapeake Bay and the Baltic Sea Region. These systems are both eutrophic and are similar in many other ways to the Great Lakes. This allowed exploration of issues of scale, from local (Chesapeake Bay) to binational (the Great lakes) to transnational (the Baltic Sea). The most important finding of this work is that the key barrier for building adaptive capacity for eutrophication governance in the Great Lakes is the lack of adequate leadership and resources. A key recommendation is therefore that the IJC be strengthened in its role to function as a collaborative leader to foster adaptive capacity. The findings from this research can inform the implementation of the Great Lakes Water Quality Protocol 2012. / Thesis / Doctor of Philosophy (PhD)

The interactions between parasites, hosts, and the ecosystems they live in are complex and diverse. This can make predicting how they will respond to pressures like nutrient enrichment difficult. However, this endeavor is important, due to the far-reaching effects it has on ecosystems functioning, industries like aquaculture, and even human health. Even with the significance of this topic, there are key parts of the picture that have received little research attention. For this reason, I chose to study the effects of nutrient enrichment on parasite-host interactions at two different scales, first investigating the interaction directly between parasites and their host, and then manipulating experimental ponds to look at trophic effects. Using the theory of ecological stoichiometry as a conceptual framework allowed for comparison across the two investigations. In both studies, I used largemouth bass and the macro parasites of their digestive tract as my study system, due to the importance of largemouth bass as sport fish, their high trophic status, and diverse parasite assemblages. My first study examined the effects of eutrophication on parasite-host interactions occurring within the host. It centered on four hypotheses: 1) the nutrient content of different host tissues (infection sites) varies within and across hosts, 2) the nutrient contents of parasite genera differ from that of their host tissue(s), 3) the nutrient contents of parasite genera differ from one another, and 4) nutrient availability within specific host tissues is related to the nutrient content and abundance of parasite genera within tissues. I quantified the nutrient content (carbon (C), nitrogen (N), and phosphorous (P) and their ratios) of parasitic infracommunities in the tissues of the liver, stomach, pyloric caeca, intestines, and visceral mesentery of 30 largemouth bass (Micropterus salmoides). I found stoichiometric variation across host tissues and that fish collection site explained variation in pyloric caeca N:P ratios. Parasitic genera differed in their nutrient content with actively feeding parasite forms having higher %N and lower C:N ratios than encysted/non-reproductive forms. In addition, the %C of both actively feeding parasites varied across organs, and, for one genus, this variation reflected differences in host tissue %C. Finally, I found that the total number of actively feeding parasites in the pyloric caeca increased with that tissue’s N:P ratio. My results suggest that parasites encounter significant variation in nutrient availability within and across hosts, and that this variation can influence the nutrient content and abundance of some actively feeding parasites within specific tissues. To determine if the effects from my first study were a result of nutrient changes to host tissues or if they were an artifact of changes occurring at other trophic levels caused by nutrient addition, I conducted an experimental manipulation of a short trophic system. I applied two treatments, a fertilized treatment and a control, to 14 ponds stocked with largemouth bass. I hypothesized that adding a low N:P fertilizer to the ponds would result in fewer parasites in the pyloric caeca of the bass in accordance with findings from my previous work. Alternatively, I hypothesized that indirect changes to intermediate hosts would be responsible for changes in parasite abundance. To measure the effects of nutrient additions on multiple trophic levels, samples of fine particulate organic matter (FPOM), benthic invertebrates, and vertebrate prey were taken from each pond. Stocked bass were retrieved and dissected to obtain samples for nutrient analysis from their pyloric caeca, and to quantify parasite abundances. My treatment was able to affect the %P, C:N, C:P, and N:P of the FPOM in the ponds. Benthic invertebrate biomass was negatively correlated with FPOM %P. I did not find a direct effect of benthic invertebrates on vertebrate prey species, but fertilized ponds had a smaller decrease in the number of vertebrate prey over the course of the experiment. Counterintuitively, the %N of the pyloric caeca of fish in the fertilized ponds decreased, and the %C and C:N increased in relation to the number of vertebrate prey, but %P did not change. The treatment status of the pond and the nutrients of the pyloric caeca did not affect the number of parasites that were found, but parasite numbers were positively associated with prey fish. This result would suggest the number of intermediate hosts, in this case, prey fish, is the determining factor for parasitic loads in the bass I collected. The indirect effects of trophic interaction and the direct effects of changes to host and parasite dynamics both play important roles in predicting the outcome of eutrophication on disease. The conflicting results of these two studies highlight the need for in-depth knowledge of the systems being affected by nutrient additions.

No description available.

Consumer-resource interactions are the basic building blocks of every food web. In spite of being a central research theme of longstanding interest in ecology, the mechanisms governing the stability and persistence of consumer-resource interactions are still not entirely understood. In particular, theoretical predictions on consumer-resource stability along gradients of temperature and nutrient enrichment diverge widely and are sometimes in conflict with empirical results. In this thesis I address these issues from the angle of the functional response, which describes a consumer’s feeding rate as a function of resource density. Specifically, I explore mechanistic, nutrient-based consumer-resource interaction models with respect to the influence of feeding behavior (the shape of the functional response), environmental temperature, nutrient enrichment, and resource quality on consumer-resource stability and persistence. In order to parameterize these models I performed extensive laboratory experiments with pairs of freshwater pelagic algae and grazers of the genus Daphnia, which are widespread, ecologically important model organisms. I found a sigmoidal type III functional response in every studied Daphnia-algae species pair. The exact form of its shape is described by an exponent b which is determined by fitting functional response models to the experimental data. A high value of b can stabilize consumer-resource systems under the otherwise destabilizing influence of nutrient enrichment, as predicted by a novel stability criterion relating b to the consumer’s prey handling time, food conversion efficiency and mortality. Estimated parameter values and, consequently, stability predictions are sensitive to the method of parameter estimation, and I propose a new estimation procedure that minimizes parameter uncertainty. Because many consumers’ feeding rates depend on temperature, warming is expected to strongly affect food web stability. In functional response experiments over a broad temperature gradient, I found that the attack rate coefficient and the maximum ingestion rate of Daphnia are hump-shaped functions of temperature. Moreover, the functional response exponent increases with warming towards stronger type III responses. Plugging these findings into a nutrient-based consumer-resource model, I found that predator persistence is a U-shaped function of temperature in nutrient enrichment-temperature space. Enrichment easily turns the system unstable when the consumer has a type II response, whereas a type III response opens up a large region of stability at intermediate, for the consumer optimal, temperatures. These findings reconcile seemingly conflicting results of earlier studies of temperature effects on consumer-resource dynamics, which can be mapped as special cases onto the enrichment-temperature space. I finally demonstrate the utility of three key model ingredients - temperature dependence of rate parameters, a mechanistic description of the dynamics of algal resources, and a type III functional response in Daphnia - by successfully implementing them in the description and explanation of phytoplankton-Daphnia dynamics in a mesocosm experiment exploring effects of warming on the spring succession of the plankton.

Made available in DSpace on 2014-12-17T14:33:04Z (GMT). No. of bitstreams: 1 FranciscoRV_DISSERT.pdf: 943640 bytes, checksum: d6134d4d93c5e755e9cda7290579f131 (MD5) Previous issue date: 2010-07-02 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The omnivorous filter-feeding fish, Nile tilapia (Oreochromis niloticus), can have negative effects on water quality enhancing the eutrophication process. These effects depend on the nutrient enrichment level in the water. We carried out a mesocosm experiment for five weeks in a tropical man-made lake in Brazil to test ifthe effects of tilapias depend on of the level of nutrient enrichment. The experiment lasted for 5 weeks and a factorial 2x5 experimental design was used where the presence and absence of tilapias were manipulated in combination to 5 different levels of nutrient load in a total of 10 treatments. A two way repeated measure ANOVA was performed to evaluate the effects of time (t), tilapia (F), nutrients (NP) and the interactions among these factors on: chlorophyll a, water transparency, total phosphorous, total nitrogen, N:P ratio, zooplankton biomass and phytoplankton biovolume. The tilapia effect was evident, but nutrient enrichment didn t have any effect on the variables analyzed. Tilapia decreased the water transparency, total zooplankton biomass, calanoid copepod biomass, nauplii copepod biomass and cladocerans biomass. On the other hand, tilapia had no effect on phytoplankton biovolume. This lack of effect on phytoplankton is probably due to tilapia grazing that may counteract the positive effect of tilapia on phytoplankton via trophic cascades and nutrient recycling. Hence, a reduction in tilapia stock would not be an effective way to reduce phytoplankton biomass and improve water quality / A til?pia do Nilo (Oreochromis niloticus) ? um peixe on?voro filtrador que pode ter efeitos negativos sobre a qualidade da ?gua favorecendo o processo de eutrofiz??o. Esses efeitos negativos dos peixes on?voros filtradores devem ser dependentes do n?vel de enriquecimento da ?gua por nutrientes. N?s realizamos um experimento em mesocosmos por cinco semanas em um lago artificial tropical para testar se os efeitos das til?pias s?o dependentes do n?vel de enriquecimento por nutrientes. O experimento teve dura??o de 5 semanas e consistiu num delineamento fatorial 2x5 onde 2 n?veis de til?pia (presen?a e aus?ncia) foram manipulados em combina??o com 5 diferentes niveis (aportes) de nutrientes num total de 10 tratamentos.. Uma ANOVA bifatorial com medidas repetidas no tempo foi realizada para testar os efeitos do tempo (t), da til?pia (F) e do nutriente (NP) e os efeitos de suas intera??es sobre a clorofila a, transpar?ncia do disco de Secchi, concentra??o de f?sforo e nitrog?nio total e a raz?o entre eles (N:P), al?m do efeito sobre a biomassa da comunidade zooplanct?nica e o biovolume de fitopl?ncton. O efeito da til?pia foi evidente, enquanto o enriquecimento por nutrientes n?o mostrou efeito algum. Quando presente, a til?pia diminuiu a transpar?ncia do disco de Secchi e a biomassa total do zoopl?ncton, de cop?podos calan?ides, na?plios de cop?podos e de clad?ceros. Por?m, nenhum efeito foi detectado da til?pia sobre o biovolume do fitopl?ncton. Essa aus?ncia de efeito pode ser devido a herbivoria da til?pia que contrabalan?a os seus efeitos positivos via cascata tr?fica e ciclagem de nutrientes. Desta forma, uma redu??o do estoque pesqueiro de til?pias para promover uma melhoria na qualidade da ?gua n?o afetaria a biomassa fitoplanct?nica e consequentemente n?o atingiria o seu objetivo