The aim of this thesis is to incorporate the smallest organisms, in particular the heterotrophic bacteria and their predators, more fully into current descriptions of aquatic community structure and dynamics. A strong, positive empirical relationship was found between bacterial abundance and chlorophyll concentration in freshwater and marine systems. Common members of the photosynthetic phytoplankton (all chrysophyceans) were shown to be major, even dominant, grazers of these bacteria. This phagotrophic capability is quantitatively important to the bacterioplankton, to the mixotrophs themselves, and in some cases, to the structure of the limnological community as a whole. Grazing by mixo- and heterotrophic protozoans is concentrated on the largest bacterial cells that also have the greatest growth rates. Relatively lower removal rates of the tiniest cells, with low growth rates, is proposed to explain their numerical dominance in lakes.

Thesis (M.S.)--University of Wisconsin--Stevens Point., 2007 / Includes bibliographical references (leaves 102-112).

Thesis (Ph.D.) in Ecology and Environmental Science--University of Maine, 2008. / Includes vita. Includes bibliographical references (leaves 115-130).

Thesis--Wisconsin. / Includes bibliographical references (leaves 105-110).

Thesis (M.Sc. Biology)--University of Waikato, 2006. / Includes bibliographical references (leaves 90-101) Also available via the World Wide Web.

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Orientador: Maria Stela Maioli Castilho Noll / Coorientador: Eliana Aparecida Panarelli / Banca: Cláudia Costa Bonecker / Banca: Maria Cristina Basílio Crispim da Silva / Resumo: Planícies de inundação são áreas úmidas onde podem ser encontradas as lagoas marginais. Devido ao período de seca e a sua baixa profundidade, estas lagoas podem apresentar caráter temporário com ocorrência sazonal. Tal perturbação pode levar algumas populações zooplanctônicas, como as de cladóceros, a entrarem em estado de dormência, produzindo os ovos de resistência que se depositam no sedimento seco formando um banco de ovos. Quando as lagoas voltam a encher, a comunidade de cladóceros rapidamente se reestabelece, provavelmente como resultado da eclosão dos ovos presentes no sedimento. Detectar espécies de cladóceros que produzem os ovos de resistência como estratégia para recolonização, bem como os fatores que influenciam a eclosão dos ovos, pode auxiliar na compreensão do papel do banco de ovos como fonte de biodiversidade zooplanctônica em lagoas marginais. O objetivo neste estudo foi verificar o potencial de cladóceros para recolonização de lagoas marginais temporárias, por meio da eclosão de ovos de resistência em condições experimentais específicas. A comunidade zooplanctônica foi amostrada em quatro lagoas marginais localizadas na planície de inundação do Rio Turvo. As amostragens dos cladóceros planctônicos foram feitas com rede de plâncton de 50 μm de malha, antes e após um período de seca. Além disso, também foram medidos parâmetros físicos e químicos: profundidade, transparência, temperatura, pH, condutividade, OD, clorofila e material em suspensão. Para a realização dos experimentos de eclosão dos ovos de resistência em laboratório, amostras do sedimento das lagoas foram obtidas com Corer (4,5 cm de diâmetro), durante a estação seca. Duas metodologias foram testadas para indicar qual a mais eficaz para a eclosão: 1. Tratamento ambiente: frascos com sedimento e água do rio Turvo mantidos em condições... / Abstract: Floodplains are wetlands where the oxbow lakes can be found. Due of the dry season and its shallow depth, these lagoons can present seasonal occurrence. Such disruption can lead some zooplankton populations, such as cladocerans, to enter in dormancy, producing resting eggs that are deposited in dry sediment forming a bank of eggs. When the lagoons back to fill the cladoceran community quickly restores, probably as a result of the hatch of eggs present in the sediment. To detect species of cladocerans that produce resting eggs as a strategy for recolonization, as well as the factors influencing the eggs hatch, may help understanding the egg bank's role as zooplankton biodiversity source in lagoons. Our goal in this study was to investigate the potential of cladocerans to recolonize of temporary lagoons, through the hatching of resting eggs in specific experimental conditions. The zooplankton community was sampled in four lagoons located in the Turvo River floodplain. Sampling of planktonic cladocerans were taken by a plankton 50 µm mesh net before and after the drying lagoons. Physical and chemical parameters as depth, transparency, temperature, pH, conductivity, OD, chlorophyll and suspended material were also measured. For the hatching experiments of resting eggs in laboratory, sediment from lagoons were sampled using a corer (4.5 cm diameter), during the dry season. Two methods were tested to indicate the most effective for the hatching: 1. Environment Treatment: bottles with sediment and water from the Turvo river kept at ambient conditions; 2. Chamber Treatment: bottles with sediment and water from the Turvo river kept under controlled conditions in a growth chamber (23 ° C and photoperiod 12:12). Every two days each replica was analyzed for physical and chemical parameters and the verification of cladocerans newly hatched. After two weeks these procedures were ... / Mestre

The objective of this research was to determine how stakeholder engagement impacts on the use and sharing of ecosystem service benefits derived from large lake systems. The Wilderness and Swartvlei lake systems, which form an integral part of the Wilderness Section of the Garden Route National Park (GRNP), were chosen as the study area. The park is juxtaposed with urban and other land uses making it one of the most integrated urban conservation areas in South Africa. The park is an open-access park with only enclosed areas being the camping and chalet areas that borders onto the Touw River Estuary. A major contribution of this research was that it classified stakeholder groups into ten meta-identities (associations, businesses, charity organisations, conservancies, government departments, informal groupings, learning/educational institutions, multiple stakeholder projects, spiritual groupings and sports clubs) and that through an iterative research approach it stimulated dialogue between individuals across the various meta-identities. Engagement is a way of allowing stakeholders to develop a sense of ownership through the decision-making process. This could also lead to a higher level of trust and cooperation. The main insights drawn from this research were that, history is important; engagement is characterised by an on-going blame-game (at least in part as a result of this particular history); meta-identities share some values, but differ in how they see the world; there is a concern over social issues (widespread concern, but few mechanisms to address the issue); management agencies are stewards of the feedbacks between social and ecological systems (responsible for regulating flows of benefits), but in open-access systems cannot do so on their own; all meta-identities are keen to contribute and this can, with appropriate facilitation, be harnessed towards collective action. Stakeholders associated with all ten meta-identities identified provisioning and cultural services as a benefit derived from the lakes. No regulating or supporting services were identified as benefits. This could indicate a gap in awareness of the importance of these services. A category that emerged from this study is the importance of employment opportunities linked to the management of natural resources. The study showed that engagement does not occur around the benefits that can be derived from the lakes, but rather around the issues that have a direct or indirect influence on the ecosystem services and therefore the suite of benefits that would be available for sharing. The issues could be divided into two broad themes; social issues and developmental pressures. The social issues pose an indirect threat to the lakes while the developmental pressures pose a direct threat. As the mandates across agencies differ, with the municipalities concerned with the social issues and SANParks with the pressures, the importance of communication and cooperative governance was highlighted.

A field investigation was carried out over two seasonal periods on an oligotrophic coastal British Columbia lake to determine the role of sinking in the formation of the chlorophyll maximum as well as some aspects of phytoplankton seasonality. Sinking rates of two diatoms were measured and found to be highest in the epilimnion and lowest at the depth of the chlorophyll maximum. Light affected sinking rate as well as the position of the chlorophyll maximum. The chlorophyll maximum formed at 10-12 m following the onset of seasonal thermal stratification and descended to ca. 22 m for the summer. A major factor in the formation of the chlorophyll maximum is the decrease of phytoplankton sinking rate at depth. Rhizosolenia eriensis is one of the first phytoplankters to bloom in the spring. Small flagellates (3-15 um) and occasionally Dinobryon sp. were also important numerically. In the summer Cyclotella spp. displaced R. eriensis as the dominant diatom in the epilimnion. The relative timing of seasonal maxima of blooms of various species remained similar during the two years investigated. Lake fertilization affected the phytoplankton standing stock. R. eriensis did not greatly benefit from fertilization since it sank out of the epilimnion and became a major constituent of the chlorophyll maximum before fertilization. Because of its large size and low C : cell volume ratio due to a large vacuole, R. eriensis is probably not a good food source for zooplankton. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

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