Thesis--University of Wisconsin--Madison. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1965. / Typescript. Vita. Includes bibliographical references.

Thesis (Ph.D.)--York University, 2007. Graduate Programme in Biology. / Typescript. Includes bibliographical references. 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:NR39060

In recent decades, many softwater lakes on the boreal shield have experienced significant reductions in aqueous calcium (Ca) concentrations. These declines are a long-term consequence of acid deposition due to the depletion of base cations from watershed soils. There is concern that in some lakes [Ca] may be falling to levels detrimental to the competitiveness of Ca-rich organisms. By examining the crustacean zooplankton remains preserved in lake sediments, this thesis provides field evidence of reduced [Ca] impacting a Ca-sensitive crustacean zooplankton species (Daphnia pulex). Additionally, a 770 lake data set compiled from several Ontario monitoring programs revealed that 62 % (an increase from 35% in the early 1980s) of the lakes were near or below the laboratory-determined Ca threshold (1.5 mg•L-1) for the growth and survival of D. pulex. To determine whether the 1.5 mg•L-1 Ca threshold could be observed in a spatial survey of crustacean zooplankton sedimentary remains, surface sediments from 36 softwater (Ca range 1-3 mg•L-1) Ontario lakes were analyzed. Significant differences in daphniid abundances across the Ca threshold were present; however, only for the D. longispina species complex, indicating differences in Ca tolerances within daphniid species complexes. Extending the analysis to a comparison of modern-day vs. preindustrial assemblages revealed that in the same 36 lakes there have been large declines (by up to 30%) in daphniid relative abundances since preindustrial times coincident with increases in Ca-poor species (i.e. Holopedium gibberum) irrespective of modern day pH. These findings demonstrate that in natural settings, the competitive disadvantages of Ca limitation may occur at a higher [Ca] than previously suspected. Finally, zooplankton sedimentary remains were analyzed from several “pristine” lakes in northwestern Ontario that have also experienced Ca declines in recent years. Reduced abundances of Ca-sensitive taxa and increases in Ca-insensitive fauna provided further evidence of the impacts of Ca decline independent of acid deposition. Collectively these analyses demonstrate the potential importance of Ca as an environmental stressor in softwater regions, as well as the need for further research in order to make better use of the available information preserved in the sediment record. / Thesis (Ph.D, Biology) -- Queen's University, 2011-03-31 16:17:57.86

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Lakes near Sudbury, Ontario, experienced widespread acidification and metal-contamination beginning in the late-19th century. These stressors caused extreme damage to regional aquatic systems and their catchments, with aquatic biota experiencing reduced species richness and, in some cases, extirpations. Emission control measures markedly improved pH, however biotic recovery continues to lag water quality improvements, prompting investigation into mechanisms leading to this phenomenon. Due to the lack of long-term monitoring data, I use paleolimnological approaches to examine temporal trends in cladoceran zooplankton, from pre-impact conditions, through the period of acidification/metal contamination, and following the implementation of emission controls. I assess the degree of biotic recovery that has taken place in these lakes, and review the mechanisms that continue to structure cladoceran assemblages. Lakes closest to Sudbury recorded increases of ~15-65% relative abundance of Chydorus brevilabris, concurrent with the late-1800s industrial development. The relative abundance of C. brevilabris remains elevated above pre-impact levels in two Sudbury lakes; however, in Middle Lake, which was neutralized with calcium carbonate, declines in C. brevilabris (to ~pre-impact levels) occurred following neutralization. Conversely, lakes located ~60 km southwest of Sudbury, in Killarney Provincial Park, experienced muted assemblage change, with minor (< ~5%) increases in grazers (e.g., Daphnia spp., Holopedium glacialis) occurring within the past ~40 years. Lakes in Sudbury and Killarney acidified to pH < ~5, however those in Sudbury additionally received high inputs of nickel and copper, which have toxic effects on aquatic organisms, including some Cladocera. Contamination with these metals may have been a primary driver of cladoceran assemblage change. Elevated metal concentrations likely continue to structure the cladoceran assemblages in the Sudbury lakes. In addition, many of the lakes contain altered food webs (e.g., large populations of yellow perch) as a legacy of the acid and metal contamination, acting as a potential barrier to recovery. Finally, warming air temperatures over the past ~40 years, which I link to increases in primary production, may alter the composition of cladoceran species found in these lakes, and therefore prevent a return to pre-impact conditions. / Thesis (Master, Biology) -- Queen's University, 2014-04-28 12:26:39.903

Made available in DSpace on 2014-06-11T19:35:42Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-08-07Bitstream added on 2014-06-13T20:26:42Z : No. of bitstreams: 1 mortari_rc_dr_botib.pdf: 2294753 bytes, checksum: 55b2364ea517b9c0c4b589914609afa2 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo deste trabalho foi estudar a distribuição temporal de cladóceros numa lagoa lateral Rio Paranapanema, abordando os seguintes aspectos: abundância total de zooplâncton, composição, freqüência relativa de ocorrência de espécies, índice de diversidade e riqueza de espécies e a influência dos fatores físicos, químicos, biológicos e ambientais. Foram realizadas coletas mensais no período de abril/06 a março/07. O zooplâncton foi coletado em três pontos ao longo da lagoa, utilizando-se uma rede de plâncton (50μm), integrando toda a coluna d’água. Simultaneamente foram medidos os seguintes parâmetros da água: profundidade, transparência, temperatura, alcalinidade, condutividade elétrica, pH, oxigênio dissolvido, material em suspensão (fração orgânica e inorgânica), fósforo e nitrogênio total e pigmentos totais. A desconexão da lagoa com o rio ocorreu em setembro/06, em conseqüência da diminuição da pluviosidade nos meses anteriores, e a sua reconexão ocorreu em janeiro/06 devido ao acumulo de chuvas dos meses de novembro/06 e dezembro/06. Em função da variação da pluviosidade a maior profundidade ocorreu em abril/06 (final do período chuvoso) e a menor em outubro/06 (início do período seco), e a maior transparência amostrada em junho/06 e a menor em novembro/06. Temperatura da água mais elevada foi encontrada durante o período quente-chuvoso e a menor no período frio-seco. Para alcalinidade e condutividade da água os maiores valores ocorreram no período de maio/06 a agosto/06. O material em suspensão, fósforo e pigmentos totais apresentaram maiores valores no período de setembro/06 a janeiro/07, e o oxigênio e nitrogênio no período de outubro/06 a janeiro/07. Conforme o índice do estado trófico a lagoa assumiu características oligo e eutrófico para transparência da água e pigmentos totais e de oligo a eutrófico... / The aim of this work was to study cladocerans temporal distribution in a lake marginal to the Paranapanema River, evaluating the following aspects: total abundance, composition, relative frequency of species occurrence, diversity, and richness and the influence of physical, chemical, biological and environmental factors. Monthly samples were carried out in the period from April/06 to March/07. Zooplankton was sampled in three stations along the lake, using a plankton net (50μm), integrating the water column. Simultaneously, the following water parameters were measured: depth, transparency, temperature, alkalinity, electric conductivity, pH, dissolved oxygen, suspended matter (organic and inorganic fractions), total phosphorus and nitrogen and total pigments. The disconnection between the lake and the river occurred in September/06 due to pluviosity decrease in previous months, and its reconnection occurred in January/06 due to the accumulation of rains from November and December/06. In function of pluviosity variation, the higher depth was observed in April/06 (end of the rainy period) and the lower in October/06 (beginning of the dry period), and the high transparency was found in June/06 and the lowest in November/06. Elevated values of water temperature were found during the warm-wet period and the lower in the cool-dry period. Alkalinity and conductivity higher values occurred in May and August/06. Suspended matter, total phosphorus and pigments were higher from Sptember/06 to January/07, and oxygen and nitrogen in the period from October/06 to January/07. According to the trophic state index, the lake assumed oligo and mesoeutrophic characteristics to water transparency and total pigments, and of oligo to eutrophic using total phosphorus as parameter. Rotifer dominated in relative abundance, followed by copepods and cladocerans. The species list was composed... (Complete abstract click electronic access below)

Made available in DSpace on 2014-06-11T19:30:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-03-18Bitstream added on 2014-06-13T19:18:37Z : No. of bitstreams: 1 portinho_jl_me_botib.pdf: 988699 bytes, checksum: 35177a563b0c79b60df1a761f31652d9 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O objetivo deste estudo foi analisar a distribuição longitudinal e os atributos ecológicos das assembléias zooplanctônicas (Copepoda, Cladocera e Rotifera) e as variáveis limnológicas na zona lacustre do reservatório de Itaipu, trecho do rio Paraná a jusante e desembocadura dos rios Iguaçu e Monday, os quais não sofrem influência de barragem. Para tanto, foram realizadas coletas em dois períodos distintos: período seco (inverno 2009) e período chuvoso (verão 2010), em nove estações de amostragem: uma em ambiente lêntico, a montante da barragem de Itaipu, seis no rio Paraná, uma na foz rio do Monday – Paraguai, e outra na foz do rio Iguaçu – Brasil/Argentina. Foram obtidas amostras de qualitativas, através de arrastos horizontais, e quantitativas (tréplicas), através de arrastos verticais de 20 m (1.143 litros), ambas com rede de 50 μm. Os seguintes parâmetros físicos e químicos da água foram medidos na região de superfície e meio do canal dos rios: transparência, temperatura, velocidade, pH, oxigênio dissolvido, condutividade elétrica, turbidez, material em suspensão (frações orgânicas e inorgânicas), nitrogênio total, fósforo total, silicato dissolvido e biomassa fitoplanctônica (clorofila a). Para auxiliar na interpretação dos dados determinou-se a riqueza de espécies (S), o índice de Shannon-Wiener (H‟), a Equitabilidade de Pielou (J‟). Foram feitas ainda análises de componentes principais (ACPs), de correspondência canônica (ACCs), de agrupamento por similaridade (UPGMA) e de variância ANOVA “two-way”, todas estas baseadas na abundância e composição dos microcrustáceos e rotíferos. As ACPs indicaram a separação dos pontos entre os períodos (seco e chuvoso) e as variáveis limnológicas atuantes na diferenciação. A região a jusante da barragem de Itaipu, no rio Paraná, foi distinta dos rios Iguaçu e Monday... / The aim of the study was to analyze the longitudinal distribution and ecological attributes of the zooplankton assemblages (Copepoda, Cladocera and Rotifera) and the limnological variables in the Itaipu Reservoir and Paraná River stretch downstream the dam –and Iguazu and Monday Rivers. Samples were collected in two distinct periods: dry season (winter 2009) and rainy season (summer 2010), in nine sampling stations: one site in lentic environment upstream of the Itaipu Dam, six sites in the Paraná River, one site in the mouth of Monday River – Paraguay River, and one site in the mouth of the Iguazu River - Brazil/Argentina. The zooplankton was collected (treplicates) through vertical hauls (20 m depth; 1,143 liters), for quantitative analyses, and through horizontal throws for qualitative analyses, both with a 50 μm plankton net. The following physical and chemical water parameters were measured on the surface water, in the middle of the river channel: transparency, temperature, water speed, pH, dissolved oxygen, conductivity, turbidity, suspended matter (organic and inorganic fractions), total nitrogen, total phosphorus, dissolved silicate and phytoplankton biomass (chlorophyll a). In order to improve the data interpretation it was calculated the species richness (S), Shannon-Wiener index diversity (H ') and Pielou evenness (J'). It was also performed Principal Component Analyses (PCAs), Canonical Correspondence Analyses (CCAs ), cluster analyses (UPGMA) and variance analyses (ANOVA two-way ), all of them based on the abundance and composition of microcrustaceans and rotifers. The ACPs indicated the separation of sites between the seasonal periods and limnological variables interfering in the distributions. Sites downstream the Itaipu Dam, in the Parana River, were distinct from the ones in Iguazu River and Monday River. These last two sites contributed to the increase... (Complete abstract click electronic access below)

Made available in DSpace on 2014-06-12T15:02:42Z (GMT). No. of bitstreams: 2 arquivo1198_1.pdf: 2322223 bytes, checksum: 7a98d6965caaa86642d656692744753a (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2008 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O objetivo deste trabalho foi testar o efeito da presença de predadores vertebrados e invertebrados sobre Ceriodaphnia cornuta, em nível de ciclomorfoses, e dinâmica populacional (densidades, taxas de fecundidade, percentual de juvenis, presença de machos, produção de efípios, etc.). Foram realizados quatro experimentos para a observação dos efeitos da presença do predador sobre Ceriodaphnia cornuta. Para os experimentos com vertebrados (Alimentados com ração e com zooplâncton) foram utilizados seis pequenos minilimnocurrais, confeccionados em PVC com o fundo composto por rede de plâncton com abertura entre malhas de 45 &#956;m com flutuadores de isopor adaptados inseridos em dois aquários de aproximadamente 150 litros de capacidade, cada um dividido em três partes iguais. Um dos aquários foi utilizado como controle e outro para o tratamento. Nos experimentos água de peixe e com invertebrados, tanto os peixes como os copépodos foram inseridos em um frasco por 48 horas, sendo depois separados em frascos de 0,30 litros. Nestes experimentos foram realizadas as análises com os organismos vivos, sendo estes devolvidos aos frascos ou limnocurrais. Os principais resultados observados foram o aumento da fecundidade das C. cornuta em todos experimentos, com exceção do Água de Peixe e a diminuição do comprimento das primíparas, excetuando-se o experimento com invertebrados que não houve diferença significativa (p< 0,05). A adição de ração para a alimentação dos peixes alterou a percepção dos resultados obtidos. A presença do predador vertebrado influenciou a dinâmica populacional das Ceriodaphnia cornuta aos níveis de fecundidades e comprimento das primíparas. Apenas a presença do predador não foi suficiente para acarretar em alterações morfológicas, como espinhos, em C. cornuta. A presença de Thermocyclops sp alterou apenas a fecundidade de C. cornuta. É possível que este cladócero apresente comportamentos de resposta distintos para cada espécie de predador

This thesis focuses on a chronological analysis of the cladoceran communities from a sediment core of a small oligotrophic lake in southwestern Québec, Canada over the past 1250 years. The sediments of the lake were varved, which allowed for accurate dating. A previously published pollen study of the lake provided a record of the paleoclimatic and landscape changes in the region. The core was then used to infer how changes in temperature and landscape changes impacted the taxonomic composition of the cladoceran community through time. Cladoceran diversity was high throughout most of the Medieval Warm Period and into the Little Ice Age and decreased during the modern period in response to increased temperatures and anthropogenic impacts. Daphnia and plant-associated species greatly decreased in the past 100 years. This shift, combined with increased temperatures and changes in the landscape opened up a niche for the colonization by the smaller Bosmina longirostris. The modern communities are unlike most of what was observed throughout the past millennium.