Stable isotope analysis (SIA) is a valuable tool in ecotoxicology because δ13C and δ15N may provide insights into the trophic transfer of contaminants in a food web. The relationship between a species’ trophic position (TP, determined from δ15N) and internal concentration of biomagnifying contaminants can be established and used for regulatory purposes. However, the exposure of organisms to xenobiotics incurs physiological costs, and the stable isotope signature of a consumer reflects not only diet but also a physiological state. The latter raises questions regarding the interpretation of stable isotope signatures in contaminated areas. Therefore, the aim of this Thesis was to evaluate the behaviour of consumers’ stable isotope signatures in stressed systems, with a primary focus on the effects of environmental contaminants. In paper I, the physiological costs of chemical exposure were found to alter incorporation rates of dietary nitrogen and carbon in a consumer by influencing both growth and metabolic turnover, with resulting changes in isotope signatures relative to a control system. In paper II, the diet-consumer discrimination factors for 15N and 13C were confirmed to increase under chemical exposure mediated via increased metabolic costs. However, the physiological response was low and translated into only minor shifts in the δ13C and δ15N. The predictability of exposure effects on the stable isotope signature was demonstrated in paper III, in which animals exposed to a chemical with a known mode of action presented expected effects on elemental composition, body size, biomarkers of oxidative stress and the stable isotope signatures. Moreover, consumers’ oxidative balance was found to be related to their δ15N values, thus providing evidence of the kinetic isotope effect on the oxidative status. However, despite the alterations in stable isotope signatures observed in laboratory settings (papers I-III), the effect of xenobiotics on the TP estimates was nil or minor in the field-collected animals. Moreover, the TP values were not significantly different between the animals in the contaminated and the reference habitats because of the high overall uncertainties in the TP estimates (paper IV). Also, the TP estimates based on δ15N in bulk material were more similar between the contaminated and the reference systems than TP estimates based on δ15N values in amino acids. Therefore, the latter method appears more sensitive towards xenobiotics (and, possibly, other environmental stressors) and thus less suitable for TP assessment in contaminated areas. This Thesis improved the overall understanding of the applicability of SIA in stressed systems by establishing relationships between various exposure regimes, physiological responses and the stable isotope signatures in consumers. In model species at low trophic levels, the exposure to xenobiotics was found to significantly affect δ13C and δ15N values, which can be expected whenever physiological responses are detected. However, because of the overall high uncertainty in TP estimates, no significant differences between contaminated and control systems were detected, although the estimated TP were consistently higher in the contaminated systems. Future research should focus on higher trophic levels, in which effects of a greater magnitude can be expected. Moreover, the effects in entire food webs should be addressed rather than single prey–consumer relationships as well as other environmental variables that may contribute to the stable isotope variability in and among systems under various environmental pressures. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.</p>

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Thermotolerance limit in aquatic organism is set by the ability to sustain aerobic scope to sudden temperature shifts. This study tested the genetic and plastic differences in thermotolerance of Daphnia that can be explained by the differences in the ability to retain mitochondrial integrity at high temperatures. Five genotypes with different biogeographic origins were acclimated to 18ᵒC and 25ᵒC. We developed a rhodamine 123 in-vivo assay to measure mitochondrial membrane potential and observed higher fluorescent in heat damaged tissues as the disruption of the mitochondrial membrane potential. Significant effects on temperature tolerance were observed with CCCP and DNP but not with NaN3. Effects of toxins were significant in temperature sensitive genotype and high concentration of lactate was observed in 18ᵒC acclimated genotype only. We conclude that genetic and physiological differences are intricately linked to the ability of sustaining aerobic respiration at high temperatures which sets limit to the thermotolerance.

Two arctic lakes differing in depth and other attributes were sampled for zooplankton and phytoplankton during one vegetation season, and their population dynamics and trophic interactions were compared.

Submitted by Marco Antônio de Ramos Chagas (mchagas@ufv.br) on 2019-02-25T11:49:18Z No. of bitstreams: 1 texto completo.pdf: 2419538 bytes, checksum: 5a19c5f0ce7bde9f77974f5153ae39e6 (MD5) / Made available in DSpace on 2019-02-25T11:49:18Z (GMT). No. of bitstreams: 1 texto completo.pdf: 2419538 bytes, checksum: 5a19c5f0ce7bde9f77974f5153ae39e6 (MD5) Previous issue date: 2018-07-13 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / As indústrias de higiene pessoal, perfumaria e cosméticos demonstram relevância no mercado consumidor mundial e no cenário econômico brasileiro, apresentando grande diversidade de produtos fabricados. Essas indústrias são responsáveis pela geração de efluentes potencialmente poluidores, com características que podem variar conforme as matérias-primas empregadas e a diversidade de produtos fabricados. Os efluentes das indústrias de produtos capilares, por exemplo, podem apresentar em sua composição poluentes que conferem elevada toxicidade e baixa biodegradabilidade, o que dificulta seu tratamento por processos convencionais. O presente estudo teve como objetivo avaliar o desempenho de um sistema combinado de eletrocoagulação e processo oxidativo avançado como tratamento de efluentes gerados pela indústria de produtos capilares. O processo de eletrocoagulação foi investigado em diferentes condições de operação, para as variáveis pH, tempo de eletrólise e densidade de corrente, com melhores resultados de remoção da DQO e da turbidez obtidos para o tratamento realizado em pH 2, 30 min e 50 A/m2. A eletrocoagulação removeu eficientemente a DQO (88%), DBO (90%), COT (85,5%), O&G (>99,5%), surfactantes aniônicos (98,9%), turbidez (97,3%) e toxicidade aguda a Daphnia similis (99,9%) do efluente bruto. Os processos oxidativos avançados H 2 O 2 /UV e TiO 2 /H 2 O 2 /UV foram investigados em diferentes condições de operação, para as variáveis dose de H 2 O 2 , pH, tempo de irradiação e dose de H 2 O 2 , concentração de TiO 2 , tempo de irradiação, respectivamente. Os melhores resultados de remoção da toxicidade aguda foram obtidos para o processo H 2 O 2 /UV, realizado em pH aproximadamente 4, 30 min de irradiação e dose de 20 mmol/L de H 2 O 2 . O processo H 2 O 2 /UV possibilitou elevada remoção (88,4%) da toxicidade aguda remanescente no efluente previamente tratado por eletrocoagulação e moderada remoção da concentração de surfactantes aniônicos (59,5%). O sistema combinado de eletrocoagulação e processo H 2 O 2 /UV removeu eficientemente a matéria orgânica (remoção de 89,4% da DQO) e a toxicidade aguda (>99,99%), porém a CE50 quantificada no efluente tratado foi 44,8%, indicando toxicidade aguda a Daphnia similis remanescente. A geração de residuais de alumínio e peróxido de hidrogênio nos processos de eletrocoagulação e H 2 O 2 /UV, respectivamente, em concentrações que causam efeitos tóxicos, foi possivelmente responsável pela toxicidade aguda remanescente no efluente tratado. / The various sectors of the personal care products industry are highly relevant in the global consumer market, including Brazil, offering a great diversity of manufactured products. This industry is responsible for generating potentially polluting effluents, with characteristics that vary depending on the raw materials used and the variety of products manufactured. For example, the hair care products sector generates effluents containing substances with high toxicity and low biodegradability, which hinders treatment by conventional processes. This study aimed to evaluate the performance of combined electrocoagulation and advanced oxidation process for hair care products manufacturing wastewater treatment. Electrocoagulation process variables investigated included pH, electrolysis time and current density (A/m2), with better COD and turbidity removals obtained for treatment at pH 2, 30 min and 50 A/m2. Electrocoagulation efficiently removed COD (88%), BOD (90%), TOC (85.5%), oils and grease (>99.5%), anionic surfactants (98.9%), turbidity (97.3%) and acute toxicity to Daphnia similis (99.9%) from the raw effluent. The advanced oxidation processes H 2 O 2 /UV and TiO 2 /H 2 O 2 /UV variables investigated were H 2 O 2 and TiO 2 doses, pH and irradiation time. Highest acute toxicity removal was obtained for the H 2 O 2 /UV process, carried out at pH approximately 4, 30 min irradiation and 20 mmol/L H 2 O 2 . The H 2 O 2 /UV process achieved high removal (88.4%) of the acute toxicity remaining after electrocoagulation and moderate anionic surfactants removal (59.5%). The combined electrocoagulation and H 2 O 2 /UV process system efficiently removed organic matter (89.4% of COD removal) and acute toxicity (>99.99%), but the EC50 measured in the treated effluent was 44.8%, which indicates acute toxicity to Daphnia similis still remained. Generation of residual aluminum and hydrogen peroxide in the electrocoagulation and H 2 O 2 /UV process, respectively, at concentrations that cause toxic effects, was possibly responsible for the remaining acute toxicity in the treated effluent.

<p>Understanding the processes that shape the spatial distribution of genetic variation within species is central to the evolutionary study of diversification and demography. Neutral genetic variation reflects past demographic events as well as current demographic characteristics of populations, and the correct interpretation of genetic data requires that the relative impact of these forces can be identified. Details of breeding systems can affect the genetic structure through effects on effective migration rate or on effective population size. Restrictions in recombination rate lead to associations between neutral marker genes and genes under natural selection. Although the effects on genetic structure can be substantial, the process will often be difficult to tell apart from stochastic effects of history or genetic drift, which may suggest erroneous conclusions about demography.</p><p>In cyclically parthenogenetic freshwater invertebrates, which alternate between sexual and asexual reproduction, demographic fluctuations and reliance on diapausing eggs for dispersal enhances neutral genetic differentiation as well as effects of selection on associated genes. Although genetic founder effects are expected to be profound and long-lasting in these species, genetic hitch-hiking may reduce initial strong differentiation rapidly if better adapted genes are introduced by mutation or immigration. Fluctuating environmental conditions have been suggested to generate rapid shifts in the frequencies of clones during the asexual phase. In the presence of egg banks resting in sediments, genetic diversity is stabilised and the importance of migration for differentiation is reduced.</p><p>Studies of unstable and young populations of cyclically parthenogenetic <i>Daphnia pulex</i> showed substantial variation for important fitness traits, within as well as between populations, despite hypothesised recent founder effects. Neutral markers indicated genetic equilibrium, but changes in clonal composition during asexuality disrupted the genetic structure in a manner compatible with local adaptation and exclusion of immigrants. This illustrates that the forces affecting sexual progeny may be markedly different from those shaping the structure among asexual individuals.</p>

<p>Poor food quality can have large negative effects on zooplankton growth and this can also affect food web interactions. The main aims of this thesis were to study the importance of different food quality aspects in <i>Daphnia</i>, to identify potentially important differences among zooplankton taxa, and to put food quality research into a natural context by identifying the importance of food quality and quantity in lakes of different nutrient content.</p><p>In the first experiment, the RNA:DNA ratio was positively related to the somatic growth rate of <i>Daphnia</i>, supporting a connection between P content, RNA content, and growth rate. The second experiment showed that EPA was important for <i>Daphnia</i> somatic growth, and 0.9 µg EPA mg C^-1 was identified as the threshold below which negative effects on <i>Daphnia</i> growth occurred.</p><p>A field survey identified patterns in the PUFA content of zooplankton that could be explained by taxonomy and trophic position. <i>Cladocera</i> enriched EPA and ARA relative to seston, and <i>Copepoda</i> primarily enriched DHA. In a whole-lake experiment, gentle fertilization of an oligotrophicated reservoir increased the seston P content and the biomass of high quality phytoplankton (<i>Cryptophyceae</i>, high EPA content). This was followed by increases in zooplankton and fish biomasses.</p><p>An empirical model based on data from a literature survey predicted that food quantity is most important for zooplankton growth in oligotrophic lakes, and that food quality factors are more important in eutrophic lakes. Thus, zooplankton growth, and energy transfer efficiency in the food web, is predicted to be highest in mesotrophic lakes. The results predict that the strength and nature of food quantity and quality limitation of <i>Daphnia</i> growth varies with lake trophic state, and that some combination of food quantity and/or quality limitation should be expected in nearly all lakes.</p>

Understanding the processes that shape the spatial distribution of genetic variation within species is central to the evolutionary study of diversification and demography. Neutral genetic variation reflects past demographic events as well as current demographic characteristics of populations, and the correct interpretation of genetic data requires that the relative impact of these forces can be identified. Details of breeding systems can affect the genetic structure through effects on effective migration rate or on effective population size. Restrictions in recombination rate lead to associations between neutral marker genes and genes under natural selection. Although the effects on genetic structure can be substantial, the process will often be difficult to tell apart from stochastic effects of history or genetic drift, which may suggest erroneous conclusions about demography. In cyclically parthenogenetic freshwater invertebrates, which alternate between sexual and asexual reproduction, demographic fluctuations and reliance on diapausing eggs for dispersal enhances neutral genetic differentiation as well as effects of selection on associated genes. Although genetic founder effects are expected to be profound and long-lasting in these species, genetic hitch-hiking may reduce initial strong differentiation rapidly if better adapted genes are introduced by mutation or immigration. Fluctuating environmental conditions have been suggested to generate rapid shifts in the frequencies of clones during the asexual phase. In the presence of egg banks resting in sediments, genetic diversity is stabilised and the importance of migration for differentiation is reduced. Studies of unstable and young populations of cyclically parthenogenetic Daphnia pulex showed substantial variation for important fitness traits, within as well as between populations, despite hypothesised recent founder effects. Neutral markers indicated genetic equilibrium, but changes in clonal composition during asexuality disrupted the genetic structure in a manner compatible with local adaptation and exclusion of immigrants. This illustrates that the forces affecting sexual progeny may be markedly different from those shaping the structure among asexual individuals.

Determining the molecular basis of heritable variation in complex, quantitative ecologically important traits will provide insight into the proximate mechanisms driving phenotypic and ecological variation, and the molecular evolutionary history of these traits. Furthermore, if the study organism is a “keystone species” whose presence or absence shapes ecological communities, then we extend our understanding of the effects of molecular variation to the level of communities. I examined the molecular basis of variation in 32 ecologically important traits in the freshwater pond keystone species Daphnia pulex, and identified thousands of candidate genes for which variation may affect not just Daphnia phenotypes, but the structure of communities. I extended the basic results to address two questions: what genes are associated with the offspring size-number trade-off in Daphnia; and can we identify candidate “keystone gene networks” for which variation may have a particularly strong influence on eco-evolutionary dynamics of limnetic communities? I found that different genes, with different biological functions, are associated with the trade-off in subsequent broods, and propose a model linking evolutionary frameworks to molecular biological functions. Next I found that quantitative genetic variation in keystone traits appears to co-vary with the selection regimes to which Daphnia is subject, and identified two candidate gene networks that may underpin this genetic variation. Not only do these results provide a host of molecular hypotheses to be tested as Daphnia matures as a model genomic organism, but they also suggest models that link molecular research with broader themes in ecology, evolution, and behavior. / text

Life history theory assumes that correlations among fitness-related life history traits should be negative among individuals, reflecting resource allocation constraints among traits such as growth and reproduction. These traits trade off because they cannot be simultaneously maximized in individuals facing finite resource acquisition. Positive correlations among traits that are expected to be negative (e.g. between energetically costly traits) have been regularly observed, however, and have usually been ascribed to genetic or resource acquisition differences. In the freshwater zooplankton Cladoceran Daphnia, positive correlations have been particularly well documented even when genetic and environmental variation have been controlled. The sign of these correlations represent a problem for life history theory, which is underpinned by the notion of universal and unavoidable costs associated with investing in a given trait. It has been suggested, however, that costs vary with environment and thus can change the sign of a correlation. A change in correlation sign over an environmental gradient may indicate that the assumed universality of costs and constraints are not as universal as expected by life history theory. Few life history experiments have examined traits in multiple environments, and fewer have done so while controlling resource acquisition and genetic variation. Here I ask whether the positive genetic correlations among somatic growth rate, egg production rate, and longevity are present in the face of equal ingestion, clonal individuals, and a finely resolved gradient of food quality, an environmental factor that frequently affects Daphnia. I partition trait covariation into genetic and residual, or environmental, sources. All resulting genetic correlations were non-significant. Residual correlations trended from significantly positive to negative between longevity and growth rate and remained near zero between longevity and egg rate. The residual correlation between growth and reproduction, two expensive traits, displayed significantly positive residual correlations across the food quality gradient remained significantly positive. Given the experimental controls in place, I suggest that differences in individual ontogeny may give rise to differential resource utilization or assimilation efficiency. This may be a mechanism for differential resource acquisition in the absence of ingestion variation. Additionally, the different ways genetic and residual correlations change over an environmental gradient may provide insight on one manner by which genotypes might coexist and provide a candidate explanation for the second paradox of the plankton. / Thesis (Master, Biology) -- Queen's University, 2014-03-31 07:01:21.774