Variation in quality and quantity of food resources can affect consumer productivity responses throughout the food chain, particularly the efficiency at which basal resources are converted to consumer biomass. I performed a manipulative feeding experiment to investigate the somatic growth and fatty acid incorporation in the benthic generalist isopod Asellus aquaticus, in response to differing ratios of autochthonous (high quality algae) to allochthonous (low quality leaf litter) foods. I used stable isotopes to quantify the assimilated diet proportions across a range of diet treatments to determine the relative resources that contributed to growth. There were significant differences in growth between treatments, being lowest in treatments A (100% leaf litter) and G (100% algae), with highest growth experienced in treatment B (90% leaf litter/ 10% algae). Stable isotope data revealed that there was very little variation in algal assimilation among combined diet treatments. Fatty acids (FA) indicators eicosapentaenoic acid (EPA):total FA and EPA:omega 3 (ω3) FA and arachidonic acid (ARA):total FA declined with increasing growth and docosahexaenoic acid (DHA):ω3 showed a positive relationship with growth. These findings provide support for previous feeding trials conducted with Asellus, though there are some contrasts with zooplankton. The results suggest a balance between allochthonous and autochthonous dietary sources combine to enhance primary consumer fitness, and the relative availability of each may interact to determine growth and accumulation of important FA compounds. In terms of FA and trophic transfer, temporal and spatial variation in consumer physiological demands might determine the retention and use of FA.

Orientadores: João Vasconcellos Neto, Gustavo Quevedo Romero / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-22T05:42:43Z (GMT). No. of bitstreams: 1 Spolon_MelissaGallo_M.pdf: 4129370 bytes, checksum: be6d435f92be5c8e9bb999df9fab8da7 (MD5) Previous issue date: 2013 / Resumo: Plantas carnívoras, além de autotróficas também capturam presas, o que lhes permite ocupar ambientes pobres em nutrientes. Na região da Serra do Cipó ¿ MG, em uma área de campos rupestres, encontra-se com freqüência a espécie de planta carnívora Drosera hirtella A. St.-Hil. var. hirtella (D. hirtella), que apresenta variação na coloração das folhas e tricomas, havendo plantas desde totalmente verdes até totalmente vermelhas. Essa variação natural permitiu a realização de experimentos para testar as quatro hipóteses que serão descritas nos parágrafos a seguir. Para a primeira hipótese, esperava-se que D. hirtella mais expostas ao sol fossem mais frequentemente vermelhas, enquanto as menos expostas fossem mais frequentemente verdes, sendo a cor vermelha provavelmente uma forma de proteção contra a fotodegradação. Esta hipótese foi corroborada pelo primeiro experimento, que mostrou forte relação da cor de D. hirtella com o nível de exposição solar além de uma grande plasticidade da coloração dessa espécie de acordo com as condições de luminosidade. A segunda hipótese de trabalho foi parcialmente corroborada, pois se esperava que D. hirtella em áreas de solos mais pobres (menor concentração de nitrogênio) fossem mais frequentemente vermelhas, enquanto que D. hirtella em áreas de solos mais férteis (maior concentração de nitrogênio) fossem mais frequentemente verdes. O segundo experimento mostrou que os nutrientes disponíveis podem interferir na coloração da planta. A cor poderia ser assim uma resposta à deficiência de nutrientes disponíveis no solo, mas não necessariamente à deficiência de nitrogênio. A terceira hipótese, em que se esperava que D. hirtella de cor vermelha atraíssem mais insetos do que as de cor verde (um maior número de presas capturadas seria importante em solos pobres em nitrogênio), foram parcialmente corroborada pelos terceiro e quarto experimentos. A atratividade da forma vermelha de D. hirtella foi verificada, no entanto o segundo e o quinto experimentos mostraram que o nitrogênio presente no solo pode não estar interferindo diretamente na cor ou no número de presas capturadas. No terceiro experimento foi possível verificar que plantas vermelhas capturaram mais presas do que plantas verdes e plantas intermediárias. No entanto não ficou claro se a maior taxa de captura foi devida à coloração ou à quantidade de mucilagem, pois plantas vermelhas apresentaram mais tricomas funcionais. O quarto experimento mostrou que simulacros de plantas vermelhas capturaram mais presas em potencial do que simulacros de plantas verdes. Por fim, o quinto experimento não corroborou as predições da quarta hipótese em que se esperava que D. hirtella vermelhas, por capturarem mais presas, deveriam acumular mais 15N em seus tecidos do que as verdes; enquanto os tecidos das plantas verdes teriam mais nitrogênio total do que os tecidos das plantas vermelhas - por estarem em solos supostamente mais ricos em nitrogênio total. A única relação significativa foi à inesperada menor quantidade de 15N (d 15N) em plantas vermelhas. No entanto os resultados também sugerem que plantas vermelhas possam estar obtendo um ganho proporcionalmente maior de d15N, sugerindo que plantas verdes e vermelhas possam utilizar formas diferentes de processar esse isótopo / Abstract: Carnivorous plants are autotrophic organisms that also capture prey, allowing them to occupy nutrient-deficient habitats. In an area of rupestrian fields in the region of Serra do Cipó ¿ MG, the species of carnivorous plant Drosera hirtella A. St.-Hil. var. hirtella (D. hirtella) is frequently observed displaying color variation of its leaves and trichomes, which goes from totally green in some plants until completely red in others. This color variation has led to the experimental tests to examine the validity of four hypotheses. For the first hypothesis we expected that plants of D. hirtella more exposed to the sun were more often red whereas the least exposed plants were more frequently green. The red color is probably a form of protection against photodegradation. The first experiment showed a strong correlation between color of D. hirtella plants with the level of sun exposure and a great plasticity of this species color in accordance with light conditions. The second hypothesis was only partially supported as we expected that D. hirtella in areas of poor soils (less nitrogen) were most often red, whereas D. hirtella in areas of more fertile soils (more nitrogen) should be most often green. The second experiment showed that the availability of nutrients might also influence plant coloration. The color variation could be a general response to nutrient-deficient soils, but not necessarily a response to nitrogen deficiency. The third hypothesis, in which we expected that red plants would attract more insects than green plants (because a greater number of captured preys would be more important in low nitrogen soils), was partially supported by third and fourth experiments. The attractiveness of the red form of D. hirtella was confirmed, but the second and the fifth experiments showed that the nitrogen present in the soil may be not directly interfering in color and/or prey capture. In the third experiment we found that red plants caught more prey than green plants and intermediate plants. However it was unclear whether the higher catch rate was due to color or to the quantity of mucilage, because red plants showed more functional trichomes than green plants. The simulations of the fourth experimental block showed that the simulacra of red plants caught more potential prey than simulacra of green plants. Finally, as mentioned above, the fifth experiment did not exhibit the expected results of the fourth hypothesis, where it was expected that the red form of D. hirtella, by capturing more prey, should accumulate more 15N in their tissues than the green one; whereas the green plants tissues - supposedly living in soils richer in total nitrogen - should have more total nitrogen than the red plants tissues. The only significant relationship was the unexpected smaller d 15N in red plants. However the results also suggest that red plants may have a proportionally greater gain of d 15N, suggesting that green and red plants may use different ways of processing this isotope / Mestrado / Ecologia / Mestre em Ecologia

Top predators can have large effects on community and population dynamics but we still know relatively little about their roles in ecosystems and which biotic and abiotic factors potentially affect their behavioral patterns. Understanding the roles played by top predators is a pressing issue because many top predator populations around the world are declining rapidly yet we do not fully understand what the consequences of their potential extirpation could be for ecosystem structure and function. In addition, individual behavioral specialization is commonplace across many taxa, but studies of its prevalence, causes, and consequences in top predator populations are lacking. In this dissertation I investigated the movement, feeding patterns, and drivers and implications of individual specialization in an American alligator (Alligator mississippiensis) population inhabiting a dynamic subtropical estuary. I found that alligator movement and feeding behaviors in this population were largely regulated by a combination of biotic and abiotic factors that varied seasonally. I also found that the population consisted of individuals that displayed an extremely wide range of movement and feeding behaviors, indicating that individual specialization is potentially an important determinant of the varied roles of alligators in ecosystems. Ultimately, I found that assuming top predator populations consist of individuals that all behave in similar ways in terms of their feeding, movements, and potential roles in ecosystems is likely incorrect. As climate change and ecosystem restoration and conservation activities continue to affect top predator populations worldwide, individuals will likely respond in different and possibly unexpected ways.

<p>Variations in stable isotope abundances of nitrogen (δ¹⁵N) and oxygen (δ¹⁸O) of nitrate are a useful tool for determining sources of nitrate as well as understanding the transformations of nitrogen within soil (Chapter 2). Various sources of nitrate are known to display distinctive isotopic compositions, while nitrogen transformation processes fractionate both N and O isotopes and can reveal the reaction pathways of nitrogen compounds. However, to fully understand the δ¹⁵N and δ¹⁸O values of nitrate sources, we must understand the chemistry and the isotopic fractionations that occur during inorganic and biochemical reactions. Among all N cycle processes, nitrification and denitrification displayed some of the largest and most variable isotope enrichment factors, ranging from -35 to 0‰ for nitrification, and -40 to -5‰ for denitrification. In this dissertation, I will first characterize the isotopic enrichment factors of ¹⁵N during nitrification and denitrification in a Midwestern agricultural soil, two important microbial processes in the soil nitrogen cycle. Nitrification incubations found that a large enrichment factor of -25.5‰ occurs during nitrification NH₄⁺ è NO₃^-, which agrees well with previous studies (Chapter 3). Additionally, oxygen isotopic exchange that occurs between nitrite and water during nitrification was also quantified and found that 82% of oxygen in NO₃^- are derived from H₂O, much greater than the 66% predicted by the biochemical steps of nitrification. The isotopic enrichment that occurs during denitrification was assessed by measuring the change in δ¹⁵N as the reactant NO₃^- was reduced to N₂ gas (Chapter 4). The incubations and kinetic models showed that denitrification can causes large isotopic enrichment in the δ¹⁵N of remaining NO₃^-. The enrichment factor for NO₂^- è gaseous N was -9.1‰, while the enrichment factors for NO₃^- è NO₂^- were between -17 to -10‰, both of which were within the range of values report in literature. The results demonstrated that nitrification and denitrification caused large isotope fractionation and can alter the presumed δ¹⁵N and δ¹⁸O values of nitrate sources, potentially leading to incorrect apportionment of nitrate sources.</p> <p>The results of the denitrification incubation experiments were applied to a field study, where the measured enrichment factor was utilized to quantify loss of N by field-scale denitrification (Chapter 5). Field-based estimates of total denitrification have long been a challenge and only limited success has been found using N mass balance, N₂O gas flux, or isotope labeling techniques. Here, the flux of nitrate and chloride from tile drain discharge from a small field was determined by measuring both dissolved ions (ion chromatography) and monitoring water discharge. The δ¹⁵N and δ¹⁸O of tile nitrate was also measured at a high temporal resolution. Fluxes of all N inputs, which included N wet and dry deposition, fertilizer application, and soil mineralization were determined. The d¹⁵N and d¹⁸O values of these nitrate sources was also determined. Using this data, I first detected shifts in δ¹⁵N and δ¹⁸O values in the tile drain nitrate, which indicated variable amounts of denitrification. Next, a Rayleigh distillation model was used to determine the fraction of NO₃^- loss by field scale denitrification. This natural abundance isotope method was able to account for the spatial and temporal variability of denitrification by integrating it across the field scale. Overall, I found only 3.3% of applied N was denitrified. Furthermore, this study emphasized the importance of complementary information (e.g. soil moisture, soil temperature, precipitation, isotopic composition of H₂O, etc.), and the evidence it can provide to nitrogen inputs and processes within the soil.</p>

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21583号 / 理博第4490号 / 新制||理||1645(附属図書館) / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)准教授 伊藤 正一, 教授 生形 貴男, 教授 山路 敦 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

The Newmarket Till is a regional aquitard in southern Ontario that overlies the Illinoian to Middle Wisconsinan Lower Sediments and is overlain by the Oak Ridges Moraine (ORM). Geological investigations have mapped the distribution of the till and it is understood that erosional channels, subsequently infilled with fluvial material, breach the till and may create enhanced hydraulic connection between overlying and underlying aquifers. However, little is known about the protective capability of the Newmarket Till where it is intact. This study used natural tracers to assess the extent of transport in the aquitard-aquifer system. Stable isotopes of water (δ18O and δ2H) showed a depletion trend versus depth. In the Newmarket Till most of the samples had isotope ratios similar to meteoric water data from the nearest location (Egbert, ON). The depleted values of δ18O in the Thorncliffe Formation suggest a remnant signature of early-Holocene precipitation (-16‰ at the depth of 60 m). Elevated levels of NO3- and Cl- were detected near the surface and because of the low permeability aquitard (Newmarket Till), they could not migrate to depth. Total extractable ammonium concentrations are ranging from 4.09 ppm from near the surface to 60 ppm in the lowest part of the Newmarket and then gradually increase to 514 ppm in the bottom of the Thorncliffe Formation. The combination of high NH4+ values and organic carbon content in the Thorncliffe Formation suggests a natural source from mineralization of organic N. The fractionation which happened between δ15Nsediment and δ15N-NH4 may have three explanations: (1) lighter isotopes diffuse faster than heavier ones, so the higher rate of diffusion can cause fractionation; (2) heavier isotopes partition to exchange sites, causing fractionation along the transport pathway; (3) dissociation of NH4+ to NH3 under anaerobic condition. Positive values for δ13C in groundwater in the Thorncliffe Formation are likely due to i) a contribution of carbonate mineral dissolution, and ii) methanogenesis - the Archea favor the lighter isotope of C (12C). Methanogenesis, therefore, enriches the δ13C-DIC was enriched; however, the δ13C in dissolved organic carbon (DOC) is depleted. These geochemical characteristics demonstrate a long residence time for the porewater in the system and indicate that the Newmarket till inhibits recharge of recent precipitation, thereby providing protection to the underlying aquifers from surface-derived contaminants.

Loess-paleosol sequences preserve information that can be used to reconstruct paleoenvironement, specifically the climatic conditions and the vegetation present at the time of their formation. A dense network of reliably analyzed sequences from different geographic locations is crucial for representation of ecological and climatic trends during the Pleistocene (Frechen, 2011). The aim of this thesis is to fill the gap in the geographical distribution of well described loess-paleosol sequences in Central Europe. Therefore, it focuses on a loess- paleosol sequence in Bůhzdař, situated 9 km NW of Prague, Czech Republic. This profile was last studied in 1952 by naturalist Vojen Ložek. This thesis uses a number of analyses in order to get a multi-proxy record of local paleoenvironmental changes archived in a sequence of alternating loess sediments and paleosols in Bůhzdař. Geochemical approaches are combined with grain size distribution to define climatic conditions at the time of formation of the strata. Key words: loess/paleosol sequences, Bůhzdař, Czech Republic, particle size distribution, total organic carbon, XRF, XRD, stable isotopes 13 C and 18 O

The objective of the Master thesis is to estimate the fog contribution on atmospheric deposition with the usage of stable isotopes. The crucial part of the thesis was to perform (first of its kind in the Czech Republic) the relative isotope composition 18 O a 2 H of fog. In the same time, the composition of rain and throughfall was performed. The collection of each type of precipitation took place in five sampling points of Academy of Science within three mountain regions including Krkonoše, Šumava and Jizerské Hory during October and November 2017. The sampling took 14 days in total and it was performed by using TC/EA ThermoBremen and mass spectrometer Delta ThermoBremen at South Bohemian University in České Budějovice. The results confirmed that fog is isotopically heavier in comparison to regular rain. As for the relative isotope composition 18 O and 2 H of each areas, no significant difference was observed. Results of the fog participation on atmospheric deposition in Krkonoše and Šumava can be seen after drafting a simple linear mixing model. The fog contribution on atmospheric deposition in Šumava for 18 O is 4,7 % and for 2 H is 6,4 18 O. For one area in Krkonoše, the average participation for 18 O is 3,6 %. Key words: stable isotopes, oxygen, hydrogen, fog

>Magister Scientiae - MSc / This study is part of the current investigation of the Elandsfontein aquifer to assist with the management of the system and to ensure the protection of the associated Langebaan Lagoon RAMSAR listed site. The Elandsfontein aquifer unit is situated adjacent to the Langebaan Road aquifer in the Lower Berg River Region. The aquifer unit is bordered by the Langebaan Lagoon (west), possible boundary toward the Langebaan Road aquifer (north), the Groen River bedrock high (southeast) and the Darling batholith (south).

Orientador: Carlos Ducatti / Coorientador: Juliana Célia Denadai / Banca: Antônio Celso Pezzato / Banca: Maria Márcia Pereira Sartori / Resumo: Este estudo avaliou o turnover do carbono-13 em sangue e plasma de poedeiras na fase de pré-postura e inicial da postura, pela substituição de dietas C4 por C3 e C3 por C4, utilizando a técnica de isótopos estáveis de carbono. Foram utilizadas 144 aves divididas ao acaso em 2 tratamentos na pré-postura que receberam por 42 dias dietas à base de quireta de arroz e farelo de soja, fosfato bicálcico ou farinha de carne e ossos bovinos. Na fase inicial da postura, as aves dos dois tratamentos da fase de pré postura, foram divididas em quatro tratamentos, consitituídos de dietas à base de milho moído e farelo de soja, fosfato bicálcico ou farinha de carne e ossos bovinos. Aos 1, 2, 3, 5, 7, 10, 14, 19, 25, 32 e 42 de cada fase foram coletados sangue e plasma de 6 aves por tratamento. Os valores de meia-vida do sangue e plasma dos tratamentos ASFB e ASFCO da pré-postura foram maiores (17;4 e 15;5 dias respectivamente) do que os tratamentos ASFB-MSFB; ASFB-MSFCO; ASFCO-MSFB e MSFCO-MSFCO da postura inicial (meias-vidas de 11;10;11 e 9 para o sangue e 2;2;2 e 2 dias para o plasma). Deste modo, pode-se concluir que houve diferença da idade, mas não houve diferença em relação a dieta no turnover do sangue e plasma das aves. Termos para indexação: aves, carbono-13, diluição ... / Abstract: This study aimed to assess the turnover of carbon-13 on blood and plasma of laying hens by replacing C4 by C3 diets and C3 by C4 diets during the pre-laying period and initial laying period using the technique of stable carbon isotopes. We used 144 laying hens ramdomly divided into two treatments of which were fed by 42 days in the pre-posture period with diets based on rice grits and soybean meal, containing dicalcium phosphate or bovine meat and bone meal. On the beginning of laying period the diets were changed and the poultry of the pre-laying period were divided into four treatments whose diets contained ground corn, soybean meal and dicalcium phosphate; or ground corn, soybean meal and bovine meat and bone meal. On days 1, 2, 3, 5, 7, 10, 14, 19, 25, 32, and 42 of each period the blood and plasma from six birds per treatment were randomly collected. The half-life of blood and plasma of ASFB and ASFCO from pre-laying period were greater (17;4 and 15;5 days, respectively) than the treatments from initial laying period: ASFB-MSFB; ASFB-MSFCO; ASFCO-MSFB e MSFCOMSFCO (half-life of 11;10;11 and 9 for blood, and 2;2;2 and 2 days for plasma. We concluded that the age of hens influenced the blood and plasma turnover whereas the diets did not influenced them ... / Mestre