Indiana University-Purdue University Indianapolis (IUPUI) / The evolution of land plant root systems occurred stepwise throughout the Devonian, with the first evidence of complex root systems appearing in the mid-Givetian. This biological innovation provided an enhanced pathway for the transfer of terrestrial phosphorus (P) to the marine system via weathering and erosion. This enhancement is consistent with paleosol records and has led to hypotheses about the causes of marine eutrophication and mass extinctions during the Devonian. To gain insight into the transport of P between terrestrial and marine domains, presented here are geochemical records from a survey of Middle and Late Devonian lacustrine and near lacustrine sequences that span some of these key marine extinction intervals. Root innovation is hypothesized to have enhanced P delivery and results from multiple Devonian sequences from Euramerica show evidence of a net loss of P from terrestrial sources coincident with the appearance of early progymnosperms. Evidence from multiple Middle to Late Devonian sites (from Greenland and northern Scotland/Orkney), reveal a near-identical net loss of P. Nitrogen and Carbon isotopes from a subset of these lakes confirm elevated input of terrestrial plant material concurrent with P perturbations. Terrestrial P input appears to be episodic in nature, suggesting land plant expansion was driven by an external catalyst in the study region. All sites analyzed are temporally proximal to significant marine extinctions, including precise correlation with the Kačák extinction event and the two pulses associated with the Frasnian-Famennian (F/F) mass extinction. The episodic expansion of terrestrial plants appears to be tied to variations in regional and global climate, and in the case of the F/F extinction, also to atmospheric changes associated with large scale volcanism. Using P data presented here as an input into an Earth system model of the coupled C-N-P-O2-S biogeochemical cycles shows that globally scaled riverine phosphorus export during the Frasnian-Famennian mass extinction generates widespread marine anoxia consistent with the geologic record. While timing precludes land plants as an initiating mechanism in the F/F extinction, these results suggest they are implicated in every marine extinction event in the Mid to Late Devonian.

[Tuncated abstract] Soil is a relatively low cost and robust geochemical sampling medium and is an essential part of most mineral exploration programs. In areas of covered terrain, however, soils are less reliable as a sampling medium because they do not always develop the geochemical signature of the buried mineralisation; possibly a result of limited upward transport of ore related elements into the surficial overburden. As economic demands on the resources industry grow, mineral exploration continues to expand further into areas of covered terrain where the rewards of finding a new deposit relative to the risks of finding it may be comparatively low. Thus, improving the costeffectiveness of a geochemical exploration program requires a sound understanding of the mechanisms by which soil geochemical anomalies form in transported overburden. This thesis examines the deep biotic uplift of ore related elements by deep rooting vegetation as a mechanism for the development of soil geochemical anomalies within transported overburdens, in semi-arid and arid regions. '...' Vegetation and soils were analysed at two Au prospects in Western Australia: Berkley, Coolgardie and Torquata, 210 km south-east of Kambalda, in semi-arid Western Australia to complement both the mass balance and the differential modelling. At Berkley, both the vegetation and soils located directly over the mineralisation showed high concentrations of Au. There may be indirect evidence for the operation of the deep plant uptake flux taking effect from the field evidence at Berkley. Firstly, anomalous concentrations of Au were found in the surface soils, with no detectable Au in the transported overburden. Secondly, the trace element concentrations in vegetation showed correlation to the buried lithology, which to our knowledge has not been reported elsewhere. The results from the samples at Torquata, in contrast, were less conclusive because the Au is almost exclusively associated with a surficial calcrete horizon (at <5 m soil depth). Strong correlations of Ca and Au in leaf samples however, suggest that the vegetation may be involved in the formation of calcrete and the subsequent association of Au with the calcrete. Among the vegetation components, the litter and leaf samples gave the greatest anomaly contrast at both prospects. Finally, three main drivers for the deep biotic uplift of elements were identified based on the results from the mechanistic numerical modelling exercise: i) the deep uptake flux; ii) the maximum plant concentration and; iii) the erosional flux. The relative sizes of these three factors control the rates of formation and decay, and trace element concentrations, of the soil anomaly. The main implication for the use of soils as exploration media in covered terranes is that soil geochemical anomalies may only be transient geological features, forming and dispersing as a result of the relative sizes of the accumulative and loss fluxes. The thesis culminates in the development of the first quantitative, mechanistic model of trace element accumulation in soils by deep biotic uplift.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

La mer Méditerranée est considérée comme un point chaud du changement climatique. Cette région très peuplée au climat aride devrait voir son climat devenir plus chaud et plus aride encore, tout en subissant une pression anthropique toujours plus forte. Dans ce contexte, de nombreuses données physiques et biogéochimiques sont actuellement relevées en mer Méditerranée, dans le cadre du projet MERMEX, afin de mieux étudier et comprendre les cycles biogéochimiques en mer Méditerranée. Complémentaire aux mesures, la modélisation est un outil unique pour aider à comprendre et quantifier les processus contrôlant la biogéochimie marine de la Méditerranée, ses spécificités et son évolution future. Dans cette étude, nous proposons la mise en place, et l’évaluation d’un modèle régional couplé dynamique - biogéochimie marine (NEMO-PISCES), à haute résolution, qui sera le premier modèle couvrant l’intégralité de la mer Méditerranée disponible pour la communauté MERMEX. Ainsi, après avoir évalué la dynamique du modèle NEMO-MED12, utilisée comme forçage, grâce à une simulation de traceurs passifs (CFC), nous effectuons les premières utilisations de cet outil, avec lequel (i) nous évaluons la quantité de carbone anthropique en mer Méditerranée grâce à une approche par perturbation, ainsi que l’acidification associée des masses d’eau ; (ii) nous effectuons une étude des régimes trophiques en mer Méditerranée, tels que perçus par le modèle, sur différentes couches de la zone euphotique. / The Mediterranean Sea is considered as a hot spot of climate change. This arid region, already under high anthropogenic influence, is said to become even warmer and drier, with still an increasing anthropogenic pressure. In this context, numerous physical and biogeochemical data are currently collected in the Mediterranean Sea, within the MERMEX project, enabling to better study and understand the Mediterranean biogeochemical cycles. Complementary to in-situ observations, modelling is an unique tool that helps to understand and quantify biogeochemical controling processes in the Mediterranean Sea, its specificity, and its evolution. In this study, we propose the setting and evaluation of a regional, high resolution, marine dynamicalbiogeochemical coupled model (NEMO-PISCES). It will be the first model available for the MERMEX community, that covers the whole Mediterranean Sea. Therefor, after the evaluation of NEMO-MED12 dynamical forcing fields, within passive tracers simulation (CFC), firsts use of this tool have been made : (i) we have evaluated anthropogenic carbon uptake and induced acidification of the Mediterranean Sea, within a perturbation approach ; (ii) we have analysed Mediterranean Sea trophic regimes, as represented by the model, for different layers of the photic zone.

In plants, phenotypic plasticity, the ability to morphologically adapt to new or broad environmental conditions, is a consequence of long-term evolutionary genetic processes. Thus, plants adapted to low phosphate (P) environments exhibit only limited plasticity to take advantage of nutrient enrichment, a global phenomenon in terrestrial and aquatic environments. In the face of anthropogenic P-enrichment, low nutrient adapted resident plant species are frequently displaced by species with high morphological and genetic plasticity. However, it remains unclear whether plasticity is systemically expressed across molecular, biochemical, physiological, and morphological processes that ultimately contribute to the root and shoot phenotypes of plants. In this study, we demonstrated high plasticity in root-borne traits of sawgrass (Cladium jamaicense), the dominant plant species of the P-impoverished Everglades, and counter the idea of inflexibility in low P adapted species. However, sawgras s expressed inflexibility in processes contributing to shoot phenotypes, in contrast to cattail, which was highly plastic in shoot characteristics vii in response to P enrichment. In fact, plasticity in cattail shoots is likely a function of its growth response to P that was globally regulated by P-availability at the level of transcription. Plasticity and inflexibility in the growth of both species also diverged in their allocation of P to the chloroplast for growth in cattail versus the vacuole for P storage in sawgrass. In the Everglades, anthropogenic P-enrichment has changed the environment from a P-limited condition, where plasticity in root-borne traits of sawgrass was advantageous, to one of light-competition, where plasticity in shoot-borne traits drives competitive dominance by cattail. / We hypothesize that these shifts in plasticity competitive advantage from root to shoots has been a major driver of cattail expansion in the Everglades ecosystem. Further, this understanding of how natural plant species adapt and shift in response to nutrient availability could also be used a model system to optimize agricultural systems to increase efficiencies in food production and protect low nutrient adapted natural systems from cultural eutrophication. / by James Webb. / Vita. / Thesis (Ph.D.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 200?. Mode of access: World Wide Web.

In recent history, C. jamaicense has been displaced by another native monocot, T. domingensis, predominantly resulting from increased phosphorous enrichment in the Everglades. This study aimed to elucidate these two species responses to low and high [Pi] in terms of allocation, photosynthate partitioning and growth. C. jamaicense growth was independent of Pi, while T. domingensis growth increased with [Pi]. Under high [Pi], allocation to younger T. domingensis shoots occurred, while C. jamaicense shoots retained more [Pi], while low [Pi] resulted in homogeneous allocation patterns for both species. Additionally, Pi deficiencies induced carbohydrate levels in older shoots of T. domingensis, while [Pi] had no effect on photosynthate partitioning patterns in C. jamaicense. ACP activity was induced by Pi deficiency in all T. domingensis shoots and increased with shoot age, while no effect was observed in C. jamaicense. Results indicate these two species differ in allocation strategies when [Pi] is altered. / by Brian Hill. / Vita. / Thesis (Ph.D.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

A qualidade da matéria orgânica e a magnitude de suas deposições estão entre os principais fatores que controlam as respostas dos organismos bênticos marinhos. Uma vez depositada nos sedimentos, a matéria orgânica é degradada por processos biogeoquímicos microbianos, que podem ser acelerados mediante a bioturbação da macrofauna. Entretanto, em regiões costeiras, a dinâmica das forçantes ambientais influencia tanto a qualidade dos recursos alimentares, quanto os mecanismos de utilização pelos organismos, implicando em alterações na remineralização da matéria orgânica. Este estudo visou investigar o sistema bêntico da área costeira de Ubatuba frente às variações da qualidade e quantidade da matéria orgânica, incluindo os impactos da bioturbação na diagênese recente e regeneração de nutrientes. Observou-se que os processos físicos da região atuaram na variação da qualidade da matéria orgânica e na estruturação dos organismos bênticos. Os microorganismos exploraram matéria orgânica de diferentes composições, exercendo também importante papel para a comunidade macrobêntica, enriquecendo os detritos orgânicos disponíveis como alimento. A meiofauna não apresentou relação direta com alta qualidade da matéria orgânica, já a macrofauna foi estruturalmente modificada pela passagem de frentes frias e pela presença de compostos lábeis, quando os mesmos apareceram em maiores concentrações. Experimentalmente, verificou-se que a mistura de partículas foi significativa somente quando altas densidades da macrofauna estiveram presentes na superfície do sedimento. Além disso, foi demonstrado em laboratório que a macrofauna exerceu pouca influência nos fluxos de oxigênio e nutrientes do sedimento para a água, porém suficiente para estimular a decomposição de material orgânico verticalmente na coluna sedimentar. Portanto, a dinâmica dos processos físicos e as variações estruturais da macrofauna são importantes fatores ecológicos na modulação de funções fundamentais do ecossistema costeiro de Ubatuba, como produtividade, metabolismo bêntico, degradação da matéria orgânica e fluxos de energia. / The magnitude and quality of organic matter inputs to the seafloor are among the main factors regulating the responses of marine benthic communities. Once deposited on the sediments, the organic matter is degraded by several microbial biogeochemical processes that may be stimulated through macrofauna bioturbation. However, in coastal regions the dynamics of environmental forcing not only influences the quality of food sources, but the food uptake by organisms, resulting in changes on remineralization rates of organic material. This study aimed to investigate the benthic system of Ubatuba coastal area in relation to quality and quantity of organic matter as well as bioturbation impacts on early diagenesis and nutrient regeneration. Data suggests that physical stresses influenced the quality of organic matter and the structure of benthic organisms. Different compositions of organic matter were assimilated by microorganisms, which in turn played an important role to the macrobenthic community, enriching the organic detritus available as food. The meiofaunal organisms did not numerically respond to the deposition of high quality organic matter, while macrofauna community structure was modified by the incidence of cold fronts and by the presence of labile compounds, whenever available. Experimentally, sediment reworking was only significant at higher levels of macrofaunal density on the sediment surface. In addition, it was demonstrated in laboratory that macrofauna imposed weak effects on the fluxes of oxygen and nutrients from sediments to the water column, but those changes were enough to stimulate vertically in the sediments, the decomposition of organic matter. Therefore, the dynamics of physical processes and the variability on macrofaunal structure are both important ecological factors modulating fundamental functions of the coastal ecosystem in Ubatuba, including productivity, benthic metabolism, degradation of organic matter and energy flow.

Este estudo teve como objetivo conhecer a dinâmica do ciclo biogeoquímico do fósforo (P) (fases dissolvidas e particuladas) no Complexo estuarino-lagunar de Cananéia-Iguape considerando a influencia antrópica causada pela abertura do canal do Valo Grande e as possíveis diferenças no fluxo bêntico de PID. Foram observados valores de P dissolvido e particulado superiores no setor norte (Iguape) indicando a influência do aporte do Valo Grande ao estuário. As concentrações de P no sedimento foram maiores também no norte, sendo dominada pela fração inorgânica. Nas estações fixas de Cananéia (verão e inverno), a influência da maré foi evidente, enquanto em Iguape não foi observado sinal considerável. O fluxo do PID observado nas campânulas bênticas foi negativo indicando a remoção para o sedimento, consequente retenção do P neste compartimento. O Valo Grande influenciou o ciclo biogeoquímico do P na região, de forma mais acentuada ao norte do sistema e, a fração particulada em suspensão foi a forma que mostrou maior potencial para exportação de P para o oceano adjacente. O estudo do ciclo biogeoquímico do P em sistemas estuarinos constitui uma excelente ferramenta para o diagnóstico da qualidade ambiental, auxiliando também, os gestores ambientais em suas ações de preservação e manejo. / This study aims to know the dynamic of phosphorus biogeochemical cycle (P) (dissolved and particulate forms) in Cananéia-Iguape Estuarine-Lagoon Complex, considering the anthropogenic influence caused by the opening of Valo Grande channel and the possible differences in DIP benthic flux. Higher values of dissolved and particulate P were observed in the northern sector (Iguape), indicating the influence of the Valo Grande contribution to the estuary. P concentrations in sediment were also higher in the north, and the inorganic fraction prevailed. In Cananéia\'s fixed stations (summer and winter), the influence of the tide was evident, while in Iguape an extensive signal was not observed. The DIP flux observed in the benthic chambers was negative, indicating the removal to the sediment, and therefore the retention of P in this compartment. The Valo Grande influenced the P biogeochemical cycle in this region, the north of the system in a more sharply way. The suspended particulate P form showed the biggest potential to exportation of P to the adjacent ocean. The study of P biogeochemical cycle in estuarine systems is an excellent tool to diagnose environmental quality, also helping environmental managers in their actions of preservation and management.

Este trabalho teve como proposta principal avaliar os efeitos de ações antrópicas sobre sistemas estuarinos com base no balanço biogeoquímico entre as formas de nutrientes (N, P e Si). Foram estudados dois sistemas estuarinos localizados em pontos extremos da costa, um no nordeste, o estuário do Rio Jaguaribe, no Ceará, e outro no sudeste, o complexo estuarino-lagunar de Cananéia e Iguape, em São Paulo. Estes sistemas estão sob os diferentes regimes climáticos e o estudo envolveu: aspectos dos períodos de seca e chuva nos dois locais; o efeito da maré; e, o aporte de águas doces quer sob a forma de chuva, quer via drenagem continental e barragens. A influência antrópica mostrou a ação sobre o excesso de silício nos dois sistemas. O fósforo foi o elemento dissolvido que recebeu maior ação neutralizadora, sendo \"tamponado\" de forma que não ofereceu sinais de eutrofização. Este não é o caso das formas nitrogenadas, que mostraram uma assinatura relativa às atividades antrópicas que mais impactam cada região. No caso do Rio Jaguaribe, o aporte de matéria orgânica e de nutrientes via atividade de carcinicultura colaborou ao destaque na forma de N-amoniacal nas águas do médio e baixo estuário, onde se localizam as fazendas de carcinicultura. Os sinais mais acima no sistema estiveram ligados aos aportes via barragem e da cidade de Aracati. No caso do complexo estuarino-lagunar de Cananéia e Iguape, o nitrato recebeu destaque junto aos aportes do Rio Ribeira de Iguape, por meio do Valo Grande, representando a drenagem de zonas agrícolas. A parte sul do sistema, Cananéia, mostrou um equilíbrio entre as formas nitrogenadas, bastante naturais, dando suporte à produção primária de populações comuns a ambientes estuarinos, enquanto que, os valores de pigmentos fotossintetizantes, mostraram que a composição das comunidades fitoplanctônicas se adapta às condições abióticas do corpo hídrico. Há produção em todos os locais, porém com distinção entre as comunidades fitoplanctônicas. Ocorreu influência sazonal e a degradação de biomassa vegetal, muitas vezes somadas as influências de feopigmentos de comunidades das margens. O diagnóstico feito com o Programa ASSETS é baseado em carga de nitrogênio, valores de clorofila e presença de macroalgas, contudo o equilíbrio entre os nutrientes pode ser uma excelente ferramenta na avaliação ambiental. / The main proposal of this work was to evaluate the effects of anthropic actions upon estuarine systems, based on biogeochemical balance between forms of nutrients (N, P and Si). Two estuarine systems were studied, localized in extreme points of the coast, one in northeast, Jaguaribe River estuary, in Ceará, and the other in southeast, Cananéia-Iguape estuarine-lagoon complex, in São Paulo. These systems are under different climatic patterns and the study involved: aspects of dry and rainy periods in both locations; tide effects; and fresh water inputs, either in the form of rain, or via continental drainage and dams. The anthropic influence showed action upon the excess of silicon in both systems. Phosphorus was the dissolved element that suffered bigger neutralizing action, being buffered, and so, didn\'t show signals of eutrophication. That is not the case of nitrogen\'s forms, they showed a signature related to anthropic activities that impact each region the most. In the case of Jaguaribe River, the input of organic matter and nutrients, due to shrimp farms activities, contributed to prominent N-ammonium form in medium and lower estuary waters, where shrimp farms are located; the signals in upper estuary were connected to inputs via dam and Aracati city. In the case of Cananéia-Iguape estuarine-lagoon complex, the form nitrate was highlighted by the inputs of Ribeira de Iguape River, through Valo Grande, representing agricultural areas drainage. The south part of the system, Cananéia, showed a quite natural balance between the nitrogen forms, supporting primary production of populations common to the estuarine environment. Meanwhile, values of photosynthetic pigments showed that the composition of planktonic communities adapt itself to the abiotic conditions of the water body. There is production everywhere, but with distinctions between the communities. Seasonal influence occurred, and also degradation of microscopic vegetal biomass, often added to influence of pheopigments of margin communities. The diagnosis made by ASSETS Program is based on nitrogen input, values of chlorophyll and macroalgae presence; nevertheless the equilibrium between nutrients can be an excellent tool for environmental evaluation

Fire is a natural process that has existed on our planet for more than ~350 million years, and is a process that continues to influence our everyday lives. On Earth, a relationship exists between the process of combustion and the natural functioning of the Earth system. Here, the process of combustion has been implicated in playing an essential role for life on Earth, where natural Earth system processes have been shown to influence ignition probability, fire spread and fire behaviour, and where fire can provide a variety of feedbacks, to the Earth system over different timescales. Over medium timescales of decades to hundreds of thousands of years, the likelihood and behaviour of fires are controlled by regional climate changes and vegetation type, whilst the occurrence of fire can play a crucial role in influencing biome persistence and development. Over long timescales (hundreds of thousands to multi-million year), the components influencing the probability of fire and fire behaviour not only involve processes occurring over local and regional spatial scales, and over short and medium timescales, but also long term processes occurring globally, such as changes in atmospheric oxygen concentration and the evolution of vegetation. Across these timescales in Earth’s past, combustion has been shown to impact global ecosystems, climate and the carbon cycle by generating feedbacks that influence Earth’s biogeochemical cycles. However, it is clear that our understanding of the role that fire plays in the Earth system, although improving is still developing. This thesis provides an analysis of these Earth system - fire relationships and feedbacks across medium and long timescales in deep time, in order to understand the role that fire may have played and what the record of fire can tell us about the functioning and re-equilibrating of the Earth system during and after significant carbon-cycle perturbation events occurring in Earth’s deep past. The results presented in this thesis contribute what is believed to be the first fossil evidence that rising atmospheric oxygen and fire feedbacks may have aided in the termination of a significant carbon-cycle perturbation event, termed the ‘Toarcian oceanic anoxic event’ that occurred ~183 million years ago during the Jurassic period, and the return of the Earth system towards ‘background functioning’. This thesis also provides an analysis of the record of wildfire in the form of fossil charcoal across the initiation of an anoxic event that occurred ~93 million years ago, during the Cretaceous period. The results illustrate that CO2 - climate driven changes in wildfire activity can be observed across medium timescales even during times of significant carbon-cycle perturbations, and modelled high atmospheric oxygen concentrations. These results illustrate how hypothesized changes in the hydrological cycle, and likely moisture content of fuel, appear to be the dominant control on wildfire activity during this period. Finally, this thesis provides an analysis of charcoal abundance variations occurring across natural, orbitally forced cycles, termed the Milankovitch cycles. The results presented illustrate that natural variations in charcoal abundance are possible over intermediate timescales within the geological record. This thesis therefore illustrates a need to take into consideration and incorporate ‘natural background’ fluctuations in fire activity occurring over medium timescales, when analysing and predicting past and future climate change patterns.