Microalgae, photosynthetic microorganisms, are rich in lipids, polyunsaturated fatty acids, carbohydrates, proteins, vitamins, as well as carotenoids, which are antioxidants that may protect human body from various diseases including obesity, cardiovascular disease, vision-related diseases such as macular degeneration and certain types of cancer. These natural pigments have applications in the pharmaceutical (nutraceutical), food (coloring, functional food, and supplements), and cosmetics industries (e.g. sunscreen), as well as in aquaculture (animal feed). The Dunaliella salina microalga can synthesize 10% of dry weight in &#946;-carotene (orange pigment, pro-vitamin A activity) under high light intensity and nitrogen and phosphorus limitation, among other stress conditions. The first chapter of this thesis presents a review focused on microalgae carotenoids: culture systems, mode of operation, and applications. In this bibliographic survey, the advantages of microalgae cultivation in relation to traditional sources (higher plants) were discussed, as well as a discussion of the main cultivation systems and their importance in cell growth. This review presented a critical analysis of the different operational regimes like batch, fed-batch, semi-continuous and continuous. Relevant information on the most important world producers of microalgae carotenoids were presented. Chapter II presents the development of a modified method of dispersive liquid-liquid microextraction (DLLME) for rapid extraction of &#946;-carotene from Dunaliella salina cultivated in tubular photobioreactor, with subsequent development of a rapid chromatographic screening method using a C4 column for separation of geometric isomer of &#946;-carotene. The use of benzene as extraction solvent and water with 50% acetone as dispersant provided the best condition for the extraction of this carotenoid. In HPLC (High Performance Liquid Chromatography), employing mobile phase composed of methanol and water (95:5, v/v), it was possible to detect/quantify &#946;-carotene at 14 min (retention time). Besides the short analysis time (<20 min), by the miniaturized extraction (< 10 mL organic waste) this method abide by green chemistry analytical principles. It is known that nitrogen, phosphorus, as well as carbon and vitamins are vital elements for the growth of microalgae, also determining the biochemical composition of biomass. In this sense, Chapter III presents the study of the influence of different amounts of sodium nitrate (1N = 75 mg L-1; 1.5N = 112.5 mg L-1, and 3N = 225 mg L-1) and phosphate monobasic dehydrate (1P = 5.65 mg L-1, 1.5P = 8.47 mg L-1, and 3P = 16.95 mg L-1) in seawater-based f/2 medium on the growth of Dunaliella salina and &#946;-carotene biosynthesis, by continuous process with different replenishment proportions (R = 20% and 80%). Best results of cell productivity were obtained by semicontinuous process (mean values of Px up to 6.7 x 104 cells mL-1 d-1 with medium 1N:1P; R =20%) in comparison with batch process cultivation. Maximum cell density (Xm) obtained in this work was not dependent of R, but the best results were obtained when using medium 1.5N:1.5P (mean values up to 5.6 x 105 cells mL-1 with R =80%) instead of 1N:1P. The content of &#946;-carotene in the cells, in general, was higher in cells grown in medium 1N:1P (mean yield values up to 57.5 mg g-1 with R =80%) in comparison with medium 1.5N:1.5P. The cultivation of D. salina with media 3N:3P led to a long lag phase, followed by decrease in cell density and cell lysis. The use of a tubular photobioreactor contributed to successfully cultivate this microalga without contamination by protozoa. The cultivation of Dunaliella salina in tubular photobioreactor with the use of 12:12 photoperiod was appropriate, as well as to induce carotenogenesis, in the second stage, by increasing the light intensity and absence of pH control / As microalgas, micro-organismos fotossintetizantes, são ricas em lipídios, ácidos graxos poli-insaturados, carboidratos, proteínas, vitaminas, além de carotenoides que são antioxidantes com potencial de proteger o organismo humano de várias doenças incluindo a obesidade, doenças cardiovasculares, doenças relacionadas à visão como a degeneração macular e certos tipos de câncer, entre outras. Esses pigmentos naturais têm aplicações em indústrias farmacêuticas (nutracêuticos), alimentícias (colorantes, alimentos funcionais e suplementos) e de cosméticos (exemplo: filtro solar) e na aquacultura (ração animal). A microalga Dunaliella salina é capaz de sintetizar, sob alta intensidade luminosa e limitação de nutrientes como fontes de fósforo e nitrogênio, dentre outras condições de estresse, 10 % do peso seco em &#946;-caroteno (pigmento laranja com atividade pró-vitamina A). Assim, neste trabalho, numa primeira etapa, foi feita uma revisão da literatura abordando a produção de carotenoides por microalgas, bem como sua aplicação. Nesse levantamento bibliográfico abordou-se, dentre outros assuntos, as vantagens do cultivo de microalgas em relação as fontes tradicionais (plantas superiores), assim como uma discussão dos diferentes sistemas de cultivos e sua importância no crescimento celular. Esse review apresentou uma análise crítica dos principais regimes operacionais como batch, fed-batch, semicontínuo e contínuo. Apresentou-se também informações relevantes sobre os mais importantes produtores mundiais de carotenoides de microalgas. Numa segunda etapa, foi desenvolvido um método modificado de microextração líquido-líquido dispersivo modificado (DLLME) para a rápida extração de &#946;-caroteno de Dunaliella salina cultivada em fotobiorreatores tubulares, com subsequente desenvolvimento de método cromatográfico em uma coluna C4 para a separação do isômero geométrico de &#946;-caroteno. A extração ótima de &#946;-caroteno foi obtida com benzeno como solvente extrator e água com 50% de acetona como dispersante. Empregando uma fase móvel composta por metanol e água (95:5, v/v) em HPLC, foi possível a detecção/quantificação de &#946;-caroteno com 14 minutos de tempo de retenção. Além dos tempos curtos de análises (<20 min), pela extração em volume reduzido (< 10 mL resíduos orgânicos) este método obedece aos princípios da química verde. Sabe-se que nitrogênio, fósforo, assim como carbono e vitaminas são elementos vitais para o crescimento das microalgas e também exercem influência na composição bioquímica da biomassa. Assim, na terceira etapa deste trabalho, estudou-se a influência das quantidades de nitrato de sódio (75 mg L-1, denominado 1N; 112,5 mg L-1, denominado 1,5N; 225 mg L-1, denominado 3N) e de fosfato monobásico dihidratado (5,65 mg L-1, denominado 1P; 8,47 mg L-1, denominado 1,5P; 16,95 mg L-1, denominado 3P) em meio f/2, que tem como base a água do mar, no crescimento e na síntese de &#946;-caroteno da Dunaliella salina por processo semicontínuo, com uso de frações de corte (R) de 20% e 80%. Foram obtidas produtividades celulares mais elevadas em processos semicontínuos do que em processo descontínuo, com produtividades médias de até 6,7 x 104 células mL-1 d-1 (meio 1N:1P; R =20%). A máxima concentração celular (Xm) obtida neste trabalho não foi dependente de R. Os melhores resultados de Xm foram obtidos quando se usou meio 1,5N:1,5P em vez de meio, com 1N:1P, com valores médios de até 5,6 x 105 células m L-1 (R =80%). O conteúdo de &#946;-caroteno nas células, de maneira geral, foi maior nas células cultivadas em meio 1N:1P do que no meio 1,5N:1,5P, com valores até 57,5 mg g-1 (R =80%). O cultivo de D. salina com o meio 3N:3P levou a uma longa fase lag, seguida por uma diminuição na concentração celular e sua lise. O cultivo de células em um fotobiorreator tubular contribuiu para um crescimento celular sem contaminação por protozoários. O cultivo de Dunaliella salina em fotobiorreator tubular com o uso de fotoperíodo 12:12 foi apropriado, assim como induzir a carotenogênese, no segundo estágio, por meio do aumento da intensidade luminosa e ausência de controle de pH.

The primary aim of this research was to investigate the bending behaviour of helically wound steel cables of various types (i.e. normal spiral strands, sheathed spiral strands and locked coil cables) in the presence of friction and to propose more efficient computational models for their analysis under combined tension and bending. The proposed model fully takes into account interwire contact forces both in the radial direction (point contact between wires in different layers) and hoop direction (line contact within the wires in the same layer). Extensive theoretical parametric studies have been undertaken on a variety of cable constructions covering a wide range of geometrical and material parameters. Explicit formulations have been developed for the smooth transition of the bending stiffness from no-slip to full slip regimes, as a function of cable curvature. Based on these formulations, it is now possible to calculate the relative displacements of the wires, as well as the tensile, bending and hoop stresses in the individual wires of the cable. Furthermore, bending stiffness of the cable is shown to decrease by a factor of 2 to 16, depending upon the friction coefficient between wires and the type of cable construction. Wherever possible, the theoretical results have been compared with experimental results from the available literature and are found in very good agreement with them. A simple method for the determination of the bending stiffness of large diameter multi-layered cable has been developed. The simplified method is further shown to provide estimates of the bending stiffness which are very close to those calculated by the original theory, allowing hand calculations for an easier use in industry. The proposed formulations have been extended to cater for the effects of external hydrostatic pressure on sheathed spiral strands in deep water applications. These forces are shown to have a great influence on the pattern of interwire contact forces and hence the interlayer slippage between the wires in the strand. Numerical results have been obtained and analysed for three different 127 mm diameter strands with lay angles of 12°, 18° and 24° respectively, experiencing a wide range of external hydrostatic pressures of 0 to 2,000 metres. The significant increase in normal contact force between wires is shown to suppress the slippage of wires in the cable. However, the no-slip and full slip values of the effective bending stiffness of the cable is shown to be independent of the level of hydrostatic pressure. A theoretical model is also proposed for estimating wire kinematics, pattern of interwire slippage, contact forces as well as the flexural rigidity of locked coil cables with outer layers made of shaped wires. In order to validate this model, numerical results are reported for two different locked coil cables. It is shown that the shaped wires in the outer layers of locked coil cables play an important role in the distribution of contact forces, slip initiation and cable unwinding.

Submitted by Luciana Sebin (lusebin@ufscar.br) on 2016-09-21T13:52:44Z No. of bitstreams: 1 DissVBF.pdf: 4418595 bytes, checksum: aaae3efb173c8760a1039251a31ea973 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-23T18:23:48Z (GMT) No. of bitstreams: 1 DissVBF.pdf: 4418595 bytes, checksum: aaae3efb173c8760a1039251a31ea973 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-09-23T18:24:01Z (GMT) No. of bitstreams: 1 DissVBF.pdf: 4418595 bytes, checksum: aaae3efb173c8760a1039251a31ea973 (MD5) / Made available in DSpace on 2016-09-23T18:24:10Z (GMT). No. of bitstreams: 1 DissVBF.pdf: 4418595 bytes, checksum: aaae3efb173c8760a1039251a31ea973 (MD5) Previous issue date: 2015-03-20 / Não recebi financiamento / The continuous demand growth for liquid fuels, alongside with the decrease of fossil oil reserves, unavoidable in the long term, induces investigations for new energy sources. A possible alternative is the use of bioethanol, produced by renewable resources such as sugarcane bagasse. Two thirds of the cultivated sugarcane biomass are sugarcane bagasse and leaves, not fermentable when the current, first-generation (1G) process is used. A great interest has been given to techniques capable of utilizing the carbohydrates from this material. Among them, production of second generation (2G) ethanol is a possible alternative. 2G ethanol requires two additional operations: a pretreatment and a hydrolysis stage. Regarding the hydrolysis, the dominant technical solution has been based on the use of enzymatic complexes to hydrolyze the lignocellulosic substrate. To ensure the feasibility of the process, a high final concentration of glucose after the enzymatic hydrolysis is desirable. To achieve this objective, a high solid consistency in the reactor is necessary. However, a high load of solids generates a series of operational difficulties within the reactor. This is a crucial bottleneck of the 2G process. A possible solution is using a fed-batch process, with feeding profiles of enzymes and substrate that enhance in the process yield and productivity. The main objective of this work was to implement and test a system to infer online concentrations of fermentable carbohydrates in the reactive system, and to optimize the feeding strategy of substrate and/or enzymatic complex, according to a model-based control strategy. Batch and fed-batch experiments were conducted in order to test the adherence of four simplified kinetic models. The model with best adherence to the experimental data (a modified Michaelis-Mentem model with inhibition by the product) was used to train an Artificial Neural Network (ANN) as a softsensor to predict glucose concentrations. Further, this ANN may be used in a closedloop control strategy. A feeding profile optimizer was implemented, based on the optimal control approach. The ANN was capable of inferring the product concentration from the available data with good adherence (Determination Coefficient of 0.972). The optimization algorithm generated profiles that increased a process performance index while maintaining operational levels within the reactor, reaching glucose concentrations close to those utilized in current first generation technology a (ranging between 156.0 g.L⁻¹ and 168.3 g.L⁻¹). However rough estimates for scaling up the reactor to industrial dimensions indicate that this conventional reactor design must be replaced by a two-stage reactor, to minimize the volume of liquid to be stirred. / A crescente demanda por combustíveis líquidos, bem como a diminuição das reservas de petróleo, inevitáveis a longo prazo, induzem pesquisas por novas fontes de energia. Uma possível solução é o uso do bioetanol, produzido de resíduos, como o bagaço de cana-deaçúcar. Dois terços da biomassa cultivada são bagaço e folhas. Estas frações não são fermentescíveis quando se usa a tecnologia de primeira geração atual (1G). Um grande interesse vem sendo prestado a técnicas capazes de utilizar os carboidratos deste material. Dentre elas, a produção de etanol de segunda geração (2G) é uma possível alternativa. Etanol 2G requer duas operações adicionais: etapas de pré-tratamento e hidrólise. Considerando a hidrólise, a técnica dominante tem sido a utilização de complexos enzimáticos para hidrolisar o substrato lignocelulósico. Para assegurar a viabilidade do processo, uma alta concentração final de glicose é necessária ao final do processo. Para atingir esse objetivo, uma alta concentração de sólidos no reator é necessária. No entanto, uma carga grande de sólidos gera uma série de dificuldades operacionais para o processo. Este é um gargalo crucial do processo 2G. Uma possível solução é utilizar um processo de batelada alimentada, com perfis de alimentação de enzima e substrato para aumentar produtividade e rendimento. O principal objetivo deste trabalho é implementar e testar um sistema para inferir concentração de carboidratos fermentescíveis automaticamente e otimizar a política de substrato e/ou enzima em tempo real, de acordo com uma estratégia de controle baseada em modelo cinético. Experimentos de batelada e batelada alimentada foram realizados a fim de testar a aderência de 4 modelos cinéticos simplificados. O modelo com melhor aderência aos dados experimentais (um modelo de Michaelis-Mentem modificado com inibição por produto) foi utilizado para gerar dados a fim de treinar uma rede neural artificial para predizer concentrações de glicose automaticamente. Em estudos futuros, esta rede pode ser utilizada para compor o fechamento da malha de controle. Um otimizador de perfil de alimentação foi implementado, este foi baseado em uma abordagem de controle ótimo. A rede neural foi capaz de predizer a concentração de produto com os dados disponíveis de maneira satisfatória (Coeficiente de Determinação de 0.972). O algoritmo de otimização gerou perfis que aumentaram a performance do processo enquanto manteve as condições da hidrólise dentro de níveis operacionais, e gerou concentrações de glicose próximas as obtidas pelo caldo de cana-de-açúcar da primeira geração (valores entre 156.0 g.L ¹ e 168.3 g.L ¹). No entanto, estimativas iniciais de ⁻ ⁻ aumento de escala do processo demonstraram que para atingir dimensões industriais o projeto do reator utilizado deve ser analisado, substituindo o mesmo por um processo em dois estágios para diminuir o volume do reator e energia para agitação.

Les calculs d'équilibres à triphasiques et quadriphasiques sont au cœur des simulations de réservoirs impliquant des processus de récupérations tertiaires. Dans les procédés d'injection de gaz ou de vapeur, le système huile-gaz est enrichi d'une nouvelle phase qui joue un rôle important dans la récupération de l'huile en place. Les calculs d'équilibres représentent la majeure partie des temps de calculs dans les simulations de réservoir compositionnelles où les routines thermodynamiques sont appelées un nombre conséquent de fois. Il est donc important de concevoir des algorithmes qui soient fiables, robustes et rapides. Dans la littérature peu de simulateurs basés sur des équations d'état sont applicables aux procédés de récupération thermique. A notre connaissance, il n'existe pas de simulation thermique complètement compositionnelle de ces procédés pour des cas d'applications aux huiles lourdes. Ces simulations apparaissent essentielles et pourraient offrir des outils améliorés pour l’étude prédictive de certains champs. Dans cette thèse, des algorithmes robustes et efficaces de calculs d’équilibre multiphasiques sont proposés permettant de surmonter les difficultés rencontrés durant les simulations d'injection de vapeur pour des huiles lourdes. La plupart des algorithmes d'équilibre de phases sont basés sur la méthode de Newton et utilisent les variables conventionnelles comme variables indépendantes. Dans un premier temps, des améliorations de ces algorithmes sont proposées. Les variables réduites permettent de réduire la dimensionnalité du système de nc (nombre de composants) dans le cas des variables conventionnelles, à M (M<<nc), et sont déjà utilisées dans certains simulateurs de réservoirs commerciaux. La méthode de réduction proposée par Nichita and Graciaa (Fluid Phase Equil. 302 (2011) 226-233) est étendue à l'analyse de stabilité et aux calculs d'équilibres multiphasiques. A l'inverse des précédentes méthodes de réduction, les variables ne sont pas bornées. La méthode de Newton nécessite une Hessienne définie positive pour pouvoir être utilisée. D'autres méthodes de minimisations sont testées permettant de s'affranchir de cette contrainte; les méthodes Quasi-Newton et Trust-Region qui garantissent une direction de descente à chaque itération. Ces dernières présentent un grand intérêt puisqu'elles permettent de réaliser des pas supra-linéaires (même lorsque la Hessienne n'est pas définie positive) et quadratiques (Trust-Region) ou proches de quadratiques (Quasi-Newton) dans le cas contraire. Un nouveau vecteur de variables indépendantes est proposé (construit afin d'obtenir une meilleure mise échelle du problème) et utilisé au sein d'un algorithme BFGS modifié. De même, une méthode de Trust-Region est développée pour les problèmes de tests de stabilités et d'équilibres multiphasiques. Ensuite, considérant le fluide comme semi-continu, une méthodologie basée sur une procédure de quadrature Gaussienne est proposée pour calculer mathématiquement les pseudo-composants capables de représenter le comportement du fluide. La méthodologie peut être vue comme une procédure de groupement/dégroupement, applicable pour tout nombre de points de quadratures et toute composition de mélange. Dans une dernière partie, un algorithme général pour le calcul d’équilibre multiphasique est présenté incluant tous les algorithmes développés. Ce dernier est testé et validé contre des données expérimentales et de la littérature. Des simulations triphasiques et quadriphasiques d'injection de CO2 démontrent la capacité du programme à traiter un nombre arbitraire de phases. Des simulations de balayages par la vapeur sont réalisées pour des réservoirs montrant d'importantes hétérogénéités. Finalement, une simulation complètement compositionnelle du processus de Steam Assisted Gravity Drainage est réalisée. A notre connaissance, il s'agit de la première simulation de la sorte pour des cas d'applications d'huiles lourdes. / Three to four phase equilibrium calculations are in the heart of tertiary recovery simulations. In gas/steam injection processes, additional phases emerging from the oil-gas system are added to the set and have a significant impact on the oil recovery. The most important computational effort in many chemical process simulators and in petroleum compositional reservoir simulations is required by phase equilibrium and thermodynamic property calculations. In field scale reservoir simulations, a huge number of phase equilibrium calculations is required. For all these reasons, the algorithms must be robust and time-saving. In the literature, few simulators based on equations of state (EoS) are applicable to thermal recovery processes such as steam injection. To the best of our knowledge, no fully compositional thermal simulation of the steam injection process has been proposed with extra-heavy oils; these simulations are essential and will offer improved tools for predictive studies of the heavy oil fields. Thus, in this thesis different algorithms of improved efficiency and robustness for multiphase equilibrium calculations are proposed, able to handle conditions encountered during the simulation of steam injection for heavy oil mixtures. Most of the phase equilibrium calculations are based on the Newton method and use conventional independent variables. These algorithms are first investigated and different improvements are proposed. Michelsen’s (Fluid Phase Equil. 9 (1982) 21-40) method for multiphase-split problems is modified to take full advantage of symmetry (in the construction of the Jacobian matrix and the resolution of the linear system). The reduction methods enable to reduce the space of study from nc (number of components) for conventional variables to M (M<<nc) and are already used in some commercial reservoir simulators. The reduction method proposed by Nichita and Graciaa (Fluid Phase Equil. 302 (2011) 226-233) is extended to phase stability analysis and multiphase-split calculations. Unlike previous reduction methods, the set of variables is unbounded and the convergence path is the same as in conventional methods using the logarithm of equilibrium constants as variables. The Newton method requires a positive definite Hessian for convergence. Other kinds of minimization methods are investigated which overcome this constraint; the Quasi-Newton and Trust-region methods always guarantee a descent direction. These methods represent an interesting alternative since they can reach supra-linear steps even when the Hessian is non-positive definite, and can reach quadratic steps (Trust-Region) or nearly quadratic steps (Quasi-Newton) otherwise. A new set of independent variables is proposed (designed to ensure a better scaling of the problem) for a modified BFGS (which ensures the positive definiteness of the approximation of the Hessian matrix) algorithm and a Trust-Region method is also proposed for the stability-testing and phase-split problems. Subsequently, by assuming the fluid composition as semi-continuous, a methodology based on a Gaussian quadrature is proposed to mathematically compute a set of pseudo-components capable of representing the fluid behavior. The methodology can be seen as a lumping-delumping procedure, applicable to any number of quadrature points and to any feed distribution. In a last part, a general multiphase flash procedure implementing all the developed algorithms is presented, and tested against experimental and literature data. Three- and four phase CO2 injection simulations demonstrate the capability of the program to handle any number of phases. Simulations of steam flooding are performed for highly heterogeneous reservoirs. Finally, a fully compositional simulation of the steam assisted gravity drainage process is realized. To the best of our knowledge, this is the first simulation of the kind for heavy oil mixtures.

In light of increasing harmful algal blooms and the need to protect human health and aquatic resources, proactive management approaches merit further study. For this purpose I conducted field samplings to characterize plankton community composition and laboratory experiments to test some approaches to new management schemes in the lower Rincon Delta. On site measurements and microscopic analysis showed that environmental parameters and plankton community composition varied considerably among sampling stations and sampling dates. A recent modeling study suggested that manipulation of freshwater inflow to estuaries might prevent phytoplankton blooms and enhance secondary productivity. To test this theory I conducted three semi-continuous design and flow-through incubation design experiments using natural plankton assemblages. I investigated the effect of two different pulsing regimes of inflow and nutrient loading on zooplankton densities, and phytoplankton biomass and diversity. Despite differences in zooplankton structure and phytoplankton community composition between the two experiment designs, the results confirmed that pulsed inflows might alter plankton dynamics. My findings showed that 3-day pulse treatments consistently supported greater zooplankton densities and higher phytoplankton species diversity when compared to 1-day pulse treatments. In addition, accumulation of phytoplankton biovolume remained low during 3-day pulse treatments. Differences in zooplankton performance between 3-day pulse and 1-day pulse inflow treatments were likely due to the ability of phytoplankton to uptake and store greater amounts of nutrients under conditions of 3-day pulse inflow. This resulted in food of higher quality for zooplankton, and might have supported greater zooplankton population growth rates. Additionally, in an attempt to understand the mechanisms leading to high biodiversity in aquatic ecosystems, I built a resource-storage model and studied the effects of resource-storage on competition of multiple phytoplankton species on multiple abiotic resources. I compared this model with a well-established multi-species competition model. My results showed that for certain species combinations a resource-storage-based model can generate dissimilar outcomes when compared to a model without resource-storage.

In light of increasing harmful algal blooms and the need to protect human health and aquatic resources, proactive management approaches merit further study. For this purpose I conducted field samplings to characterize plankton community composition and laboratory experiments to test some approaches to new management schemes in the lower Rincon Delta. On site measurements and microscopic analysis showed that environmental parameters and plankton community composition varied considerably among sampling stations and sampling dates. A recent modeling study suggested that manipulation of freshwater inflow to estuaries might prevent phytoplankton blooms and enhance secondary productivity. To test this theory I conducted three semi-continuous design and flow-through incubation design experiments using natural plankton assemblages. I investigated the effect of two different pulsing regimes of inflow and nutrient loading on zooplankton densities, and phytoplankton biomass and diversity. Despite differences in zooplankton structure and phytoplankton community composition between the two experiment designs, the results confirmed that pulsed inflows might alter plankton dynamics. My findings showed that 3-day pulse treatments consistently supported greater zooplankton densities and higher phytoplankton species diversity when compared to 1-day pulse treatments. In addition, accumulation of phytoplankton biovolume remained low during 3-day pulse treatments. Differences in zooplankton performance between 3-day pulse and 1-day pulse inflow treatments were likely due to the ability of phytoplankton to uptake and store greater amounts of nutrients under conditions of 3-day pulse inflow. This resulted in food of higher quality for zooplankton, and might have supported greater zooplankton population growth rates. Additionally, in an attempt to understand the mechanisms leading to high biodiversity in aquatic ecosystems, I built a resource-storage model and studied the effects of resource-storage on competition of multiple phytoplankton species on multiple abiotic resources. I compared this model with a well-established multi-species competition model. My results showed that for certain species combinations a resource-storage-based model can generate dissimilar outcomes when compared to a model without resource-storage.