published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

Biofuel production from microalgal biomass offers a clean and sustainable liquid fuel alternative to fossil fuels. In addition, algae cultivation is advantageous over traditional biofuel feedstocks as (i) it does not compete with food production, (ii) it potentially has a much greater areal productivity, (iii) it does not require arable land, and (iv) it can use marginal sources of water not suitable for irrigation or drinking. However, current algae cultivation technologies suffer from (i) low solar energy conversion effiencies, (ii) large thermal fluctuations which negatively affect the productivity, and (iii) large evaporative losses which make the process highly water intensive. This thesis reports a numerical study that address these key issues of planktonic as well as benthic algal photobioreactor technologies. First, radiant energy transfer in planktonic algal photobioreactors containing cells with different levels of pigmentation was studied. Chlamydomonas reinhardtii and its truncated chlorophyll antenna transformant tla1 were used as model organisms. Based on these simulations guidelines are derived for scaling the size and microorganism concentration of photobioreactors cultivating cells with different levels of pigmentation to achieve maximum photosynthetic productivity. To achieve this, the local irradiance obtained from the solution of the radiative transport equation (RTE) was coupled with the specific photosynthetic rates of the microorganisms to predict both the local and total photosynthetic rates in a photobioreactor. For irradiances less than 50 W/m2, the use of genetically modified strains with reduced pigmentation was shown to have negligible effect on increasing photobioreactor productivity. However, at irradiances up to 1000 W/m2, improvements of up to 30% were possible with cells having 63% less pigment concentration. It was determined that the ability of tla1 to transmit light deeper into the photobioreactor was the primary mechanism by which a photobioreactor using the modified strain can achieve greater productivity. Furthermore, it was determined photobioreactors using each strain have dead zones in which the local photosynthetic rate is negligible due to nearly complete light attenuation. These dead zones occur at local optical thicknesses greater than 169 and 275 in photobioreactors using the wild strain and the genetically modified strain, respectively. In addition, a thermal model of an algae biofilm photobioreactor was developed to assess the thermal fluctuations and evaporative loss rate of these novel photobioreactors under varying outdoor conditions. The model took into account air temperature, irradiance, relative humidity, and wind speed as inputs and computed the temperature and evaporative loss rate as a function of time and location in the photobioreactor. The model was run for a week-long period in each season using weather data from Memphis, TN. The range of the daily algae temperature variation was observed to be 13.2C, 12.4C, 12.8C, and 9.4C in the spring, summer, winter, and fall, respectively. Furthermore, without active cooling, the characteristic evaporative water loss from the system is approximately 6.3 L/m2-day, 7.0 L/m2-day, 4.9 L/m2-day, and 1.5 L/m2-day in the spring, summer, fall, and winter, respectively. / text

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I investigated how competitor species respond to chemical cues released from the red tide dinoflagellate Karenia brevis. K. brevis produces a mix of unstable, relatively polar, allelopathic organic molecules that are produced and released at low concentrations. The production of these compounds also varies greatly within and among strains of K. brevis. The majority of these compounds caused sublethal reductions in competitor growth. In laboratory experiments, these compounds inhibited the growth of competitors Asterionellopsis glacialis, Skeletonema grethae, Prorocentrum minimum, and Akashiwo sanguinea, although each species was susceptible to a different sub-set of K. brevis compounds. Cell physiological state and population densities were important in dictating the susceptibility of competitors to allelopathy: phytoplankton were most susceptible to K. brevis allelopathy when in earlier growth stages (rather than later stages) and in lower cell concentrations. However, these compounds have limited negative effects on natural, mixed populations of competitors from both near and offshore environments, and competitors from inshore and offshore environments appear to respond similarly to K. brevis allelopathy. In the sensitive competitor, Thalassiosira pseudonana, allelopathic compounds ultimately caused a reshuffling of cellular nitrogen pools, altered carbon storage and impaired osmotic regulation as determined using a nuclear magnetic resonance (NMR) based metabolomics approach. By characterizing the pool of primary metabolites present in the cell after exposure to K. brevis cues, we inferred which metabolic pathways may be affected by allelopathy. For instance, concentrations of betaine and the aromatic metabolite homarine were suppressed, indicating that K. brevis allelopathy may disrupt this competitor’s ability to osmoregulate. Exposure to K. brevis cues enhanced the concentrations of glutamate and the fatty acid caprylate/caprate in T. pseudonana, suggesting that protein degradation was enhanced and that energy metabolism was altered. This contrasts with the response to K. brevis allelopathy of the diatom Asterionellopsis glacialis, which was much more resistant to chemical cues produced by K. brevis, likely through as yet unidentified detoxification pathways. Overall, my dissertation research provides insight into how species-specific, antagonistic interactions among phytoplankton competitors can affect community structure through direct or indirect mechanisms, highlights the potential role of allelopathy in the maintenance of K. brevis blooms, and uses a novel tool set (i.e., metabolomics) to determine the molecular targets of K. brevis allelopathy. It further demonstrates that planktonic communities are complex and dynamic ecological systems and that interspecific interactions between phytoplankton can have unexpected, cascading impacts in marine systems.

Sea-ice ecosystem modelling is a novel field of research. In this thesis, the main organism studied is sea-ice algae. A basic introduction to algae and its importance in the aquatic food web is given first. An introduction to modeling and its purposes is presented, and this is followed by a brief description of ice algae models in practice with some physical conditions which influence ecosystem modelling. In the following Chapter, a simple mathematical model to represent the algae population is derived, and analyzed using pseudo spectral numerical methods implemented with MATLAB. The behaviour of the algae population and the boundary layers are discussed by examining the numerical results. Perturbation and asymptotic analysis is used for further analysis of the system using Maple. In the following Chapter a Nutrient Phytoplankton Zooplankton Detritus (or NPZD) model, which is a commonly used type of model in marine ecosystem modelling, is developed based on the framework of Soetaert and Herman. The model is examined under five different experimental setups (herein we mean numerical experiments) and the results are discussed. The NPZD model implemented is compared with a well-studied model in the literature. Our model can be considered somewhat simpler than other models in the literature (though it still has a much larger parameter space than the idealized model discussed in the previous Chapter). Finally we discuss future directions for research.

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This experiment manipulated water levels in boreal marshes within the Saskatchewan River Delta, a 9500 km2 region in northern Canada. Water levels in three wetland cells were lowered in a partial drawdown by a mean of 0.32 m. Water clarity, nutrient concentrations, and periphyton nutrient limitation were measured over the summer preceding and the summer following manipulation. The water levels of three adjacent control wetlands were not manipulated. Lowering wetland water levels reduced the wind velocity necessary to resuspend bottom sediments, which led to increases in turbidity, dissolved organic carbon, and concentrations of organic and inorganic nitrogen and phosphorus. Prior to drawdown, wetland periphyton communities were limited by nitrogen or co-limited by nitrogen and phosphorus. The input of nutrients from the sediment resulted in a shift from nutrient deficiency to nutrient sufficiency. Periphyton and phytoplankton production increased in response to the nutrient input. Increased turbidity, nutrient concentrations, and algal production were correlated with depth, rather than being inherent to the drawdown condition. Other water level manipulation studies have found that a reflood after a period of total drawdown caused a pulse of nutrients leaching from decomposing litter. This work suggests that these changes may not require complete drying out of sediments, or the input of large amounts of litter from drowned annual mudflat species, but rather can occur when depths are shallow enough that sediments are more frequently resuspended by wind. These findings have implications for future management of these marshes for waterfowl and muskrat production.

Didymosphenia geminata (Didymo) is a nuisance, bloom forming, invasive freshwater algae. Through an ecological survey I examined habitat associations and effects, identifying bloom preferences for stable, low nutrient rivers, often downstream of still waterbodies; with major observed changes to algal and invertebrate communities. Experimental examination of the functional significance of blooms, provided strong support for the hypothesis that blooms are an adaptive, plastic ecophysiological response to nutrient limitation, maximising internal mat cycling and phosphatase based uptake. Further experimentation identified Didymo absence from higher nutrient waterways, is explained by competition with other algae and suppression of the 'bloom' response. Research suggests Didymo is here to stay, but spread management and mitigation will minimise damage to New Zealand's waterways.

Baigiamajame darbe apžvelgiamos organinių medžiagų skaidymo ultragarsu sistemos. Didžiausias dėmesys skiriamas dumblių skaidymo ultragarsu sistemoms. Apžvelgiamos dumblių pritaikymo, jų auginimo ir išgavimo tendencijos. Nagrinėjama išilginių virpesių ultragarsinė dumblių skaidymo sistema „UIP 1000hd”. Darbo tikslas - Standartinio ultragarsinio įrenginio(UIP1000hd Set ) pagalba ištirti botanikos institute auginamų dumblių (augalinių bioląstelių) skaidymo galimybę. Darbo uždaviniai: 1. Įsisavinti naują ultragarsinę įrangą, išmokti naudoti įvairius titaninius koncentratorius, nustatyti reikiamus augalinių bioląstelių skaidymo režimus, išmokti registruoti ultragarsinės sistemos elektrinius ir mechaninius parametrus. 2. Susipažinti su pramoninių dumblių auginimo specifika. Kartu su Botanikos instituto mokslininkais organizuoti tyrimo objekto - dumblių(augalinių bioląstelių) bandomosios partijos užauginimą. 3. Išdirbti dumblių skaidymo lygio vertinimo (tyrimo) metodiką. 4. Išdirbti dumblių skaidymo tyrimo įrenginiu UIP1000hd Set metodiką. 5. Atlikti ultragarsinės sistemos ir kavituojamo skysčio su organine medžiaga virpesių pasiskirstymo analizę ( sistemos kompiuterinis modeliavimas turimomis laboratorijoje programomis). 6. Iš elektrinės ir mechaninės pusės ištirti ultragarsinę sistemą : nustatyti varžines - dažnumines ir amplitudines – dažnumines charakteristikas esant įvairioms elektrin4ms galioms, laisvame ir apkrautame režime. 7. Atlikti 2-3 rūšių pramoninių dumblių... [toliau žr. visą tekstą] / The Master’s Thesis provides an overview on the systems of organic matter decomposition by ultrasound. The focus is on the systems of algal ultrasound decomposition. The tendencies of algae adaptation, cultivation and extraction were reviewed. The ultrasonic algae decomposition system of longitudinal oscillation named “UIP 1000hd” was analyzed. The aims and objectives of the thesis: The aim - is to examine the decomposition possibility of algae (bio cells) growing in the Botanical Institute with the help of standard ultrasound device (UIP1000hd Set). Objectives: 1. To learn about the new ultrasound equipment, learn to use a variety of titanium concentrators, set the required decomposition modes of bio cells, learn to record electrical and mechanical parameters of the ultrasound system. 2. To familiarize with the specifics of industrial algae cultivation. To organize the experimental batch cultivation of the object of the research - algae (plant bio cells) - together with scientists of the Botanical Institute. 3. To master the assessment (research) methodology of the level of algae division. 4. To master the methodology of the algae decomposition equipment UIP1000hd Set. 5. To carry out the distribution of vibration analysis of the ultrasound system and the cativating with the organic matter (the system modeling by computer using programs that are in the Laboratory). 6. To investigate the electrical and mechanical sides of the ultrasound system: to set... [to full text]