Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: David L. Kirchman, College of Marine and Earth Studies. Includes bibliographical references.

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Despite being abundant in the earth's crust, the concentration of Fe in many oceanic regions is so low that it is limiting to the growth of photosynthetic plankton. Heterotrophic bacteria play key roles in the oceanic cycling of carbon and nutrients, but it is unclear whether they can be Fe-deficient in nature, or what possible effects Fe-deficiency might have on their ecology and physiology. In chapter 1, I investigated the response of a natural bacterial community to a mesoscale Fe-enrichment experiment in the northeast subarctic Pacific. The addition of Fe to surface waters caused a rapid stimulation of bacterial growth and production, and induced the organic Fe uptake systems of bacteria. These findings suggest that bacteria responded directly to increased Fe availability, and may be Fe-deficient in situ. In chapter 2, I examined the effects of Fe-deficiency on the coupled processes of carbon catabolism and adenosine triphosphate (ATP) production in cultures of the marine bacterium Pseudoalteromonas haloplanktis. In Fe-limited cells, Fe-dependent oxidative pathways of ATP production were downregulated, leading to an intracellular energy deficit. Thus, by altering carbon metabolism and energy acquisition of heterotrophic bacteria, Fe may affect the cycling of carbon in parts of the sea.

Picoplankton, cells between 0.2 - 2 μm, play a vital role in the carbon flow and nutrient cycling in marine food webs. Auto- and heterotrophic picoplankton dominate the biomass of oligotrophic tropical and subtropical oceans. However, little is known about their vertical distribution, changes in space and time and their relationships with environmental variables in the central Red Sea. The goal of this Ph.D. dissertation is to obtain baseline knowledge about their abundance, cellular characteristics (cell size, relative pigment and nucleic acid content) and biomass at seasonal and high-frequency temporal resolution (every 2 hours). This dissertation also aims at assessing picoplankton responses to separate and joint effects of nutrients additions (inorganic, organic and mixed) and temperature in order to be able to predict the relative contribution of eutrophication and warming in the future standing stocks of picoplankton in the Red Sea. I conducted a total of 63 vertical profiles (15 at around noon plus 48 more from the high-frequency diel samplings) from the surface down to the bottom (ca. 700 m) at a station situated 6 km off the coast of King Abdullah Economic City (KAEC) in the central Red Sea and performed 4 nutrient and temperature experiments lasting each 6 days with surface waters from the harbor of King Abdullah University of Science and Technology (KAUST). Flow cytometry allowed me to consistently identify five groups of autotrophs (Prochlorococcus, two populations of Synechococcus separated by their relative phycoerythrin fluorescence, and two differently-sized groups of picoeukaryotes) and two groups of heterotrophic prokaryotes characterized by their different relative nucleic acid content. One of the most surprising findings is the relatively lower abundances and to a lesser extent also growth rates of picoplankton compared with other tropical and subtropical oceans. Seasonality in environmental conditions emerged as an important factor in the response of picoplankton to nutrient additions and temperature. Picoplankton mostly responded to inorganic and mixed nutrient additions rather than warming. Overall, the information provided in this dissertation fills the gap of a critical component of Red Sea pelagic ecosystems and expands the information available on picoplankton communities in tropical waters.

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Dominant genera of bacteria were isolated from three river waters during anthracene and pentachlorophenol biotransformation studies. The genera Pseudomonas, Acinetobacter, Micrococcus, Chromobacterium, Alcaligenes, Azomonos, Bacillus, and Flavobacterium were capable of biotransforming one or both of these compounds. These isolates were subjected to further biotransformation tests, including river water and a basal salt medium with and without additional glucose. The results of these experiments were evaluated statistically. It was concluded that only a limited number of the bacteria identified were able to transform these chemicals in river water. The addition of glucose to the growth medium significantly affected the biotransformation of these chemicals. It was also determined that the size of the initial bacterial population is not a factor in determining whether biotransformation of anthracene or pentachlorophenol can occur.

Submitted by (edna.saturno@ufrpe.br) on 2017-02-14T15:59:47Z No. of bitstreams: 1 Joao Paulo Viana de Lima.pdf: 751024 bytes, checksum: 12aea5280a52c50190be7cbe5d4985dc (MD5) / Made available in DSpace on 2017-02-14T15:59:47Z (GMT). No. of bitstreams: 1 Joao Paulo Viana de Lima.pdf: 751024 bytes, checksum: 12aea5280a52c50190be7cbe5d4985dc (MD5) Previous issue date: 2007-04-27 / The accumulation of toxic nitrogenous compounds in the water is a common problem to aquaculture systems. Recent works have showed good results in terms of production and nitrogen retention efficiency, through the addition of organic carbon source (sugar, molasses, etc). This work investigated the effect of molasses addition in different C:N ratios on the water quality, microbial activity and production, in semi-intensive experimental culture tanks of Litopenaeus vannamei with no water exchange. Four treatments and three replicates were adopted, which three with daily molasses addition in 5, 10 and 15:1 C:N ratio and one control with no carbon source addition. Twelve 500 L fiber glass tanks were stocked with 25 shrimps.m-2 (1.90±0.37 g). Shrimps were fed with a 35% crude protein commercial diet offered in feeding trays at 08:00 and 16:00. Phytoplankton, bacteria and water samples were collected fortnightly during the culture. The 15:1 and 10:1 C:N ratios showed lower (P<0.05) oxygen dissolved levels (4.64 and 4.76 mg L-1, respectively) which is related with the major organic carbon supply in these ratios. Molasses addition resulted in lower (P<0.05) nitrogenous compounds levels (nitrite and nitrate), as well reducing in the cianobacteria densities in the C:N 10 and 15:1 treatments. No significant differences (P≥0.05) were found in Vibrio spp, autotrophic and heterotrophic bacterial densities. Shrimp final weight (~12.3 g)and weigth gain (~1.04 g.week-1) in high C:N ratios (10:1 and 15:1) were higher (P<0.05) than in the others treatments. Specific growth rate was high in all treatments (2.53 to 2.69 % day-1), but the 10:1 ratio was higher than the control. Yield values ranged from 267.4 to 301.0 g m-2 with no significant difference (P≥0.05) among treatments. This study shows that the molasses can be used as carbon source in order to increase C:N ratio, improving the water quality and the L. vannamei semi-intensive culture performance with no water exchange. / O acúmulo de formas tóxicas de compostos nitrogenados na água é um grande problema para os sistemas aqüícolas. Pesquisas recentes têm demonstrado resultados satisfatórios em termos de produção e eficiência de retenção do nitrogênio, através da adição de fontes de carbono orgânico (açúcar, melaço, etc.). O presente estudo investigou o efeito da adição de melaço em diferentes relações C:N sobre a qualidade da água, atividade microbiana e a produção semi-intensiva do camarão Litopenaeus vannamei, em tanques de cultivo experimental sem renovação de água. Foram adotados quatro tratamentos e três réplicas, sendo três com aplicação diária de melaço nas relações C:N 5, 10 e 15:1, e um controle, sem aplicação desta fonte de carbono. Foram utilizados 12 tanques em fibra de vidro (500 L), estocados com 25 camarões.m-2 (1,90±0,37 g). A alimentação constou de ração comercial com 35% de proteína bruta e foi ofertada diariamente em bandejas às 8 e 16h. Coletas de água para análise química e de material biológico (fitoplâncton e bactérias) foram realizadas quinzenalmente ao longo do cultivo. As relações 15:1 e 10:1 apresentaram os menores (P<0,05) níveis de oxigênio dissolvido (4,64 e 4,76 mg L-1, respectivamente) que está relacionado ao maior aporte de carbono orgânico nestas relações. O melaço reduziu significativamente (P<0,05) as concentrações dos compostos nitrogenados, nitrito e nitrato, bem como reduziu as densidadesde cianobactérias nos ambientes com relações C:N de 10 e 15:1. Nenhum efeito (P≥0,05) foi observado em relação às bactérias autotróficas, heterotróficas e Vibrio spp. O peso final dos camarões (~12,3 g) e o ganho de peso individual (~1,04 g.semana-1), nas relações C:N mais altas (10:1 e 15:1), foram superiores (P<0,05) aos demais tratamentos. A taxa de crescimento específico foi elevada em todos os tratamentos (2,53 a 2,69 % dia-1), entretanto os indivíduos na relação 10:1 foi superior (P<0,05) ao controle. Os valores de produção variaram de 267,4 a 301,0 g m-2, e não foram diferentes estatisticamente (P≥0,05) entre os tratamentos. O melaço pode ser utilizado como fonte de carbono para incrementar a relação C:N, melhorando a qualidade da água e os níveis de produtividade em cultivo semi-intensivo de L. vannamei sem renovação de água.

O monitoramento da qualidade da água de diálise caracteriza uma importante ferramenta para a tomada de decisões quando resultados laboratoriais insatisfatórios são disponibilizados em curto período de tempo. Os inconvenientes relacionados ao tempo de espera para a obtenção dos resultados têm conduzido à busca de métodos microbiológicos alternativos que permitam obter dados exatos, precisos e em menor tempo do que os obtidos por métodos clássicos. Este projeto teve por finalidade avaliar o desempenho do método microbiológico alternativo para a contagem de bactérias heterotróficas em água tratada para diálise através da técnica de detecção microbiana pelo uso de fluorescência. Inicialmente foi realizada a determinação do tempo mínimo de incubação para obtenção de valores de contagem confiáveis pelo método alternativo, seguido pela avaliação de desempenho do método contemplando todos os parâmetros estabelecidos em compêndios nacionais e internacionais e a demonstração da equivalência do método alternativo frente ao método tradicional, através da avaliação de 23 amostras de água tratada para diálise. Os resultados demonstraram que o método alternativo permite a quantificação de bactérias heterotróficas após 40 horas de incubação, com exatidão e precisão para o range de 5 a 100 UFC/placa, resultando em uma redução de aproximadamente 67% do tempo atualmente empregado no método tradicional. Portanto, a técnica de detecção microbiana pelo uso de fluorescência se mostrou uma opção viável para a implementação de um método microbiológico rápido para a contagem de bactérias heterotróficas em amostras de água tratada para hemodiálise. / Monitoring the quality of dialysis water is an important tool for decision-making when unsatisfactory results are available in a short period of time. The drawbacks related to waiting time for obtaining results have led to the search for alternative microbiological methods that allow accurate data to be obtained in less time than those obtained by classical methods. This project aimed to evaluate the alternative microbiological method performance for the heterotrophic bacteria counts in dialysis treated water through the microbial detection technique using fluorescence. Initially, the determination of the minimum incubation time to obtain reliable count values by the alternative method was performed, followed by the performance evaluation of the method, considering all the parameters established in national and international compendiums and demonstrating the equivalence of the alternative method to the traditional method, through the evaluation of 23 samples of dialysis treated water. The results demonstrated that the alternative method allows quantification of heterotrophic bacteria after 40 hours of incubation, with accuracy and precision for the range of 5 to 100 CFU/plate, resulting in a reduction of approximately 67% of the time currently used in the traditional method. Therefore, the microbial detection technique using fluorescence showed a viable option for the implementation of a rapid microbiological method for the heterotrophic bacteria counts in samples of treated water for hemodialysis.

<p>Picophytoplankton were inferior competitors for inorganic phosphorus compared to heterotrophic bacteria. This may be due to the source of energy available for the heterotrophs, while cell-size was of minor importance. However, picophytoplankton were superior to large phytoplankton in the competition for nutrients at low concentrations. </p><p>Biomass of picophytoplankton was low in brownwater lakes and high in clearwater lakes, compared to the biomass of heterotrophic bacteria. The results suggest that picophytoplankton are inferior to heterotrophic bacteria in the competition for inorganic nutrients in brownwater lakes, where the production of heterotrophic bacteria is subsidized by humic dissolved organic carbon (DOC) </p><p>Relative to large phytoplankton, picophytoplankton were most important in lakes with intermediate water colour, despite the fact that the lowest nutrient concentrations were found in the clearwater lakes. Large phytoplankton in the clearwater lakes may be able to overcome nutrient competition with picophytoplankton by vertical migration.</p><p>In conclusion, changes in nutrient content, light availability and concentrations of DOC affect the interactions of heterotrophic bacteria, picophytoplankton and large phytoplankton and are therefore important factors for the structure of the food web in the pelagic zones of lakes.</p><p>Picophytoplankton (planktonic algae and cyanobacteria, < 2 µm) constitute an important component of pelagic food webs. They are linked to larger phytoplankton and heterotrophic bacteria through complex interactions including competition, commensalism and predation. In this thesis, field and laboratory studies on the competitive ability of picophytoplankton are reported.</p>