Three strains of cyanobacteria (Anabaena PCC7120, A. variabilis and Nostoc commune), all belonging to the family Nostocaceae, were found to be capable of modulating the production and chemical composition of extracellular polysaccharides (EPS) in response to carbon and nitrogen availability as well as pH. While the carbohydrate compositions of the glycans produced by the different organisms were indicative of their recent evolutionary divergence, there were measurable differences that were dependent upon growth conditions. The EPS resulting from biofilm growth conditions was reduced in glucuronic acid levels in both Anabaena variabilis ATCC 29413 and Anabaena PCC 7120. Under planktonic conditions, the glycan from A. variabilis contained glucuronic acid when grown in nitrate-free BG-11₀ medium whereas A. PCC 7120 produced similar levels in standard BG-11 medium. This suggests that phylogeneticallyrelated cyanobacteria respond very differently to changes in their local environment. The pH of BG-11 cultures increased to 9-10 for all three strains of cyanobacteria. The increase resulted in an increase in the amount of dissolved inorganic carbon available in the medium, creating an imbalance in the carbon-nitrogen ratio, with the complete consumption of 17.65 mmol L⁻¹ nitrates raising the pH to near 10 in BG-11 medium. While increased carbon availability has been shown to induce capsulated morphologies in strains of cyanobacteria, only Nostoc commune DRH-1 exhibited this behavior, and only when grown in BG-11 medium. Carbon and nitrogen availability as well as pH modulate the monosaccharide composition of the glycan generated by cyanobacteria investigated. The different characteristics of the glycans produced can affect the survivability of the organisms and the community structure of cyanobacterial biofilms and microbial mats found in nature. As cyanobacteria are ubiquitous organism both now and in the past, they play a pivotal role in the biological and geological processes of the Earth, controlling the availability and cycling of carbon and nitrogen both actively and passively. / Master of Science in Life Sciences

O presente trabalho avaliou o efeito da relação \'C\'/\'N\' na produção biológica de hidrogênio a partir de água residuária sintética a base de sacarose. Reatores de leito fixo e fluxo ascendente, com polietileno de baixa densidade reciclado para adesão da biomassa, foram operados a 25°C e com um tempo de detenção hidráulica (TDH) de 2 horas. Analisaram-se diferentes relações \'C\'/\'N\' (40, 90, 140 e 190), usando a sacarose e a uréia como fontes de carbono e nitrogênio, respectivamente. Os valores médios de produtividade de \'H IND.2\' foram de 0,6 mol-\'H IND.2\'/mol-sac, 1,3 mol-\'H IND.2\'/mol-sac, 2,2 mol-\'H IND.2\'/mol-sac e 1,7 mol-\'H IND.2\'/mol-sac quando operados os reatores com relações \'C\'/\'N\' iguais a 40, 90, 140 e 190, respectivamente. Encontrou-se um valor ótimo para \'C\'/\'N\' de 137, que resultaria em produtividade de \'H IND.2\' de 3,5 mol-\'H IND.2\'/mol-sac, valor igual ao alcançado na relação \'C\'/\'N\' de 140. O biogás produzido foi composto de \'H IND.2\' e \'CO IND.2\', com valores médios porcentuais para o \'H IND.2\' de 53%, 49%, 61% e 52% para as relações \'C\'/\'N\' de 40, 90, 140 e 190, respectivamente. Os principais produtos intermediários produzidos durante a produção de \'H IND.2\' foram similares em todas as relações \'C\'/\'N\', sendo principalmente detectados ácido acético, ácido butírico e etanol. Sob excesso de nitrogênio, o crescimento da biomassa foi maior com efeitos negativos sobre a produção de hidrogênio, enquanto carência de nitrogênio permitiu o controle do crescimento da biomassa e resultou em maiores produtividades de hidrogênio. Durante os experimentos observou-se queda na produção do biogás provavelmente por atuação de bactérias hidrogênio-oxidantes. / This study evaluated the effect of the carbon/nitrogen (\'C\'/\'N\') ratio on the hydrogen production from a sucrose-based synthetic wastewater. Up-flow fixed-bed anaerobic reactors with recycled low-density polyethylene for biomass attachment, were operated at 25ºC and with a 2 hours time of hydraulic detention. Several \'C\'/\'N\' relationship were studied (40, 90, 140 and 190), using sucrose and urea as carbon and nitrogen sources, respectively. The average value of the hydrogen productivity were 0,6 mol-\'H IND.2\'/mol-suc, 1,3 mol-\'H IND.2\'/mol-suc, 2,7 mol-\'H IND.2\'/mol-suc e 1,7 mol-\'H IND.2\'/mol-suc they were reached when the reactors were operated with \'C\'/\'N\' of 40, 90, 140 and 190, respectively. It was found an optimal value for \'C\'/\'N\' of 137, which would result in productivity of 3,5 mol-\'H IND.2\'/mol-suc, an amount equal to that achieved in the \'C\'/\'N\' relationship of 140. Biogas produced was composed of \'H IND.2\' and \'CO IND.2\', with average \'H IND.2\' content 53%, 49%, 61% and 52% for \'C\'/\'N\' of 40, 90, 140 e 190, respectively. The mainly intermediary products during \'H IND.2\' fermentation were similar for all the \'C\'/\'N\' ratios, being specially detected acetic acid, butyric acid and ethanol. Under excess of nitrogen the biomass growth is higher with negative effects on hydrogen production while deprivation of nitrogen permits the control of biomass growth and results in higher hydrogen productivity. During the experiments it was been observed decline in the biogas production, probably because of the action of the hydrogen-oxidizing bacteria.

O presente trabalho avaliou o efeito da relação \'C\'/\'N\' na produção biológica de hidrogênio a partir de água residuária sintética a base de sacarose. Reatores de leito fixo e fluxo ascendente, com polietileno de baixa densidade reciclado para adesão da biomassa, foram operados a 25°C e com um tempo de detenção hidráulica (TDH) de 2 horas. Analisaram-se diferentes relações \'C\'/\'N\' (40, 90, 140 e 190), usando a sacarose e a uréia como fontes de carbono e nitrogênio, respectivamente. Os valores médios de produtividade de \'H IND.2\' foram de 0,6 mol-\'H IND.2\'/mol-sac, 1,3 mol-\'H IND.2\'/mol-sac, 2,2 mol-\'H IND.2\'/mol-sac e 1,7 mol-\'H IND.2\'/mol-sac quando operados os reatores com relações \'C\'/\'N\' iguais a 40, 90, 140 e 190, respectivamente. Encontrou-se um valor ótimo para \'C\'/\'N\' de 137, que resultaria em produtividade de \'H IND.2\' de 3,5 mol-\'H IND.2\'/mol-sac, valor igual ao alcançado na relação \'C\'/\'N\' de 140. O biogás produzido foi composto de \'H IND.2\' e \'CO IND.2\', com valores médios porcentuais para o \'H IND.2\' de 53%, 49%, 61% e 52% para as relações \'C\'/\'N\' de 40, 90, 140 e 190, respectivamente. Os principais produtos intermediários produzidos durante a produção de \'H IND.2\' foram similares em todas as relações \'C\'/\'N\', sendo principalmente detectados ácido acético, ácido butírico e etanol. Sob excesso de nitrogênio, o crescimento da biomassa foi maior com efeitos negativos sobre a produção de hidrogênio, enquanto carência de nitrogênio permitiu o controle do crescimento da biomassa e resultou em maiores produtividades de hidrogênio. Durante os experimentos observou-se queda na produção do biogás provavelmente por atuação de bactérias hidrogênio-oxidantes. / This study evaluated the effect of the carbon/nitrogen (\'C\'/\'N\') ratio on the hydrogen production from a sucrose-based synthetic wastewater. Up-flow fixed-bed anaerobic reactors with recycled low-density polyethylene for biomass attachment, were operated at 25ºC and with a 2 hours time of hydraulic detention. Several \'C\'/\'N\' relationship were studied (40, 90, 140 and 190), using sucrose and urea as carbon and nitrogen sources, respectively. The average value of the hydrogen productivity were 0,6 mol-\'H IND.2\'/mol-suc, 1,3 mol-\'H IND.2\'/mol-suc, 2,7 mol-\'H IND.2\'/mol-suc e 1,7 mol-\'H IND.2\'/mol-suc they were reached when the reactors were operated with \'C\'/\'N\' of 40, 90, 140 and 190, respectively. It was found an optimal value for \'C\'/\'N\' of 137, which would result in productivity of 3,5 mol-\'H IND.2\'/mol-suc, an amount equal to that achieved in the \'C\'/\'N\' relationship of 140. Biogas produced was composed of \'H IND.2\' and \'CO IND.2\', with average \'H IND.2\' content 53%, 49%, 61% and 52% for \'C\'/\'N\' of 40, 90, 140 e 190, respectively. The mainly intermediary products during \'H IND.2\' fermentation were similar for all the \'C\'/\'N\' ratios, being specially detected acetic acid, butyric acid and ethanol. Under excess of nitrogen the biomass growth is higher with negative effects on hydrogen production while deprivation of nitrogen permits the control of biomass growth and results in higher hydrogen productivity. During the experiments it was been observed decline in the biogas production, probably because of the action of the hydrogen-oxidizing bacteria.

No description available.

Recent studies have shown that permafrost soils in the northern circumpolar region store almost twice as much carbon as the atmosphere. Since soil organic carbon (SOC) pools have large regional and landscape-level variability, detailed SOC inventories from across the northern permafrost region are needed to assess potential remobilization of SOC with permafrost degradation and to quantify the permafrost carbon-climate feedback on global warming. This thesis provides high-resolution data on SOC storage in five study areas located in undersampled regions of the continuous permafrost zone (Zackenberg in NE Greenland; Shalaurovo and Cherskiy in NE Siberia; Ary-Mas and Logata in Taymyr Peninsula). The emphasis throughout the five different study areas is put on SOC partitioning within the landscape and soil horizon levels as well as on soil forming processes under periglacial conditions. Our results indicate large differences in mean SOC 0–100 cm storage among study areas, ranging from 4.8 to 30.0 kg C m-2, highlighting the need to consider numerous factors as topography, geomorphology, land cover, soil texture, soil moisture, etc. in the assessment of landscape-level and regional SOC stock estimates. In the high arctic mountainous area of Zackenberg, the mean SOC storage is low due to the high proportion of bare grounds. The geomorphology based upscaling resulted in a c. 40% lower estimate compared to a land cover based upscaling (4.8 vs 8.3 kg C m-2, respectively). A landform approach provides a better tool for identifying hotspots of SOC burial in the landscape, which in this area corresponds to alluvial fan deposits in the foothills of the mountains. SOC burial by cryoturbation was much more limited and largely restricted to soils in the lower central valley. In the lowland permafrost study areas of Russia the mean SOC 0–100 cm storage ranged from 14.8 to 30.0 kg C m-2. Cryoturbation is the main burial process of SOC, storing on average c. 30% of the total landscape SOC 0–100 cm in deeper C-enriched pockets in all study areas. In Taymyr Peninsula, the mean SOC storage between the Ary-Mas and Logata study areas differed by c. 40% (14.8 vs 20.8 kg C m-2, respectively). We ascribe this mainly to the finer soil texture in the latter study area. Grain size analyses show that cryoturbation is most prominent in silt loam soils with high coarse silt to very fine sand fractions. However, in profiles and samples not affected by C-enrichment, C concentrations and densities were higher in silt loam soils with higher clay to medium silt fractions. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.</p>

The influence of tree species on forest soils has been the subject of study for at least a century. Of particular interest have been western hemlock (Tsuga heterophylla (Raf.) Sarg.) and western redcedar (Thuja plicata Donn ex D. Don) – two of the most common tree species in coastal and southern British Columbia, but each with a different nutrient amplitude. It has generally been found that acid, mycogeneous Mor humus forms develop in hemlock stands, while less acid and more zoogenous Mormoder, Moder, or even Mull humus forms develop in redcedar stands. The objective of this study was to determine the influence of hemlock and redcedar, growing separately and together, on forest floor nutrient properties. The questions addressed were: (1) does each stand type have unique forest floor nutrient properties? and (2) can any forest floor nutrient property discriminate between stand types?