Photosynthetic efficiency and rate of CO2 assimilation by Arthrospira (Spirulina) platensis continuously cultivated in a tubular photobioreactor

Similar to other photosynthetic microorganisms, the cyanobacterium Arthrospira platensis can be used to produce pigments, single cell proteins, fatty acids (which can be used for bioenergy), food and feed supplements, and biofixation of CO2. Cultivation in a specifically designed tubular photobioreactor is suitable for photosynthetic biomass production, because the cultivation area can be reduced by distributing the microbial cells vertically, thus avoiding loss of ammonia and CO2. The aim of this study was to investigate the influence of light intensity and dilution rate on the photosynthetic efficiency and CO2 assimilation efficiency of A. platensis cultured in a tubular photobioreactor in a continuous process. Urea was used as a nitrogen source and CO2 as carbon source and for pH control. Steady-state conditions were achieved in most of the runs, indicating that continuous cultivation of this cyanobacterium in a tubular photobioreactor could be an interesting alternative for the large-scale fixation of CO2 to mitigate the greenhouse effect while producing high protein content biomass.

Stand-level patterns of carbon fluxes and partitioning in a Eucalyptus grandis plantation across a gradient of productivity, in Sao Paulo State, Brazil

Wood production represents a large but variable fraction of gross primary production (GPP) in highly productive Eucalyptus plantations. Assessing patterns of carbon (C) partitioning (C flux as a fraction of GPP) between above- and belowground components is essential to understand mechanisms driving the C budget of these plantations. Better knowledge of fluxes and partitioning to woody and non-woody tissues in response to site characteristics and resource availability could provide opportunities to increase forest productivity. Our study aimed at investigating how C allocation varied within one apparently homogeneous 90 ha stand of Eucalyptus grandis (W. Hill ex Maiden) in Southeastern Brazil. We assessed annual above-ground net primary production (ANPP: stem, leaf, and branch production) and total belowground C flux (TBCF: the sum of root production and respiration and mycorrhizal production and respiration), GPP (computed as the sum of ANPP, TBCF and estimated aboveground respiration) on 12 plots representing the gradient of productivity found within the stand. The spatial heterogeneity of topography and associated soil attributes across the stand likely explained this fertility gradient. Component fluxes of GPP and C partitioning were found to vary among plots. Stem NPP ranged from 554 g C m(-2) year(-1) on the plot with lowest GPP to 923 g C m(-2) year(-1) on the plot with highest GPP. Total belowground carbon flux ranged from 497 to 1235 g C m(-2) year(-1) and showed no relationship with ANPP or GPP. Carbon partitioning to stem NPP increased from 0.19 to 0.23, showing a positive trend of increase with GPP (R-2 = 0.29, P = 0.07). Variations in stem wood production across the gradient of productivity observed at our experimental site were a result of the variability in C partitioning to different forest system components.

Essays on firm efficiency with imperfectly competitive input markets: an empirical analysis

In the thesis I exploit an empirical analysis on firm'’s productivity. I relate the efficiency at plant level with the input market features and I suggest an estimation technique for production function that takes into account firm'’s liquidity constraints. The main results are three. When I consider services as inputs for manufacturing firm’'s production process, I find that more competition in service sector affects positively plant’s productivity and export decision. Secondly liquidity constraints are important for the calculation of firm'’s productivity because they are a second source of firm's heterogeneity. Third liquidity constraints are important for firm'’s internationalization

Modeling Responses of Diatom Productivity and Biogenic Silica Export to Iron Enrichment in the Equatorial Pacific Ocean

Using a three-dimensional physical-biogeochemical model, we have investigated the modeled responses of diatom productivity and biogenic silica export to iron enrichment in the equatorial Pacific, and compared the model simulation with in situ (IronEx II) iron fertilization results. In the eastern equatorial Pacific, an area of 540,000 km(2) was enhanced with iron by changing the photosynthetic efficiency and silicate and nitrogen uptake kinetics of phytoplankton in the model for a period of 20 days. The vertically integrated Chl a and primary production increased by about threefold 5 days after the start of the experiment, similar to that observed in the IronEx II experiment. Diatoms contribute to the initial increase of the total phytoplankton biomass, but decrease sharply after 10 days because of mesozooplankton grazing. The modeled surface nutrients (silicate and nitrate) and TCO(2) anomaly fields, obtained from the difference between the "iron addition'' and "ambient'' (without iron) concentrations, also agreed well with the IronEx II observations. The enriched patch is tracked with an inert tracer similar to the SF6 used in the IronEx II. The modeled depth-time distribution of sinking biogenic silica (BSi) indicates that it would take more than 30 days after iron injection to detect any significant BSi export out of the euphotic zone. Sensitivity studies were performed to establish the importance of fertilized patch size, duration of fertilization, and the role of mesozooplankton grazing. A larger size of the iron patch tends to produce a broader extent and longer-lasting phytoplankton blooms. Longer duration prolongs phytoplankton growth, but higher zooplankton grazing pressure prevents significant phytoplankton biomass accumulation. With the same treatment of iron fertilization in the model, lowering mesozooplankton grazing rate generates much stronger diatom bloom, but it is terminated by Si(OH)(4) limitation after the initial rapid increase. Increasing mesozooplankton grazing rate, the diatom increase due to iron addition stays at minimum level, but small phytoplankton tend to increase. The numerical model experiments demonstrate the value of ecosystem modeling for evaluating the detailed interaction between biogeochemical cycle and iron fertilization in the equatorial Pacific.

Biomass and Stored Carbohydrate Compensation after Above-Ground Biomass Removal in a Perennial Herb: Does Environmental Productivity Play a Role?

Many plant species are able to tolerate severe disturbance leading to removal of a substantial portion of the body by resprouting from intact or fragmented organs. Resprouting enables plants to compensate for biomass loss and complete their life cycles. The degree of disturbance tolerance, and hence the ecological advantage of damage tolerance (in contrast to alternative strategies), has been reported to be affected by environmental productivity. In our study, we examined the influence of soil nutrients (as an indicator of environmental productivity) on biomass and stored carbohydrate compensation after removal of aboveground parts in the perennial resprouter Plantago lanceolata. Specifically, we tested and compared the effects of nutrient availability on biomass and carbon storage in damaged and undamaged individuals. Damaged plants of P. lanceolata compensated neither in terms of biomass nor overall carbon storage. However, whereas in the nutrient-poor environment, root total non-structural carbohydrate concentrations (TNC) were similar for damaged and undamaged plants, in the nutrient-rich environment, damaged plants had remarkably higher TNC than undamaged plants. Based on TNC allocation patterns, we conclude that tolerance to disturbance is promoted in more productive environments, where higher photosynthetic efficiency allows for successful replenishment of carbohydrates. Although plants under nutrient-rich conditions did not compensate in terms of biomass or seed production, they entered winter with higher content of carbohydrates, which might result in better performance in the next growing season. This otherwise overlooked compensation mechanism might be responsible for inconsistent results reported from other studies.

Primary productivity and phytoplankton pigment measurements in the North Sea

During the culmination of the phytoplankton spring bloom in the Fladen Ground area in April-Mai 1976, gross primary production was between 1500 and 2000 mg particulate C m**-2 day**-1, at a crop density (mainly diatoms of the genus Chaetoceros) of about 1500-3500 mg C m**-2. Estimates of the C:chlorophyll a ratio in living cells were much lower than those reported in the literature, possibly because part of what is measured as "chlorophyll a" by the common fluorometric method is associated with particles that are not reported as cells. Most of the dark 14C fixation during the bloom's climax was due to abiotic processes. Excretion of 14C-labeled carbohydrates did not account for a significant fraction of the total photosynthetic rate. The low crop after the bloom period, in June, corresponded with nutrient depletion of the euphotic zone. The low photosynthetic efficiency in June may have been a gross underestimate. The presence of relatively high concentrations of chlorophyll derivatives signifies that the algal crop was consumed by heterotrophs, but at a lower rate in April/May than during the June cruise when particularly high molar ratios of phaeophorbide a and phaeophytin a relative to chlorophyll a were found. The high respiratory rate relative to autotrophic production in June manifested itself also in high dark 14C fixation values. The high concentration of phaeophorbide a in the upper 40 m and its scarcity below this depth during the spring bloom climax in April/May implies that copepod grazing at that time took place principally in the euphotic zone. The remarkably high concentration of chlorophyllide a in the surface layer during the bloom period indicates that the part of the crop that was destroyed by the grazers while eating was occasionally as high as the part that was actually ingested.

Enhancement of photosynthetic carbon assimilation efficiency by phytoplankton in the future coastal ocean

A mesocosm experiment was conducted to evaluate the effects of future climate conditions on photosynthesis and productivity of coastal phytoplankton. Natural phytoplankton assemblages were incubated in field mesocosms under the ambient condition (present condition: ca. 400 ppmv CO2 and ambient temp.), and two future climate conditions (acidification condition: ca. 900 ppmv CO2 and ambient temp.; greenhouse condition: ca. 900 ppmv CO2 and 3 °C warmer than ambient). Photosynthetic parameters of steady-state light responses curves (LCs; measured by PAM fluorometer) and photosynthesis-irradiance curves (P-I curves; estimated by in situ incorporation of 14C) were compared to three conditions during the experiment period. Under acidification, electron transport efficiency (alpha LC) and photosynthetic 14C assimilation efficiency (alpha) were 10% higher than those of the present condition, but maximum rates of relative electron transport (rETRm,LC) and photosynthetic 14C assimilation (PBmax) were lower than the present condition by about 19% and 7%, respectively. In addition, rETRm,LC and alpha LC were not significantly different between and greenhouse conditions, but PBmax and alpha of greenhouse conditions were higher than those of the present condition by about 9% and 30%, respectively. In particular, the greenhouse condition has drastically higher PBmax and alpha than the present condition more than 60% during the post-bloom period. According to these results, two future ocean conditions have major positive effects on the photosynthesis in terms of energy utilization efficiency for organic carbon fixation through the inorganic carbon assimilation. Despite phytoplankton taking an advantage on photosynthesis, primary production of phytoplankton was not stimulated by future conditions. In particular, biomass of phytoplankton was depressed under both acidification and greenhouse conditions after the the pre-bloom period, and more research is required to suggest that some factors such as grazing activity could be important for regulating phytoplankton bloom in the future ocean.

Effects of ocean acidification on Posidonia oceanica epiphytic community and shoot productivity

1. Biological interactions can alter predictions that are based on single-species physiological response. It is known that leaf segments of the seagrass Posidonia oceanica will increase photosynthesis with lowered pH, but it is not clear whether the outcome will be altered when the whole plant and its epiphyte community, with different respiratory and photosynthetic demands, are included. In addition, the effects on the Posidonia epiphyte community have rarely been tested under controlled conditions, at near-future pH levels. 2. In order to better evaluate the effects of pH levels as projected for the upcoming decades on seagrass meadows, shoots of P. oceanica with their associated epiphytes were exposed in the laboratory to three pH levels (ambient: 8.1, 7.7 and 7.3, on the total scale) for 4 weeks. Net productivity, respiration, net calcification and leaf fluorescence were measured on several occasions. At the end of the study, epiphyte community abundance and composition, calcareous mass and crustose coralline algae growth were determined. Finally, photosynthesis vs. irradiance curves (PE) was produced from segments of secondary leaves cleaned of epiphytes and pigments extracted. 3. Posidonia leaf fluorescence and chlorophyll concentrations did not differ between pH treatments. Net productivity of entire shoots and epiphyte-free secondary leaves increased significantly at the lowest pH level yet limited or no stimulation in productivity was observed at the intermediate pH treatment. Under both pH treatments, significant decreases in epiphytic cover were observed, mostly due to the reduction of crustose coralline algae. The loss of the dominant epiphyte producer yet similar photosynthetic response for epiphyte-free secondary leaves and shoots suggests a minimal contribution of epiphytes to shoot productivity under experimental conditions. 4. Synthesis. Observed responses indicate that under future ocean acidification conditions foreseen in the next century an increase in Posidonia productivity is not likely despite the partial loss of epiphytic coralline algae which are competitors for light. A decline in epiphytic cover could, however, reduce the feeding capacity of the meadow for invertebrates. In situ long-term experiments that consider both acidification and warming scenarios are needed to improve ecosystem-level predictions.

Agglomeration Economies in Japan: Technical Efficiency, Growth and Unemployment

This paper examines if the effects of agglomeration economies get manifested in technical efficiency and generate faster economic growth and higher (lower) levels of employment (unemployment). Using the prefecture level data for each of the two-digit groups of industries in Japan, the paper estimates region-specific technical efficiency index based on the stochastic frontier production function framework. The results of the factor analysis show that in most of the industry-groups (with a few exceptions) efficiency has a positive association with external scale variable(s). Though the relationship is not seen to be very strong, it would be equally erroneous to ignore the effect of agglomeration economies on efficiency. In the case of some of the light goods industries the agglomeration effect is relatively stronger. Further, economic growth varies positively with external scale variable(s) and unemployment rate tends to fall with respect to growth and concentration. All this tends to suggest that measures against industrial concentration may be counter-productive, particularly in the context of globalisation when countries are in dire need of raising productivity.

Has Low Productivity Constrained Competitiveness of African Firms? : Comparison of the Firm Performances with Asian Firms

It has been argued that poor productive performance is one of critical sources of stagnation of the African manufacturing sector, but firm-level empirical supports are limited. Using the inter-regional firm data of the garment industry, technical efficiency and its contribution to competitiveness measured as unit costs were compared between Kenyan and Bangladeshi firms. Our estimates indicated that there is no significant gap in the average technical efficiency of the two industries despite conservative estimation, although unit costs greatly differ between the two industries. Higher unit cost in Kenyan firms mainly stems from high labour cost, while impact of inefficiency is quite small. Productivity accounts little for the stagnation of garment industry in several African countries.

The impact of foreign firms on industrial productivity : evidence from Japan

With a newly constructed dataset on foreign firms in Japan for the period 1995-2008 from firm-level surveys, this paper estimates the impact of foreign firms on industrial productivity at the regional level. A Bayesian-model averaging approach is taken to account for model uncertainty resulting from various linkages between foreign firms and domestic industries. The results show that the foreign firms may contribute to industrial efficiency directly through their above-average productivity and indirectly through positive spillovers in intra-industry and local backward linkages. Forward linkages with foreign firms may have a negative impact on industrial productivity. However, these impacts depend on the nationality and entry mode of foreign investors. Aggregating foreign firms may mask their distinctive impacts on productivity.

On loader productivity, rock strength and explosive energy in metal mining

Twenty production blasts in two open pit mines were monitored, in rocks with medium to very high strength. Three different blasting agents (ANFO, watergel and emulsion blend) were used, with powder factors ranging between 0.88 and 1.45 kg/m3. Excavators were front loaders and rope shovels. Mechanical properties of the rock, blasting characteristics and mucking rates were carefully measured. A model for the calculation of the productivity of excavators is developed thereof, in which the production rate results as a product of an ideal, maximum, productivity rate times an operating efficiency. The maximum rate is a function of the dipper capacity and the efficiency is a function of rock density, strength, and explosive energy concentration in the rock. The model is statistically significant and explains up to 92 % of the variance of the production rate measurements.

CSR Policies: Effects on Labour Productivity in Spanish Micro and Small Manufacturing Companies

This paper analyses empirical evidence of efforts to enable Spanish micro and small manufacturing companies to boost their labour productivity rates through the development of the main pillars of their corporate social responsibility (CSR) policies. This study aims to develop new approaches and sensibilities towards work from an ethical, values (virtues) and CSR perspective, showing how internal dimensions of CSR, such those related to relationships with employees and responsibility in processes and product quality, can improve labour performance and labour efficiency, thereby contributing to a better society. The results of a sample of 929 small businesses indicate that the social responsibility policies that most contributed to a short-term increase in labour productivity are those related to internal aspects of the company, in particular its involvement in the quality of processes and products, promotion of innovation and employee care. However, the impact on labour productivity of CSR policies related to external factors, such as relationship with stakeholders and environmental concern, could not be empirically proven in this paper.

Irrigation efficiency and water-policy implications for river-basin resilience

Rising demand for food, fiber, and biofuels drives expanding irrigation withdrawals from surface water and groundwater. Irrigation efficiency and water savings have become watchwords in response to climate-induced hydrological variability, increasing freshwater demand for other uses including ecosystem water needs, and low economic productivity of irrigation compared to most other uses. We identify three classes of unintended consequences, presented here as paradoxes. Ever-tighter cycling of water has been shown to increase resource use, an example of the efficiency paradox. In the absence of effective policy to constrain irrigated-area expansion using "saved water", efficiency can aggravate scarcity, deteriorate resource quality, and impair river basin resilience through loss of flexibility and redundancy. Water scarcity and salinity effects in the lower reaches of basins (symptomatic of the scale paradox) may partly be offset over the short-term through groundwater pumping or increasing surface water storage capacity. However, declining ecological flows and increasing salinity have important implications for riparian and estuarine ecosystems and for non-irrigation human uses of water including urban supply and energy generation, examples of the sectoral paradox. This paper briefly considers three regional contexts with broadly similar climatic and water-resource conditions – central Chile, southwestern US, and south-central Spain – where irrigation efficiency directly influences basin resilience. The comparison leads to more generic insights on water policy in relation to irrigation efficiency and emerging or overdue needs for environmental protection.

An Evaluation of Applicant Tracking Systems for Recruiting Efficiency

The very purpose of a recruiting software program is to help the management of organizations, primarily the HR department to keep track of the job applications. An applicant tracking system can reduce an organization's overall recruitment cost, increase productivity, and raise the level of satisfaction due to faster and better completion of transactions and services. This project analyzes four software providers to discover an applicant tracking system which best suits an organization's recruiting needs. The capstone also highlights that great success an organization can be achieved by significantly improving the delivery of its recruiting services to employees, managers and applicants. The adoption of a well managed applicant tracking system can support this goal.