131 research outputs found
Data from Velthuis et al., 2017 Frontiers in Plant Science
No full textHuman activity is currently changing our environment rapidly, with predicted temperature increases of 1–5°C over the coming century and increased nitrogen and phosphorus inputs in aquatic ecosystems. In the shallow parts of these ecosystems, submerged aquatic plants enhance water clarity by resource competition with phytoplankton, provide habitat, and serve as a food source for other organisms. The carbon:nutrient stoichiometry of submerged aquatic plants can be affected by changes in both temperature and nutrient availability. We hypothesized that elevated temperature leads to higher carbon:nutrient ratios through enhanced nutrient-use efficiency, while nutrient addition leads to lower carbon:nutrient ratios by the luxurious uptake of nutrients. We addressed these hypotheses with an experimental and a meta-analytical approach. We performed a full-factorial microcosm experiment with the freshwater plant Elodea nuttallii grown at 10, 15, 20, and 25°C on sediment consisting of pond soil/sand mixtures with 100, 50, 25, and 12.5% pond soil. To address the effect of climatic warming and nutrient addition on the carbon:nutrient stoichiometry of submerged freshwater and marine plants we performed a meta-analysis on experimental studies that elevated temperature and/or added nutrients (nitrogen and phosphorus). In the microcosm experiment, C:N ratios of Elodea nuttallii decreased with increasing temperature, and this effect was most pronounced at intermediate nutrient availability. Furthermore, higher nutrient availability led to decreased aboveground C:P ratios. In the meta-analysis, nutrient addition led to a 25, 22, and 16% reduction in aboveground C:N and C:P ratios and belowground C:N ratios, accompanied with increased N content. No consistent effect of elevated temperature on plant stoichiometry could be observed, as very few studies were found on this topic and contrasting results were reported. We conclude that while nutrient addition consistently leads to decreased carbon:nutrient ratios, elevated temperature does not change submerged aquatic plant carbon:nutrient stoichiometry in a consistent manner. This effect is rather dependent on nutrient availability and may be species-specific. As changes in the carbon:nutrient stoichiometry of submerged aquatic plants can impact the transfer of energy to higher trophic levels, these results suggest that eutrophication may enhance plant consumption and decomposition, which could in turn have consequences for carbon sequestration
Elements of carbon cycling: primary producers in aquatic systems under global change
No full textIt is of crucial importance to understand the consequences of climatic changes (e.g. elevated pCO2, warming and eutrophication) on aquatic primary producers, as they play a vital role in the global carbon cycle. Therefore, the main aims of the thesis were (1) to assess the role of primary producer identity (i.e. phytoplankton vs submerged aquatic plants) in aquatic carbon cycling, and (2) to assess the effects of elevated pCO2, warming and eutrophication on aquatic carbon cycling (with the focus on primary producers). The results of this thesis show that global change can significantly alter the role of primary producers in the carbon cycle, but that the direction of this change may depend on the prominent global change stressor. Producer carbon:nutrient stoichiometry can be enhanced by elevated pCO2, but reduced by eutrophication. The effect of warming on carbon:nutrient stoichiometry is context-dependent and may be influenced by abiotic conditions such as nutrient availability. Systems dominated by aquatic plants can have significantly higher sedimentation fluxes of carbon than those dominated by phytoplankton. This difference can be attributed to standing stocks of producer biomass related to producer identity. Additionally, the results of this thesis show that consumer biomass can advance in response to climatic warming, thereby imposing top-down control on primary producers. Thus, processes hampering the build-up of producer biomass may alter the flux of carbon to the sediment. To integratively assess the effect of warming on freshwater carbon cycling, producer biomass, sedimentation and decomposition were measured in a mesocosm experiment. The results of this experiment show that warming can significantly enhance the standing stock of plant biomass, sedimentation and decomposition. When combined into a carbon budget model, these similarly enhanced carbon fluxes cancelled each other out resulting in no net change in carbon burial between temperature treatments. All in all, I conclude that global change can affect the balance of aquatic carbon cycling by altering the biomass and carbon:nutrient stoichiometry of aquatic primary producers as well as their interactions with higher trophic levels. These changes in turn can have potential consequences for our future climate
Velthuis et al., 2018, GCB
No full textData and R-scripts belonging to the published manuscript. For more detailed information see the README file
Een 100 MWe centrale op basis van verbranding van steenkool in een PFBC met regeneratieve zwavelafvangst
No full textDocument(en) uit de collectie Chemische Procestechnologie.DelftChemTechApplied Science
Report on GPR and science investigations at Macquarie island and Casey station
No full textProgress Code: completedStatement: See the report for more details.Taken from the survey report:<br/><br/>Documentation is provided for surveying tasks - by Tom Velthuis - at Macquarie Island and Casey, during the summer of 2000/1. The report is presented in five key sections:<br/>1. GPR related surveying in Thala Valley - Casey;<br/>2. Non GPR related surveying in Thala Valley;<br/>3. Surveys conducted outside of Thala Valley;<br/>4. Surveys at Macquarie Island; and<br/>5. Survey data to GIS.<br/>The first three sections relate to Casey; the fourth section to Macquarie Island; and the fifth section documents the transfer of data to GIS.<br/><br/>For more details see the report available as part of the download.<br/><br/>Taken from the readme file accompanying the data:<br/><br/>The folder named, 'shape' contains projected (UTM) and unprojected shapefiles, based on WGS84, relating to surveys by Tom Velthuis at Macquarie Island and Casey during the summer 2000/2001 season. See report: Survey Report.doc.<br/><br/>The folder named, 'excel_files' contains excel files by Tom Velthuis used for computing surveying work performed at Macquarie Island and Casey during the summer 2000/1. The 'Windmill Islands control' file is a file given to Tom by Tom Gordon.<br/><br/>The folder labelled, 'tomv pics scanned' contains photographs (by Tom Velthuis) relating to surveying work conducted at Casey during the summer 2000/1. Most of the photos are in the report labelled, 'Survey Report.doc'.<br/><br/>The folder labelled, 'TomVforGIS' contains files generated by Tom Velthuis, for the creation of shapefiles in ArcView.<br/>The files relate to Surveying work conducted at Macquarie Island and Casey during Summer 2000/1.<br/><br/>macca_levels.xls has additional notes on the levelling of buildings at Macquarie Island.<br/><br/><br/>Also, map number 13248 in the SCAR Map Catalogue shows crosses on the buildings at Macquarie Island indicating the approximate location of levelling to the buildings. <br/>macca_levels.xls has the same content as the dbf file referred to on the map.<br/>See Related URL below for the SCAR Map Catalogue entry
A feasibility study towards a self-governing equipment pool in the ground handling sector at Amsterdam Airport Schiphol
No full textSEPAMPolicy AnalysisTechnology, Policy and Managemen
Neutron depolarisation experiments on medium carbon steels
No full textTechnische MateriaalwetenschappenMechanical, Maritime and Materials Engineerin
Kunnen wateren met veel ondergedoken waterplanten CO2 uit de atmosfeer vastleggen?
No full textAquatische ecosystemen met veel ondergedoken waterplanten zijn potentiëlehotspots voor de invang van organisch materiaal. Waterplanten slaan koolstofen nutriënten op in hun biomassa, afgestorven planten en andere detritusvormen een organische laag op de bodem. Kunnen dergelijke systemen misschien de hoeveelheid CO2 in de atmosfeer omlaag brengen? En hoe verlooptdie vastlegging als het water door klimaatverandering opwarmt
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