All about the marine/sea ice diatom Nitzschia lecointei

Generally, in terms of growth N. lecointei seems quite tolerant to changes in pH and pCO2, probably due to the fact that this species grows in an environment with large seasonal variations in the carbonate system. However, increased pCO2 resulted in physiological changes that may have important ecological consequences, such as cellular stoichiometry. For instance, we observed changes in carbon metabolism, and fatty acid content and composition, that did not affect the growth rate. When the experimental period was increased (194 days, ca. 60 asexual generations), we observed a small reduction in growth at 960 µatm pCO2 after 147 days. Carbon metabolism was significantly affected, resulting in higher cellular release of dissolved organic carbon. When studying the synergism between temperature (−1.8 and 2.5°C) and pCO2 (390 and 960 μatm), synergism was detected in growth rate and acyl lipid fatty acid content. Carbon enrichment only promoted (3 %) growth rate closer to the optimal growth, but not at the control temperature (−1.8°C). Optimal growth rate was observed around 5°C in a separate experiment. The total content of fatty acids was reduced at elevated pCO2, but only at the control temperature. PUFAs were reduced at high pCO2. When combining increased temperature and different salinity conditions, the growth rate was higher at 3°C than at -1.8°C. Salinity 10 clearly limited growth rate and the highest growth rates were found at salinity 20 and 35. In another experiment, high and low temperature together with treatments simulating ice formation and melting conditions were studied. Here, the highest levels of oxidative stress were found in low temperature and ice melting treatments, respectively. With respect to 9 weeks in the dark, cell numbers were higher at -1.5°C compared to 3°C, but when retrieved to light conditions, after one week higher cell numbers were observed at 3°C versus -1.5°C. Furthermore, cell numbers were lower when acetateUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

ASSERT - Kontroll av markstabilisering med resistivitetstomografi

Ground improvement with lime-cement pillars is becoming increasingly common in the Nordic countries for exploitation of areas with poor stability. However, there is a need for non-destructive methods for volumetric quality control of the ground improvement. The quality control can be divided into two steps where the first include quality control at the installation process with monitoring of production parameters such as rotation and penetration speed, air pressure and binder feed rate. The second step involves determining the spatial continuity and the mechanical properties of the treated subsurface after curing by for example a reversed pillar penetration test, complete exposure or core drilling. ASSERT (Assessment of Soil Stabilization using Electrical Resistivity Tomography) is an on-oing research project with focus on quality control in direct connection with mixing of the binders based on electrical resistivity tomography (ERT). The ERT-method has in several cases been shown to efficiently differentiate treated soil from untreated. Hence, is the method an interesting option for direct and rapid volumetric quality control of the stabilized soil so that zones which needs to be supplemented can be identified at production stage while personnel and equipment are at site. The ASSERT project involves test and verification of the method in different geological environments and scales, including full-scale tests for different types of stabilization techniques. Additionally, method development and adaptations to make the quality control applicable are also included in the project to enable a robust, rapid and sustainable use in routine operations

Effects of seawater scrubbing on a microplanktonic community during a summer-bloom in the Baltic Sea

The International Maritime Organization (IMO) has gradually applied stricter regulations on the maximum sulphur content permitted in marine fuels and from January 1, 2020, the global fuel sulphur limit was reduced from 3.5% to 0.5%. An attractive option for shipowners is to install exhaust gas cleaning systems, also known as scrubbers, and continue to use high sulphur fuel oil. In the scrubber, the exhausts are led through a fine spray of water, in which sulphur oxides are easily dissolved. The process results in large volumes of acidic discharge water, but while regulations are focused on sulphur oxides removal and acidification, other pollutants e.g. polycyclic aromatic hydrocarbons, metals and nitrogen oxides can be transferred from the exhausts to the washwater and discharged to the marine environment. The aim of the current study was to investigate how different treatments of scrubber discharge water (1, 3 and 10%) affect a natural Baltic Sea summer microplanktonic community. To resolve potential contribution of acidification from the total effect of the scrubber discharge water, “pH controls” were included where the pH of natural sea water was reduced to match the scrubber treatments. Biological effects (e.g. microplankton species composition, biovolume and primary productivity) and chemical parameters (e.g. pH and alkalinity) were monitored and analysed during 14 days of exposure. Significant effects were observed in the 3% scrubber treatment, with more than 20% increase in total biovolume of microplankton compared to the control group, and an even greater effect in the 10% scrubber treatment. Group-specific impacts were recorded where diatoms, flagellates incertae sedis, chlorophytes and ciliates increased in biovolume with increasing concentrations of scrubber water while no effect was recorded for cyanobacteria. In contrast, these effects was not observed in the “pH controls”, a suggestion that other parameters/stressors in the scrubber water were responsible for the observed effects

Sulphur poisoning and regeneration of NOx trap catalyst for direct injected gasoline engines

Sulphur poisoning and regeneration of NOx trap catalysts have been studied in synthetic exhausts and in an engine bench. Sulphur gradually poisoned the NO x storage sites in the axial direction of the NO x trap. During sulphur regenerations, hydrogen was found to be more efficient than carbon monoxide in removing the sulphur from the trap. The sulphur regeneration became more efficient the richer the environment (λ<1) and the higher the temperature (at least 600°C). H2S was found to be the main product during the sulphur regeneration. However, it was possible to reduce the H2S formation and instead produce more SO2 by running with lambda close to one or by pulsing lambda. Even if a relatively large amount of sulphur was removed from the NOx trap, these methods gave a much less efficient regeneration per sulphur atom removed than when running relatively rich constantly. Finally, a model that could explain this observation was proposed

ASSERT - Kontroll av markstabilisering med resistivitetstomografi (ERT)

Soil stabilisation is becoming increasingly common for the development of areas withpoor bearing capacity. However, there is a need for better and volume-wide controlmethods for quality assurance. The control methods can be divided into two steps,where the first takes place in immediate connection to the mixing of binders to checkwhether the entire intended volume has been successfully treated, or whether thereare zones that need completion. The second step focuses on the strength of thestabilised volume and assumes that the binder has cured.The R&D project ASSERT focuses on quality control using electrical resistivitytomography (ERT). The idea is to use the method in immediate connection with themixing of binders to delineate the soil volume that has been treated with binders fromuntreated parts. ERT could then be used to quickly check the results of thestabilisation, so that supplementary measures can be taken in zones of insufficienttreatment while personnel and equipment are in place. Furthermore, there is potentialfor volume-wide quantification of strength growth via correlation between change inresistivity and change in strength during the curing process, but this would probablyneed to be done on a site specific basis.Testing and verification of the method takes place in different geomaterials in thelaboratory and in the field, including full-scale tests for different types ofstabilisations. Furthermore, method development and adaptation for the applicationare included, so that the method becomes sufficiently robust and fast to be usedroutinely in a sustainable manner. Field trials have been carried out by installingelectrodes in lime-cement columns and jet columns in direct connection to thestabilisation. Laboratory tests have so far been carried out for lime-cementstabilisation of clay and for stabilisation of dredged masses

Novel electrode design for non-destructive resistivity measurement on material in geotechnical standard sample cylinders

We present a novel design of an electrode arrangement for measurement of the resistivity of soil samples contained in a sample cylinder used in standard geotechnical site investigations in Sweden. The objective is to make it possible to measure the resistivity of the same samples that are to be used for mechanical tests, without disturbing the samples in order to get unbiased mechanical test data. A design with four piece-of- pie shaped electrodes integrated in the lids in each end of the sample has been tested and evaluated. Temperature sensors are embedded in the electrode lids to allow temperature compensation of the measured data.Alternative electrode designs were modelled numerically with the finite element method (FEM) prior to the prototype manufacturing. Measurement tests with water filled sample cylinders show that stacking and reciprocal errors can be kept below 1% provided that suitable measurement settings and sequences are used. The geometrical factors depends on the distance between the electrodes in each end of the cylinder, i.e. varies with the length of the sample, and must be determined experimentally or via FEM modelling

Data from: Long-term acclimation to elevated pCO2 alters carbon metabolism and reduces growth in the Antarctic diatom Nitzschia lecointei

Increasing atmospheric CO2 levels are driving changes in the seawater carbonate system, resulting in higher pCO2 and reduced pH (ocean acidification). Many studies on marine organisms have focused on short-term physiological responses to increased pCO2, and few on slow-growing polar organisms with a relative low adaptation potential. In order to recognize the consequences of climate change in biological systems, acclimation and adaptation to new environments are crucial to address. In this study, physiological responses to long-term acclimation (194 days, approx. 60 asexual generations) of three pCO2 levels (280, 390 and 960 µatm) were investigated in the psychrophilic sea ice diatom Nitzschia lecointei. After 147 days, a small reduction in growth was detected at 960 µatm pCO2. Previous short-term experiments have failed to detect altered growth in N. lecointei at high pCO2, which illustrates the importance of experimental duration in studies of climate change. In addition, carbon metabolism was significantly affected by the long-term treatments, resulting in higher cellular release of dissolved organic carbon (DOC). In turn, the release of labile organic carbon stimulated bacterial productivity in this system. We conclude that long-term acclimation to ocean acidification is important for N. lecointei and that carbon overconsumption and DOC exudation may increase in a high-CO2 world

Long-term acclimation to elevated pCO2 alters carbon metabolism and reduces growth in the Antarctic diatom Nitzschia lecointei

Increasing atmospheric CO2 levels are driving changes in the seawater carbonate system, resulting in higher pCO2 and reduced pH (ocean acidification). Many studies on marine organisms have focused on short-term physiological responses to increased pCO2, and few on slow-growing polar organisms with a relative low adaptation potential. In order to recognize the consequences of climate change in biological systems, acclimation and adaptation to new environments are crucial to address. In this study, physiological responses to long-term acclimation (194 days, approx. 60 asexual generations) of three pCO2 levels (280, 390 and 960 µatm) were investigated in the psychrophilic sea ice diatom Nitzschia lecointei. After 147 days, a small reduction in growth was detected at 960 µatm pCO2. Previous short-term experiments have failed to detect altered growth in N. lecointei at high pCO2, which illustrates the importance of experimental duration in studies of climate change. In addition, carbon metabolism was significantly affected by the long-term treatments, resulting in higher cellular release of dissolved organic carbon (DOC). In turn, the release of labile organic carbon stimulated bacterial productivity in this system. We conclude that long-term acclimation to ocean acidification is important for N. lecointei and that carbon overconsumption and DOC exudation may increase in a high-CO2 world

Diatom frustules protect DNA from ultraviolet light

The evolutionary causes for generation of nano and microstructured silica by photosynthetic algae are not yet deciphered. Diatoms are single photosynthetic algal cells populating the oceans and waters around the globe. They generate a considerable fraction (20-30%) of all oxygen from photosynthesis, and 45% of total primary production of organic material in the sea. There are more than 100,000 species of diatoms, classified by the shape of the glass cage in which they live, and which they build during algal growth. These glass structures have accumulated for the last 100 million of years, and left rich deposits of nano/microstructured silicon oxide in the form of diatomaceous earth around the globe. Here we show that reflection of ultraviolet light by nanostructured silica can protect the deoxyribonucleic acid (DNA) in the algal cells, and that this may be an evolutionary cause for the formation of glass cages.Funding Agencies|Knut and Alice Wallenberg foundation; J Gustaf Richert foundation</p

Specific PP TOT clean

Clean version of longterm data, i.e. without N