Shifts in the microbial community structure in different temperatures during sample storage from IODP Hole 325-M0058A

The objective of this study was to determine shifts in the microbial community structure and potential function based on standard Integrated Ocean Drilling Program (IODP) storage procedures for sediment cores. Standard long-term storage protocols maintain sediment temperature at 4°C for mineralogy, geochemical, and/or geotechnical analysis whereas standard microbiological sampling immediately preserves sediments at -80°C. Storage at 4°C does not take into account populations may remain active over geologic time scales at temperatures similar to storage conditions. Identification of active populations within the stored core would suggest geochemical and geophysical conditions within the core change over time. To test this potential, the metabolically active fraction of the total microbial community was characterized from IODP Expedition 325 Great Barrier Reef sediment cores prior to and following a 3-month storage period. Total RNA was extracted from complementary 2, 20, and 40 m below sea floor sediment samples, reverse transcribed to complementary DNA and then sequenced using 454 FLX sequencing technology, yielding over 14,800 sequences from the six samples. Interestingly, 97.3% of the sequences detected were associated with lineages that changed in detection frequency during the storage period including key biogeochemically relevant lineages associated with nitrogen, iron, and sulfur cycling. These lineages have the potential to permanently alter the physical and chemical characteristics of the sediment promoting misleading conclusions about the in situ biogeochemical environment. In addition, the detection of new lineages after storage increases the potential for a wider range of viable lineages within the subsurface that may be underestimated during standard community characterizations.

Fast coral reef calcifiers are more sensitive to ocean acidification in short-term laboratory incubations

To identify the properties of taxa sensitive and resistant to ocean acidification (OA), we tested the hypothesis that coral reef calcifiers differ in their sensitivity to OA as predictable outcomes of functional group alliances determined by conspicuous traits. We contrasted functional groups of eight corals and eight calcifying algae defined by morphology in corals and algae, skeletal structure in corals, spatial location of calcification in algae, and growth rate in corals and algae. The responses of calcification to OA were unrelated to morphology and skeletal structure in corals; they were, however, affected by growth rate in corals and algae (fast calcifiers were more sensitive than slow calcifiers), and by the site of calcification and morphology in algae. Species assemblages characterized by fast growth, and for algae, also cell-wall calcification, are likely to be ecological losers in the future ocean. This shift in relative success will affect the relative and absolute species abundances as well as the goods and services provided by coral reefs.

Short- versus long-term responses to changing CO2 in a coastal dinoflagellate bloom

Increasing pCO2 (partial pressure of CO2 ) in an "acidified" ocean will affect phytoplankton community structure, but manipulation experiments with assemblages briefly acclimated to simulated future conditions may not accurately predict the long-term evolutionary shifts that could affect inter-specific competitive success. We assessed community structure changes in a natural mixed dinoflagellate bloom incubated at three pCO2 levels (230, 433, and 765 ppm) in a short-term experiment (2 weeks). The four dominant species were then isolated from each treatment into clonal cultures, and maintained at all three pCO2 levels for approximately 1 year. Periodically (4, 8, and 12 months), these pCO2 -conditioned clones were recombined into artificial communities, and allowed to compete at their conditioning pCO2 level or at higher and lower levels. The dominant species in these artificial communities of CO2 -conditioned clones differed from those in the original short-term experiment, but individual species relative abundance trends across pCO2 treatments were often similar. Specific growth rates showed no strong evidence for fitness increases attributable to conditioning pCO2 level. Although pCO2 significantly structured our experimental communities, conditioning time and biotic interactions like mixotrophy also had major roles in determining competitive outcomes. New methods of carrying out extended mixed species experiments are needed to accurately predict future long-term phytoplankton community responses to changing pCO2 .

Response of a natural phytoplankton community from the Qingdao coast (Yellow Sea, China) to variable CO2 levels over a short-term incubation experiment

Since marine phytoplankton play a vital role in stabilizing earth's climate by removing significant amount of atmospheric CO2, their responses to increasing CO2 levels are indeed vital to address. The responses of a natural phytoplankton community from the Qingdao coast (NW Yellow Sea, China) was studied under different CO2 levels in microcosms. HPLC pigment analysis revealed the presence of diatoms as a dominant microalgal group; however, members of chlorophytes, prasinophytes, cryptophytes and cyanophytes were also present. delta 13CPOM values indicated that the phytoplankton community probably utilized bicarbonate ions as dissolved inorganic carbon source through a carbon concentration mechanism (CCM) under low CO2 levels, and diffusive CO2 uptake increased upon the increase of external CO2 levels. Although, considerable increase in phytoplankton biomass was noticed in all CO2 treatments, CO2-induced effects were absent. Higher net nitrogen uptake under low CO2 levels could be related to the synthesis of CCM components. Flow cytometry analysis showed slight reduction in the abundance of Synechococcus and pico-eukaryotes under the high CO2 treatments. Diatoms did not show any negative impact in response to increasing CO2 levels; however, chlorophytes revealed a reverse tend. Heterotrophic bacterial count enhanced with increasing CO2 levels and indicated higher abundance of labile organic carbon. Thus, the present study indicates that any change in dissolved CO2 concentrations in this area may affect phytoplankton physiology and community structure and needs further long-term study.

Long term low latitude and high elevation cosmogenic 3He production rate inferred from a 107 ka-old lava flow in northern Chile; 22°S-3400 m a.s.l

Available geological calibration sites used to estimate the rate at which cosmogenic 3He is produced at the Earth’s surface are mostly clustered in medium to high latitudes. Moreover, most of them have exposure histories shorter than tens of thousands of years. This lack of sites prevents a qualitative assessment of available production models used to convert cosmogenic 3He concentrations into exposure ages and/or denudation rates. It thus limits our ability to take into account the atmospheric, geomagnetic and solar modulation conditions that might have affected the production of cosmogenic nuclides in the past for longer exposure histories and in low latitude regions. We present the cosmogenic 3He production rate inferred from a new geological calibration site located in northern Chile. Five samples were collected on the surface of the largest and best-preserved lava flow of the San Pedro volcano (21.934°S-68.510°W- 3390 m a.s.l), which displays pristine crease-structure features. 40Ar/39Ar dating yield a reliable plateau age of 107±12 ka for the eruption of this lava flow. Eight pyroxene aliquots separated from the surface samples yield a weighted average cosmogenic 3He concentration of 99.3±1.2 Mat.g-1 from which a local cosmogenic 3He production rate of 928±101 at.g-1.yr-1 is calculated. The local production rate is then scaled to a sea level high latitude (SLHL) reference position using different combinations of geographic spatialization schemes, atmosphere models and geomagnetic field reconstructions, yielding SLHL production rates between 103±11 and 130±14 at.g-1.yr-1 consistent with the most recent estimates available from the literature. Finally, we use the same scaling frameworks to re-evaluate the mean global-scale cosmogenic 3He production rate in olivine and pyroxene minerals at 120±16 at.g-1.yr-1 from the compilation of previously published calibration datasets.

Short- and long-term conditioning of a temperate marine diatom community to acidification and warming

Ocean acidification and greenhouse warming will interactively influence competitive success of key phytoplankton groups such as diatoms, but how long-term responses to global change will affect community structure is unknown. We incubated a mixed natural diatom community from coastal New Zealand waters in a short-term (two-week) incubation experiment using a factorial matrix of warming and/or elevated pCO2 and measured effects on community structure. We then isolated the dominant diatoms in clonal cultures and conditioned them for 1 year under the same temperature and pCO2 conditions from which they were isolated, in order to allow for extended selection or acclimation by these abiotic environmental change factors in the absence of interspecific interactions. These conditioned isolates were then recombined into 'artificial' communities modelled after the original natural assemblage and allowed to compete under conditions identical to those in the short-term natural community experiment. In general, the resulting structure of both the unconditioned natural community and conditioned 'artificial' community experiments was similar, despite differences such as the loss of two species in the latter. pCO2 and temperature had both individual and interactive effects on community structure, but temperature was more influential, as warming significantly reduced species richness. In this case, our short-term manipulative experiment with a mixed natural assemblage spanning weeks served as a reasonable proxy to predict the effects of global change forcing on diatom community structure after the component species were conditioned in isolation over an extended timescale. Future studies will be required to assess whether or not this is also the case for other types of algal communities from other marine regimes.

The IDE geographical simulation model : predicting long-term effects of infrastructure development projects

It is important to be able to predict changes in the location of populations and industries in regions that are in the process of economic integration. The IDE Geographical Simulation Model (IDE-GSM) has been developed with two major objectives: (1) to determine the dynamics of locations of populations and industries in East Asia in the long-term, and (2) to analyze the impact of specific infrastructure projects on the regional economy at sub-national levels. The basic structure of the IDE-GSM is introduced in this article and accompanied with results of test analyses on the effects of the East West Economic Corridor on regions in Continental South East Asia. Results indicate that border costs appear to play a big role in the location choice of populations and industries, often a more important role than physical infrastructures themselves.

Imposed Deformations Measured on a Real Integral Structure: New Airport Terminal Barajas, Madrid, Spain

Experimental research on imposed deformation is generally conducted on small scale laboratory experiments. The attractiveness of field research lies in the possibility to compare results obtained from full scale structures to theoretical prediction. Unfortunately, measurements obtained from real structures are rarely described in literature. The structural response of integral edifices depends significantly on stiffness changes and constraints. The New Airport Terminal Barajas in Madrid, Spain provides with large integral modules, partially post?tensioned concrete frames, cast monolithically over three floor levels and an overall length of approx. 80 m. The field campaign described in this article explains the instrumentation of one of these frames focusing on the influence of imposed deformations such as creep, shrinkage and temperature. The applied monitoring equipment included embedded strain gages, thermocouples, DEMEC measurements and simple displacement measurements. Data was collected throughout construction and during two years of service. A complete data range of five years is presented and analysed. The results are compared with a simple approach to predict the long?term shortening of this concrete structure. Both analytical and experimental results are discussed.

Analysis of the problems associated with dynamic interaction between train, track and structure at transition zones

El gran desarrollo experimentado por la alta velocidad en los principales países de la Unión Europea, en los últimos 30 años, hace que este campo haya sido y aún sea uno de los principales referentes en lo que a investigación se refiere. Por otra parte, la aparición del concepto super − alta velocidad hace que la investigación en el campo de la ingeniería ferroviaria siga adquiriendo importancia en los principales centros de investigación de los países en los que se desea implantar este modo de transporte, o en los que habiendo sido ya implantado, se pretenda mejorar. Las premisas de eficacia, eficiencia, seguridad y confort, que este medio de transporte tiene como razón de ser pueden verse comprometidas por diversos factores. Las zonas de transición, definidas en la ingeniería ferroviaria como aquellas secciones en las que se produce un cambio en las condiciones de soporte de la vía, pueden afectar al normal comportamiento para el que fue diseñada la infraestructura, comprometiendo seriamente los estándares de eficiencia en el tiempo de viaje, confort de los pasajeros y aumentando considerablemente los costes de mantenimiento de la vía, si no se toman las medidas oportunas. En esta tesis se realiza un estudio detallado de la zonas de transición, concretamente de aquellas en las que existe una cambio en la rigidez vertical de la vía debido a la presencia de un marco hidráulico. Para realizar dicho estudio se lleva a cabo un análisis numérico de interacción entre el vehículo y la estructura, con un modelo bidimensional de elemento finitos, calibrado experimentalmente, en estado de tensión plana. En este análisis se tiene en cuenta el efecto de las irregularidades de la vía y el comportamiento mecánico de la interfaz suelo-estructura, con el objetivo de reproducir de la forma más real posible el efecto de interacción entre el vehículo, la vía y la estructura. Otros efectos como la influencia de la velocidad del tren y los asientos diferenciales, debidos a deformaciones por consolidación de los terraplenes a ambos lados el marco hidráulico, son también analizados en este trabajo. En esta tesis, los cálculos de interacción se han llevado a cabo en dos fases diferentes. En la primera, se ha considerado una interacción sencilla debida al paso de un bogie de un tren Eurostar. Los cálculos derivados de esta fase se han denominado cálculos a corto plazo. En la segunda, se ha realizado un análisis considerando múltiples pasos de bogie del tren Eurostar, conformando un análisis de degradación en el que se tiene en cuenta, en cada ciclo, la deformación de la capa de balasto. Los cálculos derivados de esta fase, son denominados en el texto como cálculos a largo plazo. Los resultados analizados muestran que la utilización de los denominados elementos de contacto es fundamental cuando se desea estudiar la influencia de asientos diferenciales, especialmente en transiciones terraplén-estructura en las que la cuña de cimentación no llega hasta la base de cimentación de la estructura. Por otra parte, tener en cuenta los asientos del terraplén, es sumamente importante, cuando se desea realizar un análisis de degradación de la vía ya que su influencia en la interacción entre el vehículo y la vía es muy elevada, especialmente para valores altos de velocidad del tren. En cuanto a la influencia de las irregularidades de la vía, en los cálculos efectuados, se revela que su importancia es muy notable, siendo su influencia muy destacada cuanto mayor sea la velocidad del tren. En este punto cabe destacar la diferencia de resultados derivada de la consideración de perfiles de irregularidades de distinta naturaleza. Los resultados provenientes de considerar perfiles artificiales son en general muy elevados, siendo estos más apropiados para realizar estudios de otra índole, como por ejemplo de seguridad al descarrilamiento. Los resultados provenientes de perfiles reales, dados por diferentes Administradores ferroviarios, presentan resultados menos elevados y más propios del problema analizar. Su influencia en la interacción dinámica entre el vehículo y la vía es muy importante, especialmente para velocidades elevadas del tren. Además el fenómeno de degradación conocido como danza de traviesas, asociado a zonas de transición, es muy susceptible a la consideración de irregularidades de la vía, tal y como se desprende de los cálculos efectuados a largo plazo. The major development experienced by high speed in the main countries of the European Union, in the last 30 years, makes railway research one of the main references in the research field. It should also be mentioned that the emergence of the concept superhigh − speed makes research in the field of Railway Engineering continues to gain importance in major research centers in the countries in which this mode of transportation is already implemented or planned to be implemented. The characteristics that this transport has as rationale such as: effectiveness, efficiency, safety and comfort, may be compromised by several factors. The transition zones are defined in railway engineering as a region in which there is an abrupt change of track stiffness. This stiffness variation can affect the normal behavior for which the infrastructure has been designed, seriously compromising efficiency standards in the travel time, passenger comfort and significantly increasing the costs of track maintenance, if appropriate measures are not taken. In this thesis a detailed study of the transition zones has been performed, particularly of those in which there is a change in vertical stiffness of the track due to the presence of a reinforced concrete culvert. To perform such a study a numerical interaction analysis between the vehicle, the track and the structure has been developed. With this purpose a two-dimensional finite element model, experimentally calibrated, in a state of plane stress, has been used. The implemented numerical models have considered the effects of track irregularities and mechanical behavior of soil-structure interface, with the objective of reproducing as accurately as possible the dynamic interaction between the vehicle the track and the structure. Other effects such as the influence of train speed and differential settlement, due to secondary consolidation of the embankments on both sides of culvert, have also been analyzed. In this work, the interaction analysis has been carried out in two different phases. In the first part a simple interaction due to the passage of a bogie of a Eurostar train has been considered. Calculations derived from this phase have been named short-term analysis. In the second part, a multi-load assessment considering an Eurostar train bogie moving along the transition zone, has been performed. The objective here is to simulate a degradation process in which vertical deformation of the ballast layer was considered. Calculations derived from this phase have been named long-term analysis. The analyzed results show that the use of so-called contact elements is essential when one wants to analyze the influence of differential settlements, especially in embankment-structure transitions in which the wedge-shaped backfill does not reach the foundation base of the structure. Moreover, considering embankment settlement is extremely important when it is desired to perform an analysis of track degradation. In these cases the influence on the interaction behaviour between the vehicle and the track is very high, especially for higher values of speed train. Regarding the influence of the track irregularities, this study has proven that the track’s dynamic response is heavily influenced by the irregularity profile and that this influence is more important for higher train velocities. It should also be noted that the difference in results derived from consideration of irregularities profiles of different nature. The results coming from artificial profiles are generally very high, these might be more appropriate in order to study other effects, such as derailment safety. Results from real profiles, given by the monitoring works of different rail Managers, are softer and they fit better to the context of this thesis. The influence of irregularity profiles on the dynamic interaction between the train and the track is very important, especially for high-speeds of the train. Furthermore, the degradation phenomenon known as hanging sleepers, associated with transition zones, is very susceptible to the consideration of track irregularities, as it can be concluded from the long-term analysis.