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52. Mars' Surface Radiation Environment Measured with the Mars Science Laboratory's Curiosity Rover

Author

MSL Science Team, Hassler, Donald M., Zeitlin, Cary, Wimmer-Schweingruber, Robert F., Ehresmann, Bent, Rafkin, Scot, Eigenbrode, Jennifer L., Brinza, David E., Weigle, Gerald, Böttcher, Stephan, Böhm, Eckart, Burmeister, Soenke, Guo, Jingnan, Köhler, Jan, Martin, Cesar, Reitz, Guenther, Cucinotta, Francis A., Kim, Myung-Hee, Grinspoon, David, Bullock, Mark A., Posner, Arik, Gómez-Elvira, Javier, Vasavada, Ashwin, and Grotzinger, John P.

Published
2014

60. fact sheet

Author

Tittmann, Angelina, Leibniz-Institut Für Gewässerökologie Und Binnenfischerei, Hilt, Sabine, Graupner, Johannes, and Köhler, Jan

Subjects
Geologie, Hydrologie, Meteorologie, Boden- und Energiewirtschaft
Published
2022
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61. The Martian surface radiation environment – a comparison of models and MSL/RAD measurements

Author

Matthiä Daniel, Ehresmann Bent, Lohf Henning, Köhler Jan, Zeitlin Cary, Appel Jan, Sato Tatsuhiko, Slaba Tony, Martin Cesar, Berger Thomas, Boehm Eckart, Boettcher Stephan, Brinza David E., Burmeister Soenke, Guo Jingnan, Hassler Donald M., Posner Arik, Rafkin Scot C. R., Reitz Günther, Wilson John W., and Wimmer-Schweingruber Robert F.

Subjects
Mars, Galactic cosmic radiation, Radiation environment, Human exploration, Numerical models, Exposure, Meteorology. Climatology, QC851-999
Abstract

Context: The Radiation Assessment Detector (RAD) on the Mars Science Laboratory (MSL) has been measuring the radiation environment on the surface of Mars since August 6th 2012. MSL-RAD is the first instrument to provide detailed information about charged and neutral particle spectra and dose rates on the Martian surface, and one of the primary objectives of the RAD investigation is to help improve and validate current radiation transport models. Aims: Applying different numerical transport models with boundary conditions derived from the MSL-RAD environment the goal of this work was to both provide predictions for the particle spectra and the radiation exposure on the Martian surface complementing the RAD sensitive range and, at the same time, validate the results with the experimental data, where applicable. Such validated models can be used to predict dose rates for future manned missions as well as for performing shield optimization studies. Methods: Several particle transport models (GEANT4, PHITS, HZETRN/OLTARIS) were used to predict the particle flux and the corresponding radiation environment caused by galactic cosmic radiation on Mars. From the calculated particle spectra the dose rates on the surface are estimated. Results: Calculations of particle spectra and dose rates induced by galactic cosmic radiation on the Martian surface are presented. Although good agreement is found in many cases for the different transport codes, GEANT4, PHITS, and HZETRN/OLTARIS, some models still show large, sometimes order of magnitude discrepancies in certain particle spectra. We have found that RAD data is helping to make better choices of input parameters and physical models. Elements of these validated models can be applied to more detailed studies on how the radiation environment is influenced by solar modulation, Martian atmosphere and soil, and changes due to the Martian seasonal pressure cycle. By extending the range of the calculated particle spectra with respect to the experimental data additional information about the radiation environment is gained, and the contribution of different particle species to the dose is estimated.

Published
2016
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65. Autoren

Author

Allescher, Hans-Dieter, Andresen, Viola, Aretz, Stefan, Beuers, Ulrich, Beyer, Georg, Boesecke, Christoph, Borowitzka, Fanny, Caca, Karel., Canbay, Ali, Chang, Johannes, Liberto, Alexander di, Dröge, Carola, Dumoulin, Franz Ludwig, Ebert, Matthias P.A., Epple, Hans-Jörg, Feurle, Gerhard E., Fibbe, Chistiane, Fischbach, Wolfgang, Frieling, Thomas, Galle, Peter R., Germer, Christoph-Thomas, González-Carmona, Maria A., Götze, Thorsten Oliver, Gundling, Felix, Halilbasic, Emina, Hartmann, Franz, Herold, Alexander, Herta, Toni, Höllerich, Jörg, Holtmeier, Wolfgang, Horvatits, Thomas, Hüneburg, Robert, Jansen, Christian, Jüngst, Christoph, Kandler, Jennis, Keitel-Anselmino, Verena, Keller, Jutta, Kestler, Angelika, Köhler, Jan Philipp, Koletzko, Sibylle, Kollmar, Otto, Krammer, Heiner, Kreis, Martin, Kruis, Wolfgang, Kubisch, Ilja, Kucharzik, Torsten, Kullak-Ublick, Gerd A., Labenz, Joachim, Lammert, Frank, Lamprecht, Georg, Layer, Peter, Leifeld, Ludger, Lügering, Norbert, Lutz, Philipp, Malfertheiner, Peter, Manekeller, Steffen, Mayerle, Julia, Meier, Benjamin, Merle, Uta, Möhler, Markus, Monin, Malte B., Müller-Lissner, Stefan, Munda, Petra, Neubrand, Michael, Neuhaus, Horst, Nowacki, Tobias, Pascher, Andreas, Pehl, Christian, Pischke, Sven, Pox, Christian C., Praktiknjo, Michael, Rahimzai, Rafique, Raithel, Martin, Reinartz Groba, Sara, Rennebaum, Florian, Repges, Sophie, Rockstroh, Jürgen K., Roeb, Elke, Sarrazin, Christoph, Sauerbruch, Tilman, Schepke, Michael, Schepp, Wolfgang, Scheyda-Yoo, Katharina, Schmitt, Annika, Schöler, David, Schulz, Christian, Schuppan, Detlef, Seufferlein, Thomas, Siegmund, Britta, Sirtl, Simon, Soysal, Savas D., Spengler, Ulrich, Stallmach, Andres, Stauch, Thomas, Stindt, Jan, Stölzel, Ulrich, Strassburg, Christian P., Tacke, Frank, Terjung, Birgit, Trauner, Michael, Trebicka, Jonel, Tröger, Hanno, Dahl, Stephan vom, Arnim, Ulrike von, Schassen, Henrike von, Vornhülz, Marlies, Vorona, Elena, Wege, Henning, Weismüller, Tobias J., Weissenborn, Karin, Wolf, Susanna, Zimpel, Carolin, and Zipprich, Alexander

Published
2024
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67. Controls on Lake Pelagic Primary Productivity: Formalizing the Nutrient‐Color Paradigm

Author

Oleksy, Isabella A., Solomon, Christopher T., Jones, Stuart E., Olson, Carly, Bertolet, Brittni L., Adrian, Rita, Bansal, Sheel, Baron, Jill S., Brothers, Soren, Chandra, Sudeep, Chou, Hsiu‐Mei, Colom‐Montero, William, Culpepper, Joshua, Eyto, Elvira, Farragher, Matthew J., Hilt, Sabine, Holeck, Kristen T., Kazanjian, Garabet, Klaus, Marcus, Klug, Jennifer, Köhler, Jan, Laas, Alo, Lundin, Erik, Parkes, Alice H., Rose, Kevin C., Rustam, Lars G., Rusak, James, Scordo, Facundo, Vanni, Michael J., Verburg, Piet, and Weyhenmeyer, Gesa A.

Abstract

Understanding controls on primary productivity is essential for describing ecosystems and their responses to environmental change. In lakes, pelagic gross primary productivity (GPP) is strongly controlled by inputs of nutrients and dissolved organic matter. Although past studies have developed process models of this nutrient‐color paradigm (NCP), broad empirical tests of these models are scarce. We used data from 58 globally distributed, mostly temperate lakes to test such a model and improve understanding and prediction of the controls on lake primary production. The model includes three state variables–dissolved phosphorus, terrestrial dissolved organic carbon (DOC), and phytoplankton biomass–and generates realistic predictions for equilibrium rates of pelagic GPP. We calibrated our model using a Bayesian data assimilation technique on a subset of lakes where DOC and total phosphorus (TP) loads were known. We then asked how well the calibrated model performed with a larger set of lakes. Revised parameter estimates from the updated model aligned well with existing literature values. Observed GPP varied nonlinearly with both inflow DOC and TP concentrations in a manner consistent with increasing light limitation as DOC inputs increased and decreasing nutrient limitation as TP inputs increased. Furthermore, across these diverse lake ecosystems, model predictions of GPP were highly correlated with observed values derived from high‐frequency sensor data. The GPP predictions using the updated parameters improved upon previous estimates, expanding the utility of a process model with simplified assumptions for water column mixing. Our analysis provides a model structure that may be broadly useful for understanding current and future patterns in lake primary production. Understanding the controls on lake productivity is essential for predicting the response of lake ecosystems to global change. Recent advances in mathematical models have provided a conceptual framework for modeling lake pelagic productivity, but these models need to be tested and refined. In this study, we used data from 58 lakes around the world to develop and improve a mathematical model of the nutrient‐color paradigm. We found that the updated model had better predictive power than previous models and accurately predicted primary production, mixed layer depth, and concentrations of nutrients in a diverse set of lakes. This improved model has the potential to be a valuable tool for understanding and predicting lake productivity in response to environmental changes. A mathematical formulation of the nutrient‐color paradigm accurately captures spatial variability in lake primary productionA data assimilation technique updated the lake process model parameters and improved model predictionsThis simple process model can be a useful tool for testing and predicting lake productivity responses to environmental change A mathematical formulation of the nutrient‐color paradigm accurately captures spatial variability in lake primary production A data assimilation technique updated the lake process model parameters and improved model predictions This simple process model can be a useful tool for testing and predicting lake productivity responses to environmental change

Published
2024
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70. Marsʼ Surface Radiation Environment Measured with the Mars Science Laboratoryʼs Curiosity Rover

Author

Hassler, Donald M., Zeitlin, Cary, Wimmer-Schweingruber, Robert F., Ehresmann, Bent, Rafkin, Scot, Eigenbrode, Jennifer L., Brinza, David E., Weigle, Gerald, Böttcher, Stephan, Böhm, Eckart, Burmeister, Soenke, Guo, Jingnan, Köhler, Jan, Martin, Cesar, Reitz, Guenther, Cucinotta, Francis A., Kim, Myung-Hee, Grinspoon, David, Bullock, Mark A., Posner, Arik, Gómez-Elvira, Javier, Vasavada, Ashwin, and Grotzinger, John P.

Published
2014

74. Mutual Facilitation Among Invading Nuttall’s Waterweed and Quagga Mussels

Author

Wegner, Benjamin, Kronsbein, Anna Lena, Gillefalk, Mikael, van de Weyer, Klaus, Köhler, Jan, Funke, Elisabeth, Monaghan, Michael T., and Hilt, Sabine

Subjects
macrophyte, lake, competition, invasional meltdown hypothesis, invasive species, Plant Science, Original Research
Abstract

Nuttall’s waterweed (Elodea nuttallii) is the most abundant invasive aquatic plant species in several European countries. Elodea populations often follow a boom-bust cycle, but the causes and consequences of this dynamics are yet unknown. We hypothesize that both boom and bust periods can be affected by dreissenid mussel invasions. While mutual facilitations between these invaders could explain their rapid parallel expansion, subsequent competition for space might occur. To test this hypothesis, we use data on temporal changes in the water quality and the abundance of E. nuttallii and the quagga mussel Dreissena rostriformis bugensis in a temperate shallow lake. Lake Müggel(see Germany) was turbid and devoid of submerged macrophytes for 20 years (1970–1989), but re-colonization with macrophytes started in 1990 upon reductions in nutrient loading. We mapped macrophyte abundance from 1999 and mussel abundance from 2011 onwards. E. nuttallii was first detected in 2011, spread rapidly, and was the most abundant macrophyte species by 2017. Native macrophyte species were not replaced, but spread more slowly, resulting in an overall increase in macrophyte coverage to 25% of the lake surface. The increased abundance of E. nuttallii was paralleled by increasing water clarity and decreasing total phosphorus concentrations in the water. These changes were attributed to a rapid invasion by quagga mussels in 2012. In 2017, they covered about one-third of the lake area, with mean abundances of 3,600 mussels m−2, filtering up to twice the lake’s volume every day. The increasing light availability in deeper littoral areas supported the rapid spread of waterweed, while in turn waterweed provided surface for mussel colonization. Quantities of dreissenid mussels and E. nuttallii measured at 24 locations were significantly correlated in 2016, and yearly means of E. nuttallii quantities increased with increasing mean dreissenid mussel quantities between 2011 and 2018. In 2018, both E. nuttallii and dreissenid abundances declined. These data imply that invasive waterweed and quagga mussels initially facilitated their establishment, supporting the invasional meltdown hypothesis, while subsequently competition for space may have occurred. Such temporal changes in invasive species interaction might contribute to the boom-bust dynamics that have been observed in Elodea populations.

Published
2019

78. Strengths and weaknesses of the Water Framework Directive (WFD)

Author

Grossart, Hans-Peter, Leibniz-Institut Für Gewässerökologie Und Binnenfischerei, Venohr, Markus, Gessner, Mark, Mehner, Thomas, Freyhof, Jörg, Hilt, Sabine, Pusch, Martin, Wolter, Christian, Jähnig, Sonja Charlotte, Graupner, Johannes, and Köhler, Jan

Subjects
Geologie, Hydrologie, Meteorologie, Boden- und Energiewirtschaft
Published
2019
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79. Stärken und Schwächen der Wasserrahmenrichtlinie (WRRL)

Author

Grossart, Hans-Peter, Leibniz-Institut Für Gewässerökologie Und Binnenfischerei, Venohr, Markus, Gessner, Mark, Mehner, Thomas, Freyhof, Jörg, Hilt, Sabine, Pusch, Martin, Wolter, Christian, Jähnig, Sonja Charlotte, Graupner, Johannes, and Köhler, Jan

Subjects
Geologie, Hydrologie, Meteorologie, Boden- und Energiewirtschaft
Published
2019
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80. Variation in species light acquisition traits under fluctuating light regimes

Author

Guislain, Alexis (Dr.), Beisner, Beatrix E., and Köhler, Jan

Subjects
ddc:570, Institut für Biochemie und Biologie
Abstract

Resource distribution heterogeneity offers niche opportunities for species with different functional traits to develop and potentially coexist. Available light (photosynthetically active radiation or PAR) for suspended algae (phytoplankton) may fluctuate greatly over time and space. Species-specific light acquisition traits capture important aspects of the ecophysiology of phytoplankton and characterize species growth at either limiting or saturating daily PAR supply. Efforts have been made to explain phytoplankton coexistence using species-specific light acquisition traits under constant light conditions, but not under fluctuating light regimes that should facilitate non-equilibrium coexistence. In the well-mixed, hypertrophic Lake TaiHu (China), we incubated the phytoplankton community in bottles placed either at fixed depths or moved vertically through the water column to mimic vertical mixing. Incubations at constant depths received only the diurnal changes in light, while the moving bottles received rapidly fluctuating light. Species-specific light acquisition traits of dominant cyanobacteria (Anabaena flos-aquae, Microcystis spp.) and diatom (Aulacoseira granulata, Cyclotella pseudostelligera) species were characterized from their growth-light relationships that could explain relative biomasses along the daily PAR gradient under both constant and fluctuating light. Our study demonstrates the importance of interspecific differences in affinities to limiting and saturating light for the coexistence of phytoplankton species in spatially heterogeneous light conditions. Furthermore, we observed strong intraspecific differences in light acquisition traits between incubation under constant and fluctuating light - leading to the reversal of light utilization strategies of species. This increased the niche space for acclimated species, precluding competitive exclusion. These observations could enhance our understanding of the mechanisms behind the Paradox of the Plankton.

Published
2018

82. Incomplete recovery of a shallow lake from a natural browning event.

Author

Kazanjian, Garabet, Brothers, Soren, Köhler, Jan, and Hilt, Sabine

Subjects
DISSOLVED organic matter, LAKES, BIOMASS production, WATER levels, WATER chemistry, LAKE restoration
Abstract

Terrestrial loads of dissolved organic carbon (DOC) have increased in recent years in many north temperate lakes, leading to widespread brownification. This process can profoundly alter the relative strength of planktonic and benthic primary production in lakes due to changes in light and nutrient availability. While most existing in situ studies of brownification focus on gradual decadal trends, short‐term flooding can induce rather sudden natural browning events in lakes.We investigated the recovery of a small, temperate, groundwater‐fed shallow lake from a strong natural flooding‐induced browning and nutrient loading event. We hypothesised that along with a return to pre‐flood lake water levels, DOC concentrations would return to pre‐flood concentrations due to bacterial and photolytic mineralisation and flocculation, while total phosphorus (TP) concentrations would show a delayed and potentially incomplete recovery due to sustaining effects of phytoplankton dominance on nutrient dynamics in the lake. Phytoplankton gross primary production (GPP), which surged in response to higher nutrient concentrations and a compressed mixing depth, was expected to follow the same recovery pattern as TP. Benthic periphyton GPP was expected to recover in tandem with improving light conditions.We measured post‐flood water levels, water chemistry, and summer pelagic and benthic GPP. The lake water level declined gradually, returning to pre‐flood levels within 4 years. As hypothesised, DOC concentrations initially declined rapidly, but remained 1.5‐fold higher (c. 22 mg/L) than pre‐flood values 3 years after peak browning. TP concentrations fluctuated greatly between seasons but remained generally elevated in subsequent years, being roughly double pre‐browning values (c. 130 µg/L) 3 years post‐flood. Measurements taken in 2019, 7 years after the initial browning event, showed both DOC and TP concentrations remaining at these elevated levels.Across the intensive study period 3 years before and after peak browning (2010–2015), TP concentrations were positively correlated to summer phytoplankton biomass, while DOC and TP concentrations were negatively correlated to summer periphyton biomass and GPP. Accordingly, the lake's recovery period exhibited a decline of pelagic GPP and a partial recovery of summer periphyton biomass and production, although a full return to pre‐flood values was not recorded in either case. Whole‐lake areal summertime GPP increased due to browning and remained higher than before the browning event.This study provides a rare examination of differences in response rates between DOC, TP, and autotrophic structure in a shallow, temperate lake following a natural flood‐induced extreme browning event. The available data provide compelling evidence that browning events can produce lasting changes in the water chemistry, trophic status, and productive pathways of a lake, persisting beyond the lake's return to pre‐flood water levels. Such delayed or incomplete recoveries from flooding‐induced browning and nutrient loading may have consequences for regional and long‐term temporal trends in lake biogeochemistry, potentially contributing to the widespread phenomenon of incremental brownification. [ABSTRACT FROM AUTHOR]

Published
2021
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83. Response of submerged macrophyte communities to external and internal restoration measures in north temperate shallow lakes

Author

Hilt, Sabine, Alirangues Nuñez, Marta M., Bakker, Elisabeth S., Blindow, Irmgard, Davidson, Thomas A., Gillefalk, Mikael, Hansson, Lars-Anders, Janse, Jan H., Janssen, Annette B. G., Jeppesen, Erik, Kabus, Timm, Kelly, Andrea, Köhler, Jan, Lauridsen, Torben L., Mooij, Wolf M., Noordhuis, Ruurd, Phillips, Geoff, Rücker, Jacqueline, Schuster, Hans-Heinrich, Søndergaard, Martin, Teurlincx, Sven, van de Weyer, Klaus, van Donk, Ellen, Waterstraat, Arno, Willby, Nigel J., Sayer, Carl D., and Aquatic Ecology (AqE)

Subjects
Aquatic Ecology and Water Quality Management, aquatic plants, LONG-TERM, PCLake, Plant Science, ZANNICHELLIA TAXA, EUTROPHIC LAKES, POTAMOGETON-PECTINATUS L, Regime shift, Lakerestoration, Biomanipulation, RESOURCE-ALLOCATION, Aquaticplants, Original Research, nutrient load reduction, plant traits, regime shift, biomanipulation, lake restoration, eutrophication, OF-THE-ART, Plant traits, WIMEK, REGIME SHIFTS, ECOSYSTEM MODEL PCLAKE, SEASONAL DYNAMICS, lake restoration. nutrient load reduction, Aquatische Ecologie en Waterkwaliteitsbeheer, Eutrophication, PE&RC, Nutrient loadreduction, international, AQUATIC MACROPHYTES, Water Systems and Global Change
Abstract

Submerged macrophytes play a key role in north temperate shallow lakes by stabilizing clear-water conditions. Eutrophication has resulted in macrophyte loss and shifts to turbid conditions in many lakes. Considerable efforts have been devoted to shallow lake restoration in many countries, but long-term success depends on a stable recovery of submerged macrophytes. However, recovery patterns vary widely and remain to be fully understood. We hypothesize that reduced external nutrient loading leads to an intermediate recovery state with clear spring and turbid summer conditions similar to the pattern described for eutrophication. In contrast, lake internal restoration measures can result in transient clear-water conditions both in spring and summer and reversals to turbid conditions. Furthermore, we hypothesize that these contrasting restoration measures result in different macrophyte species composition, with added implications for seasonal dynamics due to differences in plant traits. To test these hypotheses, we analyzed data on water quality and submerged macrophytes from 49 north temperate shallow lakes that were in a turbid state and subjected to restoration measures. To study the dynamics of macrophytes during nutrient load reduction, we adapted the ecosystem model PCLake. Our survey and model simulations revealed the existence of an intermediate recovery state upon reduced external nutrient loading, characterized by spring clear-water phases and turbid summers, whereas internal lake restoration measures often resulted in clear-water conditions in spring and summer with returns to turbid conditions after some years. External and internal lake restoration measures resulted in different macrophyte communities. The intermediate recovery state following reduced nutrient loading is characterized by a few macrophyte species (mainly pondweeds) that can resist wave action allowing survival in shallow areas, germinate early in spring, have energy-rich vegetative propagules facilitating rapid initial growth and that can complete their life cycle by early summer. Later in the growing season these plants are, according to our simulations, outcompeted by periphyton, leading to late-summer phytoplankton blooms. Internal lake restoration measures often coincide with a rapid but transient colonization by hornworts, waterweeds or charophytes. Stable clear-water conditions and a diverse macrophyte flora only occurred decades after external nutrient load reduction or when measures were combined.

Published
2018
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84. Intrinsic functional connectivity, CSF biomarker profiles and their relation to cognitive function in mild cognitive impairment.

Author

Matura, Silke, Köhler, Jan, Reif, Andreas, Fusser, Fabian, Karakaya, Tarik, Scheibe, Monika, Ehret, Felix, Hartmann, Daniel, Kang, Jun-Suk, Mayer, Christoph, Prvulovic, David, and Pantel, Johannes

Subjects
*FUNCTIONAL connectivity, *MILD cognitive impairment, *FUNCTIONAL magnetic resonance imaging, *COGNITIVE ability, *ALZHEIMER'S disease, *BIOMARKERS
Abstract

Mild cognitive impairment (MCI) often precedes Alzheimer's Dementia (AD), and in a high proportion of individuals affected by MCI, there are already neuropathological processes ongoing that become more evident when patients progress to AD. Accordingly, there is a need for reliable biomarkers to distinguish between normal aging and incipient AD. Recent research suggests that, in addition to established biomarkers such as CSF Aß42, total tau and hyperphosphorylated tau, resting state connectivity established by functional magnetic resonance imaging might also be a feasible biomarker for prodromal stages of AD. In order to explore this possibility, we investigated resting state functional connectivity as well as cerebrospinal fluid (CSF) biomarker profiles in patients with MCI (n = 30; age 66.43 ± 7.06 years) and cognitively healthy controls (n = 38; age 66.89 ± 7.12 years). CSF Aß42, total tau and hyperphosphorylated tau concentrations were correlated with measures of cognitive performance (immediate and delayed recall, global cognition, processing speed). Moreover, MCI-related alterations in intrinsic functional connectivity within the default mode network were investigated using functional resting state MRI. As expected, MCI patients showed decreased CSF Aß42 and increased total tau concentrations. These alterations were associated with cognitive performance. However, there were no differences between MCI patients and cognitively healthy controls regarding intrinsic functional connectivity. In conclusion, our results indicate that CSF protein profiles seem to be more closely related to cognitive decline than alterations in resting state activity. Thus, resting state connectivity might not be a reliable biomarker for early stages of AD. [ABSTRACT FROM AUTHOR]

Published
2020
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85. Transplanted Human Pluripotent Stem Cell-Derived Mesenchymal Stem Cells Support Liver Regeneration in Gunn Rats

Author

Spitzhorn, Lucas-Sebastian, primary, Kordes, Claus, additional, Megges, Matthias, additional, Sawitza, Iris, additional, Götze, Silke, additional, Reichert, Doreen, additional, Schulze-Matz, Peggy, additional, Graffmann, Nina, additional, Bohndorf, Martina, additional, Wruck, Wasco, additional, Köhler, Jan Philipp, additional, Herebian, Diran, additional, Mayatepek, Ertan, additional, Oreffo, Richard O.C., additional, Häussinger, Dieter, additional, and Adjaye, James, additional

Published
2018
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87. Influence of vertical mixing on light‐dependency of phytoplankton growth

Author

Köhler, Jan, Wang, Lang, Guislain, Alexis, and Shatwell, Tom

Subjects
photosynthesis, functional traits, turbulent mixing, Three Gorges reservoir, algal dynamics
Abstract

Phytoplankton growth depends not only on mean intensity but also on the dynamics of the light supply. In surface mixed layers, phytoplankton may rapidly move between strong light and almost darkness. The nonlinear light‐dependency of growth may differ between constant and fluctuating light because of the different frequency distribution of light and/or acclimation processes. The present study compares for the first time light‐dependency of photosynthesis and growth of phytoplankton communities in situ under defined mixing conditions and at fixed depths. Maximum growth rates per day were not significantly different, but the growth efficiency was much higher under constant light than under fluctuating light of sub‐saturating daily irradiance. Phytoplankton incubated under fluctuating light needed about three times higher mean daily irradiances to balance photosynthesis and losses than under constant light. The difference in growth efficiency was mostly caused by the different frequency distribution of underwater light, as was estimated by a photosynthesis model of sufficient temporal resolution. The present study indicates a considerable overestimation of phytoplankton growth at sub‐saturating light in well‐mixed water layers by the common growth measurements under constant light. This implies an underestimation of the compensation light intensities and respective overestimations of the critical mixing depths.

Published
2017
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88. Il castello di carte. La transizione all'età adulta dei giovani Neet a Roma

Author

Nerli Ballati, Enrico and Köhler, Jan

Subjects
Social sciences (General), H1-99, digestive, oral, and skin physiology, Youth Transitions, Sociology (General), Pathways to Adulthood, NEETs, HM401-1281
Abstract

The paper focuses on the transition to adulthood of young people not in education, employment or training (NEETs). In the Italian context, unemployment, inactivity and problematic transitions to work are strongly related to delayed transition to adulthood and patterns of dependency on family. Our study aims to identify pathways to adulthood of NEETs from a biographical perspective. We carry out a software-based qualitative content analysis on 32 in-depth interviews, which have been conducted with NEETs between 25 and 34 years old in Rome and its surroundings as a part of a research project founded by Sapienza University of Rome. An empirically grounded typology of transition to adulthood based on position in the household, biographical sequence of life events and subjective aspirations for autonomy is constructed and six types are presented and characterized regarding dependency patterns, expectations for the future and subjective strategies to leave NEET-condition., Cambio. Rivista sulle Trasformazioni Sociali, Vol. 5 No. 10 (2015)

Published
2016

89. Gelöste organische Stickstoffverbindungen in Seen - Vorkommen und Wirkung

Author

Fiedler, Dorothea and Köhler, Jan

Subjects
Stickstoffgehalt, Stickstoff, ddc:551
Abstract

Die Konzentration von Gesamt-DON betrug in den vier Modellseen im Jahresdurchschnitt 0.54 mg L-1 und übertraf damit die mittleren Konzentrationen von DIN (0.11-0.35 mg L-1) in allen Modellseen außer der Unterhavel. Huminstoffe und hochmolekulare Substanzen machen mit 80 - 93% den größten Anteil von DON aus, gefolgt von Harnstoff mit 6 - 16%. Die Konzentrationen von Aminosäuren sind so gering, dass ihnen im Folgenden keine weitere Bedeutung zugemessen wird. Die DON-Verbindungen sind innerhalb der einzelnen Gewässer über alle vier Jahreszeiten nahezu konstant. Dagegen zeigen die DIN-Verbindungen, besonders Nitrat, ein saisonales Muster. Sie erreichen im Winter ihre höchsten Konzentrationen und liegen im Sommer im Bereich der Nachweisgrenze. Daher ist der relative Anteil von DON-Verbindungen an der TN-Konzentration im Sommer deutlich höher. Von den DIN-Verbindungen Nitrat und Ammonium weiß man, dass sie von Algen für ihr Wachstum gut genutzt werden können. Sie werden beim Aufbau der Algenbiomasse bis zum Sommer nahezu aufgebraucht, weshalb sie im Sommer häufig nicht mehr nachweisbar sind. Daher tritt nach unseren bisherigen Untersuchungen besonders im Sommer in vielen Gewässern eine Begrenzung der Algen-biomasse durch Stickstoff auf (NITROLIMIT Diskussionspapier, Band 1). Allerdings könnten die Algen von den weiterhin reichlich vorhandenen DON-Verbindungen profitieren, wenn sie diese nutzen können. Unsere Studie zeigte, dass die verschiedenen DON-Verbindungen in unterschiedlichen Konzentrationen vorliegen und unterschiedlich durch Algen nutzbar sind. Mit zunehmender Komplexität der DON-Verbindungen nimmt die Nutzbarkeit durch Algen ab. Als am besten nutzbar erwies sich Harnstoff. Dessen relativ konstante Konzentration im Jahresverlauf trotz seiner guten Nutzbarkeit ist überraschend und am ehesten durch rasche Nachlieferung, etwa durch bakteriellen Abbau höhermolekularer N-Verbindungen, erklärbar. Die Nutzbarkeit von Huminstoffen hängt laut unseren ersten Untersuchungen auch von deren Ursprung und Alter ab. Während die frisch aus der Kläranlage Waßmannsdorf kommenden Huminstoffe von Algen für ihr Wachstum genutzt wurden, waren die schon länger in den untersuchten drei Seen befindlichen Huminstoffe kaum noch nutzbar. Der hohe Anteil von Huminstoffen und hochmolekularen Substanzen am TN könnte eine Ursache für die große Variabilität der TN-Zielwerte zum Erreichen des guten ökologischen Zustandes sein (NITROLIMIT Diskussionspapier, Band 1). Diese Substanzen können überwiegend nicht gut von Algen zum Aufbau von Biomasse genutzt werden und führen daher bei der Analyse des Zusammenhangs zwischen Biomasse und TN zu einer erhöhten Streuung (der TN-Zielwert wird hierbei über eine Regressionsanalyse zwischen Biomasse und der TN-Konzentration abgeleitet). Theoretisch sollten die Konzentrationen aller DON-Verbindungen, die nicht durch Algen nutzbar sind, von der TN-Konzentration subtrahiert werden. Die so kalkulierten Konzentrationen von durch Algen nutzbarem Stickstoff sollten einen besseren statistischen Zusammenhang mit der Algenbiomasse aufweisen als TN. Damit könnte die Streuung der Stickstoff-Zielwerte vermindert werden. Allerdings werden derartige Auswertungen erst möglich, wenn die Datenbasis zu algenverfügbaren DON-Verbindungen auf ähnlichem Niveau ist wie die zu DIN und TN. Zu letzteren liegen Daten für hunderte von Seen über mehrere Jahre vor, während Daten zu DON hier erstmals für vier Gewässer erhoben wurden.

Published
2016

95. Variation in species light acquisition traits under fluctuating light regimes: implications for non‐equilibrium coexistence.

Author

Guislain, Alexis, Beisner, Beatrix E., and Köhler, Jan

Subjects
COEXISTENCE of species, ECOLOGICAL niche, PHYTOPLANKTON, ANIMAL introduction, ECOPHYSIOLOGY
Abstract

Resource distribution heterogeneity offers niche opportunities for species with different functional traits to develop and potentially coexist. Available light (photosynthetically active radiation or PAR) for suspended algae (phytoplankton) may fluctuate greatly over time and space. Species‐specific light acquisition traits capture important aspects of the ecophysiology of phytoplankton and characterize species growth at either limiting or saturating daily PAR supply. Efforts have been made to explain phytoplankton coexistence using species‐specific light acquisition traits under constant light conditions, but not under fluctuating light regimes that should facilitate non‐equilibrium coexistence. In the well‐mixed, hypertrophic Lake TaiHu (China), we incubated the phytoplankton community in bottles placed either at fixed depths or moved vertically through the water column to mimic vertical mixing. Incubations at constant depths received only the diurnal changes in light, while the moving bottles received rapidly fluctuating light. Species‐specific light acquisition traits of dominant cyanobacteria (Anabaena flos‐aquae, Microcystis spp.) and diatom (Aulacoseira granulata, Cyclotella pseudostelligera) species were characterized from their growth–light relationships that could explain relative biomasses along the daily PAR gradient under both constant and fluctuating light. Our study demonstrates the importance of interspecific differences in affinities to limiting and saturating light for the coexistence of phytoplankton species in spatially heterogeneous light conditions. Furthermore, we observed strong intraspecific differences in light acquisition traits between incubation under constant and fluctuating light – leading to the reversal of light utilization strategies of species. This increased the niche space for acclimated species, precluding competitive exclusion. These observations could enhance our understanding of the mechanisms behind the Paradox of the Plankton. [ABSTRACT FROM AUTHOR]

Published
2019
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96. Benthic carbon is inefficiently transferred in the food webs of two eutrophic shallow lakes

Author

Lischke, Betty, Mehner, Thomas, Hilt, Sabine, Attermeyer, Katrin, Brauns, Mario, Brothers, Soren, Grossart, Hans Peter, Köhler, Jan, Scharnweber, Kristin, Gaedke, Ursula, Lischke, Betty, Mehner, Thomas, Hilt, Sabine, Attermeyer, Katrin, Brauns, Mario, Brothers, Soren, Grossart, Hans Peter, Köhler, Jan, Scharnweber, Kristin, and Gaedke, Ursula

Abstract

1. The sum of benthic autotrophic and bacterial production often exceeds the sum of pelagic autotrophic and bacterial production, and hence may contribute sub- stantially to whole-lake carbon fluxes, especially in shallow lakes. Furthermore, both benthic and pelagic autotrophic and bacterial production are highly edible and of sufficient nutritional quality for animal consumers. We thus hypothesised that pelagic and benthic transfer efficiencies (ratios of production at adjacent trophic levels) in shallow lakes should be similar. 2. We performed whole ecosystem studies in two shallow lakes (3.5 ha, mean depth 2 m), one with and one without submerged macrophytes, and quantified pelagic and benthic biomass, production and transfer efficiencies for bacteria, phytoplank- ton, epipelon, epiphyton, macrophytes, zooplankton, macrozoobenthos and fish. We expected higher transfer efficiencies in the lake with macrophytes, because these provide shelter and food for macrozoobenthos and may thus enable a more efficient conversion of basal production to consumer production. 3. In both lakes, the majority of the whole-lake autotrophic and bacterial produc- tion was provided by benthic organisms, but whole-lake primary consumer pro- duction mostly relied on pelagic autotrophic and bacterial production. Consequently, transfer efficiency of benthic autotrophic and bacterial production to macrozoobenthos production was an order of magnitude lower than the transfer efficiency of pelagic autotrophic and bacterial production to rotifer and crustacean production. Between-lake differences in transfer efficiencies were minor. 4. We discuss several aspects potentially causing the unexpectedly low benthic transfer efficiencies, such as the food quality of producers, pelagic–benthic links, oxygen concentrations in the deeper lake areas and additional unaccounted con- sumer production by pelagic and benthic protozoa and meiobenthos at interme- diate or top trophic levels. None of these process

Published
2017
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97. Evidence for indigenous nitrogen in sedimentary and aeolian deposits from the Curiosity rover investigations at Gale crater, Mars

Author

Stern, Jennifer C., Sutter, Brad, Freissinet, Caroline, Navarro-González, Rafael, McKay, Christopher P., Archer, P. Douglas, Buch, Arnaud, Brunner, Anna E., Coll, Patrice, Eigenbrode, Jennifer L., Fairen, Alberto G., Franz, Heather B., Glavin, Daniel P., Kashyap, Srishti, McAdam, Amy C., Ming, Douglas W., Steele, Andrew, Szopa, Cyril, Wray, James J., Martín-Torres, F. Javier, Zorzano, Maria-Paz, Conrad, Pamela G., Mahaffy, Paul R., Kemppinen, Osku, Bridges, Nathan, Johnson, Jeffrey R., Minitti, Michelle, Cremers, David, Bell, James F., Edgar, Lauren, Farmer, Jack, Godber, Austin, Wadhwa, Meenakshi, Wellington, Danika, McEwan, Ian, Newman, Claire, Richardson, Mark, Charpentier, Antoine, Peret, Laurent, King, Penelope, Blank, Jennifer, Weigle, Gerald, Schmidt, Mariek, Li, Shuai, Milliken, Ralph, Robertson, Kevin, Sun, Vivian, Baker, Michael, Edwards, Christopher, Ehlmann, Bethany, Farley, Kenneth, Griffes, Jennifer, Grotzinger, John, Miller, Hayden, Newcombe, Megan, Pilorget, Cedric, Rice, Melissa, Siebach, Kirsten, Stack, Katie, Stolper, Edward, Brunet, Claude, Hipkin, Victoria, Léveillé, Richard, Marchand, Geneviève, Sánchez, Pablo Sobrón, Favot, Laurent, Cody, George, Flückiger, Lorenzo, Lees, David, Nefian, Ara, Martin, Mildred, Gailhanou, Marc, Westall, Frances, Israël, Guy, Agard, Christophe, Baroukh, Julien, Donny, Christophe, Gaboriaud, Alain, Guillemot, Philippe, Lafaille, Vivian, Lorigny, Eric, Paillet, Alexis, Pérez, René, Saccoccio, Muriel, Yana, Charles, Armiens-Aparicio, Carlos, Rodríguez, Javier Caride, Blázquez, Isaías Carrasco, Gómez, Felipe Gómez, Gómez-Elvira, Javier, Hettrich, Sebastian, Malvitte, Alain Lepinette, Jiménez, Mercedes Marín, Martínez-Frías, Jesús, Martín-Soler, Javier, Torres, F. Javier Martín, Jurado, Antonio Molina, Mora-Sotomayor, Luis, Caro, Guillermo Muñoz, López, Sara Navarro, Peinado-González, Verónica, Pla-García, Jorge, Manfredi, José Antonio Rodriguez, Romeral-Planelló, Julio José, Fuentes, Sara Alejandra Sans, Martinez, Eduardo Sebastian, Redondo, Josefina Torres, Urqui-O'Callaghan, Roser, Mier, María-Paz Zorzano, Chipera, Steve, Lacour, Jean-Luc, Mauchien, Patrick, Sirven, Jean-Baptiste, Manning, Heidi, Fairén, Alberto, Hayes, Alexander, Joseph, Jonathan, Squyres, Steven, Sullivan, Robert, Thomas, Peter, Dupont, Audrey, Lundberg, Angela, Melikechi, Noureddine, Mezzacappa, Alissa, DeMarines, Julia, Grinspoon, David, Reitz, Günther, Prats, Benito, Atlaskin, Evgeny, Genzer, Maria, Harri, Ari-Matti, Haukka, Harri, Kahanpää, Henrik, Kauhanen, Janne, Paton, Mark, Polkko, Jouni, Schmidt, Walter, Siili, Tero, Fabre, Cécile, Wray, James, Wilhelm, Mary Beth, Poitrasson, Franck, Patel, Kiran, Gorevan, Stephen, Indyk, Stephen, Paulsen, Gale, Gupta, Sanjeev, Bish, David, Schieber, Juergen, Gondet, Brigitte, Langevin, Yves, Geffroy, Claude, Baratoux, David, Berger, Gilles, Cros, Alain, d’Uston, Claude, Forni, Olivier, Gasnault, Olivier, Lasue, Jérémie, Lee, Qiu-Mei, Maurice, Sylvestre, Meslin, Pierre-Yves, Pallier, Etienne, Parot, Yann, Pinet, Patrick, Schröder, Susanne, Toplis, Mike, Lewin, Éric, Brunner, Will, Heydari, Ezat, Achilles, Cherie, Oehler, Dorothy, Cabane, Michel, Coscia, David, Dromart, Gilles, Robert, François, Sautter, Violaine, Le Mouélic, Stéphane, Mangold, Nicolas, Nachon, Marion, Stalport, Fabien, François, Pascaline, Raulin, François, Teinturier, Samuel, Cameron, James, Clegg, Sam, Cousin, Agnès, DeLapp, Dorothea, Dingler, Robert, Jackson, Ryan Steele, Johnstone, Stephen, Lanza, Nina, Little, Cynthia, Nelson, Tony, Wiens, Roger C., Williams, Richard B., Jones, Andrea, Kirkland, Laurel, Treiman, Allan, Baker, Burt, Cantor, Bruce, Caplinger, Michael, Davis, Scott, Duston, Brian, Edgett, Kenneth, Fay, Donald, Hardgrove, Craig, Harker, David, Herrera, Paul, Jensen, Elsa, Kennedy, Megan R., Krezoski, Gillian, Krysak, Daniel, Lipkaman, Leslie, Malin, Michael, McCartney, Elaina, McNair, Sean, Nixon, Brian, Posiolova, Liliya, Ravine, Michael, Salamon, Andrew, Saper, Lee, Stoiber, Kevin, Supulver, Kimberley, Van Beek, Jason, Van Beek, Tessa, Zimdar, Robert, French, Katherine Louise, Iagnemma, Karl, Miller, Kristen, Summons, Roger, Goesmann, Fred, Goetz, Walter, Hviid, Stubbe, Johnson, Micah, Lefavor, Matthew, Lyness, Eric, Breves, Elly, Dyar, M. Darby, Fassett, Caleb, Blake, David F., Bristow, Thomas, DesMarais, David, Edwards, Laurence, Haberle, Robert, Hoehler, Tori, Hollingsworth, Jeff, Kahre, Melinda, Keely, Leslie, McKay, Christopher, Bleacher, Lora, Brinckerhoff, William, Choi, David, Conrad, Pamela, Dworkin, Jason P., Eigenbrode, Jennifer, Floyd, Melissa, Garvin, James, Glavin, Daniel, Harpold, Daniel, Mahaffy, Paul, Martin, David K., McAdam, Amy, Pavlov, Alexander, Raaen, Eric, Smith, Michael D., Stern, Jennifer, Tan, Florence, Trainer, Melissa, Meyer, Michael, Posner, Arik, Voytek, Mary, Anderson, Robert C, Aubrey, Andrew, Beegle, Luther W., Behar, Alberto, Blaney, Diana, Brinza, David, Calef, Fred, Christensen, Lance, Crisp, Joy A., DeFlores, Lauren, Feldman, Jason, Feldman, Sabrina, Flesch, Gregory, Hurowitz, Joel, Jun, Insoo, Keymeulen, Didier, Maki, Justin, Mischna, Michael, Morookian, John Michael, Parker, Timothy, Pavri, Betina, Schoppers, Marcel, Sengstacken, Aaron, Simmonds, John J., Spanovich, Nicole, Juarez, Manuel de la Torre, Vasavada, Ashwin R., Webster, Christopher R., Yen, Albert, Archer, Paul Douglas, Cucinotta, Francis, Jones, John H., Ming, Douglas, Morris, Richard V., Niles, Paul, Rampe, Elizabeth, Nolan, Thomas, Fisk, Martin, Radziemski, Leon, Barraclough, Bruce, Bender, Steve, Berman, Daniel, Dobrea, Eldar Noe, Tokar, Robert, Vaniman, David, Williams, Rebecca M. E., Yingst, Aileen, Lewis, Kevin, Leshin, Laurie, Cleghorn, Timothy, Huntress, Wesley, Manhès, Gérard, Hudgins, Judy, Olson, Timothy, Stewart, Noel, Sarrazin, Philippe, Grant, John, Vicenzi, Edward, Wilson, Sharon A., Bullock, Mark, Ehresmann, Bent, Hamilton, Victoria, Hassler, Donald, Peterson, Joseph, Rafkin, Scot, Zeitlin, Cary, Fedosov, Fedor, Golovin, Dmitry, Karpushkina, Natalya, Kozyrev, Alexander, Litvak, Maxim, Malakhov, Alexey, Mitrofanov, Igor, Mokrousov, Maxim, Nikiforov, Sergey, Prokhorov, Vasily, Sanin, Anton, Tretyakov, Vladislav, Varenikov, Alexey, Vostrukhin, Andrey, Kuzmin, Ruslan, Clark, Benton, Wolff, Michael, McLennan, Scott, Botta, Oliver, Drake, Darrell, Bean, Keri, Lemmon, Mark, Schwenzer, Susanne P., Anderson, Ryan B., Herkenhoff, Kenneth, Lee, Ella Mae, Sucharski, Robert, Hernández, Miguel Ángel de Pablo, Ávalos, Juan José Blanco, Ramos, Miguel, Kim, Myung-Hee, Malespin, Charles, Plante, Ianik, Muller, Jan-Peter, Ewing, Ryan, Boynton, William, Downs, Robert, Fitzgibbon, Mike, Harshman, Karl, Morrison, Shaunna, Dietrich, William, Kortmann, Onno, Palucis, Marisa, Sumner, Dawn Y., Williams, Amy, Lugmair, Günter, Wilson, Michael A., Rubin, David, Jakosky, Bruce, Balic-Zunic, Tonci, Frydenvang, Jens, Jensen, Jaqueline Kløvgaard, Kinch, Kjartan, Koefoed, Asmus, Madsen, Morten Bo, Stipp, Susan Louise Svane, Boyd, Nick, Campbell, John L., Gellert, Ralf, Perrett, Glynis, Pradler, Irina, VanBommel, Scott, Jacob, Samantha, Owen, Tobias, Rowland, Scott, Savijärvi, Hannu, Boehm, Eckart, Böttcher, Stephan, Burmeister, Sönke, Guo, Jingnan, Köhler, Jan, García, César Martín, Mueller-Mellin, Reinhold, Wimmer-Schweingruber, Robert, Bridges, John C., McConnochie, Timothy, Benna, Mehdi, Franz, Heather, Bower, Hannah, Brunner, Anna, Blau, Hannah, Boucher, Thomas, Carmosino, Marco, Atreya, Sushil, Elliott, Harvey, Halleaux, Douglas, Rennó, Nilton, Wong, Michael, Pepin, Robert, Elliott, Beverley, Spray, John, Thompson, Lucy, Gordon, Suzanne, Newsom, Horton, Ollila, Ann, Williams, Joshua, Vasconcelos, Paulo, Bentz, Jennifer, Nealson, Kenneth, Popa, Radu, Kah, Linda C., Moersch, Jeffrey, Tate, Christopher, Day, Mackenzie, Kocurek, Gary, Hallet, Bernard, Sletten, Ronald, Francis, Raymond, McCullough, Emily, Cloutis, Ed, ten Kate, Inge Loes, Arvidson, Raymond, Fraeman, Abigail, Scholes, Daniel, Slavney, Susan, Stein, Thomas, Ward, Jennifer, Berger, Jeffrey, Moores, John E., NASA Goddard Space Flight Center (GSFC), NASA Johnson Space Center (JSC), NASA, Laboratorio de Química de Plasmas y Estudios Planetarios [Mexico], Instituto de Ciencias Nucleares [Mexico], Universidad Nacional Autónoma de México = National Autonomous University of Mexico (UNAM)-Universidad Nacional Autónoma de México = National Autonomous University of Mexico (UNAM), NASA Ames Research Center (ARC), Laboratoire de Génie des Procédés et Matériaux - EA 4038 (LGPM), CentraleSupélec, ASU School of Earth and Space Exploration (SESE), Arizona State University [Tempe] (ASU), Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA (UMR_7583)), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS), Department of Astronomy [Ithaca], Cornell University [New York], Centro de Astrobiologia [Madrid] (CAB), Instituto Nacional de Técnica Aeroespacial (INTA)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Center for Research and Exploration in Space Science and Technology [GSFC] (CRESST), Centre de Recherche Public Henri Tudor [Technoport] (CRP Henri Tudor), Centre de Recherche Public Henri-Tudor [Luxembourg] (CRP Henri-Tudor), Department of Microbiology [Amherst], University of Massachusetts [Amherst] (UMass Amherst), University of Massachusetts System (UMASS)-University of Massachusetts System (UMASS), Astromaterials Research and Exploration Science (ARES), NASA-NASA, Geophysical Laboratory [Carnegie Institution], Carnegie Institution for Science, PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), School of Earth and Atmospheric Sciences [Atlanta], Georgia Institute of Technology [Atlanta], Instituto Andaluz de Ciencias de la Tierra (IACT), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Universidad de Granada (UGR), Department of Computer Science, Electrical and Space Engineering [Luleå], Luleå University of Technology (LUT), Universidad Nacional Autónoma de México (UNAM)-Universidad Nacional Autónoma de México (UNAM), Carnegie Institution for Science [Washington], Universidad de Granada (UGR)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Cornell University, Instituto Nacional de Técnica Aeroespacial (INTA)-Consejo Superior de Investigaciones Científicas [Spain] (CSIC), Department of Microbiology, IMPEC - LATMOS, Universidad de Granada (UGR)-Consejo Superior de Investigaciones Científicas [Spain] (CSIC), and Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Universidad de Granada = University of Granada (UGR)

Subjects
Martian, Multidisciplinary, 010504 meteorology & atmospheric sciences, Water on Mars, nitrates, astrobiology, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Mars, Mars Exploration Program, 01 natural sciences, nitrogen, Astrobiology, Curiosity, 13. Climate action, Rocknest, 0103 physical sciences, Sample Analysis at Mars, Physical Sciences, Aeolian processes, Composition of Mars, 010303 astronomy & astrophysics, Nitrogen cycle, Geology, 0105 earth and related environmental sciences
Abstract

International audience; The Sample Analysis at Mars (SAM) investigation on the Mars Science Laboratory (MSL) Curiosity rover has detected oxidized nitrogen-bearing compounds during pyrolysis of scooped aeolian sediments and drilled sedimentary deposits within Gale crater. Total N concentrations ranged from 20 to 250 nmol N per sample. After subtraction of known N sources in SAM, our results support the equivalent of 110–300 ppm of nitrate in the Rocknest (RN) aeolian samples, and 70–260 and 330–1,100 ppm nitrate in John Klein (JK) and Cumberland (CB) mudstone deposits, respectively. Discovery of indigenous martian nitrogen in Mars surface materials has important implications for habitability and, specifically, for the potential evolution of a nitrogen cycle at some point in martian history. The detection of nitrate in both wind-drifted fines (RN) and in mudstone (JK, CB) is likely a result of N2 fixation to nitrate generated by thermal shock from impact or volcanic plume lightning on ancient Mars. Fixed nitrogen could have facilitated the development of a primitive nitrogen cycle on the surface of ancient Mars, potentially providing a biochemically accessible source of nitrogen.

Published
2015
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98. Effects of large- and small-scale river restoration on hydromorphology and ecology:Deliverable 4.3 Results of the hydromorphological and ecological survey

Author

Kail, Jochem, Hering, Daniel, Aroviita, Jukka, Baattrup-Pedersen, Annette, Brabec, Karel, Ecke, Frauke, Gielczewski, Marek, Januschke, Kathrin, Kaufmann, Simon, Lorenz, Armin W., Paillex, Amael, Poppe, Michala, Rääpysjärvi, Jaana, Verdonschot, Piet F.M., Buijse, Tom, Köhler, Jan, Kupilas, Benjamin, Schmidt, Torsten, Schmutz, Stefan, Vermaat, Jan, Verdonschot, Ralf, Wolter, Christian, Stelmaszczyk, Mateus, Jurajda, P., Scheunig, Sabine, Hellsten, Seppo, Göthe, Emma, Timmermann, Allan, and Friberg, Nikolai

Published
2015

100. Diurnal variations of energetic particle radiation at the surface of Mars as observed by the Mars Science Laboratory Radiation Assessment Detector

Author

Rafkin, Scot C. R., Zeitlin, Cary, Ehresmann, Bent, Hassler, Donald M., Guo, Jingnan, Köhler, Jan, Wimmer-Schweingruber, Robert F., Gómez-Elvira, Javier, Harri, Ari-Matti, Kahanpää, Henrik, Brinza, David E., Weigle, Gerald, Böttcher, Stephan, Böhm, Eckart, Burmeister, Söenke, Martín, César, Reitz, Güenther, Cucinotta, Francis A., Kim, Myung-Hee, Grinspoon, David, Bullock, Mark A., Posner, Arik, MSL Science Team, and Martínez-Frías, J.

Subjects
Physics, Radiation, Meteorology, Space weather, Atmosphere, Mars, Mars Science Laboratory, Mars Exploration Program, Atmospheric sciences, Radiation assessment detector, Physics::Geophysics, Computer Science::Robotics, Geophysics, Space and Planetary Science, Geochemistry and Petrology, Diurnal cycle, Thermal, Physics::Space Physics, Earth and Planetary Sciences (miscellaneous), Astrophysics::Earth and Planetary Astrophysics, Particle radiation, Neutral particle
Abstract

The Radiation Assessment Detector onboard the Mars Science Laboratory rover Curiosity is detecting the energetic particle radiation at the surface of Mars. Data collected over the first 350 Martian days of the nominal surface mission show a pronounced diurnal cycle in both the total dose rate and the neutral particle count rate. The diurnal variations detected by the Radiation Assessment Detector were neither anticipated nor previously considered in the literature. These cyclic variations in dose rate and count rate are shown to be the result of changes in atmospheric column mass driven by the atmospheric thermal tide that is characterized through pressure measurements obtained by the Rover Environmental Monitoring Station, also onboard the rover. In addition to bulk changes in the radiation environment, changes in atmospheric shielding forced by the thermal tide are shown to disproportionately affect heavy ions compared to H and He nuclei.

Published
2014

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