Utility of Modulated Fluorescence in Measuring Photosynthetic Activity of Antarctic Plants: Field and Laboratory Studies

1995 ◽  
Vol 22 (2) ◽  
pp. 321 ◽  
Author(s):  
MJ Hovenden ◽  
RD Seppelt
Keyword(s):  
Physiological Stress ◽  
Continuous Light ◽  
Fluorescence Analysis ◽  
Pulse Amplitude ◽  
Gas Analysis ◽  
Future Research ◽  
Polar Regions ◽  
Terrestrial Vegetation ◽  
Terrestrial Plants ◽  
Modulated Fluorescence

Antarctic terrestrial plants face severe physiological stress conditions daily. In winter there is extreme cold and darkness. During summer there is continuous light for some months and plant surface temperatures may fluctuate through more than 50�C diurnally. Conditions are almost uniformly desiccative, except during spring when snow melt saturates thalli and plants may be completely inundated. The study of photosynthesis in these conditions is fundamental to a proper understanding of plant persistence, productivity and growth in polar regions. Lichens dominate the terrestrial vegetation of Antarctica and are therefore of great interest. Lichen photosynthesis has been shown to be dependent upon thallus water content and temperature as well as the irradiance incident on the thallus. Conventional infrared gas analysis (IRGA) techniques have been used most widely to study lichen photosynthesis in both the field and laboratory. Recent progress in the development of pulse amplitude modulated fluorescence systems has allowed the investigation of chlorophyll fluorescence in the field under naturally illuminated conditions. This paper highlights the utility of modulated fluorescence systems for the study of antarctic lichen photosynthesis, relates fluorescence results to those obtained by IRGA techniques, identifies problems inherent in fluorescence analysis of lichens and discusses possible areas of future research.

scholarly journals Cognitive Performance during a 24-Hour Cold Exposure Survival Simulation

2016 ◽  
Vol 2016 ◽  
pp. 1-11
Author(s):  
Michael J. Taber ◽  
Geoffrey L. Hartley ◽  
Gregory W. McGarr ◽  
Dessi Zaharieva ◽  
Fabien A. Basset ◽  
...  
Keyword(s):  
Cognitive Performance ◽  
Core Temperature ◽  
Cold Exposure ◽  
Ambient Air ◽  
Cognitive Test ◽  
Future Research ◽  
Polar Regions ◽  
Active Engagement ◽  
Metabolic Heat ◽  
Tolerable Level

Survivor of a ship ground in polar regions may have to wait more than five days before being rescued. Therefore, the purpose of this study was to explore cognitive performance during prolonged cold exposure. Core temperature (Tc) and cognitive test battery (CTB) performance data were collected from eight participants during 24 hours of cold exposure (7.5°C ambient air temperature). Participants (recruited from those who have regular occupational exposure to cold) were instructed that they could freely engage in minimal exercise that was perceived to maintaining a tolerable level of thermal comfort. Despite the active engagement, test conditions were sufficient to significantly decreaseTcafter exposure and to eliminate the typical 0.5–1.0°C circadian rise and drop in core temperature throughout a 24 h cycle. Results showed minimal changes in CTB performance regardless of exposure time. Based on the results, it is recommended that survivors who are waiting for rescue should be encouraged to engage in mild physical activity, which could have the benefit of maintaining metabolic heat production, improve motivation, and act as a distractor from cold discomfort. This recommendation should be taken into consideration during future research and when considering guidelines for mandatory survival equipment regarding cognitive performance.

scholarly journals Linking atmospheric pollution to cryospheric change in the Third Pole region: current progress and future prospects

2019 ◽  
Vol 6 (4) ◽  
pp. 796-809 ◽  
Author(s):  
Shichang Kang ◽  
Qianggong Zhang ◽  
Yun Qian ◽  
Zhenming Ji ◽  
Chaoliu Li ◽  
...  
Keyword(s):  
Atmospheric Pollution ◽  
Environmental Changes ◽  
Temporal Variations ◽  
Global Perspective ◽  
Atmospheric Pollutants ◽  
Future Research ◽  
The Tibetan Plateau ◽  
Polar Regions ◽  
Research Framework ◽  
The Third

ABSTRACTThe Tibetan Plateau and its surroundings are known as the Third Pole (TP). This region is noted for its high rates of glacier melt and the associated hydrological shifts that affect water supplies in Asia. Atmospheric pollutants contribute to climatic and cryospheric changes through their effects on solar radiation and the albedos of snow and ice surfaces; moreover, the behavior and fates within the cryosphere and environmental impacts of environmental pollutants are topics of increasing concern. In this review, we introduce a coordinated monitoring and research framework and network to link atmospheric pollution and cryospheric changes (APCC) within the TP region. We then provide an up-to-date summary of progress and achievements related to the APCC research framework, including aspects of atmospheric pollution's composition and concentration, spatial and temporal variations, trans-boundary transport pathways and mechanisms, and effects on the warming of atmosphere and changing in Indian monsoon, as well as melting of glacier and snow cover. We highlight that exogenous air pollutants can enter into the TP’s environments and cause great impacts on regional climatic and environmental changes. At last, we propose future research priorities and map out an extended program at the global scale. The ongoing monitoring activities and research facilitate comprehensive studies of atmosphere–cryosphere interactions, represent one of China's key research expeditions to the TP and the polar regions and contribute to the global perspective of earth system science.

Isoprene emission from phytoplankton monocultures: the relationship with chlorophyll-a, cell volume and carbon content

2010 ◽  
Vol 7 (6) ◽  
pp. 554 ◽  
Author(s):  
B. Bonsang ◽  
V. Gros ◽  
I. Peeken ◽  
N. Yassaa ◽  
K. Bluhm ◽  
...  
Keyword(s):  
Carbon Content ◽  
Cell Volume ◽  
Chlorophyll A ◽  
Marine Species ◽  
Emission Rates ◽  
Terrestrial Vegetation ◽  
Terrestrial Plants ◽  
Chl A ◽  
Isoprene Emission ◽  
Regional Budget

Environmental context Isoprene, a natural product of both terrestrial vegetation and marine organisms, is rapidly oxidised in the atmosphere, and thereby plays a key role in the regional budget of oxidants. Although isoprene production from terrestrial plants has been extensively investigated, production processes and emission rates from marine species are still poorly understood. We present results from laboratory experiments showing that isoprene is emitted from living phytoplankton cells at variable rates depending on the light intensity, cell volume, and carbon content of the plankton cells. Abstract We report here isoprene emission rates determined from various phytoplankton cultures incubated under PAR light which was varied so as to simulate a natural diel cycle. Phytoplankton species representative of different phytoplankton functional types (PFTs) namely: cyanobacteria, diatoms, coccolithophorides, and chlorophytes have been studied. Biomass normalised isoprene emission rates presented here relative to the chlorophyll-a (Chl-a) content of the cultures showed that the two cyanobacteria (Synechococcus and Trichodesmium) were the strongest emitters with emission rates in the range of 17 to 28 µg C5H8 g–1 Chl-a h–1. Diatoms produced isoprene in a significantly lower emission range: 3 to 7.5 µg C5H8 g–1 Chl-a h–1 and Dunaliella tertiolecta was by far the lowest emitter of our investigated plankton cultures. Despite the group specific differences observed, a high emission rate variance was observed to occur within one phytoplankton group. However, a combination of literature and our own data showed a clear relationship between the actual cell volume and the isoprene emission rates. This relationship could be a valuable tool for future modelling approaches of global isoprene emissions.

scholarly journals Microbiotic crusts on soil, rock and plants: neglected major players in the global cycles of carbon and nitrogen?

2009 ◽  
Vol 6 (4) ◽  
pp. 6983-7015 ◽  
Author(s):  
W. Elbert ◽  
B. Weber ◽  
B. Büdel ◽  
M. O. Andreae ◽  
U. Pöschl
Keyword(s):  
Nitrogen Fixation ◽  
Net Primary Production ◽  
Large Contribution ◽  
Earth System ◽  
Terrestrial Vegetation ◽  
Terrestrial Plants ◽  
Global Estimate ◽  
Carbon And Nitrogen ◽  
Annual Carbon ◽  
Microbiotic Crusts

Abstract. Microbiotic crusts consisting of bacteria, fungi, algae, lichens, and bryophytes colonize most terrestrial surfaces, and they are able to fix carbon and nitrogen from the atmosphere. Here we show that microbiotic crusts are likely to play major roles in the global biogeochemical cycles of carbon and nitrogen, and we suggest that they should be further characterized and taken into account in studies and models of the Earth system and climate. For the global annual net uptake of carbon by microbiotic crusts we present a first estimate of ~3.6 Pg a−1. This uptake corresponds to ~6% of the estimated global net carbon uptake by terrestrial vegetation (net primary production, NPP: ~60 Pg a−1), and it is of the same magnitude as the global annual carbon turnover due to biomass burning. The estimated rate of nitrogen fixation by microbiotic crusts (~45 Tg a−1) amounts to ~40% of the global estimate of biological nitrogen fixation (107 Tg a−1). With regard to Earth system dynamics and global change, the large contribution of microbiotic crusts to nitrogen fixation is likely to be important also for the sequestration of CO2 by terrestrial plants (CO2 fertilization), because the latter is constrained by the availability of fixed nitrogen.

Neuroendocrine Responses to Stressors in Lactating and Nonlactating Mammals: A Literature Review

2003 ◽  
Vol 5 (2) ◽  
pp. 79-86 ◽  
Author(s):  
Pamela D. Hill ◽  
Robert T. Chatterton ◽  
Jean C. Aldag
Keyword(s):  
Systematic Review ◽  
Literature Review ◽  
Animal Studies ◽  
Physiological Stress ◽  
Future Research ◽  
Review Of The Literature ◽  
Physiological Stress Response ◽  
Chronic Stressors ◽  
Neuroendocrine Responses ◽  
Acute Stressor

Although stress research is a popular topic of study, little is known about the neuroendocrine responses to a stressor in lactating and nonlactating humans. The purpose of this systematic review of the literature was to examine the neuroendocrine responses, specifically the glucocorticoids and catecholamines, in lactating and nonlactating animals and humans to an acute stressor. A brief overview of the physiological stress response in the human is included. Animal studies strongly suggest that lactation is associated with major changes in neuroendocrine responses to a variety of acute stressors. Neuroendocrine responses in humans to stressors are less clear due to the limited research. Future research is needed involving these responses in humans generally, as well as specifically in the patterns of neuroendocrine responses to chronic stressors in lactating and nonlactating women.

A Novel Approach of the Modelling of Dynamics of the Ice Cover Applying Microsatellites Data

2021 ◽  
Author(s):  
Magdalena Łukosz ◽  
Wojciech Witkowski
Keyword(s):  
High Resolution ◽  
Ice Cover ◽  
Image Resolution ◽  
Global Ocean ◽  
Future Research ◽  
Polar Regions ◽  
Radar Images ◽  
Novel Approach ◽  
Glacier Velocity ◽  
Offset Tracking

<p>Keywords: ice cover; glacier dynamics; microsatellites; offset-tracking; climate changes</p><p>Radar images acquired by SAR satellites allow scientists to monitor the movements of glaciers in polar regions. Observation of these areas is significant as it provides information on the process of global warming. It also makes it possible to assess the amount of ice mass that is melting and, as a result, increasing the mean level of the global ocean. Due to high speeds and loss of consistency in glacial areas, the optimal technique for estimating glacier velocity is Offset-Tracking. Its accuracy depends on the size of the terrain pixel and can therefore increase the accuracy of the results obtained by using high-resolution images. Microsatellites open up new possibilities through high resolution imagery and short revisit time.</p><p>The study uses ICEYE products. The aim of the research was to investigate the influence of SAR image resolution on the accuracy of calculated movements in the Offset-Tracking method. Additionally, a comparison of obtained results with previous studies allowed to analyze changes in the dynamics of chosen areas. The research was carried out for 2 glaciers: Jakobshavn in Greenland and Thwaites in Antarctica. It made it possible to compare the quality of results in areas that are located in various parts of the world and moving at different dynamics. Additionally, calculations were made for Sentinel-1 SAR images for comparative analysis. </p><p>As a result of research, velocities of glaciers and their directions in periods of several days were obtained. For Thwaites glacier, daily changes in dynamics were also analyzed. Moreover, by comparing results to earlier researches which were carried out in these areas, it was possible to estimate changes in ice cover during longer timespans. In the last step, the quality and accuracy of products obtained from ICEYE and Sentinel-1 satellites were compared. </p><p>This research assesses the utility of microsatellite images for monitoring glacier movements and shows possibilities of their usage in future research.</p>

Improved Retrieval Methods for Sentinel-3 SAR Altimetry over Coastal and Open Ocean and recommendations for implementation: ESA SCOOP Project Results

2020 ◽  
Author(s):  
David Cotton ◽  
Thomas Moreau ◽  
Mònica Roca ◽  
Christine Gommenginger ◽  
Mathilde Cancet ◽  
...  
Keyword(s):  
Test Data ◽  
Open Ocean ◽  
Global Navigation Satellite Systems ◽  
Future Research ◽  
Data Sets ◽  
Polar Regions ◽  
Path Delay ◽  
Data Set ◽  
Processing Scheme ◽  
Satellite Systems

<p>SCOOP (SAR Altimetry Coastal & Open Ocean Performance) is a project funded under the ESA SEOM (Scientific Exploitation of Operational Missions) Programme Element, to characterise the expected performance of Sentinel-3 SRAL SAR mode altimeter products, and then to develop and evaluate enhancements to the baseline processing scheme in terms of improvements to ocean measurements. Another objective is to develop and evaluate an improved Wet Troposphere correction for Sentinel-3.</p><p>The SCOOP studies are based on two 2-year test data sets derived from CryoSat-2 FBR data, produced for 10 regions. The first Test Data Set was processed with algorithms equivalent to the Sentinel-3 baseline, and the second with algorithms expected to provide an improved performance.</p><p>We present results from the SCOOP project that demonstrate the excellent performance of SRAL at the coast in terms of measurement precision, with noise in Sea Surface Height 20Hz measurements of less than 5cm to within 5km of the coast.</p><p>We then report the development and testing of new processing approaches designed to improve performance, including, for L1B to L2:</p><ul><li>Application of zero-padding</li> <li>Application of intra-burst Hamming windowing</li> <li>Exact beam forming in the azimuthal direction</li> <li>Restriction of stack processing to within a specified range of look angles.</li> <li>Along-track antenna compensation</li> </ul><p> </p><p>And for L1B to L2</p><ul><li>Application of alternative re-trackers for SAR and RDSAR.</li> </ul><p> </p><p>Based on the results of this assessment, a second test data set was generated and we present an assessment of the performance of this second Test Data Set generated, and compare it to that of the original Test Data Set.</p><p>Regarding the WTC for Sentinel-3A, the correction from the on-board MWR has been assessed by means of comparison with independent data sets such as the GPM Microwave Imager (GMI), Jason-2, Jason-3 and Global Navigation Satellite Systems (GNSS) derived WTC at coastal stations. GNSS-derived path Delay Plus (GPD+) corrections have been derived for S3A. Results indicate good overall performance of S3A MWR and GPD+ WTC improvements over MWR-derived WTC, particularly in coastal and polar regions.</p><p> </p><p>Based on the outcomes of this study we provide recommendations for improving SAR mode altimeter processing and priorities for future research.</p>

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