scholarly journals Ocean biogeochemistry exhibits contrasting responses to a large scale reduction in dust deposition

2007 ◽  
Vol 4 (4) ◽  
pp. 2525-2557
Author(s):  
A. Tagliabue ◽  
L. Bopp ◽  
O. Aumont
Keyword(s):  
N2 Fixation ◽  
Large Scale ◽  
Net Primary Productivity ◽  
Inorganic Nitrogen ◽  
Co2 Exchange ◽  
Lower Sensitivity ◽  
Dust Deposition ◽  
Scale Reduction ◽  
Ocean Biogeochemistry ◽  
The Impact

Abstract. Dust deposition of iron is thought to be an important control on ocean biogeochemistry and air-sea CO2 exchange. In this study, we examine the impact of a large scale, yet climatically realistic, reduction in the aeolian Fe input during a 240 year transient simulation. In contrast to previous studies, we find that the ocean biogeochemical cycles of carbon and nitrogen are relatively insensitive to a 60% reduction in Fe input from dust. Net primary productivity (NPP) is reduced in the Fe limited regions, but the excess macronutrients that result are able to fuel additional NPP elsewhere. Overall, NPP and air-sea CO2 exchange are only reduced by around 3% between 1860 and 2100. While the nitrogen cycle is perturbed more significantly (by ~15%), reduced N2 fixation is balanced by a concomitant decline in denitrification. Feedbacks between N2 fixation and denitrification are controlled by variability in surface utilization of inorganic nitrogen and subsurface oxygen consumption, as well as the direct influence of Fe on N2 fixation. Overall, there is relatively little impact of reduced aeolian Fe input (<4%) on cumulative CO2 fluxes over 240 years. The lower sensitivity of our model to changes in dust input is primarily due to the more detailed representation of the continental shelf Fe, which was absent in previous models.

scholarly journals Ocean biogeochemistry exhibits contrasting responses to a large scale reduction in dust deposition

2008 ◽  
Vol 5 (1) ◽  
pp. 11-24 ◽  
Author(s):  
A. Tagliabue ◽  
L. Bopp ◽  
O. Aumont
Keyword(s):  
N2 Fixation ◽  
Large Scale ◽  
Net Primary Productivity ◽  
Inorganic Nitrogen ◽  
Co2 Exchange ◽  
Lower Sensitivity ◽  
Dust Deposition ◽  
Scale Reduction ◽  
Ocean Biogeochemistry ◽  
The Impact

Abstract. Dust deposition of iron is thought to be an important control on ocean biogeochemistry and air-sea CO2 exchange. In this study, we examine the impact of a large scale, yet climatically realistic, reduction in the aeolian Fe input during a 240 year transient simulation. In contrast to previous studies, we find that the ocean biogeochemical cycles of carbon and nitrogen are relatively insensitive (globally) to a 60% reduction in Fe input from dust. Net primary productivity (NPP) is reduced in the Fe limited regions, but the excess macronutrients that result are able to fuel additional NPP elsewhere. Overall, NPP and air-sea CO2 exchange are only reduced by around 3% between 1860 and 2100. While the nitrogen cycle is perturbed more significantly (by ~15%), reduced N2 fixation is balanced by a concomitant decline in denitrification. Feedbacks between N2 fixation and denitrification are controlled by variability in surface utilization of inorganic nitrogen and subsurface oxygen consumption, as well as the direct influence of Fe on N2 fixation. Overall, there is relatively little impact of reduced aeolian Fe input (<4%) on cumulative CO2 fluxes over 240 years. The lower sensitivity of our model to changes in dust input is primarily due to the more detailed representation of the continental shelf Fe, which was absent in previous models.

scholarly journals Latitudinal distribution of <i>Trichodesmium</i> spp. and N<sub>2</sub> fixation in the Atlantic Ocean

2010 ◽  
Vol 7 (2) ◽  
pp. 2195-2225 ◽  
Author(s):  
A. Fernández ◽  
B. Mouriño-Carballido ◽  
A. Bode ◽  
M. Varela ◽  
E. Marañón
Keyword(s):  
Atlantic Ocean ◽  
N2 Fixation ◽  
Large Scale ◽  
Strong Association ◽  
Absolute Magnitude ◽  
South Atlantic ◽  
Equatorial Region ◽  
Latitudinal Distribution ◽  
Dust Deposition ◽  
The South

Abstract. We have determined the latitudinal distribution of Trichodesmium spp. abundance and community N2 fixation in the Atlantic Ocean along a meridional transect from ca. 30° N to 30° S in November–December 2007 and April–May 2008. The observations from both cruises were highly consistent in terms of absolute magnitude and latitudinal distribution, showing a strong association between Trichodesmium abundance and community N2 fixation. The highest Trichodesmium abundances (mean = 220 trichomes L−1) and community N2 fixation rates (mean = 60 μmol m−2 d−1) occurred in the Equatorial region between 5° S–15° N. In the South Atlantic gyre, Trichodesmium abundance was very low (ca. 1 trichome L−1) but N2 fixation was always measurable, averaging 3 and 10 μmol m2 d−1 in 2007 and 2008, respectively. We suggest that N2 fixation in the South Atlantic was sustained by other, presumably unicellular, diazotrophs. Comparing these distributions with the geographical pattern in atmospheric dust deposition points to iron supply as the main factor determining the large scale latitudinal variability of Trichodesmium spp. abundance and N2 fixation in the Atlantic Ocean. We observed a marked South to North decrease in surface phosphate concentration, which argues against a role for phosphorus availability in controlling the large scale distribution of N2 fixation. Scaling up from all our measurements (42 stations) results in conservative estimates for total N2 fixation of ~6 TgN yr−1 in the North Atlantic (0–40° N) and 1.2 TgN yr−1 in the South Atlantic (0–40° S).

scholarly journals Contrasting responses of woody and herbaceous vegetation to altered rainfall characteristics in the Sahel

2020 ◽  
Author(s):  
Wim Verbruggen ◽  
Guy Schurgers ◽  
Stéphanie Horion ◽  
Jonas Ardö ◽  
Paulo Negri Bernardino ◽  
...  
Keyword(s):  
Large Scale ◽  
Net Primary Productivity ◽  
Model Simulation ◽  
Dominant Role ◽  
Climate Extremes ◽  
Extreme Rainfall ◽  
Arid Ecosystems ◽  
Season Length ◽  
Herbaceous Vegetation ◽  
The Impact

Abstract. Dryland ecosystems form a major land cover, accounting for about 40 % of Earth's terrestrial surface and net primary productivity, and housing more than 30 % of the human population. These ecosystems are subject to climate extremes (e.g. large-scale droughts) that are projected to increase in frequency and severity under most future climate scenarios. In this modelling study we assessed the impact of single years of extreme (high or low) rainfall on dryland vegetation in the Sahel. The magnitude and legacy of these impacts were quantified on both the plant functional type and the ecosystem levels. In order to understand the signature of the rainy season characteristics, these rainfall anomalies were driven by changing either rainfall intensity, event frequency or season length. The Lund-Potsdam-Jena General Ecosystem Simulator (LPJ-GUESS) dynamic vegetation model was parameterized to represent dryland plant functional types (PFTs) and was validated against fluxtower measurements across the Sahel. Different scenarios of extreme rainfall were derived from existing Sahel rainfall products such that meteorological consistency was maintained, and applied during a single year of the model simulation timeline. Herbaceous vegetation responded immediately to the different scenarios, while woody vegetation had a weaker and slower response, integrating precipitation changes over a longer timeframe. An increased season length had a larger impact than increased intensity or frequency, while impacts of decreased rainfall scenarios were strong and independent of the season characteristics. Soil control on surface water balance explains these contrasts between the scenarios. Semi-arid ecosystems are known to play a dominant role in the trend and variability of the terrestrial CO2 sink. We showed that single extremely dry and wet years can have strong and long-term impact on the productivity of drylands ecosystems, shedding new light on potential drivers and mechanisms behind this variability.

scholarly journals N<sub>2</sub> fixation in the Mediterranean Sea related to the composition of the diazotrophic community, and impact of dust under present and future environmental conditions

2021 ◽  
Author(s):  
Céline Ridame ◽  
Julie Dinasquet ◽  
Søren Hallstrøm ◽  
Estelle Bigeard ◽  
Lasse Riemann ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Relative Abundance ◽  
N2 Fixation ◽  
Surface Composition ◽  
Saharan Dust ◽  
High Rate ◽  
Short Time Scale ◽  
Dust Deposition ◽  
The Impact ◽  
Diazotrophic Community

Abstract. N2 fixation rates were measured in the 0–1000 m layer at 13 stations located in the open western and central Mediterranean Sea (MS) during the PEACETIME cruise (late spring 2017). While the spatial variability of N2 fixation was not related to Fe, P nor N stocks, the surface composition of the diazotrophic community indicated a strong eastward increasing longitudinal gradient for the relative abundance of non-cyanobacterial diazotrophs (NCD) (mainly γ-Proteobacteria) and conversely eastward decreasing for UCYN-A (mainly -A1 and -A3) as did N2 fixation rates. UCYN-A4 and A3 were identified for the first time in the MS. The westernmost station influenced by Atlantic waters, and characterized by highest stocks of N and P, displayed a patchy distribution of diazotrophic activity with an exceptionally high rate in the euphotic layer of 72.1 nmol N L−1 d−1, which could support up to 19 % of primary production. At this station at 1 %PAR depth, UCYN-A4 represented up to 94 % of the diazotrophic community. These in situ observations of higher UCYN-A relative abundance in nutrient rich stations while NCD increased in the more oligotrophic stations, suggest that the nutrient conditions could determine the composition of the diazotrophic communities and in turn the N2 fixation rates. The impact of Saharan dust deposition on N2 fixation and diazotrophic communities was also investigated, under present and future projected conditions of temperature and pH during short term (3–4 days) experiments at three stations. New nutrients from simulated dust deposition triggered a significant stimulation of N2 fixation (from 41 % to 565 %). The strongest increase in N2 fixation was observed at the stations dominated by NCD and did not lead on this short time scale to change in the diazotrophic community composition. Under projected future conditions, N2 fixation was either exacerbated or unchanged, in that later case this was probably due to a too low nutrient bioavailability or an increased grazing pressure. The future warming and acidification likely benefited NCD (Pseudomonas) and UCYN-A2 while disadvantaged UCYN-A3 without knowing which effect (alone or in combination) is the driver, especially since we do not know the temperature optima of these species not yet cultivated as well as the effect of acidification.

scholarly journals Latitudinal distribution of <i>Trichodesmium</i> spp. and N<sub>2</sub> fixation in the Atlantic Ocean

2010 ◽  
Vol 7 (10) ◽  
pp. 3167-3176 ◽  
Author(s):  
A. Fernández ◽  
B. Mouriño-Carballido ◽  
A. Bode ◽  
M. Varela ◽  
E. Marañón
Keyword(s):  
Atlantic Ocean ◽  
N2 Fixation ◽  
Large Scale ◽  
Strong Association ◽  
Absolute Magnitude ◽  
South Atlantic ◽  
Equatorial Region ◽  
Latitudinal Distribution ◽  
Dust Deposition ◽  
The South

Abstract. We have determined the latitudinal distribution of Trichodesmium spp. abundance and community N2 fixation in the Atlantic Ocean along a meridional transect from ca. 30° N to 30° S in November–December 2007 and April–May 2008. The observations from both cruises were highly consistent in terms of absolute magnitude and latitudinal distribution, showing a strong association between Trichodesmium abundance and community N2 fixation. The highest Trichodesmium abundances (mean = 220 trichomes L−1,) and community N2 fixation rates (mean = 60 μmol m−2 d−1) occurred in the Equatorial region between 5° S–15° N. In the South Atlantic gyre, Trichodesmium abundance was very low (ca. 1 trichome L−1) but N2 fixation was always measurable, averaging 3 and 10 μmol m2 d−1 in 2007 and 2008, respectively. We suggest that N2 fixation in the South Atlantic was sustained by other, presumably unicellular, diazotrophs. Comparing these distributions with the geographical pattern in atmospheric dust deposition points to iron supply as the main factor determining the large scale latitudinal variability of Trichodesmium spp. abundance and N2 fixation in the Atlantic Ocean. We observed a marked South to North decrease in surface phosphate concentration, which argues against a role for phosphorus availability in controlling the large scale distribution of N2 fixation. Scaling up from all our measurements (42 stations) results in conservative estimates for total N2 fixation of ∼6 TgN yr−1 in the North Atlantic (0–40° N) and ~1.2 TgN yr−1 in the South Atlantic (0–40° S).

The impact of social policy on changes in professional practice within learning disability services: different standards for children and adults? A two-part examination

2011 ◽  
Vol 15 (4) ◽  
pp. 289-299 ◽  
Author(s):  
David G. Race ◽  
Nigel A. Malin
Keyword(s):  
Learning Disability ◽  
Professional Practice ◽  
Large Scale ◽  
Public Expenditure ◽  
Disability Services ◽  
Coalition Government ◽  
Scale Reduction ◽  
Adult Services ◽  
One Year ◽  
The Impact

This is the second of two articles examining links between policy developments and changes in professional practice within learning disability services in England. The first article focused on policy foundations over the last 30 years, and concluded that there was a developing gap in professional inputs between children’s and adult services. This article, written one year into the Coalition government, argues that its policies – especially the large-scale reduction in public expenditure, but also the decline in support for inclusion of children in mainstream education, the rapid growth of academies, and proposals for the reorganization of the NHS – have exacerbated the trends identified earlier. In addition, local authorities, though outwardly compliant, have variously interpreted their responsibilities under the personalization agenda, in particular in relation to individual budgets, and this has resulted in assessments of need being based on ‘service hours’ rather than service quality and staff qualifications.

scholarly journals Lianas Significantly Reduce Aboveground and Belowground Carbon Storage: A Virtual Removal Experiment

2021 ◽  
Vol 4 ◽  
Author(s):  
Félicien Meunier ◽  
Geertje M. F. van der Heijden ◽  
Stefan A. Schnitzer ◽  
Hannes P. T. De Deurwaerder ◽  
Hans Verbeeck
Keyword(s):  
Carbon Storage ◽  
Large Scale ◽  
Tree Mortality ◽  
Net Primary Productivity ◽  
Removal Experiment ◽  
Root Turnover ◽  
Turnover Rates ◽  
Belowground Carbon ◽  
The Impact

Lianas are structural parasites of trees that cause a reduction in tree growth and an increase in tree mortality. Thereby, lianas negatively impact forest carbon storage as evidenced by liana removal experiments. In this proof-of-concept study, we calibrated the Ecosystem Demography model (ED2) using 3 years of observations of net aboveground biomass (AGB) changes in control and removal plots of a liana removal experiment on Gigante Peninsula, Panama. After calibration, the model could accurately reproduce the observations of net biomass changes, the discrepancies between treatments, as well as the observed components of those changes (mortality, productivity, and growth). Simulations revealed that the long-term total (i.e., above- and belowground) carbon storage was enhanced in liana removal plots (+1.2 kgC m–2 after 3 years, +1.8 kgC m–2 after 10 years, as compared to the control plots). This difference was driven by a sharp increase in biomass of early successional trees and the slow decomposition of liana woody tissues in the removal plots. Moreover, liana removal significantly reduced the simulated heterotrophic respiration (−24%), which resulted in an average increase in net ecosystem productivity (NEP) from 0.009 to 0.075 kgC m–2 yr–1 for 10 years after liana removal. Based on the ED2 model outputs, lianas reduced gross and net primary productivity of trees by 40% and 53%, respectively, mainly through competition for light. Finally, model simulations suggested a profound impact of the liana removal on the soil carbon dynamics: the simulated metabolic litter carbon pool was systematically larger in control plots (+51% on average) as a result of higher mortality rates and faster leaf and root turnover rates. By overcoming the challenge of including lianas and depicting their effect on forest ecosystems, the calibrated version of the liana plant functional type (PFT) as incorporated in ED2 can predict the impact of liana removal at large-scale and its potential effect on long-term ecosystem carbon storage.

scholarly journals Contrasting responses of woody and herbaceous vegetation to altered rainfall characteristics in the Sahel

2021 ◽  
Vol 18 (1) ◽  
pp. 77-93
Author(s):  
Wim Verbruggen ◽  
Guy Schurgers ◽  
Stéphanie Horion ◽  
Jonas Ardö ◽  
Paulo N. Bernardino ◽  
...  
Keyword(s):  
Large Scale ◽  
Net Primary Productivity ◽  
Model Simulation ◽  
Dominant Role ◽  
Extreme Rainfall ◽  
Strong Impact ◽  
Season Length ◽  
Herbaceous Vegetation ◽  
Dryland Ecosystems ◽  
The Impact

Abstract. Dryland ecosystems are a major source of land cover, account for about 40% of Earth's terrestrial surface and net primary productivity, and house more than 30 % of the human population. These ecosystems are subject to climate extremes (e.g. large-scale droughts and extreme floods) that are projected to increase in frequency and severity under most future climate scenarios. In this modelling study we assessed the impact of single years of extreme (high or low) rainfall on dryland vegetation in the Sahel. The magnitude and legacy of these impacts were quantified on both the plant functional type and the ecosystem levels. In order to understand the impact of differences in the rainfall distribution over the year, these rainfall anomalies were driven by changing either rainfall intensity, event frequency or rainy-season length. The Lund–Potsdam–Jena General Ecosystem Simulator (LPJ-GUESS) dynamic vegetation model was parameterized to represent dryland plant functional types (PFTs) and was validated against flux tower measurements across the Sahel. Different scenarios of extreme rainfall were derived from existing Sahel rainfall products and applied during a single year of the model simulation timeline. Herbaceous vegetation responded immediately to the different scenarios, while woody vegetation had a weaker and slower response, integrating precipitation changes over a longer timeframe. An increased season length had a larger impact than increased intensity or frequency, while impacts of decreased rainfall scenarios were strong and independent of the season characteristics. Soil control on surface water balance explains these contrasts between the scenarios. None of the applied disturbances caused a permanent vegetation shift in the simulations. Dryland ecosystems are known to play a dominant role in the trend and variability of the global terrestrial CO2 sink. We showed that single extremely dry and wet years can have a strong impact on the productivity of drylands ecosystems, which typically lasts an order of magnitude longer than the duration of the disturbance. Therefore, this study sheds new light on potential drivers and mechanisms behind this variability.

Impact of COVID-19 on Nuclear Medicine in Germany, Austria and Switzerland: An International Survey in April 2020

2020 ◽  
Vol 59 (04) ◽  
pp. 294-299 ◽  
Author(s):  
Lutz S. Freudenberg ◽  
Ulf Dittmer ◽  
Ken Herrmann
Keyword(s):  
Nuclear Medicine ◽  
Health Systems ◽  
Personal Protective Equipment ◽  
Large Scale ◽  
Diagnostic Procedures ◽  
Protective Equipment ◽  
Current Crisis ◽  
Web Based ◽  
Public Versus Private ◽  
The Impact

Abstract Introduction Preparations of health systems to accommodate large number of severely ill COVID-19 patients in March/April 2020 has a significant impact on nuclear medicine departments. Materials and Methods A web-based questionnaire was designed to differentiate the impact of the pandemic on inpatient and outpatient nuclear medicine operations and on public versus private health systems, respectively. Questions were addressing the following issues: impact on nuclear medicine diagnostics and therapy, use of recommendations, personal protective equipment, and organizational adaptations. The survey was available for 6 days and closed on April 20, 2020. Results 113 complete responses were recorded. Nearly all participants (97 %) report a decline of nuclear medicine diagnostic procedures. The mean reduction in the last three weeks for PET/CT, scintigraphies of bone, myocardium, lung thyroid, sentinel lymph-node are –14.4 %, –47.2 %, –47.5 %, –40.7 %, –58.4 %, and –25.2 % respectively. Furthermore, 76 % of the participants report a reduction in therapies especially for benign thyroid disease (-41.8 %) and radiosynoviorthesis (–53.8 %) while tumor therapies remained mainly stable. 48 % of the participants report a shortage of personal protective equipment. Conclusions Nuclear medicine services are notably reduced 3 weeks after the SARS-CoV-2 pandemic reached Germany, Austria and Switzerland on a large scale. We must be aware that the current crisis will also have a significant economic impact on the healthcare system. As the survey cannot adapt to daily dynamic changes in priorities, it serves as a first snapshot requiring follow-up studies and comparisons with other countries and regions.

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