scholarly journals A two-decades (1988–2009) record of diatom fluxes in the Mauritanian coastal upwelling: Impact of low-frequency forcing and a two-step shift in the species composition

2020 ◽  
Author(s):  
Oscar E. Romero ◽  
Simon Ramondenc ◽  
Gerhard Fischer
Keyword(s):  
Coastal Waters ◽  
Temporal Dynamics ◽  
Meridional Overturning Circulation ◽  
Benthic Diatoms ◽  
Time Interval ◽  
Data Set ◽  
Specific Composition ◽  
Species Specific ◽  
The Impact

Abstract. Eastern Boundary Upwelling Ecosystems (EBUEs) are among the most productive marine regions in the world's oceans. Understanding the degree of interannual to decadal variability in the Mauritania upwelling system is key for the prediction of future changes of primary productivity and carbon sequestration in the Canary Current EBUE as well as in similar environments. A multiannual sediment trap experiment was conducted at the mooring site CBmeso (= 'Cape Blanc mesotrophic', ca. 20° N, ca. 20°40' W) in the high-productive Mauritanian coastal waters. Here, we present results on fluxes and the species-specific composition of the diatom assemblage for the time interval between March 1988 and May 2009. The temporal dynamics of diatom populations allows to propose three main diatom productivity/flux intervals: (i) early 1988–late 1996; (ii) 1997–1999, and (iii) early 2002–mid 2009. The impact of the Atlantic Multidecadal Oscillation appears to be an important forcing of the long-term dynamics of diatom population. The impact of cold (1988–1996) and warm AMO phases (2001–2009) is reflected by the outstanding shifts in species-specific composition. This AMO-impacted, long-term trend is interrupted by the occurrence of the strong 1997 ENSO. The extraordinary shift in the relative abundance of benthic diatoms in May 2002 suggests the strengthening of offshore advective transport within the uppermost layer of filament waters, and in the subsurface and in deeper and bottom‐near layers. It is hypothesized that the dominance of benthic diatoms was the response of the diatom community to the intensification of the slope and shelf poleward undercurrents. This dominance followed the intensification of the warm phase of AMO and the associated changes of the Atlantic Meridional Overturning Circulation. Transported valves (siliceous remains) from shallow coastal waters into the deeper bathypelagial should be considered for the calculation and model experiments of bathy- and pelagial nutrients budgets (especially Si), the burial of diatoms and the paleoenvironmental signal preserved in downcore sediments. Our 1988–2009 data set contributes to the distinction between climate-forced and intrinsic variability of populations of diatoms and will be especially helpful for establishing the scientific basis for forecasting and modelling future states of this ecosystem and its decadal changes.

scholarly journals A 2-decade (1988–2009) record of diatom fluxes in the Mauritanian coastal upwelling: impact of low-frequency forcing and a two-step shift in the species composition

2021 ◽  
Vol 18 (5) ◽  
pp. 1873-1891
Author(s):  
Oscar E. Romero ◽  
Simon Ramondenc ◽  
Gerhard Fischer
Keyword(s):  
Coastal Waters ◽  
Temporal Dynamics ◽  
Southern Oscillation ◽  
Low Frequency ◽  
Meridional Overturning Circulation ◽  
Benthic Diatoms ◽  
Time Interval ◽  
Data Set ◽  
The Impact

Abstract. Eastern boundary upwelling ecosystems (EBUEs) are among the most productive marine regions in the world's oceans. Understanding the degree of interannual to decadal variability in the Mauritania upwelling system is crucial for the prediction of future changes of primary productivity and carbon sequestration in the Canary Current EBUE as well as in similar environments. A multiyear sediment trap experiment was conducted at the mooring site CBmeso (“Cape Blanc mesotrophic”, ca. 20∘ N, ca. 20∘40′ W) in the highly productive coastal waters off Mauritania. Here, we present results on fluxes of diatoms and the species-specific composition of the assemblage for the time interval between March 1988 and June 2009. The temporal dynamics of diatom populations allows the proposal of three main intervals: (i) early 1988–late 1996, (ii) 1997–1999, and (iii) early 2002–mid 2009. The Atlantic Multidecadal Oscillation (AMO) appears to be an important driver of the long-term dynamics of diatom population. The long-term AMO-driven trend is interrupted by the occurrence of the strong 1997 El Niño–Southern Oscillation (ENSO). The extraordinary shift in the relative abundance of benthic diatoms in May 2002 suggests the strengthening of offshore advective transport within the uppermost layer of filament waters and in the subsurface and in deeper and bottom-near layers. It is hypothesized that the dominance of benthic diatoms was the response of the diatom community to the intensification of the slope and shelf poleward undercurrents. This dominance followed the intensification of the warm phase of AMO and the associated changes of the Atlantic Meridional Overturning Circulation. Transported valves (siliceous remains) from shallow Mauritanian coastal waters into the bathypelagic should be considered for the calculation and model experiments of bathy- and pelagic nutrients budgets (especially Si), the burial of diatoms, and the paleoenvironmental signal preserved in downcore sediments. Additionally, our 1988–2009 data set contributes to the characterization of the impact of low-frequency climate forcings in the northeastern Atlantic and will be especially helpful for establishing the scientific basis for forecasting and modeling future states of the Canary Current EBUE and its decadal changes.

scholarly journals Effects of reindeer grazing and recovery after cessation of grazing on the ground-dwelling spider assemblage in Finnish Lapland

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7330
Author(s):  
Teemu Saikkonen ◽  
Varpu Vahtera ◽  
Seppo Koponen ◽  
Otso Suominen
Keyword(s):  
Species Richness ◽  
Rangifer Tarandus ◽  
Forest Ecosystems ◽  
Grazing Pressure ◽  
Ground Vegetation ◽  
Total Abundance ◽  
Finnish Lapland ◽  
Species Specific ◽  
The Impact

The effect of reindeer Rangifer tarandus L. grazing on the ground-dwelling spider assemblage in Northern Finland was studied. Changes in species richness, abundance and evenness of spider assemblages were analyzed in relation to changes in vegetation and environmental factors in long term grazed and ungrazed sites as well as sites that had recently switched from grazed to ungrazed and vice versa. Grazing was found to have a significant impact on height and biomass of lichens and other ground vegetation. However, it seemed not to have an impact on the total abundance of spiders. This is likely caused by opposing family and species level responses of spiders to the grazing regime. Lycosid numbers were highest in grazed and linyphiid numbers in ungrazed areas. Lycosidae species richness was highest in ungrazed areas whereas Linyphiidae richness showed no response to grazing. Four Linyphiidae, one Thomisidae and one Lycosidae species showed strong preference for specific treatments. Sites that had recovered from grazing for nine years and the sites that were grazed for the last nine years but were previously ungrazed resembled the long term grazed sites. The results emphasize the importance of reindeer as a modifier of boreal forest ecosystems but the impact of reindeer grazing on spiders seems to be family and species specific. The sites with reversed grazing treatment demonstrate that recovery from strong grazing pressure at these high latitudes is a slow process whereas reindeer can rapidly change the conditions in previously ungrazed sites similar to long term heavily grazed conditions.

scholarly journals Effects of agricultural credit on wheat productivity of small farms in Sindh, Pakistan

2018 ◽  
Vol 78 (5) ◽  
pp. 592-610 ◽  
Author(s):  
Abbas Ali Chandio ◽  
Yuansheng Jiang ◽  
Feng Wei ◽  
Xu Guangshun
Keyword(s):  
Wheat Yield ◽  
Considerable Proportion ◽  
Small Scale ◽  
Small Farms ◽  
Short Term ◽  
Agricultural Credit ◽  
Data Set ◽  
Content Type ◽  
The Impact

Purpose The purpose of this paper is to evaluate the impact of short-term loan (STL) vs long-term loan (LTL) on wheat productivity of small farms in Sindh, Pakistan. Design/methodology/approach The econometric estimation is based on cross-sectional data collected in 2016 from 18 villages in three districts, i.e. Shikarpur, Sukkur and Shaheed Benazirabad, Sindh, Pakistan. The sample data set consist of 180 wheat farmers. The collected data were analyzed through different econometric techniques like Cobb–Douglas production function and Instrumental variables (two-stage least squares) approach. Findings This study reconfirmed that agricultural credit has a positive and highly significant effect on wheat productivity, while the short-term loan has a stronger effect on wheat productivity than the long-term loan. The reasons behind the phenomenon may be the significantly higher usage of agricultural inputs like seeds of improved variety and fertilizers which can be transformed into the wheat yield in the same year. However, the LTL users have significantly higher investments in land preparation, irrigation and plant protection, which may lead to higher wheat production in the coming years. Research limitations/implications In the present study, only those wheat farmers were considered who obtained agricultural loans from formal financial institutions like Zarai Taraqiati Bank Limited and Khushhali Bank. However, in the rural areas of Sindh, Pakistan, a considerable proportion of small-scale farmers take credit from informal financial channels. Therefore future researchers should consider the informal credits as well. Originality/value This is the first paper to examine the effects of agricultural credit on wheat productivity of small farms in Sindh, Pakistan. This paper will be an important addition to the emerging literature regarding effects of credit studies.

The Impact of US Monetary Growth on Bitcoin Trading Volume in the Current Economic Uncertainty

2020 ◽  
pp. 493-509
Author(s):  
İsmail Canöz
Keyword(s):  
Causal Relationship ◽  
Trading Volume ◽  
Causal Effect ◽  
Study Data ◽  
Time Interval ◽  
Time Varying ◽  
Economic Uncertainty ◽  
Causality Test ◽  
Data Set ◽  
The Impact

This study examines the effect of US monetary growth on Bitcoin trading volume. To achieve this purpose, firstly, the symmetric causality test is used. Following this test, another symmetric causality test is used to reveal a time-varying causal effect between variables. The data set covers the period from July 2010 to July 2019. The results of the first symmetric causality test, which considers the time interval of the study data as a whole, show that there is no causal relationship between variables. According to the results of the second causality test, these support the previous results substantially. However, an interesting detail is the causal relationship between variables for the period between April 2019 and July 2019. The reason for this relationship could be that investors who are indecisive during the current economic uncertainty add Bitcoin to their portfolios in response to the Federal Reserve's decisions.

scholarly journals High similarity between EEG from subcutaneous and proximate scalp electrodes in patients with temporal lobe epilepsy

2018 ◽  
Vol 120 (3) ◽  
pp. 1451-1460 ◽  
Author(s):  
Sigge Weisdorf ◽  
Sirin W. Gangstad ◽  
Jonas Duun-Henriksen ◽  
Karina S. S. Mosholt ◽  
Troels W. Kjær
Keyword(s):  
Temporal Lobe Epilepsy ◽  
Temporal Lobe ◽  
Temporal Dynamics ◽  
Real Life ◽  
High Similarity ◽  
Time Frequency ◽  
Scalp Eeg ◽  
Eeg Recordings ◽  
The Impact

Subcutaneous recording using electroencephalography (EEG) has the potential to enable ultra-long-term epilepsy monitoring in real-life conditions because it allows the patient increased mobility and discreteness. This study is the first to compare physiological and epileptiform EEG signals from subcutaneous and scalp EEG recordings in epilepsy patients. Four patients with probable or definite temporal lobe epilepsy were monitored with simultaneous scalp and subcutaneous EEG recordings. EEG recordings were compared by correlation and time-frequency analysis across an array of clinically relevant waveforms and patterns. We found high similarity between the subcutaneous EEG channels and nearby temporal scalp channels for most investigated electroencephalographic events. In particular, the temporal dynamics of one typical temporal lobe seizure in one patient were similar in scalp and subcutaneous recordings in regard to frequency distribution and morphology. Signal similarity is strongly related to the distance between the subcutaneous and scalp electrodes. On the basis of these limited data, we conclude that subcutaneous EEG recordings are very similar to scalp recordings in both time and time-frequency domains, if the distance between them is small. As many electroencephalographic events are local/regional, the positioning of the subcutaneous electrodes should be considered carefully to reflect the relevant clinical question. The impact of implantation depth of the subcutaneous electrode on recording quality should be investigated further. NEW & NOTEWORTHY This study is the first publication comparing the detection of clinically relevant, pathological EEG features from a subcutaneous recording system designed for out-patient ultra-long-term use to gold standard scalp EEG recordings. Our study shows that subcutaneous channels are very similar to comparable scalp channels, but also point out some issues yet to be resolved.

The colonial exports pattern, institutions and current economic performance

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Tania El Kallab ◽  
Cristina Terra
Keyword(s):  
Human Capital ◽  
Economic Development ◽  
Resource Curse ◽  
Data Set ◽  
Content Type ◽  
Long Run ◽  
French Colonies ◽  
Colonial Institutions ◽  
The Impact

PurposeThis paper explores the role of colonial heritage on long-term economic development from a resource-curse perspective. The authors investigate the impact of colonial exports on long-term economic development through two channels: (1) a direct impact of the economic dependency on natural resources and (2) an indirect impact via its effect on colonial institutions, which persisted over time and influenced current economic development.Design/methodology/approachTo address this issue, the authors use an original data set on French bilateral trade from 1880 to 1912. The authors use partial least square structural equation modeling (PLS-SEM) in the empirical analysis, so that the authors are able to construct latent variables (LVs) for variables that are not directly observable, such as the quality of institutions.FindingsThe authors find that exports of primary goods to France had a negative impact on colonial institutions and that for French colonies, this impact was driven by minerals exports. Despite its impact on colonial institutions, exports of French colonies had no significant indirect impact on their current institutions. The authors find no significant direct impact of colonial trade on current development for French colonies. Finally, colonial exports of manufactured products had no significant impact on colonial institutions among French colonies and a positive impact among non-French ones.Research limitations/implicationsResearch implications regarding the findings of this paper are, namely, that the relative poor performance within French colonies today cannot be attributed to the extraction of raw materials a century ago. However, human capital and institutional development, instead of exports, are more relatively important for long-term growth. Some limitations in trying to determine the simultaneous relationship among colonial trade, institutions and economic performance are the relation between colonial trade and the extent of extraction from the colonizer, which is hard to quantify, as well as its precise mechanism.Practical implicationsSince the initial institutions set in those former colonies presented a strong persistence in the long run, their governments should focus now on building sound and inclusive political and economic institutions, as well as on investing in human capital in order to foster long-term growth. Once a comprehensive set of institutional and human resources are put in place, the quality and quantity of exports might create a positive spillover on the short-run growth.Social implicationsOne social implication that can be retrieved from this study is the ever-lasting effect of both human capital investment and introduction of inclusive political and economic institutions on the long-run impact of growth.Originality/valueThe paper uses an original primary data set from archival sources to explore the role of colonial heritage on long-term economic development from a resource-curse perspective. It applies a relatively new model partial least squares path modeling (PLS-PM) that allows the construction of LVs for variables that are not directly observable, as well as channeling the impact on growth through both direct and indirect channels. Finally, it allows for the simultaneous multigroup analysis across different colonial groups.

scholarly journals THE INFLUENCE OF MAGNITUDES TYPES IN THE NONEXTENSIVITY APPLIED AT THE CIRCUM-PACIFIC SUBDUCTION ZONES

2018 ◽  
Vol 36 (4) ◽  
pp. 1
Author(s):  
Thaís Machado Scherrer ◽  
George Sand França ◽  
Raimundo Silva ◽  
Daniel Brito de Freitas ◽  
Carlos da Silva Vilar
Keyword(s):  
Solid Earth ◽  
Subduction Zone ◽  
Subduction Zones ◽  
Time Interval ◽  
Data Sets ◽  
Data Set ◽  
Different Types ◽  
Data Source ◽  
The Impact

ABSTRACT. Following our own previous work, we reanalyze the nonextensive behavior over the circum-Pacific subduction zones evaluating the impact of using different types of magnitudes in the results. We used the same data source and time interval of our previous work, the NEIC catalog in the years between 2001 and 2010. Even considering different data sets, the correlation between q and the subduction zone asperity is perceptible, but the values found for the nonextensive parameter in the considered data sets presents an expressive variation. The data set with surface magnitude exhibits the best adjustments.Keywords: Nonextensivity, Seismicity, Solid Earth, Earthquake.RESUMO. No mesmo caminho do nosso trabalho anterior, reanalisamos o comportamento não extensivo sobre as zonas de subducção do círcuo de fogo do Pacífico, avaliando o impacto do uso de diferentes tipos de magnitude nos resultados. Utilizamos o mesmo intervalo de dados e fonte de nosso trabalho anterior, do catálogo NEIC entre os anos 2001 e 2010. Mesmo considerando diferentes conjuntos de dados, a correlação entre q e a aspereza das zonas de subducção é perceptível, mas os valores encontrados para o parâmetro não extensivo no conjuntos de dados considerados apresentam uma variação expressiva. O conjunto de dados com magnitude de superfície exibe os melhores ajustes.Palavras-chave: Não extensividade, Sismicidade, Terra Sólida, Terremotos.

scholarly journals Taking Students on a Journey to El Yunque

2016 ◽  
Vol 7 (1) ◽  
Author(s):  
Steven McGee ◽  
Jess K. Zimmerman
Keyword(s):  
Temporal Dynamics ◽  
Science Curriculum ◽  
Global Climate ◽  
Ecosystem Dynamics ◽  
Long Term Ecological Research ◽  
Hurricane Impact ◽  
The Individual ◽  
Long Term Impact ◽  
The Impact

As the developers of Journey to El Yunque, we have taken a different approach to the process of designing a science curriculum. Rather than start with a specific set of concepts or skills to target as learning outcomes, we started by identifying a specific community of practice to which we sought to connect students. Researchers in the El Yunque rainforest in Puerto Rico have been studying the impact of hurricanes on ecosystem dynamics and have been modeling what the long-term impact would be if changes to the global climate increase the frequency of severe hurricanes. Therefore, hurricane impact became the focal phenomenon for the unit. We modeled the process of investigating hurricane impact after the long-term ecological research practices of researchers in El Yunque. Students begin by investigating the long-term impact of hurricanes on the producers in El Yunque. Next students investigate the long-term impact of hurricanes on various consumers in the rainforest. Finally, students investigate how hurricanes impact the cycling of resources directly as well as indirectly through changes in organisms’ use of those resources in the rainforest. A central tension in the design process is how to coherently represent the spatial relationships between the components of the ecosystem and the temporal dynamics of the individual components. In this paper, we present the evolution of the program as we sought to balance that design tension and build an environment that connects students to the central phenomenon and practices of the community of researchers in El Yunque. 

Nitrogen concentrations in flow separated river water

2020 ◽  
Author(s):  
Jørgen Windolf ◽  
Hans Thodsen ◽  
Henrik Tornbjerg ◽  
Brian Kronvang ◽  
Peter B. Sørensen
Keyword(s):  
Coastal Waters ◽  
Stream Water ◽  
Base Flow ◽  
Rate Of Change ◽  
Data Set ◽  
Flow Component ◽  
The Past ◽  
N Concentration ◽  
N Removal ◽  
The Impact

<p>Nitrogen (N) loads and concentrations have been successfully reduced in most Danish streams during the last 30 years. Thereby also reducing the impact of the main driver of marine eutrophication in Danish coastal waters. However, the trend in N-loads and concentrations vary substantially among the monitored streams. The understanding of this variation are of great importance and interest for the evaluation of measures implemented to combat N eutrophication and for forecasting of effects of further measures.</p><p>River hydrographs can be split into base flow and quick flow components and the N concentrations in these two components can, thereafter, be calculated. The N concentration in the two components varies over time showing both longer term and seasonal variation. The quick flow component typically having a high variation reflecting present days leaching of N from fields and this strata has been significantly reduced during the last 3 decades due to a more sustainable farming practices.</p><p>During base flow conditions, stream water typically holds less nitrogen due to N removal in groundwater. Reductions in agricultural nitrogen leaching over the past three decades has reduced concentrations in the quick flow component and reduced the load to ground water aquifers. As groundwater aquifers are often large with a capacity of several years of recharge, the response in base flow N-concentrations is expected to be slow compared to the response in quick flow. The low response of the N-concentrations in base flow have implications on the rate of change of the river concentrations and consequently riverine N-loads to coastal waters. In some cases, the base flow N-concentration might still be influenced by the larger N-leaching of the past (1960-1990).</p><p>We have analyzed a national data set for developments in N-concentrations during base flow and quick flow. The data set covers the in country range in catchment size, land use and geology. The data set spans 29 years covering the period 1990 – 2018. In addition, measurements from a few streams monitored for a longer period have been included in the analyses</p>

scholarly journals The impact of burning on lion Panthera leo habitat choice in an African savanna

2013 ◽  
Vol 59 (3) ◽  
pp. 335-339 ◽  
Author(s):  
Stephanie Eby ◽  
Anna Mosser ◽  
Ali Swanson ◽  
Craig Packer ◽  
Mark Ritchie
Keyword(s):  
National Park ◽  
Habitat Choice ◽  
Territory Size ◽  
Short Term ◽  
Data Set ◽  
Burned Areas ◽  
The Impact ◽  
Term Data ◽  
Prey Attraction

Abstract Carnivores play a central role in ecosystem processes by exerting top-down control, while fire exerts bottom-up control in ecosystems throughout the world, yet, little is known about how fire affects short-term carnivore distributions across the landscape. Through the use of a long-term data set we investigated the distribution of lions, during the daytime, in relation to burned areas in Serengeti National Park, Tanzania. We found that lions avoid burned areas despite the fact that herbivores, their prey, are attracted to burned areas. Prey attraction, however, likely results from the reduction in cover caused by burning, that may thereby decrease lion hunting success. Lions also do not preferentially utilize the edges of burned areas over unburned areas despite the possibility that edges would combine the benefit of cover with proximity to abundant prey. Despite the fact that lions avoid burned areas, lion territory size and reproductive success were not affected by the proportion of the territory burned each year. Therefore, burning does not seem to reduce lion fitness perhaps because of the heterogeneity of burned areas across the landscape or because it is possible that when hunting at night lions visit burned areas despite their daytime avoidance of these areas.

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