scholarly journals Functional-Structural Modelling as a Potential Tool to Assess the Impact of Resource Competition on Arable Communities

2007 ◽  
pp. 231-241
Author(s):  
A. Karley ◽  
B. Marshall
Keyword(s):  
Resource Competition ◽  
Structural Modelling ◽  
The Impact ◽  
Potential Tool

Nutrient-related selection mechanisms in marine phytoplankton communities and the impact of eutrophication on the planktonic food web

1995 ◽  
Vol 32 (4) ◽  
pp. 63-75 ◽  
Author(s):  
R. Riegman
Keyword(s):  
Algal Blooms ◽  
Algal Biomass ◽  
Resource Competition ◽  
Water Quality Management ◽  
Algal Species ◽  
Marine Phytoplankton ◽  
Commercial Fish ◽  
N Limitation ◽  
Phytoplankton Communities ◽  
The Impact

A general increase in nutrient discharges during the last few decades has caused various changes in the algal community structure along the European continental coast. Coincidentally and maybe consequently, the foodweb structure and functioning has altered in local areas causing various phenomena like oxygen depletion, mortality of groups of organisms, foam on beaches, and an increase in the productivity of benthic communities and some commercial fish species. The observed increases in algal biomass and shifts in species composition are discussed in relation to the involved key mechanisms: resource competition and selective grazing. Along the Dutch coastal zone of the North Sea eutrophication has caused a doubling of the yearly averaged algal biomass during the past three decades. The sudden appearance of Phaeocystis summer blooms coincided with a shift from P-limitation towards N-limitation in the Dutch coastal area due to a stronger increase in P-discharge relative to the increase in N-discharge. Competition experiments in continuous cultures showed Phaeocystis to become dominant under N-limitation. Additionally, the large Phaeocystis colonies, which can reach a diameter up to one centimetre, escape from microzooplankton grazing. A computer model is presented which demonstrates a shift from bottom-up towards top-down control if the pelagic environment becomes eutrophicated. Implementation of this concept in a size-differential phytoplankton control model generates the prediction that algal blooms are dominated by species that escape from grazing by those zooplankton species which have a high potential numerical response. In marine environments these are microzooplankton species. These organisms mainly feed on cyanobacteria, prochlorophytes and some nano-algal species. One of the consequences for foodweb structure and the carbon fluxes in marine foodwebs is that eutrophication will lead to the dominance of poorly edible algal species. Eutrophication favours the downward transport of carbon and nutrients towards the sediments not only due to higher algal biomasses but also as a consequence of a shift towards larger algal species with higher sedimentation characteristics. An example is given how these new insights can be used for water quality management purposes.

scholarly journals Seasonal impact of grazing, viral mortality, resource availability and light on the group-specific growth rates of coastal Mediterranean bacterioplankton

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Olga Sánchez ◽  
Isabel Ferrera ◽  
Isabel Mabrito ◽  
Carlota R. Gazulla ◽  
Marta Sebastián ◽  
...  
Keyword(s):  
Nutrient Limitation ◽  
Growth Rates ◽  
Resource Competition ◽  
Specific Growth ◽  
Light Availability ◽  
Anoxygenic Phototrophs ◽  
Nw Mediterranean ◽  
Specific Growth Rates ◽  
Card Fish ◽  
The Impact

AbstractEstimation of prokaryotic growth rates is critical to understand the ecological role and contribution of different microbes to marine biogeochemical cycles. However, there is a general lack of knowledge on what factors control the growth rates of different prokaryotic groups and how these vary between sites and along seasons at a given site. We carried out several manipulation experiments during the four astronomical seasons in the coastal NW Mediterranean in order to evaluate the impact of grazing, viral mortality, resource competition and light on the growth and loss rates of prokaryotes. Gross and net growth rates of different bacterioplankton groups targeted by group-specific CARD-FISH probes and infrared microscopy (for aerobic anoxygenic phototrophs, AAP), were calculated from changes in cell abundances. Maximal group-specific growth rates were achieved when both predation pressure and nutrient limitation were experimentally minimized, while only a minimal effect of viral pressure on growth rates was observed; nevertheless, the response to predation removal was more remarkable in winter, when the bacterial community was not subjected to nutrient limitation. Although all groups showed increases in their growth rates when resource competition as well as grazers and viral pressure were reduced, Alteromonadaceae consistently presented the highest rates in all seasons. The response to light availability was generally weaker than that to the other factors, but it was variable between seasons. In summer and spring, the growth rates of AAP were stimulated by light whereas the growth of the SAR11 clade (likely containing proteorhodopsin) was enhanced by light in all seasons. Overall, our results set thresholds on bacterioplankton group-specific growth and mortality rates and contribute to estimate the seasonally changing contribution of various bacterioplankton groups to the function of microbial communities. Our results also indicate that the least abundant groups display the highest growth rates, contributing to the recycling of organic matter to a much greater extent than what their abundances alone would predict.

Modelling multi-topic information propagation in online social networks based on resource competition

2016 ◽  
Vol 43 (3) ◽  
pp. 342-355 ◽  
Author(s):  
Liyuan Sun ◽  
Yadong Zhou ◽  
Xiaohong Guan
Keyword(s):  
Social Networks ◽  
Network Structure ◽  
Online Social Networks ◽  
Resource Competition ◽  
Propagation Model ◽  
Small Scale ◽  
Model Parameters ◽  
Information Propagation ◽  
Practical Applications ◽  
The Impact

Understanding information propagation in online social networks is important in many practical applications and is of great interest to many researchers. The challenge with the existing propagation models lies in the requirement of complete network structure, topic-dependent model parameters and topic isolated spread assumption, etc. In this paper, we study the characteristics of multi-topic information propagation based on the data collected from Sina Weibo, one of the most popular microblogging services in China. We find that the daily total amount of user resources is finite and users’ attention transfers from one topic to another. This shows evidence on the competitions between multiple dynamical topics. According to these empirical observations, we develop a competition-based multi-topic information propagation model without social network structure. This model is built based on general mechanisms of resource competitions, i.e. attracting and distracting users’ attention, and considers the interactions of multiple topics. Simulation results show that the model can effectively produce topics with temporal popularity similar to the real data. The impact of model parameters is also analysed. It is found that topic arrival rate reflects the strength of competitions, and topic fitness is significant in modelling the small scale topic propagation.

scholarly journals High functional diversity stimulates diversification in experimental microbial communities

2016 ◽  
Vol 2 (6) ◽  
pp. e1600124 ◽  
Author(s):  
Alexandre Jousset ◽  
Nico Eisenhauer ◽  
Monika Merker ◽  
Nicolas Mouquet ◽  
Stefan Scheu
Keyword(s):  
Ecosystem Services ◽  
Functional Diversity ◽  
Bacterial Communities ◽  
Evolutionary Dynamics ◽  
Resource Competition ◽  
Bacterial Species ◽  
Focal Species ◽  
Evolutionary Diversification ◽  
The Impact ◽  
High Diversity

There is a growing awareness that biodiversity not only drives ecosystem services but also affects evolutionary dynamics. However, different theories predict contrasting outcomes on when do evolutionary processes occur within a context of competition. We tested whether functional diversity can explain diversification patterns. We tracked the survival and diversification of a focal bacterial species (Pseudomonas fluorescens) growing in bacterial communities of variable diversity and composition. We found that high functional diversity reduced the fitness of the focal species and, at the same time, fostered its diversification. This pattern was linked to resource competition: High diversity increased competition on a portion of the resources while leaving most underexploited. The evolved phenotypes of the focal species showed a better use of underexploited resources, albeit at a cost of lower overall growth rates. As a result, diversification alleviated the impact of competition on the fitness of the focal species. We conclude that biodiversity can stimulate evolutionary diversification, provided that sufficient alternative niches are available.

scholarly journals The impact of resource competition on neurite outgrowth

2011 ◽  
Vol 12 (S1) ◽  
Author(s):  
Johannes JJ Hjorth ◽  
Jurjen Broeke ◽  
Huib Mansvelder ◽  
Jaap van Pelt ◽  
Arjen van Ooyen
Keyword(s):  
Neurite Outgrowth ◽  
Resource Competition ◽  
The Impact

scholarly journals Spatio-temporal modeling of the crowding conditions and metabolic variability in microbial communities

2021 ◽  
Vol 17 (7) ◽  
pp. e1009140
Author(s):  
Liliana Angeles-Martinez ◽  
Vassily Hatzimanikatis
Keyword(s):  
Microbial Communities ◽  
Extracellular Polymeric Substances ◽  
Resource Competition ◽  
Local Environment ◽  
Microbial Interactions ◽  
Relative Fitness ◽  
Flux Analysis ◽  
Scaled Particle Theory ◽  
Spatio Temporal ◽  
The Impact

The metabolic capabilities of the species and the local environment shape the microbial interactions in a community either through the exchange of metabolic products or the competition for the resources. Cells are often arranged in close proximity to each other, creating a crowded environment that unevenly reduce the diffusion of nutrients. Herein, we investigated how the crowding conditions and metabolic variability among cells shape the dynamics of microbial communities. For this, we developed CROMICS, a spatio-temporal framework that combines techniques such as individual-based modeling, scaled particle theory, and thermodynamic flux analysis to explicitly incorporate the cell metabolism and the impact of the presence of macromolecular components on the nutrients diffusion. This framework was used to study two archetypical microbial communities (i) Escherichia coli and Salmonella enterica that cooperate with each other by exchanging metabolites, and (ii) two E. coli with different production level of extracellular polymeric substances (EPS) that compete for the same nutrients. In the mutualistic community, our results demonstrate that crowding enhanced the fitness of cooperative mutants by reducing the leakage of metabolites from the region where they are produced, avoiding the resource competition with non-cooperative cells. Moreover, we also show that E. coli EPS-secreting mutants won the competition against the non-secreting cells by creating less dense structures (i.e. increasing the spacing among the cells) that allow mutants to expand and reach regions closer to the nutrient supply point. A modest enhancement of the relative fitness of EPS-secreting cells over the non-secreting ones were found when the crowding effect was taken into account in the simulations. The emergence of cell-cell interactions and the intracellular conflicts arising from the trade-off between growth and the secretion of metabolites or EPS could provide a local competitive advantage to one species, either by supplying more cross-feeding metabolites or by creating a less dense neighborhood.

scholarly journals Dynamic allocation of orthogonal ribosomes facilitates uncoupling of co-expressed genes

2017 ◽  
Author(s):  
Alexander P.S. Darlington ◽  
Juhyun Kim ◽  
José I. Jiménez ◽  
Declan G. Bates
Keyword(s):  
Resource Allocation ◽  
Circuit Design ◽  
Resource Competition ◽  
Dynamic Resource Allocation ◽  
Dynamic Allocation ◽  
16S Rna ◽  
Synthetic Circuit ◽  
Dynamic Resource ◽  
The Impact ◽  
Host Genes

AbstractIntroduction of synthetic circuits into host microbes creates competition between circuit and host genes for shared cellular resources, such as RNA polymerases and ribosomes. This can lead to the emergence of unwanted coupling between the expression of different genes, complicating circuit design and potentially leading to circuit failure. Here we demonstrate the ability of orthogonal ribosomes to alleviate the effects of this resource competition. We partition the ribosome pool by expressing an engineered 16S RNA with altered specificity, and use this division of specificity to build simple resource allocators which reduce the level of ribosome-mediated gene coupling. We then design and implement a dynamic resource allocation controller, which acts to increase orthogonal ribosome production as the demand for translational resources by a synthetic circuit increases. Our results highlight the potential of dynamic translational resource allocation as a means of minimising the impact of cellular limitations on the function of synthetic circuitry.

scholarly journals To Move Home or Move On? Investigating the Impact of Recovery Aid on Migration Status as a Potential Tool for Disaster Risk Reduction in the Aftermath of Volcanic Eruptions in Merapi, Indonesia

2019 ◽  
Author(s):  
Jonathan A. Muir ◽  
Michael R. Cope ◽  
Jorden E. Jackson ◽  
Leslie R. Angeningsih
Keyword(s):  
Risk Reduction ◽  
Regression Models ◽  
Multinomial Logistic Regression ◽  
Forced Migration ◽  
Volcanic Eruptions ◽  
Migration Status ◽  
Logistic Regression Models ◽  
The Impact ◽  
Financial Recovery ◽  
Potential Tool

Disasters are associated strongly with forced migration. Indeed, migration is a standard survival strategy for those facing disruptions of this kind. Such is the case with Mt. Merapi, Indonesia, where a series of eruptions occurred in 2010. Mechanisms related to forced migration in such scenarios are fairly well understood, yet it remains less clear what factors may influence return migration. Given local interest in facilitating resettlement out of hazardous areas as a means of risk reduction, we seek to better understand the extent to which recovery aid may create incentives for households to move on rather than move home. We draw upon data collected from a pilot study in the aftermath of the 2010 eruptions and use multinomial logistic regression models to explore the influence of various forms of aid on migration status. Of the various forms of aid considered, financial recovery aid provided to households was consistently associated with moving on. The combination of financial recovery aid with remittances resulted in an association with having moved on that was even stronger than just receiving financial recovery aid. Ultimately, analyses of "aid packages'" suggest that a combination of most, if not all, of the aid was relatively more effective in fostering resettlement, suggesting that while food and health recovery aid as well as remittances may not have been sufficient in and of themselves to increase resettlement, they may enhance the effect of financial recovery aid.

scholarly journals How Resource Scarcity and Accessibility Affect Patients’ Usage of Mobile Health in China: Resource Competition Perspective (Preprint)

2019 ◽  
Author(s):  
Qing Ye ◽  
Zhaohua Deng ◽  
Yanyan Chen ◽  
Jiazhi Liao ◽  
Gang Li ◽  
...  
Keyword(s):  
Health Care ◽  
Mobile Health ◽  
Theoretical Basis ◽  
Resource Competition ◽  
External Environment ◽  
Resource Scarcity ◽  
Medical Resources ◽  
The Impact ◽  
The Relationship ◽  
Moderating Role

BACKGROUND The last decade has witnessed many achievements in China’s health care industry, but the industry still faces major challenges among which the uneven distribution of medical resources and the imbalance between supply and demand are the most pressing problems. Although mobile health (mHealth) services play a significant role in mitigating problems associated with health care delivery, their adoption rates have been low. OBJECTIVE The objective of this study was to explore the impact of resource scarcity and resource accessibility on the adoption of mHealth from the perspective of resource competition, to examine the concerning factors, and to provide a theoretical basis for promoting mHealth in China. METHODS We used 229,516 original registration records of outpatients to conduct an empirical analysis to examine the adoption of mHealth services from the perspective of resource competition. RESULTS The adoption rate of mobile services for outpatients was low, accounting for only 31.5% (N=71,707). The empirical results indicated that resource scarcity (beta=.435, P=.01) and accessibility (beta=−.134, P=.02) have a significant impact on the adoption of mHealth. In addition, gender (beta=.073, P=.01) and age (beta=−.009, P<.001) are significantly related to adoption of mHealth. Experience with mHealth has a moderating role in the relationship between resource scarcity (beta=−.129, P=.02), accessibility (beta=.138, P=.04), and adoption of mHealth. CONCLUSIONS In this study we demonstrate that the external environment (resource scarcity and resource accessibility) has a significant impact on the adoption of mHealth. This study also demonstrates that experience with mHealth has a moderating role in the relationship between the elements of the external environment. Finally, we confirm that mHealth is a key factor in the delivery and allocation of medical resources and provide a theoretical basis for government agencies to develop policies on mHealth.

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