Análisis de la dinámica de una comunidad planctónica mediante un modelo matemático

Modelos matemáticos de variada complejidad han sido usados para explorar la estructura de la comunidad en los ecosistemas acuáticos, y no sólo como herramientas para explorar y revelar mecanismos, tanto intuitivos como contraintuitivos, y patrones (de comportamiento, sino también para orientar lineas de especulación teórica y sugerir direcciones para la investigación de carpo y de laboratorio. El ecosistema que nos interesa aquí es el sistema planctónico oceánico dominado por algas Phaeocystis spp. El modelo matemático incluye compartimentos de nutrientes, fitoplancton y zooplancton (consumidores y depredadores) y está estructurado en forma modular para analizar el impacto de distintos factores en la compleja dinámica del sistema. Los resultados de las simulaciones destacan la importancia de (1) la estructura de tamaños de la población colonial de Phaeocystis, (2) el impacto de la naturaleza de la respuesta funcional del microzooplacton a la abundancia de fitoplancton y (3) la temporalidad de la aparición de depredadores en la comunidad sobre la utilización de los nutrientes. Se explora también el efecto de la turbulencia en la ruptura de las colonias y de la incorporación de nutrientes por remineralización o descarga de ríos. Las simulaciones indican que el sistema depende fuertemente del balance de tasas de crecimiento y de remoción en las poblaciones de Phaeocystis y microzooplancton durante los días iniciales del florecimiento, con los nutrientes y los depredadores actuando como controles indirectos.Mathematical models of various degrees of complexity have been successfully used for the study of aquatic ecosystems, primarily for the exploration of community structure, not only as tools for revealing counterintuitive mechanisms and patterns, but also for orienting theoretical speculation and suggesting directions of field and lahoratory research. Here we are interested in the oceanic planktonic system dominated by the unicellular algae Phaeocystis spp. Our mathematical model includes nutrient phytoplankton and zooplankton (grazers and predators) compartments and is constructed for modular form in order to analyse the impact of different factors in the complex dynamics of the system. Simulation results show the importance of size structure in the colonial Phaeocystis population, as well as the impact the character of the functional response of microzooplankton to algal abundance and the timing of large grazers in the community have on nutrient consumption. The effects of colonial cleavage caused by shear and the inflow of nutrients caused by remineralization or discharge of rivers llave also been explored. The results of our simulations indicate that the system has a strong dependence on the balance hetween growth rates and removal rates in both Phaeocystis and microzooplankton populations, nutrients and predators playing the role of indirect controls

Diseño de herramientas para el control de gestión por indicadores

El proyecto es una actividad de investigación y transferencia con aportes científicos en el campo de la mejora de la gestión por indicadores. Cuenta con colaboradores de grupo de investigación en Informática de gestión Facultad de Ciencias Exactas, Universidad Nacional del Centro de la provincia de Buenos Aires y con miembros de Universidades extranjeras. Es una actividad de investigación y transferencia con aportes científicos en el campo de la mejora de la gestión por indicadores, en organizaciones conscientes de la importancia de tomar decisiones estratégicas a partir de la evolución de los indicadores que marcan el rumbo y el estado de salud de la organización. Los principales aportes de este proyecto se pueden resumir como una propuesta de solución integral a la metodología de gestión por indicadores compuesta por el marco metodológico, el marco tecnológico, el ciclo de vida y los procedimientos que se desarrollan en cada uno de estos aspectos.Eje: Innovación en Sistemas de SoftwareRed de Universidades con Carreras en Informática (RedUNCI

Diseño de herramientas para el control de gestión por indicadores

El proyecto es una actividad de investigación y transferencia con aportes científicos en el campo de la mejora de la gestión por indicadores. Cuenta con colaboradores de grupo de investigación en Informática de gestión Facultad de Ciencias Exactas, Universidad Nacional del Centro de la provincia de Buenos Aires y con miembros de Universidades extranjeras. Es una actividad de investigación y transferencia con aportes científicos en el campo de la mejora de la gestión por indicadores, en organizaciones conscientes de la importancia de tomar decisiones estratégicas a partir de la evolución de los indicadores que marcan el rumbo y el estado de salud de la organización. Los principales aportes de este proyecto se pueden resumir como una propuesta de solución integral a la metodología de gestión por indicadores compuesta por el marco metodológico, el marco tecnológico, el ciclo de vida y los procedimientos que se desarrollan en cada uno de estos aspectos.Eje: Innovación en Sistemas de SoftwareRed de Universidades con Carreras en Informática (RedUNCI

Improving the rigor and Usefulness of Scenarios and Models for Biodiversity and Ecosystem Services Assessment

In April 2012, over 100 governments agreed to establish IPBES, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, as the leading intergovernmental body for assessing the state of the planet’s biodiversity, its ecosystems and the essential services they provide to society. Among many other activities, the methodological assessment of scenarios and models of biodiversity and ecosystem services was initiated in order to provide expert advice on the use of such methodologies in all activities under the Platform to ensure the policy relevance of its deliverables. In particular, the work focused on providing critical analyzes of the state-of-the-art and best practices for using scenarios and models in assessments, policy design and policy implementation relevant to biodiversity and ecosystem services; on proposing means for addressing gaps in data, knowledge, methods and tools relating to scenarios and models; and on recommendations for action by IPBES to implement and encourage those best practices, engage in capacity-building, and mobilize indigenous and local knowledge. The target audiences are not only those working within IPBES but also the scientific community and funding agencies, as well as policymakers and implementers at local to global scales, and people employing scenarios and models for decision support. Because of on-going research and rapid progress on many aspects of scenario analysis and modelling of biodiversity and ecosystem services, there is a need to continually update the review of available policy support tools and methodologies for scenario analysis and modelling. The goal is to point the way forward for additional research and development that is required to take the use of models and scenarios to a whole new level of rigor and utility. Here, some relevant gaps in data availability and data access as well as gaps and shortages from the modelling point of view will be identified and discussed. The need to have guidelines for verification and validation of models, and for assessing and managing uncertainty in scenario analysis and modelling will be analyzed

Analysis of shallow lakes dynamics as related to precipitation in the Pampas region based on Landsat imagery

Shallow lakes in the Pampas are characterized by their high number as well as by frequent variations in their hydrometric level and their surface area, depending on regional rainfall and underground water balance [1],[2]. More than 150,000 shallow lakes of various sizes have been counted in the province of Buenos Aires, with at least 10,500 of them having a surface area above 10 ha [2]. They exhibit changing dynamics (seasonally and annually) without a definite pattern. Preliminary work indicates an inverse relationship between the volume of water retained in a shallow lake and trophic state indicators, linking rainfall and trophic level [3]. Thus, Pampean shallow lakes are not only conditioned by the activities taking place in their surroundings, but they also respond to climatic forces whose dynamic effect has not yet been sufficiently studied. Understanding the dynamics of interactions between climate and shallow lake ecosystems in the Pampas is essential for their conservation and resource utilization, as well as for guaranteeing the provision of ecological services. Hence the interest in linking the variation in water volume in one or more shallow lakes to precipitations over the region since the said variation is linked to nutrient concentrations and plankton abundance conditioning the ecosystem’ s food web. The purpose of this study is to analyze the temporal dynamics of the area of five shallow lakes in different basins of the Buenos Aires province over the period 1984-2015 through the application of satellite image processing tools [4]. Two images per year were selected (Landsat 4 TM, Landsat 5 TM, Landsat 7 ETM+ and Landsat 8 OLI), one corresponding to summer and the other to winter. The evolution of the free water surface of these shallow lakes could be explained using a generalized linear model (GLM) and taking as variables the accumulated precipitation and the number of rainy days over a fixed-length period prior to the capture date of the satellite image. Accumulated precipitation and frequency of rainy days were calculated for three, seven, thirty, ninety, and one hundred and eighty days, as well as for one, two, three, and four years prior to the capture date, respectively. When analyzing the interdecadal precipitation medians, a decrease was observed in all meteorological stations involved (Azul, Benito Juárez, Olavarría and Tres Arroyos). This led to splitting the series of computed lake areas into two consecutive periods: 1984-2000 and 2001-2015. The areas reconstruction for the five shallow lakes varied in regard to both the explanatory variables and in the reconstruction coefficients when the series were divided into two periods. In all cases except one, better reconstructions were obtained for the second half. The results regarding the behavior of the shallow lakes in response to antecedent rainfall differed in each of the basins, reflecting the systems characteristics [5]. It may be interpreted that when the area responds to precipitation accumulated over longer periods the underground contribution is important, meaning that the memory of the system prevails, while a significant superficial contribution would explain the shallow lake’ s response to precipitation accumulated over short periods, pointing to the importance of runoff.Fil: Maestri, María Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; ArgentinaFil: Canziani, Graciela Ana. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; ArgentinaXV Seminario Internacional de BiomatemáticaLimaPerúSociedad Peruana de Matemática Aplicada y Computaciona

A discrete model for estimating the development time from egg to infecting larva of Ostertagia ostertagi parametrized using a fuzzy rule-based system

Ostertagia ostertagi is a nematode, predominantly affecting cattle in the Pampean region of Argentina. A mathematical model parametrized using fuzzy rule-based systems of the Takagi-Sugeno-Kant type (FTSK) for estimating the development time from egg to infecting larval stage L3 of the gastrointestinal parasite Ostertagia ostertagi is here proposed. The estimation of development time of Ostertagia ostertagi is essential for the generation of appropriate control mechanisms, since this provides information about the time when parasites are ready to migrate to pastures. For the purpose of reflecting the natural environmental conditions, the mean daily temperature is taken as the main and only regulator of the development time. Humidity conditions are considered to be sufficient for the normal development of the larvae. Hence the individual?s daily growth is a function of its length and the mean temperature recorded on the previous day. It is expressed in terms of a difference equation with fuzzy parameters, which are defined using laboratory data. Model outputs are tested against results of field experiments. Simulation results are very satisfactory, yielding a mean estimation error (MEE) of 0.64 weeks, with variance 0.34, and a determination coefficient R2=0.74. The model clearly exhibits an inverse relationship between development time and temperature both in controlled and in field conditions. It also exhibits a very sensitive response both to the order in which the temperature sequence occurs, -- reproducing the differences observed between spring and autumn -- and to the amplitude of the temperature range.Fil: Chaparro, Mauro Alejandro Eduardo. Universidad Nacional del Centro de la Provincia de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; ArgentinaFil: Canziani, Graciela Ana. Universidad Nacional del Centro de la Provincia de Buenos Aires; Argentin

Epidemic metapopulation model on weighted directed networks with pulse movements between nodes

In metapopulation disease models, it is generally considered that movements between subpopulations occur in a continuous way. However, there are situations in which this assumption is not fulfilled, as in the case of cattle movements. Here we develop a SIR metapopulation model on weighted directed networks considering that pulse-like movements between subpopulations take place only at certain times, and where each node represents a well-mixed subpopulation. The model is used to analyze the dynamics of the diseases by varying the transmission rates, the time steps for the movements of the individuals through the network, the weight of the links and the network topology. The numerical results indicate that the transmission rate, the time elapsed between movements of individuals and the topology of the network significantly affect the final size of the epidemic. In addition, it can be observed that the network topology drastically affects the disease dynamics within each node. On the other hand, if vaccination is considered in a node, the effectiveness of this control measure depends on the distance between the node where the epidemic begins and the node where the control is applied.Fil: Simoy, Mario Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones en Energía no Convencional. Universidad Nacional de Salta. Facultad de Ciencias Exactas. Departamento de Física. Instituto de Investigaciones en Energía no Convencional; ArgentinaFil: Simoy, Maria Veronica. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Canziani, Graciela Ana. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentin

The effect of temperature on the population dynamics of Aedes aegypti

The mosquito Aedes aegypti, the principal vector of dengue and yellow fever viruses, is an anthropophilic species adapted to urban environments, particularly to housing. A decisive factor in the proliferation of this species is ambient temperature, which has a direct influence on the vital rates of the species.Here we present a structured matrix population model for analyzing the effect of temperature on the population dynamics of Aedes aegypti. The model is structured following the four natural stages of the species: egg, larva, pupa and adult. A set of population projection matrices (one for each temperature between 5 and 30. °C), was constructed and parameterized using published data on the biology of the species. The output of the models showed that pupation does not occur at temperatures below 8. °C. The population's growth rate was calculated for temperatures between 11 and 30. °C, resulting in an increasing function showing that temperatures above 12. °C are sufficient for population growth. For each matrix, a sensitivity and elasticity analysis of the parameters was performed. Together with the results from the population stable distribution analysis, they suggest that policies aimed at reducing the abundance of Aedes aegypti should seek to lower the survival probability in the egg and larval stages. The population dynamics was simulated under different seasonal scenarios. This seasonal analysis allows asserting that the egg stage dominates the population dynamics at all seasons.Fil: Simoy, Mario Ignacio. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario sobre Ecosistemas y Desarrollo Sustentable. Grupo de Ecología Matemática; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; ArgentinaFil: Simoy, Maria Veronica. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario sobre Ecosistemas y Desarrollo Sustentable. Grupo de Ecología Matemática; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; ArgentinaFil: Canziani, Graciela Ana. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario sobre Ecosistemas y Desarrollo Sustentable. Grupo de Ecología Matemática; Argentin

Herd dynamics age and sex structured model considering management practices and animal movements among districts

Mathematical models applied to livestock systems are an important tool for their analysis and planning, which can be used to improve their profitability, as well as for sanitary purposes. An age and sex structured model formulated in differential equations was developed for simulating the dynamics of a cattle herd population in a district. Since management practices determine the herd’s structure, this model considers explicitly common practices, such as seasonal service, calving, weaning and the replacement of animals for reproduction, usually implemented in Argentina’s livestock system. Movements between districts are also incorporated into the model, following the national livestock movements database. This model can be used to analyze the effect of different management practices. The herd population dynamics was simulated with and without movements between districts, showing how movements influence the local dynamics and in the herd structure. Population dynamics in two districts with different main productive activity (breeding and fattening) are compared and discussed.Fil: Simoy, Mario Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones en Energía no Convencional. Universidad Nacional de Salta. Facultad de Ciencias Exactas. Departamento de Física. Instituto de Investigaciones en Energía no Convencional; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; ArgentinaFil: Simoy, Maria Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; ArgentinaFil: Canziani, Graciela Ana. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentin

An individual-based model to estimate the daily energetic cost of Greater Rheas and its contribution on population recruitment

An individual-based model for estimating the energetic costs in Rhea americana was developed considering their sexual and seasonal differences in the behavioral activities. The model includes as variables the individual’s characteristics, as well as corporal weight, the time spent on different activities, and the cost associated with each activity. We estimated the daily energetic demand of an adult rhea based on the activities individuals normally develop during postreproductive, nonreproductive, and reproductive seasons, differentiating between sexes. The time spent in each activity for one given animal was calculated from field observations of individuals and the estimations of energetic costs for each activity were obtained from specialized literature. The model built varied between sexes because males and females have different reproductive costs. Both models have the same general formulation but they differ in the cost associated with reproduction. In Greater Rheas, while males assume all of the incubation, the females only lay eggs communally in a single nest. Also the possibility that the individual reproduces or not was considered. The model does not allow to determine whether the energetic costs associated with the breeding are the reason why few individuals try to reproduce but it indicates that there is a clear difference in the daily energetic costs of individuals which reproduce and those which do not reproduce. Other activities associated with parental care posthatching, not taken into account here, would increase these differences, and would explain the low number of breeding attempts observed at wild.Fil: Simoy, Maria Veronica. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Fernandez, Gustavo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Canziani, Graciela Ana. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto Multidisciplinario de Ecosistemas y Desarrollo Sustentable; Argentin