-Population rates of the three dominant amphipod species (Hyale nigra, Caprella danileviskii and Caprella penantis) associated to Bryocladia thrysigera, were calculated revealing similar values for the intrinsic growth rate. The empirical data modeled presented a good fit to the May-Leonard three-species competition model in a discrete Ricker form with periodic cycles for the carrying capacity. In adjusting model to data, a new method to calculate competition coefficients emerged in good agreement with ecological and behavior particularities. A simulation of environmental stochasticity was achieved by the insertion of random parameters for the calculation of each species carrying capacity. H. nigra presented a persistent behavior in extreme environmental stress, whereas C. penantis is highly sensitive to stress.
In this paper it is presented a gentle review of empirical and theoretical advances in understanding the role of size in biological organisms. More specifically, it deals with how the energy demand, expressed by the metabolic rate, changes according to the mass of an organism. Empirical evidence suggests a power-law relation between mass and metabolic rate, namely the allometric equation. For vascular organisms, the exponent β of this powerlaw is smaller than one, which implies scaling economy; that is, the greater the organism is, the lesser energy per cell it demands. However, the numerical value of this exponent is a theme of extensive debate and a central issue in comparative physiology. A historical perspective is shown, beginning with the first empirical insights in the sec. 19 about scaling properties in biology, passing through the two more important theories that explain the scaling properties quantitatively. Firstly, the Rubner model considers organism surface area and heat dissipation to derive β = 2/3. Secondly, the West-Brown-Enquist theory explains such scaling properties due to the hierarchical and fractal nutrient distribution network, deriving β = 3/4.
Several lines of evidence suggest that the effects of stressors on populations can be calculated accurately by population modeling. Using monitoring data of natural population, population models were applied and the possibility of establishing environmental diagnoses from strictly ecological concepts is discussed. A procedure is offered for the modeling of natural population data and the establishment of population endpoints.Key words: Ecotoxicology. Population Models. Hurst Exponent. Time series analysis.
Abordagem populacional em ecotoxicologia (Ecologia do estresse) ResumoDiversas linhas de evidências sugerem que os efeitos de estressores atuando em populações podem ser calculados acuradamente pela modelagem populacional. Usando dados de monitoramento de populações naturais, modelos populacionais foram aplicados e a possibilidade de estabelecer diagnoses ambientais a partir de conceitos estritamente ecológicos é discutida. Um procedimento é oferecido para a modelagem de dados de populações naturais e o estabelecimento de endpoints populacionais.
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