No limiar tênue entre teoria e realidade, sazonalidade e caos em sistemas planctônicos

• Ano de defesa: 2009
• Autor(a) principal: Ferreira, Heury Sousa
• Orientador(a): Marco Júnior, Paulo De
• Banca de defesa: Marco Júnior, Paulo De, Diniz Filho, José Alexandre Felizola, Silva, Daniel Brito Candido da
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Goiás
• Programa de Pós-Graduação: Programa de Pós-graduação em Ecologia e Evolução (ICB)
• Departamento: Instituto de Ciências Biológicas - ICB (RMG)
• País: Brasil
• Palavras-chave em Português: Caos; Ecologia; Plâncton; Dinâmica não linear
• Palavras-chave em Inglês: Chaos; Ecology; Plancton; Non linear dynamic
• Área do conhecimento CNPq: CIENCIAS BIOLOGICAS::BIOLOGIA GERAL
• Link de acesso: http://repositorio.bc.ufg.br/tede/handle/tede/13166

The Chaos Theory is an alternative tool to stochastic dynamic modeling when target biological systems show irregular and no predictive behavior. The plankton is a model group of organisms to theoretical and experimental investigations in chaotic dynamics due to its intrinsic biological characteristics as small size, high reproductive rate and short life cycle, with the additional advantage of its public interest related to practical problems. In this work we investigated the dynamical aspects of a NutrientPhytoplankton-Zooplankton seasonal forced model, created by means of the addition of the Zooplankton level on a Nutrient-Phytoplankton seasonal forced model that show chaotic behavior, proposed by Huppert et al. (2005). An important outcome of the Huppert’s model is that the intensity of the seasonal forcing is the control parameter of the system. We investigated the zooplankton effect on the stability of the model, and the chaos control by means of pulses in the intensity of the seasonal forcing. Our results show that strong and weak seasonal forcing implicates in cyclical fluctuations of phytoplankton populations, and those cycles had higher amplitude in strong seasonal forcing. Between those two extremes, there is chaos. The zooplankton mortality is a fundamental component of the behavior of the model. In fact, despite of seasonal forcing values that can promote chaotic behavior, the model can show cyclic behavior to some values of mortality rates. This suggests that absence of top-down control in the models built to understand phytoplanktonic dynamics (blooms are only a consequence of this), result in an over-simplification and lack of conceptual comprehension of the system. Our results show that periodic pulses can be able to control the chaos on moderate seasonal forcing, and to promote chaos to weak and strong seasonal effects. The pulses are theoretical indicatives of how climatic changes influences a seasonal variable can to affect the dynamics aspects of planktonic systems.