Tuesday, May 27, 2008
258

Network model of a periphyton based system in a coastal atlantic rainforest stream córrego da andorinha, ilha grande, RJ, brazil

Pedro de Moraes Andrade, Timothy Peter Moulton, Marcelo Luíz Souza, Felipe A. M. Krsulovic, Ernesto Fuentes Brito, Vinícius Neres Lima, and Fausto Machado Silva. Departamento de Ecologia, Universidade Estadual do Rio de Janeiro, Depto. de Ecologia, UERJ, Rua São Francisco Xavier 524, Maracanã, Rio de Janeiro, CEP 20550-013, Brazil, Rio de Janeiro, Brazil

The role of periphytic microalgae as an energy source for metazoan communities has been investigated in several freshwater systems. Working with stable isotopes of 13C and 15N we analysed the trophic levels in our study system and defined the pathways of carbon, confirming the role of microalgae as the main source of energy for the local community. We also estimated biomass standing stocks: pooled primary consumers 1.35 g m-2 DM, pooled secondary consumers 8.6 g m-2 DM, primary producers 8.05 g m-2 DM. The pyramid of biomass is apparently inverted at the level of the secondary consumers (primarily shrimps). Recent theoretical research showed that the shape of the trophic pyramid was not important for ecosystem functioning. Network parameters such as cycling, amplification, homogenization, indirect effects and synergism were independent of the pyramid’s shape being inverted or normal. We are building a mass-balance Ecopath/Ecosim® model of Córrego da Andorinha, Ilha Grande, RJ. We use the Network analysis module to investigate a) the structural consequences of different degrees of dependence on autochthonous primary production and b) the dependence of network parameters on the shape of a trophic biomass pyramid.


Web Page: periphyton, network analysis, biomass pyramid,

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