Mixed food web control and stability in a Cerrado river (Brazil)

Abstract

Understanding the mechanisms which regulate aquatic food webs dynamics have been an important focus inquiry since ecological research started to emphasize ecosystems’ structure and functioning. The objective of this study was verify if species composition were the same at three different habitats in Corrente River. If species composition were the same it will allow to model the food web by a single model, otherwise each portion should be modeled independently. Ecopath model and the keystoneness index (KSi) were used in order to evaluate the entire food web and to comprehend the system control. Five surveys in the period from June of 2003 to until June of 2005 were carried out in three different habitats in the river. Results showed that: i) there are seven fish species; ii) habitats are very similar; iii) all species reproduced in the rain y season with exception of Brycon nattereri. A single Ecopath model indicated low resilience and stability. Keystoneness rank values showed a mixed system control mechanism, where one predator, Salminus hilarii, one intermediate consumer, Astyanax altiparanae and one consumer of trophic level two (terrestrial invertebrates) had respectively, the highest keystoneness index values