Composition and distribution of benthic macroinvertebrates in
Americana Reservoir (SP, Brazil)
PAMPLIN1, P.A.Z., ALMEIDA2, T.C.M. & ROCHA3, O.
1 Departamento de Química, Centro de Ciências da Natureza, Universidade Federal do Piauí, Campus Ministro Petrônio Portella, SG-02, CEP: 64.049-550, Teresina, PI, Brasil.
e-mail: pazpamplin@click21.com.br
2 Laboratório de Ecologia Aquática, Centro de Ciências da Terra e do Mar, Universidade do Vale do Itajaí, Rua Uruguai 458, CEP 88302-202, Itajaí, SC, Brasil.
e-mail: tito@univali.br
3 Departamento de Ecologia e Biologia Evolutiva, Universidade Federal de São Carlos, Rodovia Washington Luís km 235, CEP 13565-905, São Carlos, SP.
e-mail: doro@power.ufscar.br
ABSTRACT: The structure of benthic community at the Americana Reservoir was studied in two distinct periods of one year comprised between 1997-1998. Field sampling was conducted in dry and rainy periods in 15 and 13 sites, respectively. Nutrient (nitrate, nitrite, ammonium, total phosphorus and orthophosphate) analyses revealed that the reservoir is in advanced eutrophication process. Bottom fauna of the reservoir was composed by 19 invertebrate taxa, belonging to the following faunistic groups: Gastropoda, Oligochaeta, Hirudinea, Diptera (Chaoboridae, Chironomidae, Ceratopogonidae and Stratiomyidae) and Ephemeroptera. Chironomidae was the richest group, being represented by 6 taxa. The majority of species showed low densities, being that the oligochaetes formed the most important components of benthos densities, and Limnodrilus hoffmeisteri was the dominant taxa, representing almost 50% of total benthos. Comparing both periods, major densities were registered in dry season for most taxa. Cluster analysis revealed a longitudinal gradient with total densities decreasing from riverine portion towards the dam. The actual structure of benthic community at the Americana Reservoir is probably a consequence of the advanced state of environmental degradation. In addition, the existence of exotic species, represented by the gastropod Melanoides tuberculata and the leech Barbronia weberi, can also be contributing to the biodiversity losses in this community.
Key-words: benthic macroinvertebrates, eutrophication, biodiversity, exotic species.