Community structure and temporal dynamics of cladocerans in an Amazonian lake (Lake Batata,
PA, Brazil) impacted by bauxite tailings
MAIA-BARBOSA1, P.M. & BOZELLI2, R.L.
1 Universidade Federal de Minas Gerais, Laboratório de Ecologia do Zooplâncton, ICB/I3/253. Av. Antônio Carlos, 2267. Pampulha, Belo Horizonte, Brazil. 31270-901.
2 Universidade Federal do Rio De Janeiro, Laboratório de Ecologia do Plâncton, Departamento de Ecologia, CCS, Caixa postal 68020, CEP 21 941 590, Rio de Janeiro, Brazil.
ABSTRACT: We analyzed the species composition and abundance of cladocerans weekly for one year in two areas (natural and impacted) of an Amazonian lake (Lake Batata), which has received bauxite tailing for ten years (1979-89). The possible influences of this material and the marked fluctuations of the water level on the dynamics of the five most representative species (Bosmina hagmanni, Bosminopsis deitersi, Ceriodaphnia cornuta, Diaphanosoma birgei, Moina minuta) were also studied. At both sites higher richness was registered in the flood phase and a equitable distribution of species in the drawdown phase. The highest average density was recorded in the low water period (225 and 786 x 103 org.m-3 at the natural and impacted sites, respectively) and the lowest, in the high water period (71 and 198 x 103 org.m-3, respectively) probably reflecting consequences of hydrological dilution. Irregular fluctuations were registered at both sites and at several times the densities at the impacted area were higher and determined by the increase and dominance of one only species. Changes in water level were shown to be the principal factor affecting the composition and fluctuations of the cladoceran community, sometimes enhancing the positive effects of suspended material on the species.
Key-words: Amazonian lake, impacted, cladocerans, species composition, dynamics.