Long-term patterns of the planktonic cladoceran community of Batata Lake, Amazonia, Brazil

GARRIDO¹, A.V., BOZELLI¹, R.L., ESTEVES¹, F. DE A. & ALVES¹, L.S.

¹ Laboratório de Limnologia, Departamento de Ecologia, Universidade Federal do Rio de Janeiro, Ilha do Fundão, CCS, Bloco A, Caixa Postal 68020, 21941-590 Rio de Janeiro, Brazil - bozelli@biologia.ufrj.br

ABSTRACT: We report results from an eight-year study in Batata Lake, a body of water partly affected by tailings resulting from bauxite mining. Planktonic cladocerans were sampled and certain limnological variables were measured every three months for eight years (1990 through 1997) at a natural station in a part of the lake unaffected by tailings, and at a station in an area of the lake impacted by bauxite tailings. Principal components analysis indicated that the two stations differed in the variables studied, during some periods of falling or low water. The stations were similar mainly during the periods of rising or high water. Our results indicate that low-water samples best identified the difference between the stations, caused by the suspended inorganic matter (tailings). Most of the time, there was no perceptible effect of the bauxite tailings on any aspect of the cladoceran community. The equitability parameter best estimated the influence of the tailings on the cladocerans. The observed changes in equitability indicated that under highly turbid conditions, only those species which have the proper strategies to maintain themselves in a variable and unpredictable environment could persist. The lower equitability values observed during low-water phases may indicate high instability at the impacted station, which may be related to the prevalence of tailings in the water column. In these situations, opportunist species, able to take advantage of the instability, came to dominate.

Key-words: Amazonia, cladocerans, long term, turbidity, flood pulse.