Testate amoebae as indicators for suspended inorganic material in floodplains influenced by dam

The construction of reservoirs impacts upon freshwater ecosystems, since it changes the hydrodynamics of the entire system upstream and downstream of the dam due to flow control and changes in environmental conditions. We analyzed the temporal variation in the abundance of exogenous testate amoebae related to the suspended inorganic material in Neotropical floodplain lakes, downstream of a series of dams. Sampling was carried out between 2000 and 2012 in six lakes in the upper Paraná River floodplain. The temporal variation in the abundance of the testate amoeba community was analyzed using the Threshold Indicator Taxa Analysis. Cucurbitella crateriformis, Protocucurbitella coroniformes, and C dentata f. quinquilobata had reduced population growth in higher concentrations of suspended inorganic material. On the other hand, Difflugia lobostoma, Centropyxis ecornis, and Difflugia pseudogramen populations increased under these conditions. These results showed that an increased flow of water could favor the growth of some populations due to the greater exchange of material between the lakes and the floodplain. The positive or negative responses could show better adaptation of the testate amoeba species to the planktonic environment. Furthermore, these results also highlighted the bioindicator role of these protozoa in aquatic ecosystems.