<b>Testate amoebae abundance in plankton samples from Paraná State reservoirs</b> - DOI: 10.4025/actascibiolsci.v26i4.1522

Abstract

This study aimed to investigate patterns of spatial and temporal distribution of testate amoebae (Rhizopoda) abundance in plankton of different reservoirs of Paraná State and the importance of hydrodinamical and morphometrical factors on determining these patterns. Thirty reservoirs studied are located in six different watersheds, including environments with variable area, morphometry and age. Sampling were carried out in July and November 2001, dry and rainy seasons, respectively. Samples were obtained at the surface of reservoirs, in the lacustrine region, using a motorized pump (600 liters per sample) and a plankton net with a mesh size of 68µm. Testate amoebae were registered in 23 of 30 reservoirs.Higher density were observed in JMF, Salto do Meio, Melissa, Mourão and Salto do Vau reservoirs, during dry season, and JMF, Salto Osório, Salto do Meio and Melissa reservoirs, during wet season These reservoirs present similar characteristics, as reduced depth and morphometric dimensions Besides that, most of them have hydrodynamical features similar to lotic environments, due to presenting high current velocity. On the other hand, testate amoebae were absent or presented low density, in general, in reservoirs with higher dimensions and depth. Instead of expected, seasonally, higher densities values were observed during dry season, for the most of studied reservoirs. These results can be related to the fact that the reservoirs during dry season have a remarkable reduction of their dimentions (area and depth), determining a greater influence of the benthonic organisms to the composition and abundance of the protozooplankton community