Paulo Roberto Bressan Buosi

Spatial and temporal patterns of ciliate species composition (Protozoa: Ciliophora) in the plankton of the Upper Paraná River floodplain

Spatial and temporal patterns of plankton ciliates species composition in the Paraná River floodplain were investigated. Samplings were carried out in twelve environments in two distinct hydrological periods (limnophase and potamophase). A total of 61 species of ciliates were recorded, and among them 21 are classified as pelagic while 40 are considered preferentially as littoral species. The registered species belong to eleven orders, and among them, Prostomatida was the most specious followed by Hymenostomatida and Peritrichida. The ciliate species composition was significantly distinct between periods, but not among environments. In this way, typically pelagic species characterized the ciliate community during the limnophase period, while the littoral species were predominant during the potamophase period. Our results strongly support the idea of the flood pulse as the main factor driving the composition pattern of the planktonic ciliates community in the Paraná River floodplain.

Ciliate community associated with aquatic macrophyte roots: effects of nutrient enrichment on the community composition and species richness.

The objective of this study was to identify the impact of nutrient enrichment on the diversity of the ciliate community associated with the roots of the aquatic macrophyte Eichhornia crassipes. The experiment was performed in the Garças Lake, located in the Upper Paraná River floodplain, Brazil. We conducted two treatments (fertilized and control) with three replicates each. To increase the initial nutrient concentrations in each mesocosm of the fertilized treatment, we added 1000 μgL(-1) of KNO(3) and 200 μgL(-1) of KH(2)PO(4) during each sampling date. We found a relative high number of ciliate species (85 species) and a predominance of hypotrichs. Among the recorded species, about 25% occurred exclusively in the fertilized treatment. Moreover, detrended correspondence analysis demonstrated that the ciliate community associated with E. crassipes roots changed significantly in response to the nutrient input in such a way that the species composition of the fertilized treatment was remarkably different from that of the control. In contrast to our expectations, species richness in the fertilized treatment was significantly higher than that in the control, refuting our hypothesis that species richness decreases under eutrophic conditions.

Multiple Lines of Evidence Shed Light on the Occurrence of Paramecium (Ciliophora, Oligohymenophorea) in Bromeliad Tank Water

Phytotelmata are vegetal structures that hold water from the rain, and organic matter from the forest and the soil, resulting in small, compartmentalized bodies of water, which provide an essential environment for the establishment and development of many organisms. These microenvironments generally harbor endemic species, but many organisms that are found in lakes and rivers, are also present. Here, we report, for the first time, the occurrence of the ciliate genus Paramecium in the tank of the bromeliad species Aechmaea distichantha. The identification of the Paramecium species was performed based on live observations, protargol impregnation, scanning electronic microscopy, and sequencing of the 18s rRNA. The absence of Paramecium from bromeliad tank water was highlighted in several earlier investigations, and may be due to the fact that this species is unable to make cysts. The occurrence of Paramecium multimicronucleatum in our samples may be explained by the proximity between the bromeliads and the river, a potential source of the species. Further, we also believe that the counting methodology used in our study provides a more accurate analysis of the species diversity, since we investigated all samples within a maximum period of 6 h after sampling, allowing minimum loss of specimens.

Effects of Seasonality and Dispersal on the Ciliate Community Inhabiting Bromeliad Phytotelmata in Riparian Vegetation of a Large Tropical River

This study evaluated the influence of rainfall amount on the abundance, species richness, and species occurrence and abundance distribution of the ciliate community associated with the bromeliad Aechmea distichantha. The plants were collected from a rock wall of about 10‐km long at the left bank of Paraná River. We assessed the effects of both spatial and temporal variables on the community attributes, as well as whether plants geographically closer have a similar abundance distribution and species composition. The ciliate community was substantially distinct between both hydrological periods, with greater values of species richness and abundance in the rainy period. No spatial structuring (differences in the species occurrence and abundance distribution among strata) or geographical similarity (similarity in ciliate species composition among the plants) was found. Multiple regression analysis showed a positive relationship only between the ciliate abundances and water volumes for both periods. Although few of the formulated predictions were confirmed, our study provides valuable information on the ecological aspects of the ciliate community inhabiting bromeliad phytotelmata.

Rainfall influence on species composition of the ciliate community inhabiting bromeliad phytotelmata

BackgroundIn this paper, we verified the changes in species composition of the ciliate community inhabiting phytotelmata of tank bromeliads in response to seasonality (rainfall). Plants were located at several heights of a great rocky wall on the left bank of the Parana River, southern Brazil. We also assessed if the heights of the plants in relation to the river influence the ciliate species composition. Thus, samplings were performed in the dry and rainy seasons, in three layers of the rock walls (lower, middle, and upper), with a total of 72 samples in both periods.ResultsA relative high number of species and a predominance of hymenostomatids were observed in the sampled plants. Among the recorded species, about 35% occurred exclusively in the dry season. The detrended correspondence analysis demonstrated that the ciliate community changed substantially due to rainfall. However, there was no distinctness in species composition among the strata. In contrast to expectations, the number of species recorded in the dry season was greater than that recorded in the rainy season, refuting the hypothesis that the precipitation volume favors an increase in the number of species.ConclusionsThe rainfall is, undoubtedly, the main factor structuring the community and determining the ciliate species composition in the phytotelmata of the bromeliads. We found that the closeness of the plants with the river is also an important factor for the structuration of the community, due to the dispersion of organisms from the river to the tanks. The occurrence and predominance of planktonic species in the plants at the lower stratum and soil species at the higher stratum indicates a great influence of the neighboring environments on the ciliate community inhabiting the phytotelmata.

Planktonic Protist Biodiversity and Biogeography in Lakes From Four Brazilian River-Floodplain Systems

While the biodiversity and biogeography of protists inhabiting many ecosystems have been intensely studied using different sequencing approaches, tropical ecosystems are relatively under-studied. Here we sampled planktonic waters from 32 lakes associated with four different river-floodplains systems in Brazil, and sequenced the DNA using a metabarcoding approach with general eukaryotic primers. The lakes were dominated by the largely free-living Discoba (mostly the Euglenida) and Ciliophora unlike previously sampled Neotropical environments, bu the community similarities between samples were likewise low. These protists inhabiting these floodplains potentially form part of the large diversity of unknown diversity in the tropics.

The importance of herbivory by protists in lakes of a tropical floodplain system

Inland aquatic ecosystems play a critical role in the global carbon cycle, processing a great fraction of the organic matter coming from terrestrial ecosystems, and the microbial food web is crucial in this process. Thus, we aimed to evaluate whether the food resource of planktonic protozoa comes mainly from small primary producers or heterotrophic bacteria in tropical shallows lakes, assuming the hypothesis that, in general, picocyanobacteria would be the main food resource for protists. We also expected that the autotrophic fraction would be mainly related to protists at the surface of the environments, while the heterotrophic fraction would be more important at the lower strata of the water column. We performed size-fractionation experiments to evaluate the effects of predation of protists on heterotrophic bacteria and picocyanobacteria. We also sampled planktonic organisms at the subsurface and bottom of 20 lakes in a Neotropical floodplain. We found an herbivory preference of heterotrophic flagellates, while ciliates seem to exert a stronger impact on heterotrophic bacteria. We also found no relationship between heterotrophic bacteria and protists in the field data, whereas positive relationships between picocyanobacteria and protists were observed in environments where there was sunlight. Thus, both heterotrophic bacteria and picocyanobacteria were important components in the food webs of tropical shallow lakes. Moreover, the trophic cascade caused by zooplankton predation suggests that protists are efficient in transferring the energy from the base of microbial food webs to higher trophic levels.