Diversity and Abundance of the Planktonic Rotifers in Different Environments of the Upper Paraná River Floodplain (Paraná State – Mato Grosso do Sul State,Brazil)

This study proposes that diversity and abundance of rotifers show spatial and temporal variations in the Upper Paraná River floodplain due to heterogeneity of the environment and hydrological level fluctuations of the main river. The structure and dynamics of rotifer assemblages were investigated by samplings carried out during the rainy (February) and dry period (August) of the year 2000, in 36 environments (rivers, channels, backwaters, open and isolated floodplain lakes). The influence of phytoplankton biomass on rotifer diversity and abundance was also investigated. 104 taxa of rotifers were identified. The highest species richness was found in rivers and open floodplain lakes, the highest abundances in the isolated floodplain lakes, and the highest values of species diversity in the channels, especially during the rainy period. β₂-diversity values were higher in the channels, especially during the dry period. Flow differences and food availability were predominant factors influencing the structure and dynamics of the rotifer communities.     

Testate Amoebae (Rhizopodea-Sarcodina) from Zooplankton of the High Paraná River Floodplain,State of Mato Grosso do Sul,Brazil: II. Family Difflugidae

In planktonic samples of lotic and lentic environments of the high Paraná River floodplain (States of Paraná and Mato Grosso do Sul) 25 taxa of Difflugidae (Rhizopodea-Sarcodina) were identified, of which Difflugia corona f. tuberculata, D. lobostoma f. multilobata, D. (Pseudocucurbitella) pseudogramen, D. stellastoma, D. kempnyi, D. pleustonica, D. correntina, D. lithophila, D. acuminata var. magna, D. echinulata, Cucurbitella mespiliformis var. africana, C. dentata f. quinquelobata and C. madagascarensis are new records for Brazil.     

Testate Amoebae (Rhizopodea-Sarcodina) from Zooplankton of the High Paraná River Floodplain,State of Mato Grosso do Sul,Brazil: I. Families Arcellidae and Centropyxidae

A first contribution towards the taxonomy of testate amoebae (Rhizopodea – Sarcodina) recorded in planktonic samples of lotic and lentic environments in the high Paraná River Floodplain in the States of Paraná and Mato Grosso do Sul, Brazil, is provided. Twenty-four taxa belonging to the families Arcellidae and Centropyxidae were identified, described and sketched. Among the taxa, A. vulgaris f. undulata, A. vulgaris var. penardi, A. mitrata var. spectabilis, A. nordestina and Centropyxis aculeata var. tropica represent new occurrences in Brazil.     

Zooplankton in the Floodplains of a Tributary to the Paraná River in Mato Grosso Do Sul,Brazil

Zooplankton samples were taken monthly at five sites March 1992 through February 1993 of the Guaraná lake and Baía river in the Paran floodplain, Brazil. A total of 38 cladoceran and 12 copepod species was identified. Cladocerans were mainly collected amongst macrophytes in the lake. The most commonly encountered species were Bosminopsis deitersi, Moina minuta, Ceriodaphnia cornuta, Ilyocryptus spinifer, Macrothrix spinosa, and Phryxura dadayi. The copepods were especially collected in the river with Thermocyclops minutus and Mesocyclops meridianus being abundant. The greatest number of microcrustacean species was detected during the high water period. Possible ecological conditions for the recorded distribution and abundance are discussed and compared with data from other study sites in the Neotropics.     

Temporal fluctuations of the phytoplankton community of the Baía River, in the upper Paraná River floodplain, Mato Grosso do Sul, Brazil

Subsurface samples were taken monthly (March/1993 through February/1994) in the Baía River, a tributary of the right bank of the Paraná River (22° 43 S and 53° 17 W). We analyzed temporal changes in the phytoplankton community in relation to density, biomass, richness and species diversity, equitability, size structure, and dominance. We related these to regional climate and hydrology, and to the physical and chemical variables of the water column. We determined 119 taxa, wich were numerically dominated by the class Chlorophyceae with 37 taxa. The classes Cyanophyceae and Bacillariophyceae contributed the most abundant biomass and were responsible for the two peaks that were observed. The high water period was generally characterized by lower phytoplankton biomass, higher richness and species diversity, and higher density of nannoplanktonic species such as Monoraphidium tortile in March, and Cryptomonas brasiliensis in January. During low water, however, the highest values of phytoplankton biomass were recorded, with heterocytous cyanophytes dominating during the phase of greater stability of the water column, and filamentous diatoms during periods of mixing turbulence. The fluctuations observed indicate that the hydrosedimentological regime of the Paraná River, together with the climatological factors, constitute the main forcing functions acting on the Baía River phytoplankton.     

Environmental Influence on Planktonic Cladocerans and Copepods in the Floodplain of the Upper River Paraná, Brazil

The abundance of microcrustacean species recorded in plankton samples from the littoral and pelagic zones of the Upper Paran River, State of Mato Grosso do Sul, Brazil, was evaluated in relation to abiotic and biotic environmental factors. The cladocerans Bosminopsis deitersi and Bosmina hagmann i were most abundant. The presence or absence of aquatic macrophytes also influenced abundance and species composition. The true zooplankton species were most abundant at the pelagic stations, while species of Chydoridae and Macrothricidae contributed markedly to microcrustacean abundance and species richness at littoral stations. Species abundance was also strongly affected by water level variation. Microcrustaceans, mainly bosminids, were most abundant during low water. During high water, bosminids decreased in abundance while most other species increased. The higher variation of the environmental factors during high water probably explains the shift in abundance patterns. Changes in water level increased mixing of littoral and pelagic microcrustaceans between sampling stations.     

Echinodermata from São Sebastião Channel (São Paulo, Brazil)

Faunal inventories are extremely important, especially when focused on neglected groups, such as echinoderms, and concentrated on areas under intense anthropic activity such as the SAo Sebastilo Channel in Brazil (23 degrees 41' - 23 degrees 54' S and 45 degrees 19' - 45 degrees 30' W). Intertidal and upper sublittoral zone collections were performed at five sites of the Channel's continental margin from May to August 2001. The rocky substrate down to 19 m deep was surveyed by snorkeling and SCUBA diving from August 2002 to May 2004, on both margins of the Channel: continental (14 sites) and insular (10 sites). We report a total of 38 species of echinoderms (one Crinoidea, nine Asteroidea, 13 Ophiuroidea, nine Echinoidea and six Holothuroidea). Seven of those species have been recorded here for the first time for the Channel (four Asteroidea, two Ophiuroidea and one Echinoidea).     

Larval fish assemblage in the Baía River (Mato Grosso do Sul State,Brazil): temporal and spatial patterns

Synopsis We sampled the Baía River (Mato Grosso do Sul State, Brazil) monthly, to survey taxonomic composition and temporal and spatial distribution of fish larvae. The ichthyoplankton was mainly composed by larvae of small and medium sized sedentary species and it was numerically dominated by six taxa: Plagioscion squamosissimus, Hypophthalmus edentatus, Hoplias aff. malabaricus, Bryconamericus stramineus, Serrasalmus spp. and Catathyridium jenynsii. These taxa present distinct temporal and spatial occurrence patterns: H. edentatus, B. stramineus and C. jenynsii are abundant between September and March in lentic areas; H. aff. malabaricus and Serrasalmus spp. were caught between October and February in lotic areas; whereas P. squamosissimus occurs in all sampled areas, with peak of capture in January. Hypophthalmus edentatus, H. aff. malabaricus, Serrasalmus spp. and B. stramineus were the taxa that most contributed to structure the assemblages temporally and spatially, and their abundances were influenced by the interaction of several environmental variables.     

Environmental variables and intertidal beach annelids of São Sebastião Channel (State of São Paulo,Brazil)

Benthic annelid communities were studied during a one-year period (August/95 to July/96) in two sectors of the beaches Engenho d'Agua and S?o Francisco, S?o Sebasti?o Channel (S?o Paulo, Brazil), where the substrate is composed by a mixture of sand and rock fragments. Abiotic parameters such as salinity of interstitial water and sediment properties were used to characterize the environment. The polychaetes were well represented in the two sectors and their distribution was related with sediment type. The density of individuals and the number of taxa was higher at S?o Francisco, while the diversity and the evenness were higher at Engenho d'Agua. This difference can be a consequence of organic enrichment caused by domestic input, and of the lower and more variable salinity at S?o Francisco. Due to these factors, the high density of opportunistic species, like Capitella capitata ssp., Scolelepis squamata, Laeonereis acuta and several oligochaetes, represented 75.5% of total abundance at this sector.     

Spatial and temporal variations of oligochaetes of the Ivinhema River and Patos Lake in the Upper Paraná River Basin,Brazil

The composition and spatial and temporal variation of oligochaete community were analyzed in Patos Lake and Ivinhema River, a tributary of the Paraná River Brazil, during the period March 1993 to February 1994. Lentic and lotic environments were studied, with the objective of analyzing species association and temporal changes in the function of the abiotic variables at nine sites studied. Seventeen species of oligochaetes were identified. Oligochaete association was analyzed by Detrended Correspondence Analysis (DCA) and abiotic variables, by Principal Components Analysis (PCA). This method showed that Aulodrilus pigueti predominated in Patos Lake, probably because it has adapted to mud with high organic matter in low currents. Brinkhurstia americanus predominated at the right bank of the Ivinhema River while Paranadrilus descolei predominated at the left bank. Temporal variation of organism density was influenced by hydrological cycle, and spatial variation was determined by grain size and quantities of organic matter in the sediments.     

Harpacticoid copepods from Una do Prelado River (São Paulo,Brazil): genus Schizopera

The black water Una River is the biggest river of Juréia Ecological Reserve. The association of certain conditions such as high annual rainfall, the presence of washed-out humic substances, have given rise to a peculiar kind of environment with acid pH, poor in nutrients and unstable. In spite of these conditions eleven harpacticoid species were found, and the genus Schizopera is reported here. The material analysed was collected by Por et al. (1984). Two new species are described, S. pori n.sp. and S. giselae n.sp. The first species is the most common and abundant collected in the Una River.     

Tinea cruris epidemiology (São Paulo,Brazil)

In order to determine the epidemiology of tinea cruris in São Paulo, Brazil, an investigation was carried out from April 95 to March 1997. A total of 2000 individuals were studied, of whom 105 were suspected of having tinea cruris infection. Direct microscopy and/or culture were positive in 66 [62.8%] of the cases. Erythematous-scale plaques and erythematous-liquenificated plaques were the most frequently found clinicaltypes. T. rubrum was the prevalent dermatophyte in 90% of the cases, followed by T. tonsurans (6%) and T. mentagrophytes (4%).     

Vertical Distribution of Rotifers on the Upper Paraná River Floodplain: the Role of Thermal Stratification and Chlorophyll-a

The degree of vertical aggregation by rotifers was quantified in different environments of the Upper Paraná river floodplain. The regression coefficient of the relationship between the logarithm of variance and the logarithm of mean density was used as a criterion to evaluate the pattern of vertical distribution of the populations. The lake showed the highest degree of vertical aggregation by the populations. Thermal stratification was the possible causal process. In the river, a high degree of aggregation was observed. Correlation of the mean rotifer density with chlorophyll- a concentration indicated that, in this unstratified environment, the degree of aggregation may be dependent on the food concentration. Therefore, several processes in addition to the frequently studied hydrodynamic ones may promote aggregations of rotifers in floodplain environments.     

Description of Freshwater Bacterial Assemblages from the Upper Paraná River Floodpulse System,Brazil

Bacteria were identified from a large, seasonally flooded river (Paraná River, Brazil) and two floodplain habitats that were part of the same river system yet very different in nature: clearwater Garças Lagoon and the highly humic waters of Patos Lagoon. Bacterioplankton were collected during mid-summer (Jan. 2002) from water samples (2 l) filtered first through a 1.2-μm filter then a 0.2-μm membrane filter representing the particle-attached and free-living sub-communities, respectively. DNA was extracted from filters and purified and a 16S rRNA clone library established for each habitat. Over 300 clones were sequenced and checked for similarity to existing 16S sequences in GenBank using the BLAST algorithm with default parameters. Further classification of clones was done using a species “backbone” attachment followed by parsimony analysis. The majority (85%) of sequences, referred to here as operational taxonomic units (OTUs), were most similar to uncultured bacterium 16S sequences. OTUs from each Proteobacteria sub-phylum (α, β, γ, δ, ?) were present in the Upper Paraná River system, as well as members of the Bacteroidetes. The microbial assemblage from Patos Lagoon was least like other samples in that it had no Firmicutes present and was dominated by Actinobacteria. Verrucomicrobia OTUs were only found in the free-living assemblage. This study documents the presence of globally distributed phyla in Upper Paraná River and taxa unique to habitat and particle attachment.     

Profits and social performance of small-scale fishing in the Upper Paraná River floodplain (Brazil).

Small scale fishing profits in two communities in the Upper Paraná River floodplain (Porto Rico - PRI and Porto S?o José - PSJ villages) are assessed based on interviews carried out with professional fishermen. There is a high illiteracy level in both PRI (50%) and PSJ (44.5%). The main contributions to income are "vessel costs" and "fish consumption" by the family. Specific tackle (such as cevadeira) and gear used for fishing close to dams make the gear costs higher at PSJ, emphasising the heterogeneity of the activity. The majority of fishermen in both villages have income complementation activities associated with tourism, because floodplain fishing is not a profitable occupation with any poverty alleviation capacity. Since the ecosystem is seriously disrupted, nowadays fishers are vulnerable to high oscillations in costs and income due to uncertainty in catches aggravated by flood control of the dams.     

Length-weight relationships for seven endemic fish species from streams of the last two large remaining dam-free tributaries of the Upper Paraná River Floodplain in the Paraná State,Brazil

This study reports the length-weight relationships (LWR) for seven endemic fish species from streams in the Ivaí (Characidium heirmostigmata, Corydoras lacrimostigmata, Curculionichthys oliveirai, Hisonotus pachysarkos, and Cambeva horacioi) and Ivaí and Piquiri (Apareiodon vladii and Planaltina kaingang) River basins, Paraná State, Brazil. Fish specimens measured and weighed were collected between November 1994 and July 2019, fixed with 10% formalin, and are preserved in 70% alcohol. Measurements were done for standard length (SL—0.1 cm precision) and total weight (TW—0.01 g precision). All coefficient of allometry obtained is within the general range for fishes representing useful tentatives for LWR parameters. We highlight the importance of information about the biology of the endemic fish species in a crucial area for the biodiversity conservation of the Upper Paraná River system.     

Hydrologic and climatic regimes limit phytoplankton biomass in reservoirs of the Upper Paraná River Basin,Brazil

In reservoirs of the Upper Paraná River Basin, Brazil Paraguay, phytoplankton biomass is generally low relative to reservoirs in other parts of the world. To investigate what might be limiting phytoplankton biomass in the Upper Paraná reservoirs, we used an empirical approach wherein climatic conditions in the basin as well as chemical, hydrological and morphometrical characteristics of 13 reservoirs, were compared against those prevailing in 58 reservoirs of the south-central United States. In both regions, phytoplankton biomass was correlated with chemical, hydrological and morphometrical characteristics of the reservoirs. There were no differences in phosphorus concentrations between the two regions, nitrogen levels were higher in the Upper Paraná, ionic concentrations were higher in the south-central United States and there were major differences in all physical characteristics considered. In reservoirs of the south-central United States, hydraulic retention time increased and discharges decreased during the post-spawning period allowing increases in phytoplankton biomass; in the Upper Paraná River Basin, discharges peaked during the post-spawning period, delaying the peak of phytoplankton blooms until after completion of the post-spawning period. Our comparison between the two sets of reservoirs suggests that hydrologic regimes dictate differences in phytoplankton biomass and that hydrology of the Upper Paraná River Basin, exacerbated by climatic patterns, deter phytoplankton production despite suitable levels of essential nutrients.     

Rotifers in different environments of the Upper Paraná River floodplain (Brazil): richness, abundance and the relationship with connectivity

Rotifers were collected in the open water of twenty-eight locations (3 rivers, 12 connected lagoons and 13 isolated lagoons) of the upper Paraná River floodplain during the high water (February) and low water (August) period of 2001. Greatest species richness was found in rivers during the high water period. Isolated lagoons had the lowest species richness. Abundance was highest in connected lagoons followed by isolated lagoons and then rivers, but did not show marked spatial or temporal variation. Some species dominated in isolated lagoons during high water and others in connected lagoons during the low water. These results were contrary to our expectations; we expected to observe highest species richness and abundance of rotifers in isolated lagoons during both extremes of the hydrological cycle. Our findings suggest the importance of connectivity among environments to rotifer species richness. The absence of an intense flood during 2001 facilitated development of rotifer populations during the high water period due to lack of dilution and high availability of food resources (phytoplankton).     

Fish diversity and community structure in two small tributaries of the Paraná River,Paraná State,Brazil

In eleven sites on two small tributaries of the Paraná River (North-West Paraná State), 6.8 and 4.0 km in length, 1263 fish specimens of 28 taxons and 14 families were collected using electrofishing. Up to twelve years ago the catchments of the two rivers were covered by tropical jungle; this has now been replaced by pasture and arable fields. Mean diversity indices of Simpson and Shannon indices were close to 0.6, which would indicate that human impact affected fish populations although the river beds have retained their original shape, except cleared of riparian trees. Despite their close location (about 18 km), the two streams differed from each other in their fish faunal composition. The distinctive nature of the fish communities in the two streams was a result of: conductivity, pH, also hiding places, riparian vegetation, submerged macrophytes and depth and width of the rivers.