Brazilian Pantanal Research Articles

Diet of the marsh deer in the Paraná River Delta, Argentina—a vulnerable species in an intensive forestry landscape

The marsh deer (Blastocerus dichotomus) is the largest deer native to South America, occurring in wetlands and marshy habitats. The southernmost population of the species is found in the Parana River Delta, Argentina, in a wetland system highly modified by intensive forestry activity. Foresters perceive high levels of economic losses attributed to deer herbivory which drives marsh deer poaching. We carried out the first study of the dietary composition of the marsh deer in this wetland by using microhistological analysis of feces collected seasonally. Seventy-three food items were identified in the marsh deer diet, but only eight had frequencies of > 3% in the annual diet. Macrophytes dominated the diet throughout the year (seasonal percent frequencies 31–42%) due to the high occurrence of Ludwigia bonariensis (24% of average seasonal frequency). Trees, vines, forbs, and shrubs contributed less frequently to the diet, while grasses and grass-like plants were marginally represented (i.e., < 2%). Exotic plant species comprised 38% of the annual diet, and tree species of commercial importance (Salix sp. and Populus R22) were poorly represented (≤ 5.5% per season). The marsh deer in this wetland could be categorized as a browser, differing from the feeding behavior reported for the species in the Brazilian Pantanal (grazer–browser) and suggesting a trophic elasticity in this cervid. Since commercial tree species comprised a very small portion of the diet of this deer, a change in producers’ perception toward the species is needed to diminish this conflict, and our data are important to develop context-specific conservation and management solutions.

Multi-Level, Multi-Scale Modeling and Predictive Mapping for Jaguars in the Brazilian Pantanal

Multi-level multi-scale resource selection models using machine learning were compared and contrasted for generating predictive maps of jaguar habitat (Panthera onca) in the Brazilian Pantanal. Multiple spatial scales and temporal movement levels were run within several analytical modeling frameworks for comparison. Included in the analysis were multi-scale raster grains (30 m, 90 m, 180 m, 360 m, 720 m, 1440 m) and GPS collaring temporal movement levels (point, path, and step). Various analytical methods were used for comparison of models that could accommodate data structural levels (group, individual, case-control). Models compared included conditional logistic regression, generalized additive modeling (GAM), and classification regression trees, such as random forests (RF) and gradient boosted regression tree (GBM). The goals of the study were to discuss the potential and limitations for machine learning methods using GPS collaring data to produce predictive habitat suitability mapping using the various scales and levels available. Results indicated that choosing the appropriate temporal level and raster scale improved model outputs. Overall, larger level analytical modeling frameworks and those that used multi-scale raster grains showed the best model evaluation with the inherent condition that they predict a broader scale and subset of data. The identification of the appropriate spatial scale, temporal scale and statistical model need careful consideration in predictive mapping efforts.

Anuran interactions with the bromeliad Bromelia balansae in the Brazilian Pantanal

Different frog-bromeliad associations are frequently reported from various habitats of Central and South America. Here, we present the first data on the association of two hylid species (Dendropsophus nanus and Scinax nasicus) with the bromeliad Bromelia balansae in the Brazilian Pantanal. Both treefrog species use rosettes of B. balansae as a diurnal shelter and foraging ground.

Serological occurrence for tick-borne agents in beef cattle in the Brazilian Pantanal.

This study investigated the seropositivity for five different tick-borne agents, namely Anaplasma marginale, Babesia bovis, Babesia bigemina, Coxiella burnetii, Anaplasma phagocytophilum, and Trypanosoma vivax in beef cattle in the Brazilian Pantanal. The serum samples collected from animals (200 cows; 200 calves) were used in indirect enzyme-linked immunosorbent assays (iELISA) to detect IgG antibodies against A. marginale, B. bovis, B. bigemina, and T. vivax, and Indirect Fluorescent Antibody Test (IFAT) for detecting IgG antibodies against C. burnetii and A. phagocytophilum. No correlation was observed between seropositivity for C. burnetii and A. phagocytophilum with other agents whereas moderate correlation was observed for A. marginalexB. bigemina x B. bovis. Cows were more seropositive for T. vivax whereas calves were more seropositive for B. bovis and B. bigemina. The highest number of seropositive animals by a single agent was observed for T. vivax (15.2%). Co-seropositivity for T. vivax + A. marginale was higher in cows (25.5%) and for T. vivax + B. bovis + B. bigemina + A. marginale was higher in calves (57.5%). The high seropositivity correlation for A. marginale x B. bovis x B. bigemina is probably due to the presence of the tick biological vector, Rhipicephalus microplus, in the studied farms. Common transmission pathways, mediated by hematophagous dipterans and fomites, may explain the high co-seropositivity of cows for A. marginale and T. vivax. Low seropositivity to C. burnetii is probably due to the type of breeding system employed (extensive). Seropositivity for A. phagocytophilum in only one animal suggests the occurrence of a cross-serological reaction with another agent of the genus Anaplasma.

First reports of fimicolous myxomycetes (Protozoa: Amoebozoa) from Brazilian Cerrado and Pantanal biomes

Fimicolous organisms are those that can grow on dung. These substrates offer conditions that favour colonization by microorganisms, such as high nutrient and moisture content and an alkaline-neutral pH that is especially advantageous in arid/desertic regions. There are about 250 species of myxomycetes known from Brazil, which are distributed in all geographic regions and biomes, obtained mainly from plant-derived substrates. However, there are some reports of fimicolous myxomycetes in Brazil. In this study, we expand this knowledge with new records of fimicolous myxomycetes in multiple Brazilian biomes. Between 2017 and 2018, horse and cattle dung samples were collected in municipal areas in the State of Goiás (Cerrado biome): Pirenópolis, Goiás, and Porangatu; and the State of Mato Grosso (Pantanal biome): Poconé. Samples were incubated in moist chambers and monitored for four months. Myxomycetous fructifications were observed, photographed under stereo and light microscopes, and morphologically identified. Vouchers were deposited at the HUEG Herbarium. A total of five species of myxomycetes were recorded: &lt;em&gt;Arcyria cinerea and &lt;em&gt;Physarum viride (Pirenópolis), &lt;em&gt;P. cinereum (Goiás City), &lt;em&gt;P. melleum&lt;/em&gt; (Porangatu), and &lt;em&gt;Perichaena corticalis&lt;/em&gt; (Poconé). They represent the first records of fimicolous myxomycetes from the Brazilian Cerrado and Pantanal biomes. Additionally, &lt;em&gt;P. melleum&lt;/em&gt; was reported as fimicolous for the first time in Brazil and the second time in the world; &lt;em&gt;P. corticalis&lt;/em&gt; was reported for the first time in midwest region as well as for the first time as fimicolous in Brazil; and &lt;em&gt;P. viride&lt;/em&gt; was reported for the first time as fimicolous in the world.

Flood risk assessment and management for urban areas in Brazilian Pantanal using free and open source GIS software

The present work provides city managers a tool to strategically deploy a flood risk assessment and management, with statistical, technological and graphical approaches. For risk assessment, the return period of the years between 1977 and 2017 was analysed, comprising a historical series of 40 years of maximum quotas and maximum flows. Researchers used the QuantumGis 2.18 platform to deploy flood risk mapping. Maps with flood risk levels within the urban area of study are presented, built as 3D models. The calculation of the return period estimation for flood risk is a reliable tool to understand the dynamics of a water body inserted in an urban area. Thus, it is possible to deploy scenarios with statistical background to aid decision making with regard to risk assessment. Technology-based information is key to support decision making, helping cities to raise funds to deploy risk management actions. The use of a free and open source GIS software such as QuantumGis presents a low cost, efficient and interface-friendly platform to solve flood management issues.

Flood risk assessment and management for urban areas in Brazilian Pantanal using free and open source GIS software

The present work provides city managers a tool to strategically deploy a flood risk assessment and management, with statistical, technological and graphical approaches. For risk assessment, the return period of the years between 1977 and 2017 was analysed, comprising a historical series of 40 years of maximum quotas and maximum flows. Researchers used the QuantumGis 2.18 platform to deploy flood risk mapping. Maps with flood risk levels within the urban area of study are presented, built as 3D models. The calculation of the return period estimation for flood risk is a reliable tool to understand the dynamics of a water body inserted in an urban area. Thus, it is possible to deploy scenarios with statistical background to aid decision making with regard to risk assessment. Technology-based information is key to support decision making, helping cities to raise funds to deploy risk management actions. The use of a free and open source GIS software such as QuantumGis presents a low cost, efficient and interface-friendly platform to solve flood management issues.

Vocal behavior of the Undulated Tinamou (Crypturellus undulatus) over an annual cycle in the Brazilian Pantanal: New ecological information

AbstractTinamous (Tinamidae) are a group of Neotropical birds for which little information is available. The Undulated Tinamou (Crypturellus undulatus) is one of the most widespread species but also declining. Due to its secretive habits, ecological knowledge regarding the species relies on few anecdotal descriptions. We used automated recorders to monitor the vocal activity of the species over an annual cycle at four sites in the Brazilian Pantanal. We provide a description and analyze the diel and seasonal patterns of the calling activity in this species and provide new ecological information. The daily cycle showed two significant peaks in calling activity during the early morning and late afternoon, in agreement with the vocal behavior common among tinamous. The species was vocally active throughout the year, but it was significantly higher during September–October and March. This suggests that the breeding period of the Undulated Tinamou in the Brazilian Pantanal extends from September to April. After the months with highest calling activity, there was a strong decrease in activity, which might be related to the silent behavior of male tinamous during incubation. The seasonal pattern and breeding period identified for the Undulated Tinamou in the Brazilian Pantanal are in agreement with those observed in previous studies carried out with other Crypturellus species. The use of automated recorders was found to be a useful method for monitoring the calling activity of this secretive group of birds and might be useful in the assessment of future population trends in this and other declining tinamous.Abstract in Portugese is available with online material.

Hidden in plain sight: How finding a lake in the Brazilian Pantanal improves understanding of wetland hydrogeomorphology

AbstractWetlands are permanently or seasonally flooded areas which support countless species of plants and animals. The Pantanal, in central‐west Brazil is one of the largest freshwater wetlands in the world covering an area of ~150 000 km2. The relationships between geomorphology, hydrology, sedimentation, and vegetation cover are critical for understanding how the landscape constrains the dynamics of wetlands. We provide a detailed study of the geomorphology and surface hydrology of the Negro River Interfan System (NRIS), in the southern Pantanal, by applying multiple approaches (i.e. remote sensing analysis, geomorphological zonation and hydrosedimentological surveys). A multitemporal analysis of Landsat imagery produced an inundation frequency map (2000–2011 period) that revealed a permanently flooded area in the central portion of the NRIS. A hidden fluvial lake was previously undetected due to the accumulation of floating mats and floating meadows of macrophytes. The Negro and Aquidauana feeder rivers exhibit remarkable differences in channel planform, water discharge, and sediment load. The Negro River presents a distributary pattern with marginal levees with decreasing elevation as it progrades into the lake and remains as a subaqueous landform conditioning the water flow downstream. The lake outflow to the Paraguay River occurs mainly by sheet flow during flood seasons and through small tributary channels during dry months. The lake's geometry is outlined by east–northeast and west–northwest straight borders, suggesting that the area is tectonically controlled. A cloud‐based worldwide water surface database (1984–2015) revealed frequent channel changes within the NRIS. Recent channel avulsions in the lower course of the Negro River are noteworthy mainly because the former river channel at the confluence with the Paraguay River is no longer connected with the Negro River channel. © 2019 John Wiley &amp; Sons, Ltd.

EFFECT OF THE PANTANAL’S FLOODING HISTORY IN MORPHOMETRIC ASPECTS OF THE SOLITARY PARASITOID Campsomeris dorsata (HYMENOPTERA: SCOLIIDAE)

The shape of an organism and the variation between related groups lie at the core of understanding evolution and interactions between phenotypes, genotypes, and environmental spaces. Due to the relief conditions and hydrological profile of the region, the areas inside the Pantanal have different flood histories in respect to the flood duration and the amount of water retained in the plain. The objective of this work was to evaluate the effect of the environmental flooding gradient on the geometric morphometry variation of Campsomeris dorsata (Hymenoptera: Scoliidae) wings in Pantanal, to understand if the variations in spatial distribution related to the flooding history interferes in the morphology of the wings by identifying where, how, and to what magnitude such changes occur. The wings were mounted between blade and coverslip, labeled, and prepared for morphometric measurements. The points of intersection of wing veins (landmarks) were determined using a stereoscopic microscope coupled with a camera. The linear measurements of the landmarks were transformed using Procrustes to remove the size effect, leaving only the shape of the wings. The transformed data was evaluated using PCA and MANOVA to identify if there were differences in relation to the geographical location of occurrence. Thirty-three male C. dorsata wings were measured, and there was a clear separation between 3 distinct wing form groups along the Pantanal distribution. The variation in wing shape could be associated with selection from local environmental conditions in areas with distinct flooding histories, influencing migratory aspects among populations within the Brazilian Pantanal. The data for this small species, that has low dispersal capacity, is solitary, and presents an intimate relationship with soil characteristics, which directly reflects flooding aspects in the Pantanal, only reinforces the need to conserve more areas in the Brazilian Pantanal, since genetic diversity is an important factor for conservation.

ISOLATION AND LAGOON MORPHOMETRY DEFINE FISH DIVERSITY AND COMPOSITION IN NEARSHORE AREAS OF FLOODPLAIN LAGOONS OF THE SOUTHERN PANTANAL

Floodplain lagoons support high fish diversity, but the role of local vs. regional factors in structuring assemblages is little studied in the Brazilian Pantanal. Aiming to understand the importance of limnological, biological, and regional characteristics shaping fish assemblages in the Pantanal floodplain, we sampled 26 lagoons in the Rio Negro floodplain from September 2005 through November 2006. Our results suggest that widely distributed species are also more abundant locally. Fish species richness is defined by a combination of isolation level, area and mean depth of lagoons, while evenness is determined mainly by macrophyte richness, lagoon area, water conductivity and distance to the river. Distribution of the most abundant fish species in sampled lagoons was explained by macrophyte biomass, lagoon area, shoreline development index and macrophyte richness. Overall, a general pattern of species diversity and distribution was primarily defined by a regional characteristic, namely, isolation, interacting with lagoon morphometry, and secondarily by biotic characteristics.

Effects of Climate and Land-Cover Changes on Soil Erosion in Brazilian Pantanal

The Pantanal biome integrates the lowlands of the Upper Paraguay Basin (UPB), which is hydrologically connected to the biomes of the Cerrado and Amazon (the highlands of the UPB). The effects of recent land-cover and land-use (LCLU) changes in the highlands, combined with climate change, are still poorly understood in this region. Here, we investigate the effects of soil erosion in the Brazilian Pantanal under climate and LCLU changes by combining different scenarios of projected rainfall erosivity and land-cover management. We compute the average annual soil erosion for the baseline (2012) and projected scenarios for 2020, 2035, and 2050. For the worst scenario, we noted an increase in soil loss of up to 100% from 2012 to 2050, associated with cropland expansion in some parts of the highlands. Furthermore, for the same period, our results indicated an increase of 20 to 40% in soil loss in parts of the Pantanal biome, which was associated with farmland increase (mainly for livestock) in the lowlands. Therefore, to ensure water, food, energy, and ecosystem service security over the next decades in the whole UPB, robust and comprehensive planning measures need to be developed, especially for the most impacted areas found in our study.

Microhabitat determines uneven distribution of Amblyomma parvum but not of Amblyomma sculptum ticks within forest patches in the Brazilian Pantanal.

Environmental distribution of the two most abundant ticks in forest areas in the Brazilian Pantanal was evaluated by CO2 traps methodology in the wet season (peak of adult ticks) of 2012 and 2013. Adults of Amblyomma parvum were concentrated inside agglomerates of Bromelia balansae, in the border of forest patches. Adults of Amblyomma sculptum occurred in similar numbers both in bromeliad clumps and in bromeliad-free areas. Differential distribution of ticks in this habitat could be associated to the frequent use of bromeliad clumps by wild animals (potential hosts) and to the microclimate conditions inside this vegetation in the Pantanal. It is important to verify whether larvae and nymphs of A. parvum have a similar pattern of distribution in the same areas, during the dry season. These stages are more susceptible to desiccation and their principal hosts, non-volant small mammals, also use these bromeliad areas.

The Real Stranded Assets of Carbon Lock-In

Climate debates over stranded assets are focusing on the wrong assets. Fossil-fuel companies and petrostates argue that they will suffer economic losses from climate policies. Although true, this ignores assets that will be stranded in the absence of climate policy. These are the real stranded assets of carbon lock-in and could prove much more costly.

Arsenic, lead and cadmium concentrations in caudal crests of the yacare caiman (Caiman yacare) from Brazilian Pantanal

Wetlands are environments of extreme importance due to their high biodiversity and invaluable ecosystem services. Nevertheless, wetlands worldwide are under the increasing threat of the effects of contaminants, which put at risk the biota and the ecosystems. Herein the concentrations of non-essential and toxic elements arsenic (As), lead (Pb) and cadmium (Cd) in caudal crests of the yacare caiman (Caiman yacare) from the Brazilian Pantanal, one of the largest wetlands in the world, were investigated aiming to compare concentrations in individuals from a large pristine area (Southern Pantanal) to animals from an area close to potential sources of anthropogenic emissions (Northern Pantanal). Levels above the limit of detection were found for all the elements in the majority of the analysed samples. The highest mean concentration was detected for As in samples from both sites, followed by Pb and Cd in samples from Southern Pantanal, and Cd and Pb in samples from Northern Pantanal. Significant negative correlations were found between As and Cd concentrations and the size of the individuals from the Southern Pantanal. Surprisingly, concentrations of all three elements were higher in pristine Southern Pantanal, but with significant differences only for Cd. This result suggests that natural sources and processes may be acting for the mobilisation and availability of As, Pb and Cd for Southern Pantanal biota, which reflected in the contamination of C. yacare. Data from the literature showed higher levels of As, Pb and Cd in abiotic compartments in Southern Pantanal and adjacent plateaus in comparison to Northern Pantanal, corroborating the higher concentrations detected in biotic samples from the south. Thus, natural sources seem to play a relevant role in the contamination of biota by As, Pb and Cd in Southern Pantanal, characterising an intriguing pattern that could be tested for other species.

Secondary metabolites that could contribute to the monodominance of Erythrina fusca in the Brazilian Pantanal.

Erythrina fusca is a dominant species in the Brazilian Pantanal. We hypothesized that E. fusca possess allelopathic potential and we evaluated effects of extracts on germination and development of Lactuca sativa, a bioindicator species. We tested the effect of leaves, bark, roots, and seeds extracts of E. fusca on germination and speed index, using high, moderate and low concentration (0.2, 1 and 5 mg mL-1). To evaluate effects on development, we subjected seedlings of L. sativa to the same treatments and measured root and aerial part length. High concentration of extracts reduced L. sativa germination; leaves extract caused the maximum reduction on germination of L. sativa, similar to 2,4-Dichlorophenoxyacetic acid (2,4-D); this extract has flavonoids and saponins as main compounds, classes that also occur in the bark and roots extracts in lower concentrations; bark and roots (5 mg mL-1), leaves and roots (1 mg mL-1) decreased these traits as well, but in lower magnitude. A significant reduction in root length was induced by highest concentration of all extracts (5 mg mL-1); the results suggest that erythrinic alkaloids should interfere in the root length once the seeds accumulate almost exclusively this class of compounds. Our results showed that all parts of E. fusca had adverse effects on germination or development of L. sativa, showing that different class of compounds secondary metabolites is involved in this activity. Possibly, this phytotoxicity influences monodominance of E. fusca in Pantanal, but studies are essential to evaluate effects of it on other native species.

Cellulose Nanocrystals from Fibers of Macauba (Acrocomia Aculeata) and Gravata (Bromelia Balansae) from Brazilian Pantanal.

Cellulose nanocrystals (CNC) were obtained from macauba and gravata fibers. Macauba (or Bocaiuva) is a palm tree found throughout most of Brazil and Gravata is an abundant kind of bromelia with 1–2m long leaves, found in Brazilian Pantanal and Cerrado. The raw fibers of both fibers were mercerized with NaOH solutions and bleached; they were then submitted to acid hydrolysis using H2SO4 at 45 °C, varying the hydrolysis time from 15 up to 75 min. The fibers were analyzed by X-ray diffraction (XRD), FTIR Spectroscopy, scanning electron microscopy (SEM) and thermal stability by thermogravimetric analysis (TG). XRD patterns did not present changes in the crystal structure of cellulose after mercerization, but it was observed a decrease of hemicellulose and lignin contents, and consequently an increase of cellulose content with the increase of NaOH solution concentration in the mercerization. After acid hydrolysis, the cellulose nanocrystals (CNC) were also analyzed by transmission electron microscopy (TEM) which showed an acicular or rod-like aspect and nanometric dimensions of CNC from both fibers, but the higher values of aspect ratio (L/D) were found on CNC obtained from gravata after 45 min of acid hydrolysis. The mercerization and subsequent bleaching of fibers influenced the crystallinity index and thermal stability of the resulting CNC, but their properties are mainly influenced by the hydrolysis time, i. e., there is an increase in crystallinity and thermal stability up to 45 min of hydrolysis, after this time, both properties decrease, probably due to the cellulose degradation by the sulfuric acid.

Novel Viruses in Mosquitoes from Brazilian Pantanal.

Viruses are ubiquitous and diverse microorganisms arising as a result of interactions within their vertebrate and invertebrate hosts. Here we report the presence of different viruses in the salivary glands of 1657 mosquitoes classified over 28 culicinae species from the North region of the Brazilian Pantanal wetland through metagenomics, viral isolation, and RT-PCR. In total, 12 viruses were found, eight putative novel viruses with relatively low similarity with pre-existing species of viruses within their families, named Pirizal iflavirus, Furrundu phlebovirus, Pixé phlebovirus, Guampa vesiculovirus, Chacororé flavivirus, Rasqueado orbivirus, Uru chuvirus, and Bororo circovirus. We also found the already described Lobeira dielmorhabdovirus, Sabethes flavivirus, Araticum partitivirus, and Murici totivirus. Therefore, these findings underscore the vast diversity of culicinae and novel viruses yet to be explored in Pantanal, the largest wetland on the planet.

Phylogenetics, patterns of genetic variation and population dynamics of Trypanosoma terrestris support both coevolution and ecological host-fitting as processes driving trypanosome evolution

BackgroundA considerable amount of evidence has favored ecological host-fitting, rather than coevolution, as the main mechanism responsible for trypanosome divergence. Nevertheless, beyond the study of human pathogenic trypanosomes, the genetic basis of host specificity among trypanosomes isolated from forest-inhabiting hosts remains largely unknown.MethodsTo test possible scenarios on ecological host-fitting and coevolution, we combined a host capture recapture strategy with parasite genetic data and studied the genetic variation, population dynamics and phylogenetic relationships of Trypanosoma terrestris, a recently described trypanosome species isolated from lowland tapirs in the Brazilian Pantanal and Atlantic Forest biomes.ResultsWe made inferences of T. terrestris population structure at three possible sources of genetic variation: geography, tapir hosts and ‘putative’ vectors. We found evidence of a bottleneck affecting the contemporary patterns of parasite genetic structure, resulting in little genetic diversity and no evidence of genetic structure among hosts or biomes. Despite this, a strongly divergent haplotype was recorded at a microgeographical scale in the landscape of Nhecolândia in the Pantanal. However, although tapirs are promoting the dispersion of the parasites through the landscape, neither geographical barriers nor tapir hosts were involved in the isolation of this haplotype. Taken together, these findings suggest that either host-switching promoted by putative vectors or declining tapir population densities are influencing the current parasite population dynamics and genetic structure. Similarly, phylogenetic analyses revealed that T. terrestris is strongly linked to the evolutionary history of its perissodactyl hosts, suggesting a coevolving scenario between Perissodactyla and their trypanosomes. Additionally, T. terrestris and T. grayi are closely related, further indicating that host-switching is a common feature promoting trypanosome evolution.ConclusionsThis study provides two lines of evidence, both micro- and macroevolutionary, suggesting that both host-switching by ecological fitting and coevolution are two important and non-mutually-exclusive processes driving the evolution of trypanosomes. In line with other parasite systems, our results support that even in the face of host specialization and coevolution, host-switching may be common and is an important determinant of parasite diversification.

Seasonal variation of biochemical parameters of hemodialysis patients in a tropical climate area

The results of hemodialysis laboratory tests guide the monitoring of the patient’s health conditions, nutritional status and the quality of the procedure. The objective is to analyze the seasonal variations of biochemical parameters of hemodialysis patients in a tropical area of Brazil. This is a longitudinal epidemiological study of the seasonal variation of repeated measurements for hemoglobin, hematocrit, calcium, potassium, phosphorus, glucose, glutamic-pyruvic transaminase, pre- and postdialysis urea, KtV, and urea reduction rate in hemodialysis patients in the city of Caceres, Brazilian Pantanal in the year 2014, in the savannah tropical climate area. January was used as the reference month and linear mixed effects regression models were used. All laboratory variables analyzed presented significant seasonal variation in at least two months in 2014. Hemoglobin and hematocrit displayed the lowest values in autumn and the highest in winter. Calcium remained stable and showed two high peaks in autumn and winter. Phosphorus, potassium and glutamic-pyruvic transaminase showed higher values in autumn and lower values in spring. KtV, urea reduction rate, predialysis and postdialysis urea, had the lowest peaks in winter and the highest in spring. Glucose showed instability with a high peak in spring and a lower peak in autumn. It is concluded that the biochemical parameters of chronic renal patients on hemodialysis display seasonal variations related to climatic seasonal variation in a tropical savannah climate area in Brazil. The variations observed tend to become inverted in the months with higher and lower temperatures.