Feeding ecology of Eigenmannia desantanai (Gymnotiformes: Sternopygidae) in southern Pantanal, Brazil

Aim This study investigated changes in the dietary composition and trophic niche breadth of Eigenmannia desantanai in the context of hydrological periods, rivers, and ontogeny. Methods Collections were performed monthly on the Paraguay and Amonguijá Rivers between February 2009 and January 2011. Results A total of 338 specimens of E. desantanai were collected, 224 of which came from the Amonguijá River and 114 from the Paraguay River. In all, 21 food items were identified. Fully remains of digested animals (RDA), Chironomidae, Cladocera, and Ostracoda showed greater importance in the diet of E. desantanai. Dietary composition was influenced by hydrological periods, followed by differences between sampled rivers, and ontogeny. In contrast, only hydrological periods explained variation in the E. desantanai trophic niche breadth. Conclusions The diet of E. desantanai is mainly composed of Chironomidae, Cladocera, and Ostracoda; however, individuals consumed other food items owing to changes in hydrological periods, followed by characteristics of the Amonguijá and Paraguay Rivers and ontogenetic variation. In this respect, the results of this study are germane to the food ecology of E. desantanai, providing guidelines for the management and conservation of the species.

New records of the occurrence of Megaleporinus macrocephalus () (Characiformes, Anostomidae) from the basins of the Itapecuru and Mearim rivers in Maranhão, Northeastern Brazil

The “piaussu”, Megaleporinus macrocephalus is an anostomatid fish species native to the basin of the Paraguay River, in the Pantanal biome of western Brazil. However, this species has now been recorded in a number of other drainages, including those of the upper Paraná, Uruguay, Jacuí, Doce, Mucuri, and Paraíba do Sulrivers. This study presents two new records of the occurrence of M. macrocephalus, in the basins of the Itapecuru and Mearim rivers in the state of Maranhão, in the Brazilian Northeast. The piaussu is a large-bodied fish of commercial interest that is widely raised on fish farms, and its occurrence in the Itapecuru and Mearim rivers is likely the result of individuals escaping from fish tanks when they overflow during the rainy season. Morphological analyses and sequences of the Cytochrome Oxidase Subunit I (COI) gene confirmed the taxonomic identification of the specimens as M. macrocephalus. The COI sequences were 99.66% similar to those of M. macrocephalus deposited in the BOLDSystems database. These records extend the known distribution of M. macrocephalus to the basins of the Itapecuru and Mearim rivers in the Brazilian Northeast, highlighting a new case of introduction of exotic fish species into Brazilian river basins.

Hydropeaking by Small Hydropower Facilities Affects Flow Regimes on Tributaries to the Pantanal Wetland of Brazil

Hydroelectric facilities often release water at variable rates over the day to match electricity demand, resulting in short-term variability in downstream discharge and water levels. This sub-daily variability, known as hydropeaking, has mostly been studied at large facilities. The ongoing global proliferation of small hydropower (SHP) facilities, which in Brazil are defined as having installed capacities between 5 and 30 MW, raises the question of how these facilities may alter downstream flow regimes by hydropeaking. This study examines the individual and cumulative effects of hydropower facilities on tributaries in the upland watershed of the Pantanal, a vast floodplain wetland system located on the upper Paraguay River, mostly in Brazil. Simultaneous hourly discharge measurements from publicly available reference and downstream gage stations were analyzed for 11 reaches containing 24 hydropower facilities. Most of the facilities are SHPs and half are run-of-river designs, often with diversion channels (headraces). Comparison of daily data over an annual period, summarized by indicators of hydrological alteration (HA) that describe the magnitude, frequency, rate of change, and duration of flows, revealed differences at sub-daily scales attributable to hydropeaking by the hydropower facilities. Results showed statistically significant sub-daily HA in all 11 reaches containing hydropower facilities in all months. Discharge indicators that showed the highest percentage of days with increased variability were the mean rates of rise and fall, amplitude, duration of high pulses, maximum discharge, and number of reversals. Those that showed higher percentages of decreased variability included minimum discharge, number of high pulses, duration of stability, and number of low pulses. There was no correlation between HA values and physical characteristics of rivers or hydropower facilities (including installed capacity), and reaches with multiple facilities did not differ in HA from those with single facilities. This study demonstrates that SHPs as well as larger hydropower facilities cause hydrological alterations attributable to hydropeaking. Considering the rapid expansion of SHPs in tropical river systems, there is an urgent need to understand whether the ecological impacts of hydropeaking documented in temperate biomes also apply to these systems.

Effect of Flood Pulse on the Functional Diversity and Traits Composition of Birds With Different Degrees of Wetland Dependence in the Brazilian Pantanal

Hydrological dynamics of the Pantanal wetland drive the availability of resources and niche for aquatic and terrestrial fauna. We consider that changes in the hydrological regime of this floodplain can affect species richness, abundance and functional structure of waterbirds, wetland birds and non-wetland birds. Our study aimed to assess whether the degree of wetland dependence influences the response of bird groups to the flood pulse. We conducted the bird survey in the Paraguay River floodplain system, in five sampling sites, covering the periods of drought, flooding, full flood and ebb of the 2017–2018 hydrological cycle. Species richness and abundance were higher for non-wetland birds than waterbirds and wetland birds. On the other hand, we found that the higher the degree of wetland dependence by birds, the higher the differences in the functional-trait values. Species richness, abundance and all metrics of functional diversity varied significantly when there was an interaction between the degree of wetland dependence and the hydrological period. In all hydrological periods, bird groups occupied distinct niches. Traits such as foraging around or below the water surface were among the dominant functional traits in all hydrological periods. We emphasize the need to consider the functional traits of species in ecological studies of wetlands since measuring only species richness may not reflect the characteristics inherent to this type of ecosystem. In addition, the conservation of wetlands directly implies the maintenance of various niches throughout the hydrological periods, either for dependent or non-dependent bird species in wetlands.

Marine heatwaves in the dynamics of the Pantanal´s historical drought and unprecedented fires

<p>Fire is a natural disturbance in the Neotropical savannas, and rather frequent in the relatively<br>dry and well-drained seasonal savannas of the Brazilian Cerrado. The neighboring Pantanal, on<br>the other hand, is a seasonally flooded savanna and the largest wetland in the world (≈138,000<br>km 2 ). Due to its wetter condition, fires in the Pantanal are much less frequent and spatially<br>restricted. But, given an ongoing extreme drought, the 2020’s fires in the Pantanal have been<br>unprecedented in extent and duration: About one third (≈45,000 km 2 ) of the area of this<br>important wetland has gone up in flames since last January. Regarding this historical drought,<br>climate change has been identified as one of the most important threats to the Pantanal.<br>Reductions in precipitation may cause significant disturbances in its ecological functioning,<br>affecting hydrological, floodplain inundation dynamics, as well as fire regime. Climate change<br>models from a recent study (Thielen et al. 2020, doi:10.1371/journal.pone.0227437) indicate<br>that, for the Pantanal, extended severe droughts are to be expected from the warming of Sea<br>Surface Temperatures (SST) at Northern Hemisphere oceans.<br>The present study analyses the spatial and temporal dynamics of precipitations during the<br>series 1981-2020 in the Upper Paraguay River Basin (UPRB), which comprises the Pantanal and<br>the neighboring Highlands, along with a co-evaluation of the SST trends at three oceanic<br>regions from Northern Hemisphere. Precipitation anomalies were analyzed by mean of the<br>Standardized Precipitation Drought Index (SPDI) based on the 1981-2010 climate normals.<br>Results show that for the UPRB, negative precipitation anomalies occur in pulses lasting<br>several years. A drought starting in 2019 has been the strongest and most extended on record,<br>persistently reaching the Extremely Dry condition (SPDI≤-2.0) during 2020. As early as Mar,<br>over 64% of the Pantanal is affected by such drought, and around 83% by Dec. For the UPRB,<br>four distinctive groups of subregions were identified according to their temporal dynamics of<br>mean SPDI values, mainly during Sep2019/Feb2020 and Mar2020/Dec2020. Here, precipitation<br>anomalies from southernmost subregions of the Pantanal were less intense and even not<br>affected by the drought.<br>As for SST, the Northeast Pacific region (PAC-NE) showed the most important dynamics. In this<br>region, SSTs have been anomalously warm since Jun 2019, with 64% of the time SSTA<br>surpassing the 90 th percentile: reaching the Heatwave condition. With a lead of one to two<br>months, PAC-NE showed the strongest (and negative) correlation with precipitation at UPRB<br>(r=-0.87) during Jan2019 to Dec2020. There is a significant trend for an increase in SST at the</p><p>Northeast Pacific, a trend that will certainly generate a rather continuous Heatwave in PAC-NE.<br>As a result, one expects an extension of the current extreme drought in the Pantanal area, at<br>least during 2021, and the intensification of fires with unprecedented duration and intensity,<br>extending now to areas historically flooded or perhumid. Concomitantly, we predict a most<br>definite impact on non-fire-resistant vegetation cover, as well as ecosystem functioning and<br>biodiversity.</p>

Extreme Drought in the Brazilian Pantanal in 2019–2020: Characterization, Causes, and Impacts

The Pantanal region in South America is one of the world's largest wetlands. Since 2019, the Pantanal has suffered a prolonged drought that has spelled disaster for the region, and subsequent fires have engulfed hundreds of thousands of hectares. The lack of rainfall during the summers of 2019 and 2020 was caused by reduced transport of warm and humid summer air from Amazonia into the Pantanal. Instead, a predominance of warmer and drier air masses from subtropical latitudes contributed to a scarcity of summer rainfall at the peak of the monsoon season. This led to prolonged extreme drought conditions across the region. This drought had severe impacts on the hydrology of the Pantanal. Hydrometric levels fell all along the Paraguay River. In 2020, river levels reached extremely low values, and in some sections of this river, transportation had to be restricted. Very low river levels affected the mobility of people and shipping of soybeans and minerals to the Atlantic Ocean by the Hidrovia -Paraná-Paraguai (Paraná-Paraguay Waterway). This study is directed to better understand the hydroclimatic aspects of the current drought in the Brazilian Pantanal and their impacts on natural and human systems. As a consequence of the drought, fires spread and affected natural biodiversity as well as the agribusiness and cattle ranching sectors. While fires had serious socioecological and economic consequences, we do not intend to investigate the effect of the downstream low-level waters on the Pantanal ecosystems or the drought in the risk of fire.

A New Variant B Chromosome in Auchenipteridae: The Role of (GATA)n and (TTAGGG)n Sequences in Understanding the Evolution of Supernumeraries in Trachelyopterus

Basic and molecular cytogenetic techniques were carried out in 3 Neotropical region populations of catfishes, two of Trachelyopterus galeatus (one from the marshlands of Paraguay River basin and another from Lago Catalão, Amazon River basin) and one of Trachelyopterus porosus, a sympatric population to T. galeatus from the Amazon River basin. This study aimed to describe and understand the structure and evolution of Trachelyopterus B chromosomes, mainly through physical mapping of repetitive elements. A diploid number of 58 chromosomes was found for all individuals, as well as the presence of B chromosomes. For T. porosus this is the first report of a supernumerary. The sympatric species of T. galeatus and T. porosus from Amazon River had 1–3 B chromosomes and T. galeatus from Paraguay River had 1–2 B chromosomes, all of them showed intra- and interindividual numerical variation. Two females of T. porosus exhibited a new variant B chromosome (B2), previously not seen in Auchenipteridae, which might have originated from B1 chromosomes. All B chromosomes were entirely heterochromatic. In contrast to all complement A and B2 chromosomes, in which the telomeric sequences were found in the telomeric regions, B1 chromosomes of all populations were totally marked by (TTAGGG)n probes. (GATA)n sequence sites were found through all complement A chromosomes, but B1 and B2 chromosomes exhibited only a clustered block in one of the chromosome arms. The most frequent B chromosomes (B1) in all populations/species, including those previously studied in Auchenipteridae catfishes, share the following characteristics: totally heterochromatic, small, metacentric, with accumulation of repetitive (TTAGGG)n sequences, and a low number of (GATA)n copies, which might suggest a common ancient origin in Trachelyopterus species/populations.

Changes in the structure of bird communities over 10 years in the Ecological Corridor of Paraguay River, Pantanal wetland

Studies with bird communities related to the hydrogeomorphological characteristics of climatic rivers associated with flood areas are important to identify short and long term temporal space changes. In this perspective, this research aims to evaluate the structure of the bird community of the Paraguay River, through the richness of descriptors, the quantity and the diversity and equability index over an interval of 10 years, 2008 / 9-2018 / 19 , considering the economies of the hydrological cycle, floods, floods, emptiness and drought and sampled macrohabitats. The study was developed addressing a connected hydrology of the Paraguay River, in the longitudinal and lateral dimensions. A study area comprised of three functional sectors of the Paraguay River, meandering, rectilinear and transitional, beginning in the urban period of the municipality of Cáceres-MT, up to a Descalvada Farm, with a 134 km course of the river, with 13 points in total. Each functional sector of the river, had a sampling point and 10 parental bays, with different degrees of lateral connectivity, were sampled. A survey analyzed and compared two hydrological sampling cycles, the first between June 2008 and March 2009, and the second between August 2018 and April 2019. The protocol for the sampling consisted of four campaigns corresponding to the hydrological drought studies, flood, full and ebb. The results pointed to a distinction in the community structure between the two cycles 2008/2009 - 2018/2019 show a difference in the relative scope and in the composition of the species in the sampled locations. The main change registered between the two cycles (2008/2009 and 2018/2019) was the disappearance of three nests - habitat for feeding and reproduction of colonial birds, identified in the first and without registration in the second cycle. The dominance of Mycteria americana is highlighted, a species sensitive to environmental changes, not observed in the first cycle of studies. The absence of nests in 2018/2019, coupled with the dominance of Pitangus sulphuratus, a generalist species, may indicate anthropic changes that occurred along the Paraguay River in this time interval. It is hoped that the results of this comparison will be able to subsidize or influence the effective decision-making for the conservation of the biodiversity of birds and the Paraguay and Pantanal river itself.