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Studies on zooplankton in lakes, ponds, and rivers have always received more attention, while zooplankton from streams remains understudied worldwide. Therefore, the role of zooplankton in neotropical stream functioning is still poorly understood. In order to remedy this situation, we aimed to answer the following questions: (1) How many papers have been published on the zooplankton from Brazilian streams? (2) In which hydrographic regions were these studies conducted? (3) Are there specific patterns of zooplankton species occurrence in neotropical streams? (4) What are the main types of studies and what are the main environmental factors influencing zooplankton in streams? In order to answer these questions, we performed a systematic review of indexed scientific papers. We indeed observed a paucity of studies on zooplankton in Brazilian streams. But despite the low number of studies (24), many species (276 taxa) were reported from seven Brazilian hydrographic regions. The species composition showed great variability within the hydrographic regions and fourteen environmental variables (physical, chemical, and spatial), which can represent environmental filters and influence dispersion processes, were related to zooplankton occurrences. These bibliographic data helped to clarify patterns in species composition and community structure of zooplankton in these streams. More studies are needed to further investigate the role of zooplankton in neotropical streams, which can help to develop conservation strategies. [ABSTRACT FROM AUTHOR]

Perspectives on the Environmental Implications of Sustainable Hydropower gathers scientific papers from three of the worlds most important hydropower producers to discuss aspects of sustainable hydropower and the means by which it can be studied and achieved. The papers examine the application and use of new technologies and protocols for studying hydropower, adaptive management and the implications and use of long-term data sets for minimizing hydropower impacts on fish populations. The papers include a cross section of biological and hydrological experts. The implicit among country comparisons highlight a number of common hydropower themes, particularly the need to expand from single species studies to include broader consideration of the ecosystem, the importance of maintaining habitat, trait and species diversity and the need for consistently collected long-term data sets. [ABSTRACT FROM AUTHOR]

The phoretic behaviour of ostracods ( Elpidium bromeliarum) andannelids ( Dero superterrenus) that inhabit tank bromeliads was studied. Our previous field observations had shown that bromeliad ostracods can be found attached to the skin of amphibians and reptiles that move among bromeliads, probably allowing the ostracods to colonise new tanks. In this paper, we present the first record of bromeliad annelids found attached to frogs moving among bromeliads in the field. We have also enlarged the database on bromeliad ostracods engaged in phoretic association with terrestrial vertebrates in three locations in southeastern Brazil. In our laboratory experiments bromeliad annelids show a strong significant tendency to climb onto papers that had been in contact with frog skin when compared with control papers, indicating a kind of chemically oriented behaviour. Bromeliad ostracods, on the other hand, attached themselves to treated and untreated papers with same frequency. When brought into contact with various species of frogs and lizards, the bromeliad annelids and ostracods both presented preference to attach themselves to frogs, but the annelids showed a stronger preference to attach to frogs and to avoid attachment to lizards. Another experiment demonstrated that bromeliad annelids are much more prone to dehydration than are ostracods. We suggest that the chemically oriented behaviour presented by bromeliad annelids toward frogs could diminish the risk of death by dehydration during the transport among bromeliads due to the moist characteristic of frog skins. [ABSTRACT FROM AUTHOR]

Sustainable global energy production is back-stopped by hydropower which is responsible for a significant share of the green energy produced worldwide. Hydropower, however, does not come without some environmental impacts but has worked to reduce those impacts. Here, we discuss the historical, legislative, and design configurations of hydropower facilities located in three of the world's most important producers: Brazil, Canada, and Norway. The background is intended to inform the collection of scientific papers from each country aimed at assessing and improving the sustainability of hydropower production that form the core of this special issue on sustainable hydropower. We review the development and key legislative history for hydropower in each country and point out the common backgrounds and interests each nation has in the continued sustainable development of its hydropower resources. [ABSTRACT FROM AUTHOR]

The intermediate disturbance hypothesis (IDH) has been thoroughly investigated, but much controversy has been found for supporting its assumptions, which rely largely on the nature of the disturbance, spatial scale, and biological predictors tested. In this paper, richness of native and non-native species along a suite of Neotropical aquatic ecosystems across a broad latitudinal and geographical range was used to test the IDH predictions. An extensive literature survey was performed to compile native species richness and the occurrence of several taxonomic groups listed as non-native for twenty-four coastal rivers and bays evenly distributed into three climatic zones (tropical, transitional, and subtropical). The climatic gradient was confirmed by NMDS and PERMANOVA, but IDH predictions were only significantly supported for native and total species richness in the coastal bays. The distribution patterns of non-native marine species showed a linear instead unimodal pattern of increase with latitudinal climatic gradient, but the responses are complex and dependent of many non-exclusive factors, such as the sampling effort per ecosystem and the potential interference of other disturbance gradients that should be further addressed to unravel the role of IDH for non-native species distribution. [ABSTRACT FROM AUTHOR]

Low-order streams and riparian wetlands are important contributors to the drainage network in the landscape. However, there has been little research into the nature of these ecosystems in Brazil. Our estimates show that riparian wetlands of low-order streams and other small associated wetlands cover at least 25% of the forested part of the Amazon basin and about 10% of the Cerrado region. Information on the semi-arid Caatinga is lacking, but ~ 3% of the area may be occupied by riparian wetlands and other small wetland types, many of which are periodically dry. Riparian vegetation includes a very large richness in tree species. The amount and species richness of herbaceous plants depend on light availability. In-streams of the semi-arid region of Brazil, hydrophytes are restricted by unpredictable flash floods and periodic drought. Aquatic food webs are largely based on the organic matter produced by the riparian vegetation. Large-scale agriculture and cattle ranching pose a serious threat to riparian wetlands, their biodiversity, and their function as a buffer in the hydrological cycle of the landscape. A nation-wide screening program would provide a more detailed picture and allow the elaboration of a national conservation and restoration program for the Brazilian riparia. [ABSTRACT FROM AUTHOR]

In the last three decades, several studies have suggested that the structure of stream macroalgal communities is shaped by local environmental variables, but some recent papers have shown that the relevance of the environment on these communities may be overestimated. Using Partial Redundancy Analysis (pRDA), we analyzed macroalgal communities (considering all macroalgae and Phyla Chlorophyta, Cyanobacteria, and Rhodophyta individually) from 105 streams in southern Brazil to test the hypothesis that the relative contributions of the environment and space on the taxonomic composition of these communities is mainly determined by the biological traits and dispersal mechanisms typical for each group. The pRDA showed that the taxonomic composition of the entire community and green algae were explained by both space and environment, whereas for cyanobacteria, only the environment was significant, and for red algae, only space was significant. These divergences in the relative contribution among algal phyla were consistent with our initial hypothesis and can be ascribed to the differences in the ecological features of each group. Our results also support the idea that the community structure of organisms with low dispersal is influenced more significantly by spatial processes, whereas for organisms with high dispersal the local environmental variables are more influential. [ABSTRACT FROM AUTHOR]

The purpose of this paper was to assess the influence of basic limnological variables on bacterioplankton abundance in twenty lagoons in the Upper Paraná River floodplain, Brazil. Twelve abiotic (depth, total nitrogen, total phosphorus, dissolved organic carbon (DOC), water transparency, temperature, dissolved oxygen, alkalinity, pH, turbidity, electrical conductivity and total inorganic carbon), and two biotic (chlorophyll-a and rotifers abundance) limnological factors were used as independent variables to explain bacterial countings. Principal component analysis (PCA) was used to reduce the dimensionality of the abiotic data and chlorophyll-a. Subsequently, multiple regression analysis was used to examine the relationship between bacterial abundance and the principal component axes and rotifer densities. Bacterioplankton abundance fluctuated from 1.8 to 5.9 × 106 cells.ml-1 during the high water phase and from 1.4 to 4.0 × 106 cells.ml-1 during the low water phase and they were significantly higher during the former phase (t=3.06; p=0.007). Bacterial abundance was not significantly correlated with chlorophyll-a and rotifers abundance. On the other hand, it was positively correlated with principal components 1 and 2, indicating that DOC, total nitrogen and phosphorus concentration, temperature and pH are important to explain bacteria abundance. These results indicate that the input of different sources of DOC and inorganic nutrients from the floodplain into the lagoons during the high water phase is more important to explain bacterial abundance than autochthonous phytoplanktonic organic matter or predation by rotifers. [ABSTRACT FROM AUTHOR]

As human-induced environmental changes reduce niche opportunities from global to local scales, permanent shifts in species traits alter ecosystem processes. Disentangling multiscale mechanisms driving temporal changes in coastal fish biodiversity is thus critical to conservation aims. From seasonal to multiyear periods, we investigated how local environmental variation and landscape features shape temporal beta diversity (abundance-based and trait-based dissimilarities, and their components of replacement and nestedness) per zones in bays and coastal lagoons, Southeastern Brazil. At larger temporal dimensions, unaccounted processes in individual systems influenced primarily taxonomic dissimilarity, whereas functional responses to variation in marine influence varied between types of system and zones. From 2 years to seasons, taxonomic and functional dissimilarities decreased with abundance-based species replacement, and both trait-based components, respectively. Replacement processes were primarily related to marine influence (transparency, salinity, pH, and tidal phase) at larger temporal dimensions, and habitat availability (mangroves and nearby estuaries) and complexity (forest cover and landscape urbanization) in seasons. Seasonal variations in tidal phase (lower) and pH (higher), respectively, promoted taxonomic (abundance gradients) and functional (fish trait loss) nestedness under shorter environmental gradients. Spatial and temporal balances between marine influence, habitat quality, and seascape connectivity drive temporal dissimilarities in coastal fish assemblages. [ABSTRACT FROM AUTHOR]

Several hypotheses try to explain the factors that limit the distribution of tree species in wetlands. Among them, the stress-gradient hypothesis states that interspecific ecological interactions (facilitation and competition) vary inversely across abiotic stress gradients, with facilitation being more common under conditions of high abiotic stress than under more benign conditions. We investigated the effects of ecological interactions on the biomass of two native tree species, Crateva tapia (highly flood-tolerant) and Hura crepitans (low flood tolerant) exposed to different experimental flooding conditions in a greenhouse. Individual and paired plants were submitted for 120 days to four treatments: (1) non-flooding and non-ecological interaction; (2) flooding and non-ecological interaction; (3) non-flooding and ecological interaction; (4): flooded and ecological interaction. Flooding reduced biomass allocation in H. crepitans. C. tapia biomass was reduced by interspecific interaction with H. crepitans. Flood and interspecific ecological interactions together facilitated the accumulation of biomass in H. crepitans. Our results support the stress-gradient hypothesis, showing that in a flooded environment, the species with low tolerance to flooding (H. crepitans) is favored by the presence of other species. Additional tests with other species can confirm whether this is a pattern that helps explain the establishment of tree species in wetlands. [ABSTRACT FROM AUTHOR]

Macrophytes play an important role in maintaining biodiversity. However, little is known about the relationships between different types of macrophytes and the diversity of aquatic communities. The purpose of this study was to determine the relationships between floating and submerged macrophytes and the temporal variation in the taxonomic and functional diversity of phytoplankton in two tropical reservoirs (Cursaí and Cajueiro) located in Northeastern Brazil. A field study was carried out quarterly between November 2018 and November 2019 to analyze the taxonomic (richness, equitability, and Shannon index) and functional (FRic, FEve, and FDiv) diversity indices of phytoplankton in relation to the presence of macrophytes. Taxonomic and functional diversity indices varied over time in sampling sites. Macrophytes had positive effects on taxonomic richness, Shannon index, and FDiv in Cajueiro, and negative effects on the taxonomic equitability and FEve of phytoplankton in Cursaí. Functional diversity of phytoplankton was negatively influenced by water transparency and positively by total dissolved solids, pH, and nitrate in sites with macrophytes, while taxonomic richness was positively influenced by total phosphorus. Our results showed that taxonomic and functional diversity of phytoplankton responded differently to spatial and temporal variation, and species richness, Shannon index and FDiv were related to macrophytes. [ABSTRACT FROM AUTHOR]

We developed the Trophic Diatom Index for Reservoirs (TDIR), the first index proposal for water trophic quality assessment of tropical reservoirs in Brazil. Furthermore, we applied four borrowed diatom indices to compare their performances with TDIR. The proposal development considered a calibration set from surface sediment diatoms (n = 113) from reservoirs ranging from ultraoligotrophic to hypereutrophic. Weighted averaging methods were applied to infer optimum (values) and tolerances for total phosphorous for each diatom species. Indicative values were categorized within the trophic classification for tropical reservoirs, and sensitivity values were classified according to the range of tolerances of diatom species. The TDIR index scores ranged from 1 (ultraoligotrophic) to 6 (hypereutrophic). The TDIR showed good performance for the trophic classification of reservoirs. In contrast, the borrowed diatom indices developed in subtropical rivers underestimated the water quality, whereas the diatom index developed for lakes in temperate regions overestimated the water quality of our reservoirs. Moreover, we calculated new records of indicative values, and some well-cited species had different optimum and tolerances values concerning other well-known studies. TDIR provides an applicable index and contributes as a reliable tool for assessing the water quality and ecological status of tropical reservoirs. [ABSTRACT FROM AUTHOR]

Freshwater ecosystems are among the most threatened habitats on Earth, due mainly to anthropogenic pollutants made up of complex mixtures. The Iguaçu River is world famous for the Iguaçu Falls and highlighted by its endemism. Unfortunately, it is considered the second most polluted urban river in Brazil. We aimed to perform an environmental evaluation of Neotropical streams in the Iguaçu River basin, using a multibiomarker approach from a land use and landscape perspective. A set of biomarkers in the fish Psalidodonbifasciatus was analyzed using an Integrated Biomarker Response (IBR) index and correlated with surrounding land uses. Agricultural and urban sites presented more alterations compared to references sites, with elevated protein carbonyls at agricultural sites, increased DNA damage and depletion of glutathione S-transferase at urban sites and decreased glutathione associated with higher histopathological indices at urban and agricultural sites. The IBR shows a consistent increase in negative effects in anthropized areas, with similar values at agricultural and urban sites. The multibiomarker approach, associated with a well-elaborated sample design and a statistical analysis, is an ideal method to obtain more conclusive results about the effects of human activities, revealing the effective result of exposure in the real world. [ABSTRACT FROM AUTHOR]

Even after more than a century of research, the processes underlying species abundance distribution patterns are controversial. Here, we gathered abundance and size (standard length) data of fish species in 54 streams in the Midwest of Brazil to test whether subordinate species abundances (i.e., any species that is not dominant in a community) in each stream are correlated with the absolute size difference between dominant and subordinate species. A negative relationship between these variables would suggest a predominant role of environmental filtering because those species that differ more from the dominant species (the one with the optimum trait value) would become progressively less abundant. On the other hand, a positive relationship would suggest a limit to the similarity as the abundances of subordinate species that differ more from the dominant species would increase. Our results clearly indicated that subordinate species were those that most differed from the dominant species in terms of size. In addition, we found that the subordinate species were larger than the dominant species. Taken together, we infer that environmental filters favoring small body sizes (e.g., shallow water depth and scarcity of large shelters) are the main processes determining species abundance distributions in the streams we studied. [ABSTRACT FROM AUTHOR]

Habitat fragmentation caused by hydroelectric dams has depleted fish populations worldwide. Restocking actions are usually adopted to recover those populations, but hatchery management protocols rarely guarantee the maintenance of genetic diversity and a balanced contribution among captive breeders each generation. Here, a set of 10 microsatellite markers was used to assess the genetic diversity (average allelic richness AR = 10.87 and expected heterozygosity HE = 0.742, respectively) and structuring of Megaleporinus obtusidens, a migratory freshwater fish inhabiting over 2500 km of the São Francisco River in Brazil. Three main genetic clusters were identified in this species across the river basin that could be related to the sharply different climatic and hydrologic regimes from the Upper to the Lower course. A significant reduction (> 50%) in genetic diversity was observed in the broodstock when compared to their wild conspecifics, especially in the allelic richness. The information here presented will aid for management of genetic resources of this species in the São Francisco River taking as reference the genetic clusters identified. Furthermore, the results indicated that restocking is not necessary unless signals of population depletion occurs and, if so, hatchery reproductive protocols should rely on artificial fertilization rather than mass spawning. [ABSTRACT FROM AUTHOR]

Trait-based classifications can efficiently capture species' responses to environmental gradients and their impacts on ecosystem functioning. Thus, the clustering of phytoplankton species into functional groups can improve the understanding of their relationships with the environment and help to predict their response to environmental changes. Accordingly, this study aimed to create habitat templates of Reynolds phytoplankton functional groups (RFGs) in tropical drinking water reservoirs to describe, explain, and predict their occurrence and formation of blooms. We analyzed the structure of RFGs in 10 tropical reservoirs, in humid and semiarid regions of Brazil, and defined their relationships with 10 environmental variables. We designated the habitat template based on niche differentiation, thresholds for the occurrences and bloom formation, cluster analyses, and generalized additive models. We identified 136 species, assembled in 20 RFGs. Six groups of habitat templates were recognized based on environmental conditions and dominant RFGs, usually represented by bloom-forming species of cyanobacteria, dinoflagellates, green algae, and diatoms. The functional groups D, X1, and P presented the most restrictive occurrences, while RFGs M and SN displayed the widest, occurring in almost all sets of conditions. Moreover, salinity was the best predictor of RFGs' biomass (higher R2), followed by depth, soluble reactive phosphorus, irradiance, water transparency, and dissolved inorganic nitrogen. Our approach improves the understanding of how RFGs interact with environmental gradients in tropical reservoirs, helping water managers to adopt sustainable practices to control algal blooms, based on predictions of the future state of dominance. [ABSTRACT FROM AUTHOR]

The use of species traits offers a promising approach to the understanding of the main processes underlying metacommunity patterns. We analyzed samples of periphytic algae in 30 environments of the Upper Paraná River floodplain in southeastern Brazil, to test the hypotheses that variation in species composition of algal groups with low dispersal abilities would be mainly explained by spatial variables; on the other hand, algal groups with higher dispersal abilities would be better explained by environmental variables. The variation in community structure was mainly correlated with environmental variables. This result is in line with a growing body of evidence indicating a predominant role of species-sorting processes. The more-refined prediction that the spatial variables would gradually become more important across a gradient of adherence or size was, however, not supported by our analyses. Also, the large unexplained variation suggested that these periphytic communities were assembled by idiosyncratic events, or that other variables that are often neglected in studies of aquatic metacommunities needed to be included. [ABSTRACT FROM AUTHOR]

Based on a literature survey, we evaluated the periods of cyanobacterial dominance in Brazil. We hypothesized that variability of environmental forces along the country will promote or facilitate temporal and spatial mosaic in cyanobacterial dominance. The most striking outcomes are related to the dominance of Cylindrospermopsis, Dolichospermum, and Microcystis. Although they share important adaptive strategies (e.g., aerotopes, large size and toxins production), our findings suggest that they have different environmental preferences. Dolichospermum and Microcystis dominated mainly in warm-rainy periods whereas Cylindrospermopsis was more common during dry periods and in mixed systems, or formed perennial dominance. Maximum phosphorus concentrations were observed in reservoirs dominated by Cylindrospermopsis. Although the main genera reached high biomass levels individually, different abilities to form dominance and co-dominance were observed. The number of co-dominance of Chroococales and Nostocales was almost the same as the individual occurrence of the main genera from these groups. This dataset reveals patterns of dominance of these cyanobacteria and also indicates that physiological features will cause differences in the mechanisms of interactions between species. The understanding of these processes and their relationship to environmental conditions will promote better understanding of cyanobacterial dominance and increase our ability to predict and manage these events. [ABSTRACT FROM AUTHOR]

This study tests if rainfall regime and estuary hydrodynamics affect ecological picocyanobacterial patterns. We statistically related rainfall with picocyanobacteria (flow cytometry) and water quality data from a seven-year-long survey of Guanabara Bay (GB). The quality of GB's water varies spatially, depending on pollution hotspots, tidal influence, and water circulation patterns. It also varies seasonally, depending on the rainfall regime. Our results showed that rainfall regularly makes water quality and microbiology of the inner estuarine regions more like the tributaries' environment. We found that phycocyanin-rich and phycoerythrin-rich picocyanobacterial abundances are associated with riverine and marine waters, respectively. Besides affecting GB's water quality, rainfall governs its picocyanobacterial distribution and ecology. Thus, climate changes may influence the balance of the picocyanobacterial groups in tropical estuaries. Furthermore, the omnipresence of picocyanobacterial groups found in GB, such as Synechococcus and Cyanobium, highlights their ecological role in tropical estuaries, as seen in the open ocean. [ABSTRACT FROM AUTHOR]

In this study, we investigate the main ecological interactions between fouling aquatic organisms (both invasive and native) present in the reservoir of the Governador José Richa hydroelectric plant, located in southern Brazil, and to identify the most suitable period for the interruption of machinery operation for cleaning and maintenance of the hydraulic systems of this plant. A total of 32 experimental plates were fixed to a metallic structure positioned close to the plant's water intake. Three species of invasive fouling were identified in our samples (Limnoperna fortunei [Mollusca], Cordylophora sp., and Hydra sp. [Cnidaria]) and six native taxa belonging to the phyla Protozoa, Ciliophora, Amoebozoa, and Arthropoda. Spring and summer were the seasons with the highest fouling rates, as well as densities of fouling organisms. The highest levels of diversity were recorded during the colder seasons. Several interactions between the organisms were identified, such as mutualism, commensalism, competition, epibiosis, cannibalism, and predation. The data obtained suggest that, from the biological point of view, the most suitable period for machine shutdown destined for the removal of biological fouling in the hydraulic systems of the studied plant is between the end of spring and the beginning of summer. [ABSTRACT FROM AUTHOR]

The flood pulse concept refers to seasonal variation in river water levels promoting landscape spatial heterogeneity, connectivity, and nutrient cycling among nearby environments, in addition to contributing to the ecological functioning of river-floodplain systems. This seasonal variation is inherent to river-floodplain systems and responsible for establishing their natural pattern, as frequently observed in nature. In Brazil, the Upper Parana River and its floodplain constitute a river-floodplain system of interest, where an upstream reservoir cascade has altered the flood regime. This regime has been explored in the past; however, research has focused only on its time-domain. In this study, I sought to analyze the flood pulse in the Upper Paraná River Floodplain through a set of spectral (frequency-domain) and nonlinear analyses using a time-series of water level fluctuations (1968–2017) in the system. In doing so, I believe to bring novel information on this system flood regime in terms of its dynamic invariants. I divided the data into four periods: (i) natural regime period, (ii) transitional period, (iii) dam cascade period, and (iv) Primavera dam period. Spectral analysis demonstrated a decrease in the annual cycle amplitude, reflected in its power spectrum, which indicates a weakening in the difference between flood and drought events. Additionally, nonlinear dynamical analysis revealed a less deterministic and predicable behavior leading to more erratic fluctuations, thus jeopardizing the temporal heterogeneity of the system. Such altered dynamics is harmful for threatening the ability of organisms to harmonize their biological cycles with seasonal phenomena, consequently raising concerns about the maintenance of ecological integrity in the system. [ABSTRACT FROM AUTHOR]

Harmful effects of the toxic cyanobacterium Nodularia spumigena were observed in experimental marine shrimp production ponds in Brazil. Strains of this cyanobacterial species were isolated and cultured, and in the present study, we evaluated the influence of light intensity and the concentration of dissolved inorganic nitrate and phosphate on the growth, toxin concentration, heterocyte formation and akinete germination of N. spumigena. A factorial experiment (3 × 3) was performed to test three light intensities and nutrient concentrations with a reduced nitrate concentration, a reduced phosphate concentration and a nutrient-replete f/2 medium. The influence of light intensity on growth and akinete formation was varied: the highest cell density and chlorophyll a were recorded at the lowest light intensity, while the high light treatment stimulated akinete formation. The availability of phosphate was the main factor favouring the growth of N. spumigena and the formation and germination of akinetes, while the concentration of nodularin per cell was highest under phosphate deficiency. This information is useful in the management of aquaculture ponds and other brackish and marine environments where the goal is to reduce N. spumigena blooms. [ABSTRACT FROM AUTHOR]

The high diversity of fish species found in Brazilian streams has attracted scientific interest in recent years. However, it is not clear how studies have addressed biodiversity knowledge shortfalls. We conducted a scientometric analysis of stream fish studies in Brazil to identify trends and gaps in how objectives, spatial coverage, and biodiversity knowledge shortfalls have been studied. Our review covered 690 articles published between 1981 and 2019, and we found an increase in the number of publications, the spatial scale of studies, and the number of streams studied. We also found biases in the distribution of publications concerning regions, biomes, basins, and biodiversity knowledge shortfalls. The Southeast region, the Paraná River basin, the Atlantic Forest biome, and the Hutchinsonian shortfall contributed to a greater number of studies while the Northeast region, the Pantanal biome, Parnaíba basin, Western Northeast Atlantic basin, and the Prestonian shortfall were less represented. Therefore, to improve our knowledge about stream fish, we recommend new collection efforts in under-sampled regions and new studies focused on filling less-addressed biodiversity knowledge shortfalls. Moreover, we emphasize the importance of standardized sampling protocols, a complete sharing of data, and an increase in scientific collaboration. [ABSTRACT FROM AUTHOR]

We evaluated the association between the El Niño Southern Oscillation (ENSO), an important climatic phenomenon on Earth, with water level variation and fish assemblage attributes (i.e., abundance, species richness and structure of the assemblage) of the Paraná (dammed) and Ivinhema (undammed) rivers, located in the upper Paraná River floodplain, Brazil. Cross-Correlation Function analyses were performed using the Oceanic Niño Index (ONI; which indexed ENSO events) as the influential time series on water level and fish assemblage attributes time series. ONI were positively associated with water level and with most of the fish assemblage attributes tested, but these patterns differed between the two rivers. This indicates that El Niño events affect the structure of the fish assemblages, mainly in the Ivinhema River, which presented more assemblage attributes associated with ONI. In addition, dams may play a regulatory effect over the water level of the Paraná River, which probably explains the different patterns of assemblage attributes in both rivers. Thus, ENSO events are associated with the composition and structure of the fish assemblages in the studied area, and their effects are apparently minimized in the Paraná River due to the presence of upstream dams. [ABSTRACT FROM AUTHOR]

Despite the ability of mangrove trees to allocate a large proportion of the total biomass to the underground roots, little is known about the benthic macrofauna–root system relationships. We evaluated the above- and belowground structures of plants, soil properties, algal cover and their relationship with macrofauna as a function of soil strata (0–2.5, 2.5–5 and 5–10 cm) and distance (0–0.30 and 3–3.5 m) from trunks in three mangrove sites in southern Brazil. Coarse root biomass was higher near the trunks and in shallower layers, while fine root biomass predominated far from trunks and indifferent to the soil stratum. The macrofauna was more associated with changes in the root systems than with other soil properties. Most of the benthic taxa occurred in the upper layers of the soil (0–2.5 cm) and near trunks (< 0.30 m), where there was a lower proportion of fine roots. Fine root entanglement inhibited the presence of organisms with more complex body plans, which may hamper their locomotion and feeding activities. Therefore, the structure and function of macrofauna varied according to the depth stratum and distance from the trunks. [ABSTRACT FROM AUTHOR]

Headwater streams subjected to anthropogenic impacts are prone to environmental quality decay, which may affect stream functioning. To investigate the effects of loss of environmental quality in stream functioning, we tested the hypothesis that leaf breakdown is faster in streams with higher environmental quality, and that invertebrate community structure and microbial biomass are negatively affected by habitat simplification resulting from environmental degradation. We submerged Alchornea glandulosa leaves in litter bags in nine streams, in Southern Brazil, in an environmental gradient. We characterized breakdown rates (k), physical in-stream characteristics, abundance of invertebrate taxa, and functional groups and microbial biomass for each stream, with three mesh exclusions (fine, medium, coarse). Breakdown was faster in the most preserved stream (k = − 0.032 ± 0.005) and decreased towards the most disturbed stream (k = − 0.0034 ± 0.001). Breakdown rates were positively associated with underwater habitat complexity, equitability of macroinvertebrate taxa, and abundance of Stenochironomus sp., which together explained 51% of breakdown rate variability. Breakdown rates from the less disturbed streams (n = 7, excluding urban-influenced) were lowest in medium-mesh, intermediate in fine-mesh, and highest in coarse-mesh bags, and the only taxon that differed according to this pattern was the mining-chironomid Stenochironomus sp., which suggests that this taxon had a significant activity of leaf processing. [ABSTRACT FROM AUTHOR]

We aimed to study the responses of fish functional diversity to El Niño Southern Oscillation (ENSO) in different environments from the upper Paraná River floodplain (UPRF), Brazil. We predicted that (i) El Niño events intensify floods in the UPRF and, consequently, promote functional convergence of the fish assemblage and (ii) different functional traits will be favored in El Niño or La Niña events. The functional convergence was measured through functional dispersion and functional redundancy indexes, wherein lakes presented higher similarity during El Niño and lower similarity during La Niña. ENSO did not have a strong effect in rivers. The functional richness and functional evenness did not respond to ENSO events. Fish with parental care and invertivorous fish were favored during El Niño, while piscivorous and herbivorous fish were favored during La Niña. Due to their distinct lifecycles, long-distance migratory fish responded to this climatic oscillation 1 year after El Niño. Overall, the influence of ENSO on fish diversity in the UPRF is a complex phenomenon. However, even with other local and regional factors acting on the ichthyofauna, fish diversity responded to these climatic fluctuations. [ABSTRACT FROM AUTHOR]

Fishers' ecological knowledge (FEK) has contributed to a better understanding about the reproduction of fishery resources, especially where biological data are scarce or unavailable. We analyzed FEK on the reproduction of five fishery resources in the Paranaguá estuarine complex and adjacent coastal area, Brazil, including fishes (Genidens barbus, Centropomus parallelus, Chaetodipterus faber, Pseudobatos sp.) and shrimp (Litopenaeus schmitti). We also sought to compare FEK with biological data and investigate which characteristics (age, fish evisceration and fishers' location) influence fishers' knowledge. We interviewed 132 artisanal fishers. FEK indicated reproductive peaks in the spring and summer for the fish species and in late winter and early spring for the shrimp. The maturation sizes according to FEK did not differ from sizes at first maturity (L50) as reported by biological studies for G. barbus and L. schmitti. Fishers' residence sites and fish evisceration influenced more their knowledge related to species reproduction than age. Fishers showed a detailed ecological knowledge about some reproductive aspects, including size at first maturity of females, site of occurrence and reproductive peaks. Furthermore, fishers were able to identify sexual dimorphism, parental care and ovoviviparity. These results can be applied to improve fisheries management in the context of data poor fisheries. [ABSTRACT FROM AUTHOR]

While warming and eutrophication have increased the frequency and magnitude of harmful cyanobacterial blooms globally, the scenario for many eutrophic tropical freshwaters is a perennial year-round bloom. Yet, the drivers of persistent blooms are less understood when conditions such as light, temperature, and nutrients favor cyanobacteria growth year-round, and especially in regions facing recurrent periods of drought. In order to understand the drivers of cyanobacteria dominance, we assessed the abiotic conditions related to the abundance and dominance of the two dominant bloom-forming genera Raphidiopsis and Microcystis, in six shallow, man-made lakes located in the semiarid Northeastern region of Brazil during a prolonged regional drought. Lower water level corresponded to increased phosphorous and nitrogen concentration and, consequently, phytoplankton biomass. Cyanobacterial biomass was also proportional to phosphorus concentrations during year-round blooms. Yet, the two dominant cyanobacterial genera, Raphidiopsis and Microcystis, seldom co-occurred temporally and the switch between them was driven by water transparency. Our results illustrate the effects of drought induced water level reductions on the biomass and composition of cyanobacterial blooms in tropical shallow man-made lakes. Given the ideal year-round conditions (i.e., high light and temperature), droughts may be expected to intensify the risk and multitude of problems associated with eutrophication. [ABSTRACT FROM AUTHOR]

Agribusiness is one of the main economic activities in Brazil, which caused the removal of much of its natural vegetation for the expansion of monoculture areas. Once aquatic environments have a direct relationship with the surrounding terrestrial environment, it is essential to understand the monocultures' impact on adjacent streams and, especially, how aquatic communities react to these impacts. Our aim was to verify the effects of different monoculture types on stream benthic macroinvertebrate and fish communities' structure. We compared the environmental characteristics and these communities' structure in four streams located in native vegetation areas and four in each of three monoculture types (sugarcane, citrus, and eucalyptus), all belonging to the Paranapanema River basin, Southeastern Brazil. We found lower pH and dissolved oxygen and higher total phosphorus and fine substrate values in monoculture streams and these variables were also related to the lower abundance of macroinvertebrate groups more sensitive to environmental impacts. However, we did not find differences in fish communities or in their relationship with the different environmental characteristics observed. We also did not observe differences between the monoculture types in all comparisons made, which demonstrate that these plantations, although have different cultivation characteristics, cause similar negative impacts in the streams. Our study demonstrates the physical and chemical impacts of monoculture development on stream headwater communities. Regulatory measures such as increased riparian vegetation and contour farming and terracing may be critical to protect and restore headwater streams from monoculture impacts. [ABSTRACT FROM AUTHOR]

Inter-basin water transfer (IBWT) involves the transport of water from one geographically distinct basin to another to balance the distribution of water resources. Although the socio-economic benefits of implementing these projects are well recognized, little is known about the subsequent effects on the water quality of the receiving systems. We evaluated the effects of an IBWT on the water quality of three receiving reservoirs of an intermittent river in a semi-arid region. We compared the similarity among the reservoirs before and after the IBWT to assess how the reservoirs responded to the introduction of water. Although the last two reservoirs that have received water have become similar in terms of physical and chemical characteristics and algal biomass (chlorophyll-a), the first reservoir has not. The IBWT resulted in an improvement in the water quality of the first reservoir but a decrease in the water quality of the two successive reservoirs, along with a significant increase in algal biomass. Long river sections located upstream that were dry at the time of IBWT probably contributed nutrients to the water as it moved downstream and into the reservoirs. Significant differences in the water quality were observed for different sampling months after the IBWT, but not for different sampling depths. Before the IBWT, the predictor variables for algal biomass were basically transparency and non-algal turbidity, with which it established a positive relationship. After IBWT, however, algal biomass also showed a positive relationship with pH and temperature. We conclude that IBWT affects the water quality of receiving reservoirs and that the responses are reservoir specific. IBWT also increases the complexity of the correlations of physical and chemical variables with algal biomass. [ABSTRACT FROM AUTHOR]

Non-native freshwater fish introduced via the aquarium trade can cause major changes at the community level over time and space, resulting in dynamics context dependencies within homogenization process. We investigated fish biodiversity in anthropogenically impacted headwater creeks (i.e., under elevated propagule pressure) located in southeastern Brazil, through a standardized sampling program. We assessed ichthyological community composition with the aim of quantifying spatio-temporal dynamics across creeks. We divided the sampling period according to decades, in which "2000s" represented 2003, 2004, 2005, and 2006, while "2010s" represented 2015. Changes in pairwise community similarity indicated biotic homogenization in the 2000s (i.e., communities became more similar over time). In contrast, changes in pairwise similarity in the 2010s indicated biotic differentiation. We suggest that these changes are caused by the extirpation of both native and non-native species due to environmental degradation and the occurrence of six new non-native species. The beta-diversity increased between sampling seasons and creeks across decades, also indicating biotic differentiation. Our study provides strong evidence for a transition phase from biotic homogenization to differentiation of fish communities over time, caused by interaction between older environmental degradation and more recent impacts from the Brazilian aquarium trade, reinforcing the importance of simple, practical, and inexpensive long-term studies to understand biodiversity-related processes. [ABSTRACT FROM AUTHOR]

Paraleucilla magna was the first sponge recognised as alien in the Atlantic. It was first registered in Rio de Janeiro (Brazil) and soon became very abundant in the southeastern and southern coasts of Brazil and also in the Mediterranean. Its origin is still unknown but recurrent introductions seem to have occurred in the Mediterranean. In this study, we used genetic markers (microsatellites) to test if Brazilian and Adriatic populations share a single source or if multiple introductions occurred in both regions. We also compared the genetic composition of populations established almost 30 years ago (Brazil) with a recently founded population (Adriatic—less than 10 years). Populations of P. magna were sampled in four localities across 900 km in the Southwestern Atlantic (Brazilian coast) and in one locality in the Adriatic (Croatian coast). Our results suggest the presence of five genetically distinct populations possibly originated by multiple human-mediated introductions from different sources and show that the putative most recently established population is genetically more diverse. [ABSTRACT FROM AUTHOR]

Floodplain lakes are good metacommunity systems to study the environmental and spatial processes structuring local assemblages. They are more connected during high-water periods and are more isolated during low-water periods. We evaluated the effects of lake spatial patterning and water and sediment conditions on Unionida species assemblages. Moran Eigenvector Maps were used to generate spatial variables representing spatial patterns at different scales. We sampled 35 lakes from the Pantanal floodplain, Brazil. To understand the effects of environmental and spatial variables, we performed Redundancy Analyses and variation partitioning to separate environmental and spatial pattern effects. Environmental variables explained almost twice the variation in the Pantanal mussel assemblages than did spatial variables. Unionida species presence was driven mainly by variations in sediment coarse sand and silt contents. The weak spatial patterns observed may be related to increased connectivity between lakes during floods, which facilitates mussel host fish dispersal. Mussel abundances were driven mainly by organic matter availability, but varied between species. Changes in lake connectivity can affect the regional sediment dynamics and affect mussel assemblages. [ABSTRACT FROM AUTHOR]

Studies based on functional approach seek to understand the ecological roles developed by species as well as their interactions with the environment in which they are inserted. The hypothesis tested was that functional richness and diversity of molluscan community will be higher at the most complex macroalgal habitat. The study was carried out at Casqueira river estuary (Rio Grande do Norte, Brazil). Three species of macroalgae were collected—Gracilaria domingensis (Kützing) Sonder ex Dickie 1874, Gracilaria cuneata Areschoug 1854, and Solieria filiformis (Kützing) P.W.Gabrielson 1985—and the composition of seven functional traits of the mollusk fauna associated to the algae was characterized in 22 categories. The highest values of functional richness and diversity were for macroalgae with greater habitat complexity (G. domingensis). Some functional traits were influenced more by macroalgal morphology, like 'life way,' feeding strategy, body size, and larval development. Thus, we show that the greatest richness and functional diversity of the communities is related to sites with more complex habitat, sites with more shelter and refuge, and food. This highlights the importance of the quality of habitat for shellfish communities and shows that it can be assessed from the use of a functional approach. [ABSTRACT FROM AUTHOR]

Integrative approaches are particularly useful to resolve taxonomic uncertainties in species-rich groups that have undergone explosive radiation, such as Hypostomini (suckermouth armored catfishes). This tribe encompasses the genera Hypostomus and Pterygoplichthys, but the actual number of species in each genus and the intergeneric interrelationships are confusing or unknown for some ecoregions in the Neotropics. Here, we analyzed three endemic species Hypostomus chrysostiktos, H. jaguar and H. unae from Northeastern Mata Atlântica in northeastern Brazil based on meristic characters, geometric morphometrics, chromosomal data, DNA barcode and species delimitation algorithms. The current taxonomic status of these catfishes is challenged. While H. unae and H. jaguar revealed a close evolutionary relationship similar to those observed within Hypostomus from other basins, H. chrysostiktos was herein more closely related to Pterygoplichthys, being invariably recovered as a highly distinctive taxonomic unit than to Hypostomus. Therefore, we recommend the reallocation of H. chrysostiktos as Pterygoplichthys chrysostiktos and a thorough systematic review of Pterygoplichthys, particularly focusing on putative convergence traits in relation to Hypostomus. [ABSTRACT FROM AUTHOR]

Coastal ecosystems can vary considerably in their habitat characteristics and environmental conditions, resulting in divergent fish community structures. However, comparisons among coastal systems, such as oceanic beaches, bays and coastal lagoons, have not been thoroughly evaluated. We test the hypothesis that coastal systems that differ in wave exposure, habitat structure, salinity gradients and productivity show different assemblages and feeding guilds. The fish assemblages were significantly different among the systems. The bays had the largest number of species, whereas the lagoons had the highest numerical abundance and biomass. The planktivorous guild dominated in numerical abundance in all systems, whereas the opportunists dominated in biomass. The benthivores contributed greatly in abundance to the bays, the opportunists to the coastal lagoons, and the hyperbenthivores to the oceanic beaches. Water transparency and temperature explained a small portion of the variation in the community structure. This study highlighted the complex role that local factors have on the distribution of fishes at the species and trophic levels. These approaches were efficient to describe the structure and functioning of the assemblages in these different coastal systems. This should be viewed as essential for any comparisons of coastal systems, and in particular for conservation planning. [ABSTRACT FROM AUTHOR]

The saddled blenny Malacoctenus triangulatus is a widely distributed species of cryptobenthic reef fish that occurs from the Caribbean to southeastern Brazil, including the oceanic islands. Subtle morphological differences have been observed between populations, suggesting some degree of structuring along its distribution, especially between insular and coastal environments. In this study, we conducted phylogeographic analyses of M. triangulatus based on mitochondrial (cytochrome oxidase I and cytochrome b) and nuclear (rhodopsin) genes, including sequences of M. brunoi, a closely related species endemic to the oceanic islands of southeastern Brazil. Three highly structured lineages were identified within the M. triangulatus complex: one restricted to the Caribbean province probably isolated by the Amazon barrier, and two in the Brazilian province, one in the northeastern oceanic islands (NOI) and another along the coast (including M. brunoi). This result indicates that divergent evolutionary processes have driven the evolution of the saddled benny in the Tropical Southwestern Atlantic: an ancient isolation of the NOI lineage during the Neogene and a recent ecological speciation event in the southeastern oceanic islands, which were connected to the coast during Pleistocene marine regressions. Together, these results provide insights on the evolutionary patterns and oceanographic barriers in the Western Tropical Atlantic. [ABSTRACT FROM AUTHOR]

This paper describes a previously unknown ctenopod crustacean of thefamily Sididae, collected in Brazil and Venezuela which, along with the forms known as Diaphanosoma volzi, displays distinctive characteristics that are here recognized as being of generic magnitude. Phenetic analysis of the species within the family Sididae, supports the hypothesis that Neodiaphanosoma constitutes a well defined group, differentiated enough from Diaphanosoma to be accepted as a different genus. The new genus seems to be a group of specialized species, close toDiaphanosoma with advanced features. Some features shared with Sarsilatona, Latonopsis and Pseudosida probably reflect convergence related to littoral habitat more than ancestry. [ABSTRACT FROM AUTHOR]

In the present work, we attempted to characterize two isolates of Cylindrospermopsis raciborskii, LP1 and LP2, from Peri Lagoon, for their morphology, ecophysiology, and toxin profiles. The genetic identity of the isolates was confirmed by amplifying and sequencing 16S rRNA. The isolates showed different morphologies and significant differences in the length of trichomes. LP2 showed a trend for higher growth rates than LP1 at the different temperatures and N:P ratios. Both isolates showed low light requirements, but were able to tolerate irradiances of around 200 μmol photons m s. LP2 showed higher concentrations of saxitoxin than LP1 and wider range of analogs, therefore being considered more toxic. These results support the hypothesis of ecotype selection for this species, which probably originated in response to environmental fluctuations in Peri Lagoon. Dominance during almost the entire year can be explained by the alternation of these ecotypes in the total biomass contribution according to their physiological advantages, contributing to the ecological success of this species. [ABSTRACT FROM AUTHOR]

Dam construction alters flow regimes and can change the composition of aquatic communities. Using data from three Brazilian hydrographic basins, we tested the hypothesis that reservoir cascades act as environmental filters for fish traits. This dataset included information on different environmental variables and fish traits (diet, migration, fecundation, parental care, position in the water column, and body size), and we used multivariate analysis (partial RLQ) to quantify the relationships between environmental variables, species abundance and traits. We found that the abundance of migratory species declined towards downstream reservoirs, which tend to be smaller and less turbid with a shorter water residence time than upstream reservoirs. We also found evidence of an association between reservoir age and the domination of fish communities by small-sized species with parental care, external fecundation, and benthic habits. Our findings suggest that particular fish traits are selected for across reservoir cascades. [ABSTRACT FROM AUTHOR]

Understanding the distribution patterns of species and how spatial and environmental factors drive the structure of communities is crucial to the preservation of biodiversity. We evaluate, during the low and high water periods, the phytoplankton diversity in lakes of four Brazilian floodplain systems (FPs): Amazon, Araguaia, Pantanal, and Paraná. We hypothesized that (i) species variation/replacement among floodplains (β) is the predominant mechanism in shaping phytoplankton gamma diversity; (ii) the variation in phytoplankton taxonomic composition within each floodplain (β) is mainly governed by local environmental conditions due to the high dispersal ability of phytoplankton at small spatial scales; and (iii) variation in the phytoplankton taxonomic composition among floodplains (β) is mainly influenced by dispersal limitation. Variation partitioning was used to evaluate the influence of spatial and environmental factors on species richness. Higher γ diversity was found in the Araguaia and Amazon FPs. The high contribution of β (large scale) to γ diversity revealed the high degree of environmental heterogeneity in each floodplain. β (small scale) was more influenced by environmental variables, and β by both spatial and environmental factors. Our findings showed that γ diversity was explained by the interaction between the two factors, and that these processes influencing variation were scale dependent. [ABSTRACT FROM AUTHOR]

The discontinuity in rivers caused by the construction of reservoirs disrupts the longitudinal gradient and decreases the natural connectivity of lotic systems. We evaluated the dynamics of Reynolds functional groups (RFGs) in response to the formation of a subtropical reservoir, in relation to the environmental changes between the pre- and post-impoundment periods. We hypothesized that the disruption of longitudinal connectivity and the changes in the light and mixing regime after the impoundment would directly influence the phytoplankton functional structure. Significant changes in the light and mixing regimes were observed after the impoundment, with the formation of a lacustrine zone, influencing the dynamics of RFGs. Fourteen RFGs were recorded. RFG C (diatoms) dominated in the pre-impoundment period. In the post-impoundment period, RFGs C, P (diatoms), and J (chlorophyceans) codominated with the highest mean values of biovolume. RFGs MP, N, H1, W2, F, E, A, W1, B, X1, and S1 contributed relatively little to the biovolume, although with higher values in the post-impoundment period. RFGs F and S1 were recorded only after the impoundment. This study revealed the important roles of physical processes and nutrients in the spatial and seasonal gradient, and in the selection of phytoplankton functional groups in a subtropical reservoir. [ABSTRACT FROM AUTHOR]

We analysed the fishermen's perceptions on the South American sea lions ( Otaria flavescens) and its interactions with the local fishery close to the Wildlife Refuge of Ilha dos Lobos, a marine protected area in southern Brazil. Sea lions prey upon the same resources targeted by the fishermen. They repeatedly hunt on the nets and consequently damage them. In response, fishermen persecute sea lions. However, in conflicts with high-profile animals, the perceived damage often exceeds the actual evidence. Results from 100 interviews revealed that fishermen's perception of damage and their attitudes were affected by age, hierarchical position in the crew, if fishing was the only source of income, and level of formal education. Greater perception of damage and more negative attitude were found among older, less educated sailor fishermen who had no other source of income besides fishing. The average fisherman had a relatively good knowledge about sea lions, but also a negative attitude towards them. We recommend actions addressing these negative attitudes through environmental education, with emphasis on adjusting exaggerated perceptions of impact and the potential of the species for wildlife tourism, as a vital step towards the conciliation of sustainable fisheries and O. flavescens conservation in the Brazilian coast. [ABSTRACT FROM AUTHOR]

Two coastal locations situated inside and outside an upwelling area were investigated to assess the influence of environmental factors on the structure of marine shrimp assemblages. The locations were Macaé in the state of Rio de Janeiro (RJ), influenced by upwelling from Cabo Frio (RJ), and Ubatuba in the state of São Paulo, with no upwelling. Samples were collected monthly with trawl nets, in three sites in each location at depths of 5-20 m. The relationship between species abundance and environmental factors was tested by redundancy analysis. The total of 148,266 shrimp captured (102,832 from Macaé and 45,434 from Ubatuba) included 15 species, 13 genera, and 7 families. The caridean Periclimenes paivai was collected for the first time on the RJ coast, expanding its known geographical distribution. Higher richness and J′ and H′ values were obtained in the location under upwelling influence (Macaé). Environmental variables (granulometric composition and organic-matter content of sediment, bottom temperature, and salinity) were associated with the abundance of shrimp. Our results suggest that sediment type and temperature are among the most important variables affecting seasonal distribution of the species. However, other factors such as intraspecific migration might have also influenced the observed patterns. [ABSTRACT FROM AUTHOR]

Five years of water quality data from six stations across the mesotrophic and oligomictic Lajes Reservoir (Brazil) were utilized to develop 7-day ahead forecasting models for the picocyanobacteria Cyanodictyon imperfectum, Cyanogranis ferruginea and Synechococcus sp. by means of the hybrid evolutionary algorithm HEA. The data included physical and chemical water quality parameters as well as abundance data of the three picocyanobacteria. Models based on site-specific data of six monitoring stations forecasted population dynamics of Synechococcus with coefficients of determination ( r) between 0.58 for and 0.88, of Cyanodictyon with r between 0.5 and 0.89 and of Cyanogranis with r between 0.53 and 0.77. Despite phosphorus limiting conditions the sensitivity analysis revealed that the three picocyanobacteria responded much stronger to nitrate rather than to phosphate concentrations throughout the Lajes Reservoir suggesting that cyanobacteria may have adopted the sulphur-for-phosphorus strategy by utilizing sulfolipids instead. Cyanogranis displayed a negative relationship with increasing water temperature indicating its higher competitiveness at internal nutrient supply and low light levels during winter turnover. The resulting models will inform operational intervention and prevention of fast growth and dispersal of picocyanobacteria in Lajes Reservoir, and reveal environmental thresholds for outbreaks of such events. [ABSTRACT FROM AUTHOR]

Ecological studies are usually based on species abundance data per sample. As a consequence, the research can be time-consuming and require a significant amount of financial resources to overcome uncertainties in taxonomic identifications and estimations of relative abundances. We assessed the use of genus-level data as a surrogate for species-level data in studies attempting to describe the beta-diversity patterns of several aquatic communities. Furthermore, we investigated whether presence-absence data is sufficient to describe ecological patterns and whether the spatial variation of rare species can also be described by genus-level data. We used data from five biological aquatic groups sampled over periods of up to 2 years in different sites of the Upper Paraná River floodplain. We found strong evidence that beta-diversity patterns in species-level data can be successfully described using genus-level and presence-absence data in all biological groups, although efficacy of using genus-level data as a surrogate for species-level may depend on the species:genus ratio. Moreover, communities with both taxonomic resolutions had similar responses to environmental variation. Our results indicate ecological studies in floodplains with different biological groups can benefit from strategy based on genus-level or presence-absence data to reduce cost and time. [ABSTRACT FROM AUTHOR]

Groupers are large-bodied fishes with broad global distribution and commercial and ecological importance. Many grouper species are endangered, but information on trophic ecology of groupers outside the Mediterranean Sea is limited. We integrated stomach contents analyses (SCA) and stable isotope analyses (SIA) to test the hypotheses that diets of dusky grouper Epinephelus marginatus differ between littoral and neritic zones in the southwestern Atlantic, but exhibit similar ontogenetic shifts in prey size and consumption of fishes. SCA were dominated by fishes, crabs, and shrimp and differed significantly between habitats, but prey size and consumption of fishes increased with grouper body size at both sites. Grouper stable isotope ratios were similar between sites and among size classes, but integrating SCA and SIA distinguished ingested versus assimilated dietary components, improved dietary resolution, and provided a more comprehensive assessment of grouper in the food webs. Dusky grouper integrate benthic and pelagic trophic pathways, as well as estuarine and marine food webs via consumption of migratory prey. Our findings have applications to other threatened grouper populations, for example, in managing fragmented populations or for reserve designs considering inclusion of artificial substrates as grouper habitat, and more broadly for approaches examining trophic ecology of generalist predators. [ABSTRACT FROM AUTHOR]

Small and shallow lakes make up most of the lake-covered area in the world, and immature Chironomidae generally constitute the dominant group among invertebrates in these systems, exhibiting a wide distribution and tolerance to various levels of water quality. The changes in trophic features associated with the dominance of different major primary producers (macrophyte and phytoplankton) are reflected in the functioning of these ecosystems and likely in their phytophilous Chironomidae species richness and abundance. These were thus studied in a Brazilian shallow lake over a 11-year period characterized by both clear and turbid water conditions in relation to water quality and dominant macrophytes. The results revealed differences in Chironomidae composition but not in richness associated with clear and turbid waters. The Goeldichironomus genera predominated during all years and for different macrophyte types (freefloating, floating leaf, and submerged). We attribute the variability of Chironomidae assemblages to changes in macrophyte dominance and water trophic status, such as the concentration of nutrients and chlorophyll- a, during the 11-year period. Submerged macrophytes were associated with clear waters and harbored the highest diversity, which emphasized the importance of these environmental conditions for preserving the biodiversity of Chironomidae in shallow lakes. [ABSTRACT FROM AUTHOR]

In the last decade, dozens of indices based on macroinvertebrates were developed to evaluate lotic ecosystems. In contrast, very few of these indices have been applied in lentic ecosystems. Natural wetlands in southern Brazil are increasingly threatened by the expansion of irrigated rice. The main objective of this study was to develop a multimetric index based on macroinvertebrates to evaluate the water quality of natural wetlands and rice fields in southern Brazil. Three samplings were carried out over the rice growth cycle in four conventional and four biodynamic rice fields, and four natural wetlands. The wetlands were considered as reference sites, and the conventional and biodynamic rice crops were considered as manipulated sites at different levels of degradation. Seven metrics were included in the final index after passing though sensitivity and correlation tests. The results indicated that our index has a power to detect a gradient of variation in water quality. Natural wetlands had the best water quality, biodynamic crops had intermediate water quality, and the conventional crops had the lowest water quality. We believe that development of this macroinvertebrate-based multimetric index of water quality could be an important tool for monitoring natural wetlands and rice crops in southern Brazil. [ABSTRACT FROM AUTHOR]