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Cell coverings can be observed in all major groups of organisms, which include animals, plants, fungi, protists and prokaryotes. They play a key role in assuring cell survival or adaptation to certain environmental conditions. Since the term algae refers to a polyphyletic and very artificial group, the cell coverings of these organisms are very diverse in molecular composition and with different arrangements. Differences have taxonomic value since they allow microalgae phyla or even minor taxonomic groups, such as classes, orders or families, to be distinguished. Understanding the structure of cell coverings is also fundamental for the use of microalgae to obtain products of commercial value. Despite its importance, the composition and architecture of microalgae coverings is still poorly understood, especially considering the great diversity of organisms. Diatom frustules are the most studied coverings due their uses in areas of bio- and nanotechnology. There is a lack of information about the cell wall, lorica, periplast, amphiesma and scales. This study is a review with the aim of synthesizing literature information on microalgae cell coverings to describe their compositions, arrangements, functions and industrial uses.

We have studied the isolated and combined effects of metals (Fe and Mn) and NaCl the on growth, physiology, and metal-uptake capacity of two photosynthetic periphytic species—Synechococcus elongatus (Cyanobacteria) and Chlorococcum infusionum (Chlorophyta)—isolated from an impacted area of the Rio Doce River (Brazil) after the Fundão dam collapse. The effective concentrations found to reduce 10 and 50% growth were 15.2 and 31.6 mg Fe L−1, and 2.5 and 7.9 mg Mn L−1 for S. elongatus and 53.9 and 61.6 mg Fe L−1, and 53.2 and 60.9 mg Mn L−1 for C. infusionum. Although the metal toxicity was related to oxidative stress, both species showed activation of antioxidant systems under phytotoxic concentrations of Fe and Mn. By binding large concentrations of metals on its cell surface and thus avoiding their entrance into the cells, C. infusionum presents greater resistance to Fe and Mn than S. elongatus. Under environmental realistic concentrations of Fe and Mn in river water from the Rio Doce Basin, S. elongatus and C. infusionum showed a metal removal efficiency of 42 and 65% and 53 and 79%, respectively after 96 h. These species were insensitive to increased NaCl concentrations which, in addition, did not disrupt the metal removal capacity of the species. Due to their salt and metal tolerance, S. elongatus and C. infusionum can be used for the remediation of waters contaminated with Fe and Mn.

We investigated the occurrence and risk assessment of three anti-HIV drugs [(tenofovir (TNF), lamivudine (LMV) and efavirenz (EFV)] in urban rivers from Curitiba (Brazil), as well as the individual and combined effects of their environmental representative concentrations on the freshwater periphytic species Synechococcus elongatus (Cyanobacteria) and Chlorococcum infusionum (Chlorophyta). The three studied drugs, except TNF, were found in 100% of the samples, and concentrations in samples ranged from 165 to 412 ng TNF L

Made available in DSpace on 2021-06-25T10:29:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-08-10 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) It has been postulated that eutrophication causes replacement of n3 highly unsaturated fatty acids (n3 HUFA) rich taxa, such as Bacillariophyta, Cryptophyta and Dinophyta, with taxa poor in these fatty acids (FA), such as Chlorophyta and Cyanobacteria. Such a change in community composition at the basis of the food web may alter the FA composition of consumer tissues. Here, we investigated the effects of eutrophication on phytoplankton composition and FA profiles of seston and muscle of two omnivorous fish species (Astyanax fasciatus and Astyanax altiparanae) from reservoirs of different trophic status in Southeast Brazil. The phytoplankton composition and seston FA profiles reflected the degree of eutrophication at most of the studied sites. Three of the five most eutrophic sites were dominated by cyanobacteria and had the highest saturated fatty acid (SFA) and lowest polyunsaturated fatty acid (PUFA) relative contents among all sites. In contrast, the remaining two sites presented a higher phytoplankton diversity and higher relative contribution of sestonic PUFAs with 18 carbons (C18) and HUFAs than less eutrophic systems. However, there were no clear effects of sestonic FA profiles on the FA profiles of muscle of both fish species. A higher percentage of n3 HUFAs was found in the fish samples from a hypereutrophic and cyanobacteria dominated reservoir than in those from sites with a more diverse phytoplankton community in which fish mainly showed higher percentages of C18 PUFA. These results suggest a lack of a direct relationship between the degree of eutrophication and the percentage of n3 HUFAs in both fish species, which can be caused by specific characteristics of the reservoirs that may modulate eutrophication effects. Therefore, consumer FA biochemistry seemed to be dictated by their ability to select, accumulate, and modify dietary FAs, rather than by the eutrophication degree of the studied tropical reservoirs. Departamento de Fisiologia Instituto de Biociências Universidade de São Paulo, Rua do Matão, 101 Departamento de Geociências Universidade Federal São João del-Rei Universidade Anhembi Morumbi, Campus Mooca Departamento de Botânica Universidade Federal de Minas Gerais Centro de Pesquisa de Recursos Hídricos Instituto de Pesca Departamento de Ecologia Instituto de Biociências Universidade de São Paulo Universidade Estadual Paulista (Unesp) Instituto de Ciência e Tecnologia Universidade Estadual Paulista (Unesp) Instituto de Ciência e Tecnologia FAPESP: 2014/16320-7 FAPESP: 2016/07363-0 FAPESP: 2017/11530-1

Discharge of untreated wastewater into freshwater ecosystems increases nutrient concentrations, causing eutrophication and demanding more intensive monitoring and control activities, particularly in developing areas. Two approaches are commonly used for assessing trophic states of rivers: (1) physicochemical trophic state indexes (TSIs), and (2) trophic indexes based on bioindicators, mainly periphytic diatoms (TDIs). Even when these two approaches seem to be very different, they can be complementary under certain circumstances. This is the case with Rio Chili (Arequipa, Peru), a shallow regulated river used for multi-purpose activities, but which is highly polluted due to the discharge of municipal wastewater. The present study assessed the suitability of different TSIs and TDIs by processing data from historical water quality registers and recent monitoring, including periphytic diatom sampling. TDIs were compared with TSIs applied to both recent and historical records. Results indicated that TSIs can be easily obtained from measurements of phosphorus concentrations, but they are less sensitive and resulted in a high degree of homogeneity among the classification of trophic conditions along the urban path of the river. Alternatively, TDIs showed higher precision and sensitivity, reporting detailed classifications of the sampling points. TDIs suggested that Rio Chili presented conditions that varied from mesotrophic to eutrophic as consequence of wastewater discharges and soil occupation. A routine use of TDIs with occasional assessment by physicochemical TSIs may contribute to water quality sustainability by informing managers of the effects of organic and phosphorus pollution on eutrophication at a lower cost.

Phytoplankton community assessment using functional groups is a powerful tool for lake and reservoir biomonitoring, but its efficiency has only been tested in intersite, low-frequency datasets. Here, we took advantage of a gradient of spatially close, but environmentally contrasting, meso- to hypereutrophic reservoirs in Southeast Brazil, to compare the efficiency of morphology-based functional classification (MBFC), phylum-level, and species-level classification for high-frequency, i.e. monthly, biomonitoring. Monitoring of water physical and chemical characteristics revealed the presence of two independent environmental gradients, with the first being related to total phosphorus and suspended solids concentrations, as well as Secchi depth, and the second related to dissolved inorganic nitrogen, water temperature and pH. The species approach had the highest power to explain environmental variation in assemblage structure (21% vs 16% and 17%, in the phylum and MBFC approaches). Although both simplified classifications showed similar explanatory power, MBFC allowed a better differentiation of reservoir assemblages. As the MBFC approach is also the least resource intensive, it may be preferable for routine biomonitoring, or to process large sample numbers. Nonetheless, species-level classification provided the most detailed information on assemblage dynamics and is therefore an important option for scientific studies.

Low red-LED irradiances are an attractive alternative for enhancing microalgae photobioreactors treating digestate due to their potential contribution in decreasing area footprints with low energy consumptions. However, more information is required regarding the influence of digestate load on treatment performance and biomass valorisation when low-intensity red-LEDs are applied. Thus, this study assessed microalgae-based photobioreactors treating food waste digestate under different concentrations (5%, 25%, 50%, and 75%, v/v) at low red-LED irradiance (15 µmol·m−2·s−1). The removal efficiencies of soluble chemical oxygen demand (sCOD) at the end of the experiment ranged from 45% to 75% when treating influent loads between 5.3 and 79.1 g sCOD·m−3·d−1 (5% and 75%-digestate), respectively. Total ammonia nitrogen (TAN) was applied in loading rates between 3.2 and 48.5 g TAN·m−3·d−1 (5% and 75%, respectively) and removed with maximum efficiencies of 90%–100% in all trials. Nitrification-denitrification was proportionally more relevant when treating 5%-digestate, whereas volatilisation was the primary process in 25%, 50% and 75% concentrations. Microalgae presented adequate yields in all treatments, except in 75%-digestate, likely due to the blocking of light by the high solids concentrations. The assessment of the microalgae community and chlorophyll-a and carotenoids suggested that chlorophytes, mainly Dictyosphaerium pulchellum and Scenedesmus sp. grew autotrophically, whereas cyanobacteria Pseudanabaena sp. grew mixotrophically. Moreover, the sustainability of red LED lighting applications can be increased by anaerobic digestion or agricultural valorisation of the biomass, enabled by its high N and P contents. Low-intensity red-LEDs may have promissory applications in the treatment of high-strength wastewaters.

Aquaculture impacts on aquatic organic matter and ecosystem integrity are poorly understood, especially in tropical regions. Here, we investigated the impacts of Nile tilapia net cage farming on the elemental stoichiometry, fluorescence components, and stable isotopes of dissolved organic matter (DOM) of the large, tropical Furnas Reservoir (SE Brazil). Early-stage fish farming, i.e., relatively small and recently implemented farms, had detectable incipient effects on DOM characteristics, and these effects differed between reservoir branches. In the less eutrophic Rio Grande branch of the reservoir, we found a reduction in natural humic-like DOM components and an increase in a protein-like DOM component as far as 100 m away from fish farms. Further, we observed a decrease in δ15N-TDN due to fish farming. In the more eutrophic Rio Sapucai branch, there were only local decreases in C:N ratios, as well as rises in C:P and N:P of DOM due to fish farming. These results suggest that early-stage fish farming had local but detectable effects on aquatic DOM that depended on previous eutrophication levels and highlight the need to assess the early impacts of fish farming on tropical reservoirs by combining different monitoring strategies.

Fatty acids (FAs) and their metrics have been used to detect and assess the impacts of urbanization and agriculture on aquatic ecosystems. Here, we investigated whether seston FAs are also useful to characterize and understand early-stage aquaculture impacts in a large tropical reservoir (Furnas Reservoir, SE Brazil). We tested the hypothesis that single FAs, as well as selected FA metrics in the seston fraction, are efficient markers of net-cage fish farming effects. In general, fish farming had only minor effects on standard water chemical variables, mainly small increases in ammonium, nitrate, and dissolved organic nitrogen concentrations. By increasing concentrations of several polyunsaturated FAs, early-stage fish farming improved sestonic food quality in the more oligotrophic branch of the reservoir under drought conditions. However, in general, increases in concentrations of bacterial FAs, due to fish farming, suggested organic matter (OM) subsidies from non-ingested and non-assimilated fish feed. In the more eutrophic reservoir branch, seston FA profiles suggested that fish farming caused an increase of low-quality food resources, such as cyanobacteria. Thus, background impact levels may determine the biochemical responses of tropical reservoirs to fish farming. Higher contributions of potentially sewage-derived and bacterial FAs during drought conditions, especially at reference sites of the more oligotrophic branch, suggested that drought shifted OM inputs towards anthropogenic sources, thereby overwriting land-use related differences between reservoir branches and homogenizing their environmental conditions. In conclusion, FA variables were useful to evaluate and understand environmental conditions, as well as the effects of early-stage fish farming and drought, and should be considered in impact assessments in tropical lentic ecosystems.

Producción Científica, Microalgae-based technologies, usually configured as high rate algal ponds (HRAP), are efficient, sustainable, and cost-effective alternatives for wastewater treatment due to their high removal efficiencies at low energy demand, ability to recover nutrients and ease of operation. HRAPs and other photobioreactors have been intensively studied in recent years for the treatment of high-strength wastewaters, which are mainly characterised by high and unbalanced (in terms of microalgae requirements) concentrations of organic carbon and nutrients. This review critically evaluated research papers that used microalgae-based systems for the removal of carbon and nitrogen from high-strength wastewaters. These systems can provide removal efficiencies up to 100% for organic matter and ammonium nitrogen. Relatively large area requirements, high evaporative losses, ammonia inhibition, poor light penetration and scattering, carbon dioxide limitation, and unbalanced nutrient ratios rank among the main current limitations of these technologies. Optimisation strategies, including modifications in bioreactor design and operation, can broaden their full-scale application for the treatment of high strength wastewaters., Conselho Nacional de Desenvolvimento Científico e Tecnológico—CNPq (Grant number 141428/2016-3), Global Challenges Research Fund (United Kingdom, grant GCRFNGR4-1207), Junta de Castilla y León y el Programa Europeo FEDER (CLU 2017-09)

Tadpoles are important components of food webs at aquatic ecosystems; however, their trophic roles remain understudied compared to fish. Morphology indicates general aspects of tadpole diets (e.g., food size), but a fine association between preferred microhabitats and diet composition remained to be tested. We tested whether syntopic tadpoles differed in microhabitat use and in diet composition according to food availability in different microhabitats. We also tested whether types of microhabitats were consistent in food availability or if food availability would vary among streams. Considering volumes of different food groups ingested, the diets of tadpoles could be partly explained by the microhabitats where they were sampled, but not by streams or even species. Considering number of items of each food group, the diet of tadpoles varied according to stream, microhabitat, and species. Volumes of items of each food group differed among microhabitats, but not among streams. All the studied species could be classified as primary consumers based on the dominance of algae (especially Zygnematophyceae and Bacillariophyceae) in their diets. Patterns of food consumption of tadpoles were complex and responded to variables at a very fine spatial scale, suggesting that they may be sensitive even to small alterations in stream dynamics.

Our objective was to determine how different morphological traits of microalgae influence their settling rates, since settling is important to population dynamics and the loss of individuals affects phytoplankton communities. We hypothesized that different morphological characteristics can affect phytoplankton settling rate, and that surface to volume ratio (S:V) would be especially important in determining the settling rhythm than any other morphological trait alone. Experiments were conducted in settling columns, which generate subsamples for quantification of phytoplankton and allow the calculation of settling rate. The dependence of settling rate on various cell characteristics was assessed by predictive models generated by non-linear regression analyses in which settling rate was the independent variable, while the dependent variable was biovolume, surface area or S:V ratio. The resulting statistical coefficients were used to compare models in terms of their capacity to describe and predict settling. The results show that phytoplankton did not follow Stokes Law of particle settling. As expected, the model based on S:V ratio was the best predictor of phytoplankton settling rate. The balance between volume and surface was more important than each characteristic alone because although increasing volume could positively affect settling rates, surface area is fundamental to determine resistance to settling.

Tadpole diet is likely to vary in response to environmental conditions and nutritional needs throughout growth and development. We investigated seasonal variation in diet composition of Bokermannohyla saxicola tadpoles and compared diets between two developmental stages with a significant difference in size. We found that the diet of B. saxicola tadpoles was dominated by periphytic algae, in accordance with their benthic habits. Considering number of cells ingested, tadpole trophic niches were broader in more advanced developmental stages. Tadpole trophic niches were narrower during the summer (wet season) than during the winter (dry season), which may reflect increased consumption of more energetic food items during the warm period when primary productivity is expected to be higher. Tadpole metabolism is likely to be higher in the summer and increased energetic needs might be supplied in this manner. However, results differed when biovolume was considered instead of number of cells ingested, with larger items assuming a greater importance and niches being usually larger in the summer. In these cases, the increased ingestion of diatoms (likely to be more nutritive) in the summer may decrease the relative importance of large algae (e.g., Mougeotia sp.) that form the bulk of the diet. Both food availability/accessibility and tadpole feeding behaviour driven by nutritional needs may influence patterns of food acquisition. Given the importance of biofilms to tadpole diet, studies on the mechanisms by which tadpole nutritional needs and environmental conditions interact are likely to provide important insights into the dynamics of aquatic food webs.

We investigated the ability of the aquatic fern Azolla to take up ciprofloxacin (Cipro), as well as the effects of that antibiotic on the N-fixing process in plants grown in medium deprived (-N) or provided (+N) with nitrogen (N). Azolla was seen to accumulate Cipro at concentrations greater than 160 μg g-1 dry weight when cultivated in 3.05 mg Cipro l-1, indicating it as a candidate for Cipro recovery from water. Although Cipro was not seen to interfere with the heterocyst/vegetative cell ratios, the antibiotic promoted changes with carbon and nitrogen metabolism in plants. Decreased photosynthesis and nitrogenase activity, and altered plant's amino acid profile, with decreases in cell N concentrations, were observed. The removal of N from the growth medium accentuated the deleterious effects of Cipro, resulting in lower photosynthesis, N-fixation, and assimilation rates, and increased hydrogen peroxide accumulation. Our results shown that Cipro may constrain the use of Azolla as a biofertilizer species due to its interference with nitrogen fixation processes.

High Rate Algal Ponds (HRAP) are a sustainable alternative for wastewater treatment. However, HRAPs must be shallow (h = 0.2–0.3 m) for adequate sunlight penetration and require relatively long hydraulic retention times (HRT, >5 d) for effective pollutant removal, which results in high area footprints. In this context, a deep HRAP (h = 1.2 m) was equipped with red light-emitting diodes (LED, 660 nm) to provide photosynthetic active radiation in the aphotic zone. A conventional HRAP (HRAP1) and the LED-enhanced HRAP (HRAP2) were operated with identical working volumes (1.25 m3) and HRT (10 d), treating digestate dilutions of 5% (Stages S-0, S-I), 25% (S-II, S-III) and 50% (v/v) (S-IV to S-VI). The HRAP2 used only 25% of the area needed by the HRAP1 but LEDs used 1.4 (S-0 to S-II), 2.3 (S-III, S-IV) and 3.4 (S-V) times the energy consumed in HRAP1. HRAP2 presented similar performance to HRAP1 during the treatment of 5% and 25%-digestate, achieving removals above 75% for TSS, COD, TAN, and TKN. However, HRAP1 showed better treatment performance at 50%-digestate, likely due to more intense light radiation induced by its shallow depth, resulting in higher microalgal activity. Biomass productivity decreased with increasing digestate concentration, showing averages in HRAP1 and HRAP2 of 9 and 3 gVSS·m−2d−1, respectively, during feeding with 5%-digestate. With 25%, average productivities ranged from 2 to 5 and 2 to 6 gVSS·m−2d−1, and from 0 to 6 and 0 to 4 gVSS·m−2d−1 with 50%-digestate, respectively. Both systems showed reasonable nitrogen and phosphorus recoveries in the biomass (TN: 8–17% and 6–34%; TP: 10–45% and 5–48% for HRAP1 and HRAP2, respectively). Nitrogen volatilization, likely as NH3, N2O, and N2, was caused by stripping and nitrification-denitrification in both systems. Our data suggest that using LED-lighting to complement sunlight in deeper HRAPs is a promising alternative for enhancing microalgae-based reactors for digestate treatment.

Allelopathy is an important ecological phenomenon influencing ecosystem dynamics. Currently, it has gained attention due to the potential applications of allelochemicals in agriculture. Allelopathic interactions have been reported in ecological relationships between plants and microorganisms, and between species of each group. These studies have been relatively descriptive, however, without interconnected views of how these molecules can affect cell biology and how they are integrated into environmental interactions. The present review provides an overview of the history, physiology, and ecological effects of allelopathy, with special focus on its occurrence between macro- and microorganisms and its ecological roles in terrestrial and aquatic environments. We have attempted to examine the interconnections between terrestrial and aquatic systems in relation to the production, dynamics, and ecological effects of allelochemicals and to discuss the possible effects of climate changes on allelopathic interactions.

A reliable and representative monitoring of phytoplankton abundance, especially cyanobacteria, is mandatory for choosing the best management or restoration strategy and for assessing its effectiveness in worldwide eutrophic lakes and reservoirs. In vivo and in situ fluorometry is expected to be faster than the traditional methods of phytoplankton counting and chlorophyll- a (chl a ) extraction and quantification. Contrary to water bodies in temperate climate, the technique still needs investigation in tropical freshwaters. We assessed the performance of a spectrofluorometer, the FluoroProbe (FP) in Lake Pampulha (Minas Gerais, Brazil), a water body where cyanobacteria are the dominant group most of the time. FP chl a concentrations were in average almost three times lower than spectrophotometric chl a concentrations and underestimation was larger when Chroococales were the dominant species. The linear response of the probe was limited to 100 μg chl a L −1 . The correlation between FP and spectrophotometric measurements was significant only for FP measurements below 100 μg chl a L −1 ( r = 0.84 , p 0.001 , n = 25 ). The correlations between FP measurements and biovolumes of phytoplankton ( r = 0.64 , p = 0.001 , n = 23 ) and cyanobacteria ( r = 0.60, p = 0.002 , n = 23 ) were significant but weaker than reported in temperate water bodies. Oscillatoriales fingerprint was the most distant from FP default fingerprint for cyanobacteria, presenting a lower relative fluorescence at 610 nm. Applying an average experimental fingerprint obtained from four dominant cyanobacteria species in Lake Pampulha allowed us to improve FP measurements compared to spectrophotometric data, especially when a single species, Planktothrix isothrix , was highly dominant. Even so, high phytoplankton biomass in Lake Pampulha led to high optical density, which disturbs FP measurements. Thus, in highly eutrophic water bodies, additional laboratory analysis is necessary to validate in situ spectrofluorometer measurements, more than in oligotrophic and mesotrophic environments.

Worldwide, eutrophication and cyanobacteria blooms in lakes and reservoirs are a great concern for water resources management. Coupling a catchment hydrological model and a lake model has been a strategy to assess the impact of land use, agricultural practices and climate change on water quality. However, research has mainly focused on large lakes, while urban reservoirs and their catchments, especially in tropical regions, are still poorly studied despite the wide range of ecosystem services they provide. An integrated modelling approach coupling the hydrological model Storm Water Management Model SWMM and the lake ecological model DYRESM-CAEDYM is proposed for Lake Pampulha (Brazil). Scenarios of increased imperviousness of the catchment and of reduction in the load of nutrients and total suspended solids (TSS) in dry weather inflow were simulated. Runoff water quality simulations presented a fair performance for TSS and ammonium (NH4+) while the dynamics of total phosphorus (TP) and nitrate (NO3&minus, ) were poorly captured. Phytoplankton dynamics in the lake were simulated with good accuracy (Normalized Mean Absolute Error, NMAE = 0.24 and r = 0.89 in calibration period, NMAE = 0.55 and r = 0.54 in validation period). The general trends of growth, decline and the magnitude of phytoplankton biomass were well represented most of the time. Scenario simulations suggest that TP reduction will decrease cyanobacteria biomass and delay its peaks as a consequence of orthophosphate (PO43&minus, ) concentration reduction in the lake surface layers. However, even decreasing TP load into Lake Pampulha by half would not be sufficient to achieve the water quality objective of a maximum concentration of 60 &micro, g chla L&minus, 1. Increased imperviousness in the catchment will raise runoff volume, TSS, TP and NO3&minus, loads into Lake Pampulha and promote greater cyanobacteria biomass, mainly in the beginning of the wet season, because of additional nutrient input from catchment runoff. Recovering Lake Pampulha water quality will require the improvement of the sanitation system. The lake water quality improvement will also require more sustainable and nature-based solutions for urban drainage in order to reduce non-point pollution through infiltration and retention of stormwater and to enhance natural processes, such as chemical sorption, biodegradation and phytoremediation. The integrated modelling approach here proposed can be applied for other urban reservoirs taking advantage of existing knowledge on Lake Pampulha.

Cell recognition, adhesion, and internalization are involved in infectious, reproductive, and inflammatory processes and are generally mediated by interactions between molecules located in the cell membrane and the extracellular matrix. These processes can decrease proliferation rates and they are well known for bacteria, fungi, and animals, but there is a lack of knowledge regarding autotrophic cells. Carbohydrates and proteins (e.g., lectins) are important molecules for cell interactions and information about these molecules is essential to better understand many biological phenomena in uni- or multicellular organisms. Most studies focus on the identification of the carbohydrates present on the cell surface by using labeled lectins. Alternatively, here we present a pioneer research performed by using three different labeled carbohydrates in a multivalent presentation (glycodendrons) to detect the presence of carbohydrate receptors (e.g., lectins) on cell surfaces of 12 algal species. The goal of this study was to detect some specificity in these molecular interactions, but in a reverse way in comparison to that commonly described in the literature. We tested trivalent molecules containing residuals of D-mannose, L-fucose, or N-acetyl-galactosamine to identify their bindings with the corresponding lectins expressed on cell surfaces. We envisage that our new approach could be an alternative tool for taxonomic and physiological studies on microalgae or even on other groups of organisms. Based on our results, the receptors found in the cell surface of the algal species tend to differ in composition, quantity, and distribution. The differences were mainly species-specific, since no patterns were identified at higher taxonomic level. Moreover, like lectins, labeled carbohydrates were proved to be a reliable tool for the study of cell surface composition.

Autotrophic microorganisms can be useful for the green synthesis of nanoparticles (NPs), but there is a lack of knowledge to affirm if the high variety of microorganisms is connected to a potential high diversity of NPs. Here, aqueous extracts of two cyanobacteria (Synechococcus elongatus and Microcystis aeruginosa) and four microalgae (the chlorophytes Coelastrum astroideum and Desmodesmus armatus; and the charophytes Cosmarium punctulatum and Klebsormidium flaccidum) were used for the biosynthesis of silver nanoparticles (AgNPs). The nanoparticle characterization was performed by UV–Visible absorption spectrum, Fourier Transforms Infrared (FT-IR), Transmission Electron Microscopy (TEM) and Energy Dispersive X-Ray Spectroscopy (EDS). This is the first study trying to establish some connection between the taxonomical diversity of microalgae and cyanobacteria and the synthesis of different silver nanoparticles. All algal and cyanobacterial extracts resulted in the synthesis of well-disperse and crystalline AgNPs, with no agglomerate formation. TEM analysis showed spherical AgNPs shape with size range within 1.8–5.4 nm. FTIR analysis demonstrated the presence of hydroxyl groups of peptidoglycan nature acting as stabilizing agents in the surface of the AgNPs. The nanoparticle shape and kind of stabilizing biomolecules were highly similar, but their size was significantly different, which can affect the NP properties. There was no pattern for the AgNPs in terms of the microorganism phyla. Our results showed a very high potential for the use of cyanobacteria and microalgae in the green synthesis of NPs since the variety of AgNPs obtained was species-specific.

Dissolved organic matter (DOM) can be an important source of energy and nutrients in aquatic ecosystems and play important roles in carbon and nutrient dynamics of natural and impacted environments. In order to assess the effects of early stage fish farming on dissolved organic carbon (DOC) concentrations as well as DOM fluorescence indices, we took water samples along transects from six fish farms towards reference sites in a large tropical reservoir (Furnas Reservoir, Southeast Brazil) between April 2013 and December 2016. While DOC concentrations did no change along transects, small but significant changes in fluorescence indices were detectable in up to 100 m from fish farms. Higher fluorescence index (FI) values near fish farms pointed to small increases in microbial production due to fish farming. Only in the more pristine of the two main reservoir branches, small differences in the freshness index (β:α) and the peak T/peak C ratio along transects indicated that the relative contribution of recently produced DOM and the biochemical oxygen demand of DOM increased due to aquaculture. The humification index did not respond to fish farming. In summary, current early-stage fish farming did not appear to cause major impacts on DOM quantity and quality, but future increases in net cage and fish farm densities, as well as longer operation times may change this assessment. The fluorescence indices FI, β:α and peak T/peak C ratio may be useful early warning signals for monitoring fish farm impacts in tropical reservoirs.

Cyanobacterial blooms are characterized by intense growth of one or few species that will dominate the phytoplankton community for periods of few months to an entire year or more. However, even during persistent blooms, important seasonal changes among dominant species can be observed. Pampulha reservoir is a tropical eutrophic reservoir presenting permanent blooms. To identify the main species in this environment, a closer analysis performed by microscopy and 16S-rRNA DGGE revealed Cylindrospermopsis raciborskii as highly dominant throughout the year. The second most abundant group comprised species belonging to the Microcystis genus. They followed a well-defined seasonal pattern described by interesting species-specific ecological trends. During thermal stratification in the rainy/warmer season, C. raciborskii dominated in the water column, while Microcystis spp. were abundant at the end of the dry season, a period characterized by higher total phosphorus concentrations. Phylogenetic analyses confirmed the two dominant taxa and their seasonal trends. The results showed that cyanobacteria major controlling factors were strongly species dependent, shifting from physical/climate related (stratification) to more chemical driven (nutrients/eutrophication). Identifying these drivers is therefore essential for the understanding of the bloom dynamics and the real risks associated with each species, and to eventually adopt the most appropriate and effective management strategies.

Anaerobic digestion of food wastes coupled with digestate post-treatment using microalgae-based systems could recover large amounts of energy and nutrients worldwide. However, the development of full-scale implementations requires overcoming microalgae inhibition by high ammonia concentrations and low light transmittances affecting photosynthesis. This study evaluated the potential of microalgae-based reactors supplied with red light-emitting diodes (LEDs) at low intensity (660 nm and 15 µmol·m−2·s−1) to treat food waste digestate. LED reactors were compared with control reactors exposed to solar radiation. From a range of species in the inoculum, Chlorella vulgaris showed high adaptation to both lighting regimes and digestate environmental conditions, characterized by a C:N:P ratio of 74:74:1. Removal efficiencies for control and LED reactors were 84.0% and 95.8% for soluble chemical oxygen demand (COD) and 89.4% and 53.0% for ammonia, respectively. Approximately 50% of ammonia in control reactor and 15% in LED reactor was lost from the systems, whereas 17% and 36% of ammonia was transformed to organic nitrogen in control and LED reactors, respectively. Low-intensity LEDs maintained microalgae growth in levels similar to solar radiation and supported efficient digestate treatment, showing a potential for further application in optimization of full scale reactors at a relatively low energy cost.

The physiological responses of the aquatic liverwort Ricciocarpus natans to ciprofloxacin (Cipro) exposure under different growth temperatures were investigated. Cipro appears to act as an inhibitor of mitochondrial Complex III by blocking the oxidation of quinol, resulting in the formation of hydrogen peroxide (H2O2). H2O2 accumulation upon Cipro exposure is responsible for decreased photosynthesis in plants. The amount of H2O2 in plants is kept under control by antioxidant enzymes, whose activities are central to the responses of plants to Cipro yet are influenced by temperature. Increased temperature favored Cipro uptake by plants as well as its deleterious effects on mitochondrial activity; however, it also favored the activity of antioxidant enzymes, thereby preventing the exacerbation of the deleterious effects of Cipro. The uptake of Cipro by plants appears to be largely a passive process, although some uptake must be driven by an energy-consuming process. Ricciocarpus natans should be considered for programs aimed at the reclamation of Cipro since this plant exhibits high Cipro-tolerance, the capacity for accumulation and increased uptake rates of the antibiotic with increasing temperatures (from 20 to 30 °C).

We isolated phytoplankton assemblages from five tropical lakes differing in environmental conditions and incubated them under different extreme growth conditions. Conditions were: under light with nutrient addition (L þ N), under light with nutrient and organic carbon addition (L þ N þ OC), and in the dark with nutrient and organic carbon addition (N þ OC). These were intended to simulate phytoplankton succession during early, intermediate and late eutrophication stages, respectively. Decreases in species diversity and richness in N þ OC assays from all lakes, except the most eutrophic one, suggested consistent diversity and richness declines during late eutrophication stages. Declines in species diversity were generally caused by a stronger reduction in species richness than evenness, indicating that species exclusion is a more probable response to eutrophication than co-existence and dominance of strong competitors. Under N þ OC conditions, the osmotrophic chlorophyte Chlamydomonas was generally dominant, indicating that this flagellate may prevail in late eutrophic communities in the tropical lakes studied. The L þ N and L þ N þ OC assays did not differ from each other in species diversity, but exhibited differences in species composition and richness. This suggests that the changing role of the phytoplankton community in whole-lake matter fluxes during early eutrophication stages could be a more important research question, than predicting the community’s diversity response in tropical lakes.

We investigate the physiological responses and antibiotic-uptake capacity of Lemna minor exposed to ciprofloxacin. Ciprofloxacin (Cipro) induced toxic effects and hormesis in plants by significantly modifying photosynthesis and respiration pathways. A toxic effect was induced by a concentration ≥1.05mg ciprofloxacin l-1 while hormesis occurs at the lowest concentration studied (0.75mg ciprofloxacin l-1). By impairing normal electron flow in the respiratory electron transport chain, ciprofloxacin induces hydrogen peroxide (H2O2) production. The ability of plants to cope with H2O2 accumulation using antioxidant systems resulted in stimulation/deleterious effects to photosynthesis by Cipro. Cipro-induced oxidative stress was also associated with the ability of L. minor plants to uptake the antibiotic and, therefore, with plant-uptake capacity. Our results indicate that instead of being a photosystem II binding molecule, Cipro induces oxidative stress by targeting the mitochondrial ETC, which would explain the observed effects of the antibiotic on non-target eukaryotic organisms. The selection of plants species with a high capacity to tolerate oxidative stress may constitute a strategy to be used in Cipro-remediation programs.

Eutrophication has impacted water bodies around the world. Knowledge on how to manage and restore these systems is urgently needed in order to maintain adequate water quality. However, causes and consequences of eutrophication may differ among lakes located in tropical and temperate regions. The eutrophication process is better understood for temperate lakes due to the availability of a larger number of studies and longer time-series of data sets. In tropical regions, long-term studies are rare, but could exemplify the particularities of eutrophication speed under conditions of higher temperatures. The purpose of this work was to analyze the evolution of the eutrophication process in an urban tropical reservoir, using a 15-year time series (with occasional interruptions). The dataset comprised monthly sampling of several environmental variables and the phytoplankton community. We found a continuous process of water quality deterioration, mainly related to increasing levels of nutrient and phytoplankton biomass, as well as decreasing water transparency, even after the installation of a municipal wastewater treatment plant. The ongoing eutrophication resulted in a steep trend of increasing cyanobacteria biomass that turned from a seasonal appearance into more persistent blooms in the most recent decades, while the relative contribution of other algal phyla to total phytoplankton biomass declined, which resulted in a loss of phytoplankton diversity. Phosphorus was the major determinant of the persistent blooms. Even though nitrogen concentrations were very high in this system, they were not significantly correlated with phytoplankton or cyanobacteria biomass. Total-P concentrations increased about three times during the study period, indicating that the reservoir did not respond to recent restoration efforts. The average water temperature, always sufficiently high to allow phytoplankton growth all year round, is an additional factor that makes tropical reservoirs especially sensitive to eutrophication. In contrast to temperate systems, the constantly favorable temperatures in the tropics may facilitate the persistence and dominance of cyanobacteria in the plankton community.

RESUMO No processo de urbanização, o aumento na proporção de superfícies impermeabilizadas e as mudanças no uso do solo são responsáveis por maiores volumes e velocidades do escoamento superficial, refletindo em uma maior capacidade de arraste e em um maior aporte de nutrientes nos corpos d'água receptores. O objetivo deste trabalho foi implementar uma ferramenta matemática capaz de reproduzir o impacto de mudanças na bacia hidrográfica sobre a dinâmica do fitoplâncton em um lago urbano. Neste artigo são apresentados o desenvolvimento e os resultados de um modelo integrado constituído de um modelo hidrológico, para simular vazões escoadas em uma bacia hidrográfica, e de um modelo hidrodinâmico e ecológico, para simular a biomassa fitoplanctônica em um corpo d'água urbano. A Lagoa da Pampulha (Belo Horizonte, Minas Gerais), escolhida como estudo de caso, foi intensamente monitorada, assim como sua bacia de drenagem, entre outubro de 2011 e junho de 2013. Os dados obtidos foram utilizados para calibrar e validar ambos os modelos. Os resultados obtidos com o modelo hidrológico mostraram-se coerentes com as medidas realizadas em campo (o coeficiente de Nash variou entre 0,70 e 0,88). O modelo da lagoa representou corretamente a evolução da comunidade fitoplanctônica (erro médio absoluto normalizado: 0,25-0,42 e o coeficiente de Pearson: 0,82-0,89; p

Conservational studies of the threatened Atlantic Forest biome are frequently restricted to terrestrial ecosystems. We know little about the water bodies, specially considering that this biome covers the third largest system of lakes in Brazil. Some of these lakes are located inside the protected "Rio Doce State Park", but many others are found outside this reserve. These external lakes are seldom studied, but understanding their response to human activities is essential for the conservation and the protection of the lakes inside the Park. We evaluated the effects of degradation in a lake outside the Park, which shows a constant bloom of the toxic invasive cyanobacteria Cylindrospermopsis raciborskii. Phytoplankton, climate and physico-chemical variables were assessed from 2011 to 2013 to evaluate which were the major determinants of the lake dynamics. Despite the seasonal changes, the lake was always eutrophic, and cyanobacteria, transparency and nutrients were the major indicators of water characteristics. The lake seems to be nitrogen-limited and cyanobacteria were negatively correlated with nitrogen levels, since the constantly dominant C. raciborskii is a superior competitor for N. We suggest that the monitoring of nitrogen levels is fundamental to establish management strategies to avoid harmful algae blooms in this Atlantic Forest lake.

The global distribution of the toxic cyanobacterium Cylindrospermopsis raciborskii has recently increased, and it has now been identified in tropical, subtropical and temperate freshwater bodies. The mechanisms underlying its success and expansion are still unknown. Several hypotheses have been proposed, including climate change, natural selection and physiological tolerance to different environmental conditions. In this study, we determined the phenotypic and genotypic characteristics of two recently isolated South American strains of C. raciborskii obtained from Uruguay. We analyzed the morphology, growth preferences, tolerance to low temperature (14 °C) and toxin production of the strains and performed phylogenetic analyses based on the ITS and nifH gene sequences. Both isolates showed significantly different morphology and growth behavior under different light intensities and phosphate supply. When genetic differences were assessed by BOX PCR, cluster analyses revealed that they could also be distinguished genotypically and were clearly distinct from C. raciborskii isolated from other continents. Phylogenetic analysis showed that the Uruguayan strains were closely affiliated to other C. raciborskii isolated from the Americas, especially to those from Brazil. Similar to previous studies, we found three solid clusters (Africa-Australia, Europe and America) according to the geographical origin of the isolates. Interestingly, based on nifH sequences, subclusters were identified in American populations indicating an early spread of the species within the continent. We propose that phenotypic and genetic variability of C. raciborskii populations is linked to the existence of different ecotypes whose success is subject to the local environmental conditions.

We investigated how the lipid composition (fatty acids and sterols) of benthic microbial mats, which represent an important basal food resource for stream food webs, differs between tropical streams located in protected pristine and agricultural Cerrado savannah areas. The total microbial biomass and lipid composition differed significantly between pristine and agricultural streams in parallel with differences in water quality and hydrodynamic characteristics. Agricultural streams exhibited lower total biomass of benthic microbial mats than pristine streams. However, the higher concentrations of essential polyunsaturated fatty acids, such as linoleic acid (LIN, 18:2ω6), α-linolenic acid (ALA, 18:3ω3), and eicosapentaenoic acid (EPA, 20:5ω3), that were observed in agricultural streams suggest enhanced lipid complexity and a higher nutritional quality of the microbial community relative to pristine streams. Meanwhile, pristine stream microbial communities had higher total concentrations of saturated fatty acids and cholesterol than those of agricultural streams, reflecting their heterotrophic microbial communities. Moreover, stream morphotype and associated differences in the hydrodynamic characteristics affected the community composition and thereby also the lipid composition of microbial mats. Land-use-induced changes in the total biomass and lipid composition of microbial communities may affect the trophic transfer of energy in stream food webs, leading to changes in the composition and productivity of primary consumers and their predators, and thereby affecting stream ecosystem functioning.

This study presents data on seasonal changes of the phytoplanktonic community of a small tropical lake, Lagoa Santa, in the Brazilian cerrado. Temporal variation in the community structure was small and we observed a permanent dominance of the cyanobacteria Cylindrospermopsis raciborskii . This dominance could be associated to the stability of several environmental conditions. Especially water temperature, always within the optimal growth range for C. raciborskii , and the constant mixed water column may have been important factors driving to the long term dominance of this species in the lake. Remarkable seasonal variation in rainfall, as well as the occasional and non-seasonal variation in nutrient concentrations, were important to explain changes in environmental and biological variables, but were not related to the dominance of C. raciborskii . Pearson's correlation and PCA could just in part explain the stable dominance of this cyanobacterium. Meteorological and chemical factors seem to have no clear control on the variability of the phytoplankton dynamics in Lagoa Santa. The weak relationship between C. raciborskii abundance and environmental variables points to additional intrinsic factors associated to this species that may be important in structuring the phytoplankton assemblage.

During photosynthesis, absorbed energy that is not used in photochemical reactions dissipates as fluorescence. Fluorescence provides important information on the physiological conditions of the studied organisms and its measurement is widely used by plant physiologists and can be valuable in phytoplankton studies. We describe a method adapting a plant fluorometric equipment to measure the photosynthetic capacity of microalgae. Unialgal cultures of three planktonic chlorophytes were exposed to 3(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), an inhibitor of photosystem II, at concentrations of 0.1, 1.0 and 10.0 µmol.L-1. Estimates were made of photosynthetic parameters, including operational and potential photosystem II quantum yield and electron transport rate between photosystems, using algal cells concentrated on glass-fiber filters. The technique allowed reliable measurements of fluorescence, and detection of distinct levels of inhibition. Physiological or morphological characteristics of the selected species might provide an explanation for the observed results: differences on the surface/volume ratio of the cells and colony morphology, for example, were associated with contrasting resistance to the toxicant. To characterize inhibition on phytoplanktonic photosynthesis, we suggest operational quantum yield and electron transport rate as best parameters, once they were more sensitive to the DCMU toxicity. Durante os eventos fotossintéticos, a energia absorvida que não é usada em reações fotoquímicas pode ser dissipada como fluorescência. Sua medida fornece importantes informações acerca das condições fisiológicas dos organismos, sendo amplamente utilizada na fisiologia vegetal e podendo ser valiosa nos estudos do fitoplâncton. Este estudo descreve um método no qual um equipamento elaborado para a realização de medidas de fluorescência em plantas é utilizado para medir a capacidade fotossintética de microalgas. Culturas unialgais de três clorófitas planctônicas foram expostas a três concentrações de 3(3,4-diclorofenil)-1,1-dimetiluréia (DCMU), um inibidor do fotossistema II. Foram quantificados alguns parâmetros fotossintéticos, como os rendimentos quânticos efetivo e potencial do fotossistema II e a taxa de transporte de elétrons entre os fotossistemas. Para tal, as células algais foram concentradas em filtros de fibra de vidro. Esta técnica permitiu a quantificação da fluorescência proveniente do aparato fotossintético destas microalgas, possibilitando a detecção de diferentes níveis de inibição, segundo a espécie. Características fisiológicas ou morfológicas das espécies poderiam justificar os resultados observados: diferenças na razão superfície/volume das células e na forma das colônias, por exemplo, foram associadas aos níveis distintos de resistência ao DCMU. Para a avaliação da inibição da fotossíntese fitoplanctônica, nós sugerimos o rendimento quântico efetivo e a taxa de transporte de elétrons como os parâmetros mais adequados, uma vez que foram os mais sensíveis à toxicidade do DCMU.

Cylindrospermopsis raciborskii (Wolosz.) Seenayya et Subba Raju is a planktonic filamentous cyanobacterium whose sudden worldwide proliferation and ability to produce toxins are a reason for concern. In this paper, we suggest that its ecological dominance might be explained by antagonistic interaction with other phytoplankton species due to production of allelopathic metabolites. To test this hypothesis, experiments were run with exudates of natural phytoplankton and C. raciborskii strains isolated from Lagoa Santa, a small natural lake in southeastern Brazil, where this species has become dominant in recent years. The exudates were added to different algal species obtained from the same environment and maintained in culture. After 24 h incubation, PAM fluorometry was used to compare control and treatment photosynthetic responses (relative electron transport rate) to the dissolved extracellular products. Results indicate that most of the target species were sensitive to C. raciborskii exudates, which showed strong inhibitory effects on their photosynthetic activities. These results provide evidence that allelopathy may offer a competitive benefit to C. raciborskii and contribute to its stable dominance in Lagoa Santa. A potential allelopathic advantage could also help to explain the geographic expansion of this species at midlatitudes.

Summary 1. Exotic invasive species modify natural food webs in a way frequently hard to predict. In several aquatic environments in Brazil the introduction of Oreochromis niloticus (tilapia) was followed by changes in water quality. Yet, because of its rapid and easy growth, this fish has been used in many aquaculture programmes around the country. 2. To measure the effects of tilapia on the phytoplankton community and on water conditions of a large tropical reservoir in south-eastern Brazil (Furnas Reservoir), we performed two in situ experiments using three controls (no fish) and three tilapia enclosures (high fish density). Abiotic and biotic parameters were measured at 4 day intervals for 28 days. 3. Fish presence increased nitrogen (N) and phosphorus (P) availability (ammonium 260 and 70% mean increase – first and second experiment; and total phosphorus 540 and 270% mean increase) via excretion. Nutrient recycling by fish can thus be significant in the nutrient dynamics of the reservoir. The higher chlorophyll a concentration in the experimental fish tanks (86 and 34 μg L−1, first and second experiment, respectively) was the result of a positive bottom-up effect on the phytoplankton community (approximately 2 μg L−1 in the reservoir and control tank). 4. Because tilapia feed selectively on large algae (mainly cyanobacteria and diatoms), several small-sized or mucilaginous colonial chlorophyceans proliferated at the end of the experiments. Thus, the trophic cascade revealed strong influences on algal composition as well as on biomass. 5. Tilapia can contribute to the eutrophication of a waterbody by both top-down and bottom-up forces. In particular, by supplying considerable amount of nutrients it promotes the increase of fast growing algae. Tilapia must be used cautiously in aquaculture to avoid unexpected environmental degradation.

Neste trabalho foram descritos 28 táxons de algas planctônicas pertencentes às divisões Euglenophyta, Chrysophyta, Pyrrophyta e Cyanobacteria, encontradas no reservatório da Pampulha, estado de Minas Gerais. Foram analisadas amostras no período de maio/1992 a fevereiro/1997. Em número de espécies, Euglenophyta foi a que apresentou maior número (13 espécies em uma família), seguidas de Cyanobacteria (oito espécies), Pyrrophyta (cinco espécies) e Chrysophyta (duas espécies). Vinte e três táxons são primeiras citações para o estado de Minas Gerais. This paper contains descriptions of 28 taxa of planktonic algae distributed in four divisions (Euglenophyta, Chrysophyta, Pyrrophyta and Cyanobacteria) found in the Pampulha reservoir in Minas Gerais state. Samples from May/1992 to February/1997 were analyzed. The best represented division was Euglenophyta (13 species in one family), followed by Cyanobacteria (eight species), Pyrrophyta (five species) and Chrysophyta (two species). Twenty three taxa are reported for the first time to the State of Minas Gerais.

CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior O rompimento da barragem de Fundão impactou diretamente alguns rios da bacia hidrográfica do rio Doce, causando alterações imediatas quanto ao uso e a qualidade de suas águas, bem como sobre sua biota. As comunidades perifíticas se destacam por serem representantes da base trófica de rios e são comumente usadas na bioindicação. Nosso objetivo foi analisar a estrutura destas comunidades a fim de verificar se há diferenças em sua composição segundo um gradiente de impacto pelos rejeitos. Amostras de água (para análises físicas, químicas e quantificação de metais) e das comunidades perifíticas foram obtidas semestralmente, entre novembro de 2017 e junho de 2019, em três sítios: rio do Carmo (referência, não impactado), rio Gualaxo do Norte (altamente impactado) e rio Doce (impacto intermediário). Utilizamos também a base de dados do monitoramento realizado na região pelo IGAM (Instituto Mineiro de Gestão das Águas) para comparar seus resultados e aqueles obtidos em nossas análises. Foi verificada uma separação espacial do rio Gualaxo do Norte em relação aos demais que parece estar relacionada a uma carência nutricional e química, visto que este rio foi caracterizado justamente pelas menores concentrações tanto de nutrientes quanto de metais. Tanto os resultados deste estudo, quanto aqueles obtidos pelo IGAM mostraram que todos os elementos avaliados estiveram abaixo dos valores estabelecidos pela legislação, exceto Al e Mn. Assim, a comunidade perifítica, ao apresentar menores valores de biomassa e de riqueza de espécies no sítio mais impactado na maioria das amostras, indicou que a onda de rejeitos que atingiu a bacia do rio Doce pode ter impactado a estrutura de suas comunidades. Além dessas variáveis, houve diferenças significativas na composição das comunidades perifíticas entre os rios estudados, com o rio Gualaxo do Norte sendo composto predominantemente pela espécie Achnanthidium minutissimum, relatada como tolerante a condições extremas. Foi evidenciado por esse estudo que as comunidades perifíticas usadas como bioindicadoras podem ser ferramentas complementares às tradicionalmente usadas no monitoramento dos sistemas aquáticos. The collapse of the Fundão dam impacted some rivers in the Doce river hydrographic basin. Periphytic communities are important because they are the base of trophic chains in rivers and they can also be used for bioindication. Our objective was to analyze the structure of these communities in order to verify if there are differences in their composition according to a gradient of impact by tailings from Fundão dam. Water samples (for physical, chemical and metal analyses) and periphytic communities were obtained every six months, between November 2017 and June 2019, at three sites: Carmo river (reference, non-impacted), Gualaxo do Norte river (highly impacted) and Doce river (intermediate impact). We also used the database produced by a monitoring carried out in the region by the IGAM (Minas Gerais Water Management Institute) to compare its results with those obtained in our analyses. the analyses showed that Gualaxo do Norte river was specially different from the others sampled sites. Results suggest that many differences were related to a nutritional and chemical deficiency, since this river was characterized by the lowest concentrations of both nutrients and metals. The results of this study and also those obtained by IGAM showed that all the elements evaluated were below the values established by legislation, except Al and Mn. Thus, the commonly observed lower biomass and richness of the periphytic community in the most impacted site indicated that the tailings wave may have impacted the structure of the communities in a different way than we supposed in the beginning of our study. Furthermore, there were significant differences in the composition of periphytic communities between the rivers studied, with the Gualaxo do Norte river being predominantly composed by Achnanthidium minutissimum, reported as tolerant to extreme conditions. It was evidenced by this study that the periphytic communities are interesting bioindicators that can complement the role of other variables that are traditionally used in the monitoring of aquatic systems.