RESUMO
Cyanobacteria stand out among phytoplankton when they form massive blooms and produce toxins. Because cyanotoxin genes date to the origin of metazoans, the hypothesis that cyanotoxins function as a defense against herbivory is still debated. Although their primary cellular function might vary, these metabolites could have evolved as an anti-predator response. Here we evaluated the physiological and molecular responses of a saxitoxin-producing Raphidiopsis raciborskii to infochemicals released by the grazer Daphnia gessneri. Induced chemical defenses were evidenced in R. raciborskii as a significant increase in the transcription level of sxt genes, followed by an increase in saxitoxin content when exposed to predator cues. Moreover, cyanobacterial growth decreased, and no significant effects on photosynthesis or morphology were observed. Overall, the induced defense response was accompanied by a trade-off between toxin production and growth. These results shed light on the mechanisms underlying zooplankton-cyanobacteria interactions in aquatic food webs. The widespread occurrence of the cyanobacterium R. raciborskii in freshwater bodies has been attributed to its phenotypic plasticity. Assessing the potential of this species to thrive over interaction filters such as zooplankton grazing pressure can enhance our understanding of its adaptive success.
Assuntos
Cylindrospermopsis , Daphnia/metabolismo , Feromônios/metabolismo , Saxitoxina , Zooplâncton/metabolismo , Animais , Cylindrospermopsis/genética , Cylindrospermopsis/crescimento & desenvolvimento , Cylindrospermopsis/metabolismo , Cadeia Alimentar , Regulação Bacteriana da Expressão Gênica , Genes Bacterianos , Saxitoxina/biossíntese , Saxitoxina/genéticaRESUMO
Cylindrospermopsis raciborskii is a potentially toxic freshwater cyanobacterium that can tolerate a wide range of light and temperature. Due to climatic changes, the interaction between light and temperature is studied in aquatic systems, but no study has addressed the effect of both variables on the saxitoxins production. This study evaluated the combined effect of light and temperature on saxitoxins production and cellular quota in C. raciborskii. Experiments were performed with three C. raciborskii strains in batch cultures under six light intensities (10, 40, 60, 100, 150, and 500 µmol of photons m-2 s-1) and four temperatures (15, 20, 25, and 30 °C). The growth of C. raciborskii strains was limited at lower temperatures and the maximum growth rates were obtained under higher light combined with temperatures equal or above 20 °C, depending on the strain. In general, growth was highest at 30 °C at the lower light intensities and equally high at 25 °C and 30 °C under higher light. Highest saxitoxins concentration and cell-quota occurred at 25 °C under high light intensities, but were much lower at 30 °C. Hence, increased temperatures combined with sufficient light will lead to higher C. raciborskii biomass, but blooms could become less toxic in tropical regions.
Assuntos
Cylindrospermopsis , Luz , Saxitoxina/metabolismo , Temperatura , Cylindrospermopsis/crescimento & desenvolvimento , Cylindrospermopsis/metabolismo , Cylindrospermopsis/efeitos da radiaçãoRESUMO
In tropical and subtropical lakes, eutrophication often leads to nuisance blooms of Cylindrospermopsis raciborskii. In laboratory experiments, we tested the combined effects of flocculant polyaluminum chloride (PAC) and lanthanum-modified bentonite (LMB) on the sinking and growth rates of three C. raciborskii strains. We tested the hypothesis that the combination of PAC and LMB would (1) effectively sink C. raciborskii in a test tube experiment and (2) impair C. raciborskii growth, irrespective of the biomass of the inoculum (bloom) and the strain in the growth experiment. We tested the recommended (LMB1) and a three-times higher dose of LMB (LMB3). The combined addition of PAC and LMB enhanced the sedimentation of all C. raciborskii strains. Moreover, both the PAC and LMB doses decreased the phosphate concentration. PAC and LMB1 decreased the growth rate of all strains, but the efficacy depended on the biomass and strain. The combined addition of PAC and LMB3 inhibited the growth of all strains independently of the biomass and strain. We conclude that a low dose of PAC in combination with the recommended dose of LMB decreases C. raciborskii blooms and that the efficiency of the technique depends on the biomass of the bloom. A higher dose of LMB is needed to obtain a more efficient control of C. raciborskii blooms.
Assuntos
Hidróxido de Alumínio , Bentonita , Cylindrospermopsis/crescimento & desenvolvimento , Lantânio , Bentonita/química , Biomassa , Clorofila/metabolismo , Clorofila A , Cylindrospermopsis/metabolismo , Lantânio/química , Fósforo/metabolismoRESUMO
Toxicity and morphology may function as defense mechanisms of bloom-forming cyanobacteria against zooplankton grazing. Yet, the relative importance of each of these factors and their plasticity remains poorly known. We tested the effects of chemical and morphological traits of the bloom-forming cyanobacterium Cylindrospermopsis raciborskii on the feeding response of the selective feeder Eudiaptomus gracilis (Calanoida, Copepoda), using a saxitoxin-producing strain (STX+) and a non-saxitoxin (STX-)-producing strain as food. From these two chemotypes, we established cultures of three different morphotypes that differed in filament length (short, medium, and long) by incubating the strains at 17, 25, and 32 °C. We hypothesized that the inhibitory effects of saxitoxins determine the avoidance of C. raciborskii, and that morphology would only become relevant in the absence of saxitoxins. Temperature affected two traits: higher temperature resulted in significantly shorter filaments in both strains and led to much higher toxin contents in the STX+ strain (1.7 µg eq STX L(-1) at 17 °C, 7.9 µg eq STX L(-1) at 25 °C, and 25.1 µg eq STX L(-1) at 32 °C). Copepods strongly reduced the ingestion of the STX+ strain in comparison with STX- cultures, regardless of filament length. Conversely, consumption of shorter filaments was significantly higher in the STX- strain. The great plasticity of morphological and chemical traits of C. raciborskii and their resultant contrasting effects on the feeding behavior of zooplankton might explain the success of this cyanobacterium in a variety of aquatic environments.
Assuntos
Copépodes/fisiologia , Cylindrospermopsis/metabolismo , Água Doce/microbiologia , Animais , Cylindrospermopsis/química , Cylindrospermopsis/citologia , Comportamento Alimentar/fisiologia , Lagos/microbiologia , Fitoplâncton/fisiologia , Saxitoxina/biossíntese , Saxitoxina/toxicidade , Zooplâncton/fisiologiaRESUMO
The development of cyanobacterial blooms in inland aquatic ecosystems is greatly promoted by nutrient availability, especially nitrogen and phosphorous. When blooms are dominated by toxigenic species the harmful effects of nutrient loading becomes particularly relevant. Among toxic species, Cylindrospermopsis raciborskii found in South American ecosystems is characterized by the production of saxitoxin and analogs (Paralytic Shellfish Poisoning, PSP), for which the factors that trigger their production have not been elucidated. In this study, the effect of nitrate availability on the relative transcript abundance of two genes (sxtU and sxtI), both involved in different steps of PSP biosynthetic pathway, was addressed in C. raciborskii MVCC19 by qPCR. The relative transcript abundance of both genes significantly increased from the beginning to the end of growth, independent of nitrate availability in the culture medium. Differences between the genes in terms of the levels of relative expression were also found, implying that during growth in nitrate-rich or nitrate-deprived conditions C. raciborskii MVCC19 has the ability to produce different kind of PSP molecules. The presence of nifH transcripts in the nitrogen-depleted treatment confirmed that in the absence of nitrate C. raciborskii fixed atmospheric N2. Moreover, after transferring filaments to nitrate-rich conditions the synthesis of nifH mRNA continued for few hours, suggesting that cell adjustments enabling the utilization of soluble nitrogen sources are not immediate. Our results show that biosynthesis of saxitoxin and analogs in C. raciborskii is not related to nitrate availability, but rather is linked to cyanobacteria growth rate.
Assuntos
Cylindrospermopsis/genética , Cylindrospermopsis/metabolismo , Regulação Bacteriana da Expressão Gênica , Nitrogênio/metabolismo , Saxitoxina/genéticaRESUMO
Different environmental nitrogen sources play selective roles in the development of cyanobacterial blooms and noxious effects are often exacerbated when toxic cyanobacteria are dominant. Cylindrospermopsis raciborskii CS-505 (heterocystous, nitrogen fixing) and Raphidiopsis brookii D9 (non-N2 fixing) produce the nitrogenous toxins cylindrospermopsin (CYN) and paralytic shellfish toxins (PSTs), respectively. These toxin groups are biosynthesized constitutively by two independent putative gene clusters, whose flanking genes are target for nitrogen (N) regulation. It is not yet known how or if toxin biosynthetic genes are regulated, particularly by N-source dependency. Here we show that binding boxes for NtcA, the master regulator of N metabolism, are located within both gene clusters as potential regulators of toxin biosynthesis. Quantification of intra- and extracellular toxin content in cultures at early stages of growth under nitrate, ammonium, urea and N-free media showed that N-sources influence neither CYN nor PST production. However, CYN and PST profiles were altered under N-free medium resulting in a decrease in the predicted precursor toxins (doCYN and STX, respectively). Reduced STX amounts were also observed under growth in ammonium. Quantification of toxin biosynthesis and transport gene transcripts revealed a constitutive transcription under all tested N-sources. Our data support the hypothesis that PSTs and CYN are constitutive metabolites whose biosynthesis is correlated to cyanobacterial growth rather than directly to specific environmental conditions. Overall, the constant biosynthesis of toxins and expression of the putative toxin-biosynthesis genes supports the usage of qPCR probes in water quality monitoring of toxic cyanobacteria.
Assuntos
Proteínas de Bactérias/metabolismo , Toxinas Bacterianas/biossíntese , Cianobactérias/metabolismo , Cylindrospermopsis/metabolismo , Regulação Bacteriana da Expressão Gênica , Fixação de Nitrogênio , Venenos/metabolismo , Alcaloides , Compostos de Amônio/metabolismo , Proteínas de Bactérias/genética , Toxinas Bacterianas/química , Técnicas de Cultura Celular por Lotes , Brasil , Cianobactérias/crescimento & desenvolvimento , Cianobactérias/isolamento & purificação , Toxinas de Cianobactérias , Cylindrospermopsis/crescimento & desenvolvimento , Cylindrospermopsis/isolamento & purificação , Água Doce/microbiologia , Estrutura Molecular , Nitratos/metabolismo , Venenos/química , Queensland , Uracila/análogos & derivados , Uracila/biossíntese , Uracila/química , Ureia/metabolismoRESUMO
The present study aimed to test the effects of raw water samples from a eutrophic reservoir and of a saxitoxin-producing strain of Cylindrospermopsis raciborskii on the swimming behavior of 2 key herbivore species of Daphnia. Two complementary approaches were used, acute bioassays and behavioral assays using an automated movement tracking system for measuring the following activity parameters: swimming time, resting time, distance traveled, and mean velocity. In both assays, animals were exposed to field samples or to toxic filaments in different concentrations and observed for 2 h to 3 h. In the acute bioassays, there was a decrease in the number of swimming individuals during the exposure period and a recovery following removal from toxic algae. A significant relationship was found between median effective concentration and the saxitoxin content of seston (r(2) = 0.998; p = 0.025) in the acute bioassays with raw water samples. Behavioral assays also showed significant effects in the activity parameters with both field samples and the strain of C. raciborskii, with some recovery during the exposure period. Both approaches corroborated previous research on the effects of neurotoxic C. raciborskii on the swimming activity of Daphnia, and these effects are compatible with the mechanism of action of saxitoxins. The present study showed that activity parameters of aquatic organisms may be a useful tool in the evaluation of sublethal toxicity and detection of neurotoxins in raw water.
Assuntos
Cylindrospermopsis/metabolismo , Daphnia/efeitos dos fármacos , Neurotoxinas/toxicidade , Saxitoxina/toxicidade , Animais , Comportamento Animal/efeitos dos fármacos , Cylindrospermopsis/isolamento & purificação , Daphnia/fisiologia , NataçãoRESUMO
The cosmopolitan and increasing distribution of Cylindrospermopsis raciborskii can be attributed to its ecophysiological plasticity and tolerance to changing environmental factors in water bodies. In reservoirs in the semi-arid region of Brazil, the presence and common dominance of C. raciborskii have been described in waters that are considered hard. We investigated the response of a Brazilian C. raciborskii strain to water hardness by evaluating its growth and saxitoxin production. Based on environmental data, a concentration of 5 mM of different carbonate salts was tested. These conditions affected growth either positively (MgCO3) or negatively (CaCO3 and Na2CO3). As a control for the addition of cations, MgCl2, CaCl2 and NaCl were tested at 5 or 10 mM, and MgCl2 stimulated growth, NaCl slowed but sustained growth, and CaCl2 inhibited growth. Most of the tested treatments increased the saxitoxin (STX) cell quota after six days of exposure. After 12 days, STX production returned to concentrations similar to that of the control, indicating an adaptation to the altered water conditions. In the short term, cell exposure to most of the tested conditions favored STX production over neoSTX production. These results support the noted plasticity of C. raciborskii and highlight its potential to thrive in hard waters. Additionally, the observed relationship between saxitoxin production and water ion concentrations characteristic of the natural environments can be important for understanding toxin content variation in other harmful algae that produce STX.
Assuntos
Cylindrospermopsis/metabolismo , Saxitoxina/biossíntese , Água/química , Brasil , Cloreto de Cálcio/química , Cylindrospermopsis/crescimento & desenvolvimento , Cloreto de Magnésio/química , Cloreto de Sódio/química , Fatores de TempoRESUMO
Paralytic shellfish poisoning toxins (PSTs) are a family of more than 30 natural alkaloids synthesized by dinoflagellates and cyanobacteria whose toxicity in animals is mediated by voltage-gated Na(+) channel blocking. The export of PST analogues may be through SxtF and SxtM, two putative MATE (multidrug and toxic compound extrusion) family transporters encoded in PSTs biosynthetic gene cluster (sxt). sxtM is present in every sxt cluster analyzed; however, sxtF is only present in the Cylindrospermopsis-Raphidiopsis clade. These transporters are energetically coupled with an electrochemical gradient of proton (H(+)) or sodium (Na(+)) ions across membranes. Because the functional role of PSTs remains unknown and methods for genetic manipulation in PST-producing organisms have not yet been developed, protein structure analyses will allow us to understand their function. By analyzing the sxt cluster of eight PST-producing cyanobacteria, we found no correlation between the presence of sxtF or sxtM and a specific PSTs profile. Phylogenetic analyses of SxtF/M showed a high conservation of SxtF in the Cylindrospermopsis-Raphidiopsis clade, suggesting conserved substrate affinity. Two domains involved in Na(+) and drug recognition from NorM proteins (MATE family) of Vibrio parahaemolyticus and V. cholerae are present in SxtF/M. The Na(+) recognition domain was conserved in both SxtF/M, indicating that Na(+) can maintain the role as a cation anti-transporter. Consensus motifs for toxin binding differed between SxtF and SxtM implying differential substrate binding. Through protein modeling and docking analysis, we found that there is no marked affinity between the recognition domain and a specific PST analogue. This agrees with our previous results of PST export in R. brookii D9, where we observed that the response to Na(+) incubation was similar to different analogues. These results reassert the hypothesis regarding the involvement of Na(+) in toxin export, as well as the motifs L(398)XGLQD(403) (SxtM) and L(390)VGLRD(395) (SxtF) in toxin recognition.
Assuntos
Proteínas de Bactérias/metabolismo , Cylindrospermopsis/metabolismo , Toxinas Marinhas/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Transporte Biológico Ativo , Simulação por Computador , Cylindrospermopsis/química , Cylindrospermopsis/genética , Toxinas Marinhas/química , Toxinas Marinhas/genética , Proteínas de Membrana Transportadoras/química , Proteínas de Membrana Transportadoras/genética , Modelos Moleculares , Família Multigênica , Filogenia , Conformação Proteica , Saxitoxina/análogos & derivados , Saxitoxina/genética , Saxitoxina/metabolismoRESUMO
The toxin producing nitrogen-fixing heterocystous freshwater cyanobacterium Cylindrospermopsis raciborskii recently radiated from its endemic tropical environment into sub-tropical and temperate regions, a radiation likely to be favored by its ability to fix dinitrogen (diazotrophy). Although most heterocystous cyanobacteria differentiate regularly spaced intercalary heterocysts along their trichomes when combined nitrogen sources are depleted, C. raciborskii differentiates only two terminal heterocysts (one at each trichome end) that can reach >100 vegetative cells each. Here we investigated whether these terminal heterocysts are the exclusive sites for dinitrogen fixation in C. raciborskii. The highest nitrogenase activity and NifH biosynthesis (western-blot) were restricted to the light phase of a 12/12 light/dark cycle. Separation of heterocysts and vegetative cells (sonication and two-phase aqueous polymer partitioning) demonstrated that the terminal heterocysts are the sole sites for nifH expression (RT-PCR) and NifH biosynthesis. The latter finding was verified by the exclusive localization of nitrogenase in the terminal heterocysts of intact trichomes (immunogold-transmission electron microscopy and in situ immunofluorescence-light microscopy). These results suggest that the terminal heterocysts provide the combined nitrogen required by the often long trichomes (>100 vegetative cells). Our data also suggests that the terminal-heterocyst phenotype in C. raciborskii may be explained by the lack of a patL ortholog. These data help identify mechanisms by which C. raciborskii and other terminal heterocyst-forming cyanobacteria successfully inhabit environments depleted in combined nitrogen.
Assuntos
Cianobactérias/genética , Cianobactérias/metabolismo , Cylindrospermopsis/genética , Cylindrospermopsis/metabolismo , Regulação Bacteriana da Expressão Gênica , Genes Bacterianos , Luz , Nitrogênio/metabolismo , Fixação de Nitrogênio , Nitrogenase/genética , Nitrogenase/metabolismo , Oxirredutases/genética , Oxirredutases/metabolismoRESUMO
INTRODUCTION: The increasing contamination of aquatic environments motivates studies on the interactions among natural dissolved organic matter, metals, and the biota. This investigation focused on the organic exudates of the toxic cyanobacteria Cylindrospermopsis raciborskii as a Cu carrier through a three-level aquatic trophic chain (bacteria, protozoa, and copepod). DISCUSSION: The effects of bacteria activity and growth on the metal-organic complexes were evaluated through changes in free Cu(2+) ions, total dissolved, and total particulate Cu. To be sure that the added copper would be complexed to the exudates, its complexing properties were previously determined. The cyanobacteria exudate-Cu complexes were furnished to bacteria that were further used as a food source to the protozoan Paramercium caudatum. This was then furnished as food to the copepod Mesocyclops sp. The results showed that, in general, the cyanobacterial exudates decreased Cu bioavailability and toxicity to the first trophic level (bacteria), but because the heterotrophic bacteria accumulated Cu, they were responsible for the transference for the otherwise low availability metal form. Both the bacteria and protozoan organisms accumulated Cu, but no metal accumulation was detected in the copepods.
Assuntos
Cobre/farmacocinética , Cobre/toxicidade , Cylindrospermopsis/metabolismo , Cadeia Alimentar , Animais , Disponibilidade Biológica , Cátions , Copépodes/efeitos dos fármacos , Copépodes/metabolismo , Cylindrospermopsis/efeitos dos fármacos , Água Doce/química , Água Doce/microbiologia , Água Doce/parasitologia , Paramecium/efeitos dos fármacos , Paramecium/metabolismo , Espectrofotometria AtômicaRESUMO
Cylindrospermopsis raciborskii (Woloszynska) Seenaya & Subba Raju is a freshwater cyanobacterium of worldwide distribution. In the North-eastern region of Brazil many eutrophic water reservoirs are characterized by the dominance of C. raciborskii, with recurrent occurrence of blooms. These water bodies have high conductivity due to a high ionic concentration, and are defined as hard (with high values of CaCO3). In this study, we investigated the long-term effect (12 days) of high calcium concentration (8 mM Ca2+) on C. raciborskii (T3 strain) growth, morphology, toxin content, and metabolism. Changes in protein expression profiles were investigated by proteomic analysis using 2D gel electrophoresis and mass spectrometry. A continued exposure to calcium had a pronounced effect on C. raciborskii (T3): it limited growth, decreased thricome length, increased chlorophyll-a content, altered toxin profile (although did not affect PST content, saxitoxin + neosaxitoxin), and inhibited the expression of proteins related to primary metabolism.
Assuntos
Toxinas Bacterianas , Cylindrospermopsis/crescimento & desenvolvimento , Cylindrospermopsis/isolamento & purificação , Cylindrospermopsis/metabolismo , Eletroforese em Gel de Ágar , Proteoma/análise , Tanques Elevados/análise , Microbiologia Ambiental , Concentração de Íons de Hidrogênio , Métodos , Métodos , Amostras de ÁguaRESUMO
We report the occurrence of cyanobacterial blooms and the presence of cyanotoxins in water samples from the Armando Ribeiro Gonçalves reservoir (06 degrees 08 S and 37 degrees 07 W), located in the state of Rio Grande do Norte, in the semiarid region of northeastern Brazil. The cyanobacterial species were identified and quantified during the rainy and dry seasons in the year 2000. Cyanotoxins such as microcystins, saxitoxins and cylindrospermopsins were analyzed and quantified using HPLC and ELISA methods. The mixed toxic blooms of Cylindrospermopsis raciborskii, Microcystis spp (M. panniformis, M. protocystis, M. novacekii) and Aphanizomenon spp (Aphanizomenon gracile, A. cf. manguinii, A. cf. issastschenkoi) were persistent and represented 90-100% of the total phytoplankton species. Toxic cyanobacterial blooms from the Armando Ribeiro Gonçalves reservoir were analyzed and found to have three phases in relation to the annual cycle. During the rainy season, an intense toxic bloom of Cylindrospermopsis raciborskii was recorded along with saxitoxins (3.14 microg.L(-1)). During the transition period, between the rainy and dry seasons, different species of Microscytis occurred and microcystin as high as 8.8 microg.L(-1) was recorded. In the dry season, co-dominance of Cylindrospermopsis raciborskii, Microcystis spp and Aphanizomenon spp occurred and the concentrations of saxitoxin remained very low. Our results indicate the presence of microcystins (8.8 microg.L(-1)) and saxitoxins (3.14 microg.L(-1)) into the crude water, with increasing concentrations from the second fortnight of April to late May 2000. The occurrence of toxic blooms in this reservoir points to a permanent risk of cyanotoxins in supply waters, indicating the need for the implementation of bloom control measures to improve the water quality. Exposure of the local population to cyanotoxins through their potential accumulation in fish muscle must also be considered.
Assuntos
Aphanizomenon/isolamento & purificação , Toxinas Bacterianas/análise , Cylindrospermopsis/isolamento & purificação , Microcystis/isolamento & purificação , Microbiologia da Água , Aphanizomenon/metabolismo , Toxinas Bacterianas/biossíntese , Brasil , Cromatografia Líquida de Alta Pressão , Cylindrospermopsis/metabolismo , Monitoramento Ambiental/métodos , Ensaio de Imunoadsorção Enzimática , Microcystis/metabolismo , Densidade Demográfica , Estações do AnoRESUMO
Nós relatamos a ocorrência de florescimentos de cianobactérias e a presença de cianotoxinas em amostras de água do reservatório Armando Ribeiro Gonçalves (06º 08Æ S; 37º 07Æ W) situado no Estado do Rio Grande do Norte, na região semi-árida do Brasil. Cianobactérias foram identificadas e quantificadas nos períodos seco e chuvoso do ano 2000. Cianotoxinas tais como, microcistinas, saxitoxinas e cilindrospermopsinas foram quantificadas por HPLC e ELISA. Florescimentos tóxicos mistos de Cylindrospermopsis raciborskii, Microcystis spp (M. panniformis, M. protocystis, M. novacekii) e Aphanizomenon ssp (Aphanizomenon gracile, A. cf. manguinii, A. cf. issastschenkoi) foram persistentes e representaram 90-100% da comunidade fitoplanctônica ao longo do período estudado. No período de chuvas, florescimentos tóxicos de Cylindrospermopsis raciborskii coincidiram com maiores valores de saxitoxinas (3,14 µg.L-1). Entre o período de chuva e estiagem, ocorreram florescimentos tóxicos de Microcytis spp, excedendo o valor mínimo aceitável para consumo humano (8,8 µg.L-1). Na estiagem, baixas concentrações de saxitoxinas foram detectadas em florescimentos menos intensos com co-dominância de Cylindrospermopsis raciborskii, Microcystis spp e Aphanizomenon spp. Nossos resultados revelaram a presença de microcistinas (8,8 µg.L-1) e saxitoxinas (3,14 µg.L-1) na água bruta, a partir da segunda quinzena de abril até o final de maio de 2000. A ocorrência de blooms tóxicos de cianobactérias no reservatório em estudo aponta um risco permanente de cianotoxinas em águas de abastecimento e indica a necessidade da implementação de medidas de controle das florações, visando à melhoria da qualidade da água. A exposição das populações locais às cianotoxinas, pela sua potencial acumulação em musculatura de peixes, também deve ser considerada.