Dados da Tese de Doutorado
Author: Iame Alves Guedes
Títle: Biotic and abiotic factors related to cyanobacterial blooms
Year: 2017. Full text (in Portuguese)
Abstract:
Cyanobacterial blooms occur in freshwater environments around the world, mainly as result of eutrophication. In contrast to abiotic factors, the role of biotic interactions on cyanobacterial bloom dynamics is less explored. Cyanobacterial adaptive advantages are insufficient to explain the prevalence of one species over another in a bloom period, which may be related to specific strategies and interactions with other components of the plankton community. This study aims to evaluate the influence of biotic and abiotic factors on the succession of cyanobacterial species during a bloom. The Funil reservoir was used as model, it is a eutrophic tropical reservoir in which cyanobacterial blooms have been reported over the last 20 years. In the first chapter, we present an integrative view of a mixed cyanobacterial bloom approaching temporal shifts in the dominance of cyanobacteria genera as well as in the associated heterotrophic bacteria community. The major bacteria phyla were Cyanobacteria and Proteobacteria, followed by Actinobacteria, Bacteroidetes, Verrucomicrobia, and Planctomycetes. The first period of the bloom was characterized by high abundances of Microcystis and Bacteroidetes. The second period was dominated by Synechococcus and C. raciborskii, together with Planctomycetes. Both significant positive and negative correlations were observed between certain cyanobacterial and heterotrophic bacteria taxa, pointing to potential ecologically significant associations. In the second chapter, we addressed the population structure of the main cyanobacterial genera involved in the bloom, exploring the intraspecific diversity from 16S rRNA gene sequences. While Microcystis, Pseudanabaena and Cylindrospermopsis were characterized by the dominance of one genotype, Synechococcus and Dolichospermum presented a higher number of sporadic genotypes. Microcystin (MC) and potentially MC producing cells were detected in all samples but no significant correlation between MC and genotypes were found. The results suggest that the populations of these genera are structured in different ways which can be relevant as an adaptation to persist during the bloom. Since in the reservoir phosphorous (P) concentrations are decreasing over the years we investigated the response of the two main cyanobacterial species to P restriction. So, in the third chapter, we tested five strains of C. raciborskii and M. aeruginosa, measuring Growth, photosynthethic efficiency, alkaline phosphatase activity, and maximum uptake rate under phosphorus deprivation. All strains were able to grow, maintain photosynthetic activity, and activate alkaline phosphatase, pointing to their ability to tolerate P deprivation. The level of intraspecific varation precludes generalization and reinforce that the physiological diversity of freshwater cyanobacteria is underscored in studies based in only one or few strains. Altogether, this work highlights the importance of biotic factors in the ecophysiology of cyanobacteria.
Author: Roberta Fernandes Pinto
Title: Phosphate influence on growth, morphology and lipid accumulation in a chlorophyceae microalgae, Ankistrodesmus
Year: 2017. Full text (in Portuguese)
Abstract:
Microalgae have been used in different biotechnological applications, such as lipid production for biofuels, and production of carotenoid, vitamins and pigments. These applications favor studies on metabolism and structure of some of these microrganisms. Currently, it is known that diminishing nutrients in the medium, such as phosphate, promotes the accumulation of neutral lipids, such as triacylglycerols, inside lipid bodies in lineages of Chlorophycea microalgae. Therefore, the objective of this study was to select, characterize and evaluate a lineage of Chlorophyceae cultivated in medium with different phosphate concentrations, aiming for the accumulation of lipids that are of interest in biofuels production. The Ankistrodesmus, Monoraphidium, and Scenedesmus strains were previously selected. The three strains were observed by scanning electron microscopy and showed thin structures not yet described at the end of the cells of Ankistrodesmus and Scenedesmus, as well as wall structures of Monoraphidium and Ankistrodesmus. Based on the accumulation of lipid bodies and intracellular phosphate in the form of polyphosphate granules, Ankistrodesmus was selected as working strain, which was identified by molecular analysis of the sequence from the large subunit (LSU) from ribosomal DNA (rDNA) as Ankistrodesmus stipitatus. The selected microalgae were evaluated for growth, average volume, chlorophyll, photosynthetic rate, phosphate uptake from the medium, changes in polyphosphate granules, relationship between them and lipid accumulation under different concentrations of phosphate in the medium, and most common fatty acids. It was established that the absence of phosphate in the medium promoted a small diminishing in growth, variations in the average biovolume, but even without affecting the concentration of chlorophyll per cell, it diminished its photosynthetic activity. After addition of phosphate in the medium, the cells showed growth recovery, reduction in the average biovolume, elevation of photosynthetic activity and diminishing of lipids. It was observed that consumption of polyphosphate granules in Ankistrodesmus alters their morphology, allowing them to acquire a half-moon shape or present a central region less electron dense than the other part of the granule. Also, an accumulation of lipidic material was observed next to the polyphosphate granules, suggesting a direct relationship between these and the lipid bodies. Absence of phosphate in the medium promoted an increase in the accumulation of neutral lipids and favored the accumulation of saturated and monounsaturated fatty acids, with the five main fatty acids found corresponding to 80% of the total, being these C18: 3, C18: 1, C16: 0, C18: 2, and C16: 5. It is concluded that intracellularly accumulated phosphate is capable of supporting the growth of Ankistrodesmus microalgae, with a direct relationship between formation of lipid bodies and polyphosphate granules, and that the absence of phosphate in the culture medium favors the accumulation of fatty acids of lipids of interest for the production of biofuels. In summary, with this work we identified that Ankistrodesmus stipitatusis apropriated for utilization in the development of biofuels and can be a model to understand better the function of polyphosphate granules in microalgae.
Author: Carolina Tolomini Miranda
Títle: Variation of nutritional conditions for growth optimization and lipid production by microalgae
Year: 2017. Full text (in Portuguese)
Abstract:
Culture medium optimization is a crucial step for viability of biodiesel production from lipids of microalgae. In this work were evaluated the effects of nutrients limitation, salinity increase and CO2 addition in lipid production by two strains of Chlorophyceae microalgae, Ankistrodesmus sp. (ANRF-01) e Chlamydomonas sp. (CHLRN-01), to determine the optimal condition for these production. The results revealed that the reduction to 75% of ASM-1 nitrate and phosphate concentrations presented superior results of biomass and lipid production, in order of 23,0 g.L-1 and 31,4% for ANRF-1 and 60 g.L-1 and 22.5% for CHLRN-1, respectively. Both strains were suitable for cultivation in brackish medium containing 0,5g L-1 NaCl. ANRF-1 showed an expressive increase in biomass production and lipid yield in ASM-1 medium 5% CO2 added, showing an important potential for CO2 mitigation from combustion gases. In other hand, for CHLRN-1 the 5% CO2 addition leaded to an inhibitory effect on cell growth with a decrease in lipid production. Being therefore the addition of 5% CO2 not recommended for this strain. The Fatty acid profile produced by ANRF-1 and CHLRN-1 was mainly composed of C16:0 (palmitic acid), C18:1n-9c (oleic acid), 18:2n-6c (linolenic acid) and C18:3n-3 (α-linolenic acid) promising not for biofuels industry only, but also for the pharmaceutical and food industries, due to the high variety of polyunsaturated fatty acids of omega3 and omega 6.
Author: Ricardo Rogers Paranhos
Title: Physiological, chemical and molecular efects of high concentrations of CO2 in Cylindrospermopsis raciborskii (Cyanobacteria)
Year: 2017 Full text (in Portuguese)
Abstract:
CO2 is a gas that has received great attention in recent years, since it is the main cause of the greenhouse effect and its high increase is related to industrialization processes. It is estimated that by the end of this century the current concentrations (400 ppm) will triplicate, causing even more serious impacts on the climate and consequently harming the environment and its organisms. Cyanobacteria is one of the oldest group of organisms (3.8 billion years old) and therefore have evolved in face of the great number of environmental changes that happened so far. One of these events was the increase of CO2 concentrations in the Paleocene period reaching levels 10 fold higher than current (4000 ppm). Though, the present study evaluated the physiological, chemical (saxitoxin and cyanopeptides) and transcriptomic responses of toxin producing and non-producing Cylindrospermopsis raciborskii strains, against concentrations of 400 and 4,000 ppm of CO2, in order to understand this harmfull algal bloom former would behave. Saxitoxin producing lineages (CYRF and T3), in general, had a stable growth and toxin production. However, when analyzing the growth rates of non-producing strains (CYLP and NPCS-1) and their transcriptomes, it was observed that the groups exposed to high CO2 had lower rates of growth and increased RNA regulation. The comparative analysis of the extracts of cyanopeptides allowed to observe that CYLP and T3 varied the production of those molecules of greater molecular weight under higher CO2. It was observed that the main variations occurred among strains, varying physiology and metabolism in different ways, drawing attention to the fact that different strains respond differently to stress. The results also call attention to the need to improve knowledge on cyanopeptides and their ecological roles and also the need to deepen expertise on transcriptomic techniques applied to cyanobacteria.
Author: Rodrigo de Cássio da Silva.
Title: Study of oxidative stress caused by cylindrospermopsin in tilapia (Oreochromis niloticus) under laboratory conditions.
Year: 2003. Full text (in Portuguese)
Abstract
Cylindrospermopsin is a cyanotoxin which can be produced by different species of cyanobacteria. Therefore their presence in water bodies is a public health concern worldwide. In mammals its action is systemic, but little is known about their toxicity in fish. Thus, the use of an experimental model of native tropical fish - Hoplias malabaricus - was used for this purpose in the present work. This thesis is organized into three chapters: the first and the second with exposure in vivo where after exposure to a single dose of CYN (aqueous extract and purified toxin) damage and its accumulation in the brain and muscle tissue after 14 days were assessed. In the brain and muscle were no significant changes in the activity of acetylcholinesterase. In addition, oxidative damage (lipid peroxidation) in the brain indicated that CYN is capable to crossing the blood brain barrier. In Chapter II, CYN concentration, biochemical biomarkers of oxidative stress, damage to macromolecules and histopathological aspects were evaluated. Injuries were corroborated by histological and biochemical biomarkers. Some damage to macromolecules, such as increase in the concentration of hydroperoxides and protein carbonylation, were observed. In vitro assays constituted the third chapter, in which a reduction in cellular viability of hepatocytes exposed to either extract and purified toxin was observed. The responses of different biomarkers indicated a change in the redox milieu of hepatocytes, which was more pronounced in cells exposed to the aqueous extract. In conclusion, this work presents novel aspects since there are few data regarding the toxicology of CYN in tropical fish species.
Author: Elisabete Lourdes do Nascimento
Títle: Environmental factors regulating the cyanobacteria dynamics in the Samuel’s reservoir hydreletric powerplant, Rondônia (Western Amazon,Brazil).
Year: 2012. Full text (in Portuguese)
Abstract
Cyanobacteria are photosynthetic prokaryotes with extensive development in eutrophic environments, a phenomenon called bloom. Besides the social and environmental damage caused by blooms, these may become a public health problem due to some cyanobacteria be able to synthesize cyanotoxins. In a previous study conducted in the Samuel’s hydroelectric powerplant reservoir (Rondônia), located in Jamari sub-basin,an increase was observed in the density of Microcystis sp (Cyanobacteria) with the increase of flow. Therefore, this study aimed to evaluate, through field and laboratory studies, environmental factors related to the cyanobacteria and cyanotoxins dynamics in this reservoir. Data are presented in three chapters. Chapter I deals with environmental variables and their correlation with phytoplankton, from data obtained over a hydrological cycle (Feb/2007-Feb/2008). The dominance of cyanobacteria occurred in March (Aphanocapsa holsatica and Microcystis panniformes) and May (Merismopedia tenuissima), however in most of the studied period the Chlorophycea were dominant. The Cyanobacteria dominance occurred in the rainy months, which showed nutrients in high concentrations. In February the Microcystins concentrations were detected in raw water above the maximum permissible value recommended by the national legislation 518/2004/MS (1μg.L-1). Knowing that the left bank of the reservoir has large areas deforested for cattle ranching and the bare soil contributes to the allochthonous input of nutrients, Chapter II presents data of an experiment in microcosms whose objective was to determine the effects of nutrient enrichment in phytoplankton community, specifically investigating the growth of cyanobacteria. Only when the P treatment was added alone (250 μg.L-1), Dolichospermum solitariumit was observed dominance of at 24th and 35th day of the experiment. In this period have limited the DIN concentrations were low (150 μ.L-1)and that might have limited growing of other phytoplankton species and favored D. solitarium, since this one is able to fix atmospheric nitrogen. Chapter III describes the physiological response of M. panniformis isolatedfrom reservoir, when growing under different iron concentrations (0, 23 e 223 μg.L-1/controle) for 8 days. After 7 days of Fe complete deprivation resulted in slower growth and reduced chlorophyll synthesis starting on the 4th day. Higher concentrations of microcystin-LR were observed in 23 μg.L-1 Fe and control. The information generated contributed to elucidate the environmental variables related to cyanobacteria development in the reservoir and the concentration of microcystins, among which stand out the N and P whose input to reservoir may increase due to the form of land, and Fe, the characteristic element of the region geology.
Author: Maria Isabel de Almeida Rocha.
Title: Evaluation of factors that contribute to the dominance of cyanobacteria in reservoir Funil and propose measures to improve water quality..
Year: 2012. Full text (in Portuguese)
Abstract
The loss of environmental quality of the Funil Reservoir (Itatiaia, Rio de Janeiro) is a consequence of multiple human impacts that have occurred in the watershed of the Paraíba do Sul River, upstream of the reservoir. Cyanobacterial blooms are common and its dominance is frequent in this environment. This study aimed to evaluate, through field analyzes, which factors affect the cyanobacterial dominance in the reservoir. Also, laboratory studies were done to investigate the behavior of phytoplankton community under reduced nutrient concentrations. The past data of the Paraíba do Sul watershed showed a deficiency in livestock waste treatment and sanitation in some municipalities of Paraíba Valley as the main causative agents of water quality loss along the river and reservoir. The field analysis generated 6 samples in rainy and dry seasons between 2009 and 2010, at 11 sampling points along the river, upstream of the reservoir. In this last one there were 5 sampling points. In general, high concentrations of nutrients were found where the municipalities had little sewage treatment. From Jacareí city sampling point (PS-3), the results indicated an increase in conductivity, NID, orthophosphate and turbidity. The concentrations of dissolved oxygen and pH were quite high in the reservoir, because of cyanobacterial blooms. The analysis indicated high densities of phytoplankton in the river and the reservoir in summer months, being dominated by Cyanogranis ferruginea in the river and Dolychospermum spp. at reservoir. Sphaerocavum brasiliensis, Cylindrospermopsis raciborskii and Eucapsis sp. were more abundant in the months of higher temperature in the reservoir, when Microcystis spp. was in low density. High temperature associated with increased turbidity and rainfall promoted an increase in the density and richness of the zooplankton community. The experimental results showed that the community composition has been altered at the end of 30 days in all treatments. It is suggested that the replacement of a quarter of the water volume received by the Funil Reservoir with a better quality would be enough change to occur in the phytoplankton community, leading to a reduction in the occurrence of cyanobacterial blooms.
Author: Andreia Maria da Anunciação Gomes.
Title: Ecophysiological study of cyanobacteria forming blooms in Jacarepaguá lagoon..
Year: 2011. Full text (in Portuguese)
Abstract
Jacarepaguá Lagoon is located in the South coast of Rio de Janeiro State, in the metropolitan zone of Rio de Janeiro City, Brazil. It is an oligohaline, shallow lagoon that has undergone intense eutrophication in the past decades, with cyanobacterial blooms reported since the 90'. Sporadically, a break of cyanobacteria dominance is followed by an increase of phytoplankton diversity. The aim of this study was to evaluate, through field and laboratory studies, which factors influence phytoplankton succession in this environment. During a seasonal cycle (2007-2008) we analyzed phytoplankton community and water chemical and physical parameters. During cyanobaterial blooms, the most prominent species were Microcystis aeruginosa, Aphanizomenon sp. and Planktothrix sp. Although still dominant, a significant reduction in biomass was observed during winter, when water temperature decreased from about 30oC(summer) to 18oC. Bloom collapse resulted in the release of a large quantity of DIN, allowing other species to occupy the niche released by cyanobacteria: Cyclotella sp. among diatoms and Desmodesmus quadricauda. among green algae. Considering these field observations, we tested, in laboratory, the effect of nutrient reduction on phytoplankton, as well as the effect of temperature on direct and indirect competition among the main species of Jacarepaguá lagoon. The reduction in nutrient concentration decreased cyanobacterial biomass but did not reduce their dominance. Even so, the low nutrient condition favored other phytoplanktonic groups, especially diatoms. The reduction of phosphate input in Jacarepaguá lagoon could recover this system. Temperature can influence growth and phytoplanktonic species replacement. We established, under laboratory conditions, optimum growth temperatures for P. agardhii (27oC), C. meneghiniana (18 and 21oC), D. quadricauda (18 and 30oC) and M. aeruginosa, (all those tested between 18 and 30oC). In competition tests with mixed cultivation M. aeruginosa was more competitive than others in both temperatures (18 and 30oC). In cultivation with exudates, different allelopathic responses (growth inhibition or stimulation) were attained in different temperatures. Observing the community dynamics in the lagoon, M. aeruginosa is favored during periods of higher temperatures. Exudates of its competitors stimulated its growth at 30oC, but not at 18oC. Adaptation of one strain to a specific temperature will determine not only its vulnerability to allelopathic compounds, but also its ability to express the allelochemical potential. Finally, it is difficult to point one factor that dictates the occurrence of cyanobacterial blooms in the Jacarepaguá lagoon. A synergy of environmental and biological factors combined with the physiology of the species will determine the dynamics of phytoplankton in this system.
Author: Alessandra Delazari-Barroso
Title: Factors controlling the development of phytoplankton in a reservoir of public supply in Espirito Santo State, with an emphasis on cyanobacteria.
Year: 2005. Full text (in Portuguese)
Abstract
Knowledge about key forcing functions that regulate tropical freshwater ecosystems is still under development. Physical regime, nutrient availability and trophic state are some relevant issues in tropical limnology. The contribution of these factors were evaluated on the dynamics of the Duas Bocas Reservoir (DBR) (Espírito Santo State, southeastern Brazil), a small (0.51 km2) and shallow (< 10 m) water supply reservoir surrounded by a protected forest. Monthly samplings were carried out from October 2002 to September 2003 to analyze phytoplankton community focused on physical (mixing regime and light) and chemical (mainly nutrients) properties. From October to April, strong thermal stratification and nutrient limitation for phytoplankton growth in the mixing layer were registered, besides anoxia and high nutrient concentrations in the hypolimnion. In May and June, mixing events took place. The average concentrations of total phosphorus and chlorophyll a were in agreement with meso-eutrophic systems. Nutrient concentrations showed co-limitation by N and P, suggesting that nutrient limitation rather than light limitation regulates the phytoplankton growth in the DBR most of the time. During the stratification period, the dominant small desmids (groups X3 and N) were positively associated with temperature, pH and N NO3 - and negatively associated with total phosphorus, N NH4 + and N/P ratio. On circulation period, desmids were replaced by nonheterocytic filamentous cyanobacteria (S1), associated positively with total phosphorus and NH4 + and negatively with temperature and pH, and by Cylindrospermopsis raciborskii (Sn), which showed significant positive correlation with pH, total phosphorus, and N NO3 -, and negative correlation with zeu and N NH4 +. A metalimnetic maximum of biomass composed by Limnothrix bicudoi and L. redekei were registered during high thermal stability. From 23 September to 27 October 2003, a nutrient enrichment experiment was carried out in the lacustrine zone of the reservoir, presenting mesotrophic characteristics. Nine enclosures (2,200 L each one), were set up. After P PO4 -, N NO3 - and N NH4 + additions at three days intervals, water samples for phytoplankton, chlorophyll a, and nutrients were collected from each enclosure and from the reservoir. At the beginning of the experiment, phytoplankton in controls, treatments, and reservoir were dominated by picoplanktonic and nanoplanktonic desmids, followed by cyanobacteria, coccal green, and criptophytes. The phytoplankton growth response to the enrichment was more rapid at long eutrophication than that at short eutrophication treatment. Biomass and diversity in enriched enclosures were higher than at controls and water reservoir, although no statistical significances were found. The dominance of desmids (functional group X3 and N) was replaced by filamentous cyanobacteria (groups Sn and S1), which showed a rapid growth response related to the increasing pH values and water x turbidity. The growth of C. raciborskii (Sn) was more pronounced in short eutrophication treatment, where it was associated to higher temperatures and low ammonium concentrations. Desmids increased significantly after 10th day of the experiment and were related to decreasing pH and high growth rates under higher temperatures. Nutrient input from rainfall was important as external sources that improved the phytoplankton development in a reservoir with N-limitation characteristics.
Author: Simone Maciel da Costa Gouvea.
Title: Effects of saxitoxins produced by Cilindrospermopsis raciborskii and other cyanotoxins on cladocerans (Branchiopoda)
Year: 2005. Full text (in Portuguese)
Abstract
In the last years, cyanobacterial blooms have been occurred frequently all around in the world, due to the increase in eutrophication processes. In Brazil, Cylindrospermopsis raciborskii produces saxitoxins and is dominant in several Brazilians water bodies. In the present study we investigate the effects of a saxitoxin producer strain (T3) and a non-toxic strain (NPLP-1) of Cylindrospermopsis raciborskii and of the water of the Funil reservoir, with occurrence of C. raciborskii, in the mobility, survivor, reproduction and fecundity of three species of cladocerans. We performed bioassays with different strains of cyanobacteria producers of different toxins, using intact cells and extract of lyophilized cells with the aim of proposing standard protocols to monitor toxins in water public supply impoundments, through bioassays with cladocerans. D. pulex and M. micrura showed an inhibition in their swimming movements when exposed to T3 strain and to Funil reservoir water. Strain NPLP-1 (nontoxic) did not show inhibition on their swimming movements, suggesting that this effect was really caused to saxitoxins. This is the first report on inhibition of swimming movements in cladocerans exposed to saxitoxins. In chronic bioassays, the cladocerans D. pulex e M. micrura were sensitive to T3 strain and were resistant to NPLP-1 strain, while D. gessneri was resistant to strains T3 and sensitive to strain NPLP-1. Bioassays performed with different strains, showed no adverse effect (CYP-030 and ITEP-024), inhibition in swimming movements (T3), until death (NPLJ-4). D. pulex was a good biomonitor to saxitoxins. The present study showed that, in using bioassay to the detection of cyanotoxins, it should be considered the sensitivity of cladocerans to toxins, mechanism of their action (paralysis or death) and accessibility to toxins (intact cells or extracts). In the performed bioassays were observed different sensitivity to cyanobacteria strains and their toxins among the cladocerans.
Author: Raquel Moraes Soares.
Title: Aspects of the biodistribution and effects of microcystins (cyanobacteria hepatotoxins) in mammals..
Year: 2005. Full text (in Portuguese)
Abstract
The most commonly reported cyanobacteria toxicosis is caused by microcystins, cyanotoxins described as potent and specific inhibitors of protein phosphatases, especially PP1 and PP2A in liver. The general objective of this study was to contribute to elucidation of MCYSTs accumulation and redistribution processes in animals and human beings, as well as analyzing the effects of these toxins on liver and lung of mice through experiments using sub-lethal doses intraperitoneally injected. The results showed that sub-lethal doses of microcystins damaged the physiology of liver and lung in young and adult animals. However, adult animal livers showed signs of recovery, observed by the increase in protein phosphatases activity as well as the return of glutathione concentration to the control levels. In mice lungs, MCYSTs caused alveolar collapse and an acute inflammatory process since the first hours, being characterized by PMN cells infiltration and intersticial edema. The inflammation probably caused to the observed increase in resistive and viscoelastic pressures and in elastances as well, indicating damage to the respiratory process. The results of studies with serum indicated that microcystins can remain in the organism for a long period. These toxins were detected over 2 months in serum of renal patients who were exposed to water containing MCYSTs during hemodialysis treatment at HUCFF-UFRJ. Therefore, this study contributed to demonstrate that it is always worthed to stand out the importance of monitoring and control of cyanobacteria blooms in recreational and source waters, once this a critical issue to the public health.
Author: Renato José Reis Molica
Title: Contribution to the knowledge of ecology, toxicology and phylogeny of Cylindrospermopsis raciborskii (Cyanobacteria).
Year: 2003. Full text (in Portuguese)
Abstract
The increasing concern about Cylindrospermopsis raciborskii is due to the potential of this cyanobacterium to produce toxins and form blooms and mainly due to the raise of reports on its occurrence in aquatic ecosystems of many countries, including Brazil. In this sense, the objectives of this work were: 1) to evaluate the limnological characteristics of two drinking water suppliers - Tapacurá and Ingazeira reservoirs both located in Pernambuco State -, where C. raciborskii blooms are frequent, 2) to characterize the saxitoxins produced by a C. raciborskii strain (ITEP-018), 3) to identify the neurotoxins present during C. raciborskii and Anabaena spiroides bloom in Tapacurá reservoir and 4) to examine the genetic diversity of C. raciborskii strains. The results have shown that an environmental stability associated with a high level of nutrients and low light availability favored C. raciborskii blooms in Tapacurá and Ingazeira reservoirs. The strain ITEP-018 produces six saxitoxins, including a new analogue. The neurotoxins identified during a cyanobacterial bloom in Tapacurá reservoir were saxitoxins and an acetilcholinesterase inhibitor, probably anatoxin-a(s), produced by C. raciborskii and A. spiroides, respectively. The phylogenetic analyses have shown a high homology between Cylindrospermopsis sp. strains from the same geographical origin and those could be assembled in three different clusters: strains of European, American and African/Australian origins. The results show the necessity of continuous monitoring of toxic cyanobacterial blooms and implementation of management plans to diminish the trophic state of aquatic ecosystems.
Author: Ana Cláudia Pimentel de Oliveira.
Title: Effects of physical and chemical factors in the degradation of microcystin..
Year: 2003. Full text (in Portuguese)
Abstract
Toxic cyanobacterial blooms have been frequently occurring in several reservoirs and water supplies in Brazil. The conventional water treatment train generally leads to break of cyanobacteria cells, promoting release of cyanotoxins to the water, which are poorly removed by that treatment. Taking this into account, this work had as proposal to investigate degradation process of dissolved microcystins under different environmental conditions as well as to investigate the removal of Microcystis aeruginosa cells (NPLJ-4 strain) and microcystins by slow sand filtration and granular activated carbon. The results of the microcystins degradation experiments using different conditions of pH (3,0; 5,0 and 7,0) and temperatures (12, 22 and 30oC) showed that the degradation of these molecules was extremely slow. However, in acidic medium and higher temperatures, the degradation was more intense. The application of different concentrations of ferric chloride (3,5; 7,5 and 10.1mg L-1) and aluminum sulfate (5,14 and 28 mg L-1) favored the breakage of NPLJ-4 cells. Nevertheless, microcystins were not detected in the dissolved fraction. It could be also verified that the water quality influenced on the quantitative analyses of dissolved microcystins. High conductivity water, Fe and Al concentrations promoted a great deal of reduction on the detection of these molecules, as well as on its biologic activity. On the other hand, water with high dissolved organic carbon concentrations favored the degradation of dissolved microcystins and bacteria growth, which makes evident the influence of the bacteria community on the biodegradation of microcystins. Concerning the removal experiments, the results indicated the slow sand filtration system was effective to the complete removal of NPLJ-4 cells in concentrations up to 105 cells.m L-1 with ration flow rate of 2 m3/m2.day. Under these conditions, either intracellular and extracellular microcystins was not detected in filtered water. The experiments carried out to verify the microcystins adsorption capacity of different types of granular activated carbon, commolly used in the purification systems of dialysis centers in Brazil, reveled that those activated carbons were ineffective to complete the adsorption of the dissolved microcystins on the concentrations tested (1,10 e 18 μg L-1). Consequently, the filtered water was considered unsuitable to production of injectable solutions and to the dialysis treatment.
Author: Gina Luísa Boemer Deberdt.
Title: Cyanobacterial study in high trophic degree reservoir (Salto Grande Reservoir - Americana - SP).
Year: 2002. Full text (in Portuguese)
Abstract
The study of the bloom of potential toxic cyanobacteria is of paramount significance, mainly when a reservoir endowed with great social and economical values due to both its multiple uses and its nearness to big urban centres such as the Salto Grande reservoir, located near the city of Americana in the inland of the State of São Paulo, Brazil is concerned. Based on such actuality, this work was aimed at supplying resources to devise forecasting the occurrence of cyanobacteria as well as the production of toxins in aquatic environments in which high eutrophication levels are observed. Towards this target, the research was carried out in the three steps that follow. In macrocosmic level (reservoir), the variations of the occurrence of both the cyanobacteria species and the remaining phytoplankton classes were found out, and then the toxic potentiality of the samples collected during the rainy season (January, February and March 1998) and the dry season (June, July, August and September 1998) in two sampling stations at the Salto Grande reservoir was analysed. In mesocosmic scale (tanks), the variations in the occurrences of the classes of phytoplankton and of the cyanobacteria species as well as the variations in production of toxins as a function of the ratio N/P that was dealt with by means of dosing nitrogen and phosphorus in the water were observed during the dry season. In microcosmic level (glass bottles “in lab”), the effect of reducing phosphorus (and consequently increasing the ratio N/P) on the growth and the production of toxins in cultures of Microcystis aeruginosa (Kützing) Kützing strains isolated from bloom samples of this species at the Salto Grande reservoir, during the wet and the dry seasons was tested. At the environment, the presence of microcystin in the water of all the samples, with the exception of the 25th of February 1999, was detected. Apart from the station 2 during January 27th 1999 (39.53 μg.L-1) and March 22th 1999 (3.98 μg.L-1), the concentrations stayed below the limit of acceptability (1 μg.L-1). At the experiments in mesocosmic scale, in 3 different conditions, increasing in phytoplankton density was observed. At the control condition (without manipulation), both reasonable augmentation of the percentage of the cyanobacteria contribution and diminishment of the other groups during the 11 days were detected. Under the condition of low N/P ratio, a slight rise of the percentage of the cyanobacteria and chlorophycea contribution and a decrease of the cryptophycea were observed; the other groups did not present much change. Under the condition of high N/P ratio, it was seen that the cyanobacteria increased, the chlorophycea remained unaffected and the cryptophycea decreased in comparison to the initial percentages. The conditions of the tanks that had been maintained at low N/P ratio favoured more the chlorophycea. The cyanobacteria presented biomass augmentation under the conditions of the tanks that had been maintained with high N/P ratio. For every test at the microcosmic level, the exponential stage had begun at the 8th development day. After being experimented for nearly 18 days, yield decrease of the cultures at the environment ASM-1 with phosphorus reduction was observed. In every scale that had been studied, it was noted that the microcystin concentration is related to unfavourable factors as far as the development of the toxic species is concerned. However, the determining causes for the growth of toxic cyanobacteria played different roles in each scale studied. At the macrocosmic level, enrichment was the responsible for increasing the density of the toxic species. At the microcosmic level, phosphorus availability had been directly related to Microcystis aeruginosa growth rate and, therefore, to the increase of microcystin concentration.
Author: Patrícia Domingos.
Title: Dominance of cyanobacteria producing microcystins in Jacarepaguá Lagoon, RJ
Year: 2001. Full text (in Portuguese)
Abstract
The phytoplankton community and the occurrence of toxic cyanobacterial blooms in Jacarepaguá lagoon, Rio de Janeiro, were studied in field and in laboratory. This is a shallow brackish lagoon (0 to 10S) and has been receiving domestic and industrial waste for the two past decades, becoming hypereutrophic (136µg.L-1) annual average of chlorophyll a). A study of annual cycle was made (08/96 to 09/97) and the samples were collected each two weeks in three stations. From the begin of the study until the end of spring (11/96) the phytoplankton was dominated by green algae, specially Chlorocoecalcs (61%) being replaced by cyanobacteria (87%), specially Microcystis aeruginosa, the dominant species until the end of studies. The green algae biomass was positively related with nitrate (r= 0.72) and phosphorus concentration (r= 0.55), and with the deep meter (r= 0.90). The correlation was negative with salinity (r= -0.41), temperature (r= -0.31) and ammonium concentration (r= -0.33). The cyanobacteria biomass was directly related to salinity (r=0.59) and ammonium concentration (r=0.42) and indirectly to water transparence (r= -0.40) and temperature (r= -0.30). The HPLC analysis showed the presence or microcrocystins (MC), hepatotoxic cyclic heptapeptides, in the séston samples (0.8 to 979.2 µg.L-1). After the beginning of M.aeruginosa, but not dissolved in the water. The M.aeruginosa biomass, séston MC concentration and cell quota of microcystins (MC/cell of M. aeruginosa) were higher in station 3(Arroio Pavuna) where the waste input is greater. The success of M. aeruginosa in the lagoon was related to salinity (r= 0.58) and ammonium concentration (r=0.41). The variation of salinity was important to explain the development of cyanobacteria in this water system. The experiments in different salinity conditions (0S, 2S, 5S and 10S) with M.aeruginosa (NPLJ_37) growth and microcystins production reveled that salinity has not favored the cyanobacteria. The M.aeruginosa culture with and without Eichhornia crassipes, abundant macrophyte in the lagoon, showing the risk of M.aeruginosa blooms to the environment, since these intermediate values are the most frequent. The constant salinity variations in this lagoon could contribute to increase the hepatotoxic M.aeruginosa biomass, and to increase the microcystins concentration, with consequences for fishing and pleasure activities in this environment.
Author: Marcelo Manzi Marinho.
Title: Ecology of phytoplankton in the reservoir Juturnaíba, Araruama-RJ, Brazil: Structure and dynamics of the community, ecophysiological and methodological aspects.
Year: 2000. Full text (in Portuguese)
Abstract
The phytoplankton community dynamics of a water supply reservoir (Juturnaíba reservoir, RJ, Brazil - 22°33’S; 42°18’W) was analysed relating it with the variations of some physical and chemical factors, usually considered as the main regulators of phytoplankton biomass and composition. Laboratory experimental studies on the ecophysiology of main phytoplankton species, were performed for verification of some hypotheses postulated from field observations. Besides the ecological aspects, methodological aspects were also approached about the application of quantitative analysis of photosynthetic pigment technique for phytoplankton evaluation. The general pattern of phytoplankton biomass and composition variability assessed through the photosynthetic pigment analysis, were consistent with the results obtained by the classic method of organisms counting by the inverted microscope and confirmed the applicability of this technique for the study and monitoring of the phytoplankton. Analysis and comparison of the results under ecological theories, made easy a better understanding of the ecological processes driving phytoplankton structure and function. Our data supports the view that the delimitation of assemblages applies reasonably to the one found in tropical enriched systems, despite the original formulation for temperate regions. Another theoretical aspect also considered was the analysis of the empirical relationships between the resources and species abundance considering species ecophysiology. Both statistical descriptions and observations demonstrated the strong interactions among limitation conditions, in general, and the relative resource variability, in particular, in the regulation phytoplankton community structure. Concerning these considerations, nitrogen availability was considered one of the main regulating factors of seasonal succession observed in the Juturnaíba reservoir. Then, considering a competition scenery among the main registered species (Microcystis aeruginosa and Aulacoseira distans) it would be expected that the growth rates of these algae were influenced by N/P ratio. However, the results obtained in the experiments did not show significant differences among growth rates. Even so, M. aeruginosa presented superior capacity of production biomass, especially in low N/P ratios. Besides, the experiments demonstrated that M. aeruginosa has a larger potential than A. distans to influence the proportional availability of nutrients. Thus, N/P ratio variation in the Juturnaíba reservoir can have been consequence of cyanobacteria high capacities for nitrogen and phosphorus uptake, that suggests M. aeruginosa success and A. distans decline, seem to have been due to the largest capacity of the cyanobacteria in growing under smaller nitrogen availability. Our results pointed that it is important to do experimental studies linked with field observations, for a better understanding of the ecological processes in the phytoplankton community.
Author: Aloysio da Silva Ferrão Filho.
Title: Influence of cyanobacterial bloom in populational dynamics of zooplankton in Jacarepaguá Lagoon (RJ): Toxic effects of Microcystis aeruginosa on cladocerans.
Year: 1998. Full text (in Portuguese)
Abstract
In this work, we studied the zooplankton communities of Jacarepaguá Lagoon (RJ) and the influences of the Microcystis aeruginosa bloom on cladoceran populations of this coastal lagoon. Sampling work was performed from August/96 to September/97 at tree stations for the analysis of zooplankton community and physical and chemical variables. Several laboratory experiments were performed to test the toxic effects of M aeruginosa strains and natural assemblages of this cyanobacteria on cladoceran species. The experiments consisted of acute and chronic toxicity experiments, weight gain experiments and measures of filtering rates in cladocerans submitted to toxic cyanobacteria. The field data analysis showed a strong influence of temperature and salinity on the zooplankton community dynamics. The highest density of zooplankton organisms occurred in summer and in low salinity conditions. The cladoceran populations showed signals of food limitation during the M aeruginosa bloom, as reduced egg production and appearance of ephypia. The increase in microcystin in the seston, however, has not excerted a clear effect on zooplankton populations. The laboratory experiments showed that M aeruginosa can excert toxic effects on cladoceran populations. These effects were more evident with laboratory strains of cyanobacteria than with natural assemblages, and can be enumerated as reductions in survivorship, fecundity, weight gain and filtering rates. However, the toxic effects of M aeruginosa depend on: toxic cell concentration, colony size, availability of nutritious resources and sensitivity of cladoceran species.
Author: Pedro Antonio Zagatto.
Title: Ecotoxicological evaluation of reservoir Guarapiranga - SP - Brazil regarding the problem of toxic algae and algaecides.
Year: 1995. Full text (in French)
Abstract
This biomonitoring study was carried out in Guarapiranga reservoir which is an important source for drinking water in Sao Paulo city, Brazil. Physico-chernical, biological and ecotoxicological results of the water and sediments from the Guarapiranga reservoir are hereby reported with the results of copper bioaccumulation. Toxicity of cyanophyces isolated from this reservoir, toxin retention by active charbon, toxicity studies of the algicides, hydrogen peroxide and copper sulfate, towards aquatic organisms and the proposition of the maximal allowable limits of the toxic algae in the water are presented too. Based on the total phosphate, orthophosphate, cWorophyll-a contents, as well as on the phytoplancktonic communities and water transparency, the Guarapiranga reservoir could be described as meso-hypereutrophic. Phosphate and copper leveis exceeded the standards of water quality required for preservation of aquatic !ife. Among the isolated species of cyanophyces, Oscillatoria quaaripunctulata, O. limnetica, O. amphibia, Phormidium sp, Microcystis incena as well as one of three strains of M. aeruginosa, ali were acutely toxic to rnice. For Daphnia only O. redekei caused acute toxicity. Hydrogen peroxide and copper sulfate were then tested for their algicidal activities. Filamentous algae were more sensitive to the hydrogen peroxide than to copper. However, these two products were more toxic to rnicrocrustaceans than to algae and fish species . The acute toxicity of these algicide rnixtures is less than additive. Nevertheless, phancktonic organisrns were good indicators for copper concentration in water. ln fact, copper was slightly bioaccumulated in fish muscles. Fish could still be considerated as acceptable for human consumption. The retention capability of activated charcoal was tested for the algal toxins. IS mg of the adsorbant was sufficient to retain up to 5mg of toxic algae dry weight. The Guarapiranga sediments could be considered as moderately to highly polluted by copper, although the sediments did not cause toxicity to Hyallela. The highest polluted area of this reservoir is located near the water catchrnent. Qur results show that the reservo ir is characterized by a dystrophic process, high algicide concentrations and subsequent toxicity of the water.
Links
 |