Search

Odor problems in source water caused by 2-methylisoborneol (MIB) have been a common issue in China recently, posing a high risk to drinking water safety. The earthy-musty odorant MIB has an extremely low odor threshold (4–16 ng/L) and is hard to remove via conventional processes in drinking water plants (DWP), and therefore could easily provoke complaints from consumers. This compound is produced by a group of filamentous cyanobacteria, mainly belonging to Oscillatoriales. Different from the well-studied surface-blooming Microcystis, filamentous cyanobacteria have specific niche characteristics that allow them to stay at a subsurface or deep layer in the water column. The underwater bloom of these MIB producers is therefore passively determined by the underwater light availability, which is governed by the cell density of surface scum. This suggests that drinking water reservoirs with relatively low nutrient contents are not able to support surface blooms, but are a fairly good fit to the specialized ecological niche of filamentous cyanobacteria; this could explain the widespread odor problems in source water. At present, MIB is mainly treated in DWP using advanced treatment processes and/or activated carbon, but these post-treatment methods have high cost, and not able to deal with water containing high MIB concentrations. Thus, in situ control of MIB producers in source water is an effective complement and is desirable. Lowering the underwater light availability is a possible measure to control MIB producers according to their niche characteristics, which can be obtained by either changing the water level or other measures.

Background Cyanobacteria are among the first photoautotrophic component of soil microorganism communities which play a key ecological role in nutrient cycles and soil productivity. However, the sustainability of these soil biodiversity ecosystem services is increasingly compromised, especially in urban and peri-urban areas where soils are heavily exploited and used for a wide range of human activities. The aim of this study is to assess the impact of different types of human disturbances on cyanobacteria diversity and distribution in suburban soils of Marrakesh. Soil and cyanobacteria sampling were carried out during two campaigns at six sites located along an anthropogenic gradient from the least urbanized suburbs of Marrakesh to the highly anthropized suburban area. In the laboratory, soil physicochemical characteristics were measured. The morphological identification of cyanobacteria species was based both on microscopic observation and on soil cultures in solid and liquid Z8 media. Results The results showed a total of 25 cyanobacteria taxa belonging to ten genera, four families, and two orders (Oscillatoriales 88% and Chroococcales 12% of taxa). Among the taxa identified, seven strains were isolated in soil culture in nutrient media and purified in monoalgal culture. The highest cyanobacterial diversity was recorded in irrigated soil with treated wastewater compared to the non-cultivated control soil. In Principal Component and Cluster Analysis, suburban soils were subdivided into three groups depending on the chemical properties and cyanobacteria composition. Cyanobacteria diversity was significantly associated with the soil moisture, total organic carbon (TOC), PO4-P, NO3-N, and NH4-N contents. Conclusions While diversity and microalgal biomass were significantly lower in the soils affected by municipal and mining solid wastes, the input of organic matter and nutrients from treated wastewater appears to be beneficial for the increasing of the biodiversity of soil cyanobacteria. This survey provides a first inventory of the soil cyanobacterial communities and shows their spatial variability and high sensitivity to the land-use practices and anthropogenic disturbances on urban soil in Moroccan drylands.

Sampling of fungi in a grassland on a hill in Rojkov, Central Slovakia, revealed a new species of Luticola (Diadesmidaceae). Its terrestrial populations were found close to the basis of the fertile part of the geoglossoid fungi (Geoglossaceae) that were overgrown with filamentous cyanobacteria of the orders Oscillatoriales and Synechococcales. Luticola rojkoviensis sp. nov. is characterized by the valve outline and the structure of the external valve face: valves are weakly dorsiventrally asymmetrical, rhombic-lanceolate in larger cells to rhombic-elliptic and tri-undulate in smaller cells, with shortly protracted and broadly rounded valve apices. Valve face is minimally concave, as the axial area is lowered and the area around distal raphe elevated. The surface of the valve is mostly uneven due to many depressions, so the external shape of the areolae and the impression of irregular longitudinal rows depend on the extent of these valve ornamentations. Proximal raphe endings are unilaterally slightly deflected, expanded into small central pores. The shape of both the proximal and the distal raphe fissures is slightly asymmetrical. The morphological characteristics of Luticola rojkoviensis sp. nov. are remarkably similar to those of L. hustedtii Levkov, Metzeltin et A.Pavlov, L. ectorii Levkov, Metzeltin et A.Pavlov and L. acidoclinata Lange-Bertalot. The association of Luticola rojkoviensis sp. nov. with geoglossoid fungi and epiphytic cyanobacteria is discussed.

Winter snowpack is an important source of moisture that influences the development of biological soil crusts (BSCs) in desert ecosystems. Cyanobacteria are important photosynthetic organisms in BSCs. However, the responses of the cyanobacterial community in BSCs to snowpack, snow depth and melting snow are still unknown. In this study, we investigated the cyanobacterial community composition and diversity in BSCs under different snow treatments (doubled snow, ambient snow and removed snow) and three snow stages (stage 1, snowpack; stage 2, melting snow; and stage 3, melted snow) in the Gurbantunggut Desert in China. In stages 1 and 2, Cyanobacteria were the dominant phylum in the bacterial community in the removed snow treatment, whereas Proteobacteria and Bacteroidetes were abundant in the bacterial communities in the ambient snow and doubled snow treatments. The relative abundances of Proteobacteria and Bacteroidetes increased with increasing snow depth. The relative abundances of Cyanobacteria and other bacterial taxa were affected mainly by soil temperature and irradiance. In stages 2 and 3, the relative abundance of Cyanobacteria increased quickly due to the suitable soil moisture and irradiance conditions. Oscillatoriales, Chroococcales, Nostocales, Synechococcales and unclassified Cyanobacteria were detected in all the snow treatments, and the most dominant taxa were Oscillatoriales and Chroococcales. Various cyanobacterial taxa showed different responses to snowpack. Soil moisture and irradiance were the two critical factors shaping the cyanobacterial community structure. The snowpack depth and duration altered the soil surface irradiance, soil moisture and other soil properties, which consequently were selected for different cyanobacterial communities. Thus, local microenvironmental filtering (niche selection) caused by snow conditions may be a dominant process driving shifts in the cyanobacterial community in BSCs.

The Laguna Madre-Tamaulipas is the world’s largest hypersaline lagoon and is equally located in south Texas, USA, and Tamaulipas, Mexico. Over 40% of its American surface area is covered by wind-ti...

Blooms of cyanobacteria cause enormous losses in both the economy and environment. Cyanophages are of great potential for fighting blooming cyanobacteria. Research report on cyanophage of bloom-forming cyanobacterium, Microcystis elabens is deficient. vB_MelS-Me-ZS1 (abbreviated as Me-ZS1) was isolated from fresh water by double-layer agar plate method using M. elabens. TEM exhibited that cyanosiphovirus Me-ZS1 has an icosahedral head about 60 nm in diameter, and a noncontractile tail approximately 260 nm. Experimental infection against 15 cyanobacterial strains showed that Me-ZS1 can infect 12 strains across taxonomic orders (Chroococcales, Nostocales and Oscillatoriales). High-throughput sequencing and bioinformatics analysis revealed that Me-ZS1 has a double-stranded DNA genome of 49,665 bp, with a G + C content of 58.22%, and 73 predicted open reading frames (ORFs). BLASTn and ORF comparisons showed that Me-ZS1 shares very low homology with the public sequences, and the phylogenetic tree based on TerL indicated that Me-ZS1 may delegate a novel and genetically distinct clade of Siphoviridae phages. In microcosm experiment, Me-ZS1 represented apparent effect on reducing relative abundance of cyanobacteria, increasing relative abundance of Saprospiraceae and protecting brocade carp (Carassius auratus) in cyanobacterial bloom water. This study isolated and characterized a novel broad-host-range Microcystis phage Me-ZS1 presenting a genetically distinct clade of freshwater cyanophage. The features of cyanophage Me-ZS1 provide a potential solution to the loss caused by cyanobacterial bloom.

Two types of Wilmottia (Cyanobacteria) were collected from the tree-bark of a tree on Mt. Gwanggyo in Suwon City, Gyeonggi-do and a rock wall of Haje Port, Geum River in Jeollabuk-do, Republic of Korea. Morphological observations using light microscopy (LM) and transmission electron microscopy (TEM) revealed that one species was Wilmottia murrayi (Coleofasciculaceae, Oscillatoriales) and the other had similar morphology to W. murrayi, with considerable genetic variations, and thus, it was described as a new species named Wilmottia koreana. Phylogenetic analyses of the 16S rRNA revealed that the family Coleofasciculaceae was clearly separated into taxonomic groups of each genus, and in them, Wilmottia forms a monophyletic lineage. W. koreana diverged the earliest, forming a unique clade separate from the others. Statistical analyses showed that the inter-species genetic distances of Wilmottia were significantly different from the intra-species distances (t-test, P < 0.001). Additionally, the secondary structures of D1–D1’, Box-B, and the V3 helices were different among the Wilmottia species. These results demonstrated that the proposed new Wilmottia species was unique in molecular traits. Therefore, we propose this to be a new species belonging to the genus Wilmottia with the name Wilmottia koreana sp. nov.

A new, cyclic carbonate eudesmane-type sesquiterpene, eudesmacarbonate (1), was isolated from marine filamentous cyanobacterial mats associated with apparent ingestion-related intoxications of capt...

Present paper deals with the diversity and distribution pattern of the genus Oscillatoria in Tripura, India. The genus Oscillatoria is a filamentous, unbranched, Non heterocystous and motile Blue-green Alga. In the present investigation we report sixteen species of the genus Oscillatoria from Tripura, India, out which, all the species are new addition to the flora of Tripura and seven species are new addition to Indian flora. Our study also revealed that out of total sixteen species of Oscillatoria, thirteen grow in rice fields and as well as in other habitats, but rest three taxa flourish only on specific habitats of Tripura, India.

The sesquiterpene geosmin, mainly originating from cyanobacteria, is considered one of the problematic odor compounds responsible for unpleasant-tasting and -smelling water episodes in freshwater supplies. The biochemistry and genetics of geosmin synthesis in cyanobacteria is well-elucidated and the geosmin synthase gene (geo) has been cloned and characterized in recent years. However, understanding the diversity, origin, and evolution of geo has been hindered by the limited availability of geo sequences to date. On the basis of the cloned geo sequences from16 filamentous geosmin-producing cyanobacterial species, representing 11 genera in Nostocales and Oscillatoriales, the diversity and evolution of geo in cyanobacteria was systematically analyzed in this study. Homologous alignment revealed that geo is highly conserved among the examined cyanobacterial species, with DNA sequence identities >0.72. Phylogenetic reconstruction and codon bias analysis based on geo suggest that cyanobacterial geo form a monophyletic branch with a common origin and ancestor for cyanobacteria, actinomycetes, and myxobacteria. The global ratio of nonsynonymous/synonymous nucleotide substitutions (dN/dS) was 0.125, which is substantially

A new terrestrial coccoid cyanobacterial strain was isolated in depression of a rough concrete surface in village Zengkeng, Fujian Province, China. This strain, named CHAB 6571, was characterized by a polyphasic approach. The strain exhibited morphological similarity to the Aliterlella species but differed in its larger cell sizes and irregular arranged thylakoids. 16S rRNA gene sequences of the strain had the maximum homology as 94.13 % to the genus Aliterella. The phylogeny based on 16S rRNA gene sequences revealed that there were four separated coccoid cyanobacterial clusters formed in the position representing Chroococcidiopsidales, at the vicinity of Nostocales and away from other coccoid cyanobacterial orders such as Chroococcales, Pleurocapsales and Synechococcales. These four main clusters as the CHAB 6571 in cluster A, genus Aliterella of the family Aliterellaceae in cluster B, Chroococcidiopsis sensu stricto of Chroococcidiopsidaceae in cluster C, and genera Chroogloeocystis and Gloeocapsopsis in cluster D, were likely to represent four different families with their 16S rRNA gene sequences similarities as 90–94%. However, the 16S rRNA phylogenetic results also revealed that the Chroococcidiopsidales were not monophyletic since the organisms belonging to Oscillatoriales such as Cephalothrix, Aerosakkonema and Microseira were phylogenetically mixed into the Chroococcidiopsidales. Combining the morphological, ecological and molecular features, CHAB 6571 as a new genus and species, as well as a novel family were therefore established, named Sinocapsa zengkensis (Sinocapsaceae, incertae sedis).

Rock art sites containing petroglyphs are found throughout the Negev Desert of southern Israel. Recently, as more sites have been revealed, there has been an increasing awareness of their importance as a cultural heritage resource. However, the rocks on which the petroglyphs were engraved are exposed to natural and anthropogenic weathering processes. In order to characterize the bacterial communities that may play a role in the weathering of rock surfaces and petroglyphs panels, we undertook culture-independent (Next Generation Sequencing technologies) and culture-dependent methods to identify the bacterial communities on these rock surfaces. The Results reveal that the most common bacterial components at two petroglyphs sites studied were Actinobacteria (33%), Cyanobacteria (30%), Proteobacteria (15%) and Bacteriodetes (7%). Further study and isolation revealed several Cyanobacteria strains related to the Oscillatoriales and Synecococcales orders. This study provides an important first step in understanding the bacterial community structure that may be associated with the weathering of petroglyphs in this region.

Raphidiopsis mediterranea is a freshwater cyanobacterium that forms toxic blooms in eutrophic water bodies. Factors controlling its proliferation have not been explored in detail. We investigated R. mediterranea autecology by (i) analyzing its dynamics in a hypertrophic shallow lake dominated by Planktothrix agardhii (Oscillatoriales) and its relationship with environmental factors; and (ii) studying the effect of light intensity and phosphate availability on R. mediterranea isolates growing in mono or in co-cultures with P. agardhii. The redundancy analysis demonstrated that water temperature, light, and phosphate concentrations were important driving factors for the seasonal succession of the two species. When grown together with P. agardhii, R. mediterranea growth was strongly promoted under the highest light intensity treatment. On the other hand, in monoalgal cultures under phosphorus starvation, both strains exhibited a significant increase in total alkaline phosphatase activity, and changes in the expression of homologs to phoA-like and phoD genes (members of the Pho regulon). However, R. mediterranea showed higher phosphatase activity than P. agardhii, suggesting greater tolerance to phosphate limitation. Taken together, we conclude that physiological features of R. mediterranea play an important role in the coexistence with P. agardhii under environmental changes., Facultad de Ciencias Naturales y Museo, Instituto de Limnología "Dr. Raúl A. Ringuelet"

The Lower Devonian Rhynie chert contains abundant fossil evidence of cyanobacteria. However, only a few of these fossils have been described. A newly discovered type of cyanobacterial filament is 22 to > 30 µm wide, and thus substantially larger than all filamentous cyanobacteria previously known from the Rhynie chert. Trichomes are uniseriate, composed of short, discoid cells not constricted at the cross walls, and enveloped in a distinct sheath. Because the filaments correspond in morphology to Palaeolyngbya barghoorniana, a fossil cyanobacterium described from the Precambrian, they are assigned to the fossil genus Palaeolyngbya and formally proposed as a new species, P. kerpii. Palaeolyngbya is attributed to the Oscillatoriaceae (Oscillatoriales) and compared to the modern genus Lyngbya sensu lato. All specimens of P. kerpii occur in a small area of clear chert intercalated between substrate layers, and thus support the hypothesis that substrate served as a conservation trap for delicate microbial life in the Rhynie setting.

This study aimed to better understand the biodiversity and ecological aspects of benthic filamentous cyanobacteria along the coast of an extensive Brazilian tropical region with underestimated biodiversity. We collected samples between 2010 and 2012 in 24 areas along the coast of the State of Bahia, Northeastern Brazil. We analyzed biodiversity, life form, and spatial distribution of filamentous cyanobacteria on various marine substrata. The intertidal area was divided into three microhabitats according to hydrodynamics: tidal pools, protected reef region, and front reef region. Thirty-two taxa were identified and Oscillatoriales showed the highest biodiversity (16 taxa), followed by Nostocales (9), Synechoccocales (5) and Spirulinales (2). We reported 22 new references to Bahia State. Twenty-two taxa occurred only in one beach, and Symploca cf. hydnoides Gomont was the only widely distributed along the coast of Bahia. Epilithic (21 taxa) and epiphytic (15) showed the greatest species richness. Only two species presented epizoic life form. We observed the highest species richness in the protected reef region (17 taxa). We found eleven and eight taxa in the tidal pool and supralittoral zone, respectively. No cyanobacteria were found in the front reef region, an area with high hydrodynamics. This research presented many taxa in common with previous studies on cyanobacterial diversity developed in other tropical regions around the globe. The great biodiversity and new records reported in this study highlight the need of further surveys in tropical coastal environments, areas still underexplored in terms of biodiversity of cyanobacteria.

In both natural and built environments, microbes on occasions manifest in spherical aggregates instead of substratum-affixed biofilms. These microbial aggregates are conventionally referred to as granules. Cryoconites are mineral rich granules that appear on glacier surfaces and are linked with expanding surface darkening, thus decreasing albedo, and enhanced melt. The oxygenic photogranules (OPGs) are organic rich granules that grow in wastewater, which enables wastewater treatment with photosynthetically produced oxygen and which presents potential for net autotrophic wastewater treatment in a compact system. Despite obvious differences inherent in the two, cryoconite and OPG pose striking resemblance. In both, the order Oscillatoriales in Cyanobacteria envelope inner materials and develop dense spheroidal aggregates. We explore the mechanism of photogranulation on account of high similarity between cryoconites and OPGs. We contend that there is no universal external cause for photogranulation. However, cryoconites and OPGs, as well as their intravariations, which are all under different stress fields, are the outcome of universal physiological processes of the Oscillatoriales interfacing with goldilocks interactions of stresses. Finding the rules of photogranulation may enhance engineering of glacier and wastewater systems to manipulate their ecosystem impacts.

Filamentous cyanobacteria belonging to the ‘marine Geitlerinema’ cluster are spread worldwide in saline environments and considered to play an important ecological role. However, the taxonomy of this group remains unclear. Here, we analyzed the phylogeny, ecology and biogeography of the ‘marine Geitlerinema’ cluster representatives and revealed two subclusters: 1) an ‘oceanic’ subcluster containing PCC7105 clade and BBD clade with free-living and pathogenic strains distributed in Atlantic, Indian and Pacific Ocean-related localities, and 2) a Sodalinema subcluster containing free-living strains from marine, hypersaline, saline-alkaline and soda lake habitats from the Eurasian and African continents. Polyphasic analysis using genetic and phenotypic criteria demonstrated that these two groups represent separate genera. Representatives of Sodalinema subcluster were phylogenetically attributed to the genus Sodalinema. Our data expand the ecological and geographical distribution of this genus. We emended the description of the genus Sodalinema and proposed three new species differing in phylogenetic, geographic and ecological criteria: Sodalinema orleanskyi sp. nov., Sodalinema gerasimenkoae sp. nov. and Sodalinema stali sp. nov. Additionally, a new genus and species Baaleninema simplex gen. et sp. nov. was discribed within the PCC7105 clade. By this, we put in order the current confusion of the ‘marine Geitlerinema’ group and highlight its ecological diversity.

Cyanobacteria are ecologically versatile microorganisms, occupying diverse habitats, from terrestrial caves to coastal shores and from brackish lakes to thermal springs. Cyanobacteria have also been linked with hydrogen cyanide (HCN), mainly for their ability to catabolize HCN by the nitrogenase enzyme. In this context, we sampled disparate environments, spanning from Canary Islands and Iceland to Estonia and Cyprus. Eighty-one (81) strains were isolated and characterised with taxonomic indices and molecular markers (16S-23S rRNA region and cpcBA region), whilst their ability to produce HCN was evaluated. This approach resulted in the description of five new genera (Speleotes, Haliplanktos, Olisthonema, Speos, and Iphianassa) and their type species (S. anchialus, H. antonyquinny, O. eestii, S. fyssassi, I. zackieohae) representing Chroococcales, Chroococcidiopsales, Oscillatoriales, Synechococcales, and Nostocales orders, respectively. We also found unique lineages inside the genera Komarekiella, Stenomitos, Cyanocohniella, and Nodularia, describing four new species (K. chia, S. pantisii, C. hyphalmyra, N. mediterannea). We report for the first time a widespread production of HCN amongst different taxa and habitats. Epilithic lifestyle, where cyanobacteria are more vulnerable to grazers, had the largest relative frequency in HCN production. In this work, we show novel cyanobacteria diversity from various habitats, including an unexplored anchialine cave, and possible correlation of cyanobacteria chemo- with species diversity, which may have implications on strategic focusing of screening programs on underexploited taxa and/or habitats.

[This corrects the article DOI: 10.3389/fbioe.2022.932695.]., (Copyright © 2023 Koch, Noonan, Qiu, Dofher, Kieft, Mottahedeh, Shastri and Hallam.)

Abstract FigureThe morphology, 16S rRNA gene phylogeny and the 16S-23S rRNA gene ITS secondary structures of three strains of marine Cyanobacteria, isolated from inter- and subtidal environments from north Portugal were studied, resulting in the description of Zarkia subtidalensis gen. et. sp. nov. (Zarkiaceae fam. nov.) and Romeriopsis marina gen. et. sp. nov (Leptolyngbyaceae). No diacritical morphological characters were found either for the new family or for the new genera. The 16S rRNA gene Maximum Likelihood and Bayesian phylogenies supported that Zarkia and Zarkiaceae are members of the Oscillatoriales, positioned close to Microcoleaceae genera, but distant from Microcoleus. Romeriopsis is positioned within the Leptolyngbyaceae and is closely related to Alkalinema. The secondary structures of the D1-D1’, Box B, V2 and V3 helices corroborate with the phylogenetic results. Furthermore, our study supports previous observations of polyphyletic Oscillatoriales families and reinforces the need for their taxonomical revision.

Antarctic microorganisms are characterized for living under extreme conditions such as low temperatures, and high UV-radiation, including and freeze-thaw stress derived from annual environmental changes. Microbial mats are successful microbial consortia in these extreme environments, yet much is unknown regarding their diversity and functional role in terrestrial polar regions. The bacterial diversity in microbial mats from Fildes Peninsula in Maritime Antarctica and their genetic potential for nitrogen acquisition has been explored in our laboratory. The results showed that microbial mats were clustered within two main groups according to their 16S rRNA genetic diversity, separating those collected nearby scientific stations from those in coastal plains. The later showed a lower relative proportion of Proteobacteria and a higher proportion of Cyanobacteria, Planctomycetes, and Thaumarchaeota, possibly due to physicochemical and biological factors associated with sea-land interactions. All microbial mats had a strong nifH genetic signal, mainly associated with Cyanobacteria and Proteobacteria, suggesting the relevance of both oxygenic and anoxygenic bacteria potentially involved in N-fixation. The capacity of Oscillatoriales and Acaryochloris marina to assimilate Nitrogen was also evidenced. This study showed the diversity and structure of microbial mats in the Fildes Peninsula and the importance of cyanobacteria in microbial mats based on their role for N2 fixation and N- assimilation.

Cyanobacteria are an important part of phytoplankton communities, however, they are also known for forming massive blooms with potentially deleterious effects on recreational use, human and animal health, and ecosystem functioning. Emerging high-frequency imaging flow cytometry applications, such as Imaging FlowCytobot (IFCB), are crucial in furthering our understanding of the factors driving bloom dynamics, since these applications provide community composition information at frequencies impossible to attain using conventional monitoring methods. However, the proof of applicability of automated imaging applications for studying dynamics of filamentous cyanobacteria is still scarce. In this study we present the first results of IFCB applied to a Baltic Sea cyanobacterial bloom community using a continuous flow-through setup. Our main aim was to demonstrate the pros and cons of the IFCB in identifying filamentous cyanobacterial taxa and in estimating their biomass. Selected environmental parameters (water temperature, wind speed and salinity) were included, in order to demonstrate the dynamics of the system the cyanobacteria occur in and the possibilities for analyzing high-frequency phytoplankton observations against changes in the environment. In order to compare the IFCB results with conventional monitoring methods, filamentous cyanobacteria were enumerated from water samples using light microscopical analysis. Two common bloom forming filamentous cyanobacteria in the Baltic Sea, Aphanizomenon flosaquae and Dolichospermum spp. dominated the bloom, followed by an increase in Oscillatoriales abundance. The IFCB results compared well with the results of the light microscopical analysis, especially in the case of Dolichospermum. Aphanizomenon biomass varied slightly between the methods and the Oscillatoriales results deviated the most. Bloom formation was initiated as water temperature increased to over 15°C and terminated as the wind speed increased, dispersing the bloom. Community shifts were closely related to movements of the water mass. We demonstrate how using a high-frequency imaging flow cytometry application can help understand the development of cyanobacteria summer blooms.

The influence of environmental variables on planktonic biodiversity is widely known. However, the absence of information about the cyanobacterial community in tropical estuarine regions motivated this work, whose objective was to investigate the spatio-temporal variation of cyanobacterial density related to physicochemical factors in a Brazilian Amazonian estuary. For the qualitative and quantitative study of cyanobacteria and physicochemical variables, samples were collected in April/July/2009 and April/August/2010. We identified 31 species of the orders Chroococcales, Oscillatoriales and Nostocales. Species of the genera Aphanocapsa, Dolichospermum, Komvophoron, Microcystis, Pseudanabaena and Merismopedia were frequent and abundant throughout the study period. Some of the found genera have already been described as potential toxin producers. The dynamics of cyanobacteria were temporal, the highest densities occurred in 2010 (average= 1080.86 ± 702.86 cells.mL-1) mainly influenced by the high values of pH, temperature, electrical conductivity, total dissolved solids, ammonium nitrogen which led cyanobacteria to present different responses in terms of richness, density and diversity between the years.