Dolichospermum and Aphanizomenon as neurotoxins producers in some Russian freshwaters.

Last decades, cyanobacterial blooms have been commonly reported in Russia. Among the boom-forming species, potential toxin producers have been identified. The aim of this paper was to study the presence of neurotoxic compounds - saxitoxins and anatoxin-a - in water bodies from different regions of Russia. We also made attempts to identify the neurotoxin-producing genera. The good convergence of the results obtained by light microscopy, PCR and LC-MS/MS analyses indicated the presence of active neurotoxin producing species in all investigated water bodies. Saxitoxin was detected in phytoplankton from 4 water bodies in Central European Russia and West Siberia, including lake and reservoirs used as a source for potable water. The water bodies differed with the respect of saxitoxin producers which belonged to Aphanizomenon and/or Dolichospermum genera. For the first time, we obtained quantitative data on the intracellular saxitoxin concentration in Russian freshwaters using LC-MS/MS. Anatoxin-a was detected only in lakes of Northwestern Russia. In the eutrophic shallow Lower Suzdal Lake, Aphanizomenon was the stated anatoxin-a-producing genus. In the large shallow artificial hypertrophic Sestroretskij Razliv Lake, it was very likely that both dominant species - Aphanizomenon flos-aquae and Dolichospermum planctonicum - were anatoxin-a producers.

High cell-specific rates of nitrogen and carbon fixation by the cyanobacterium Aphanizomenon sp. at low temperatures in the Baltic Sea.

Aphanizomenon is a widespread genus of nitrogen (N2)-fixing cyanobacteria in lakes and estuaries, accounting for a large fraction of the summer N2-fixation in the Baltic Sea. However, information about its cell-specific carbon (C)- and N2-fixation rates in the early growth season has not previously been reported. We combined various methods to study N2-fixation, photosynthesis and respiration in field-sampled Baltic Sea Aphanizomenon sp. during early summer at 10°C. Stable isotope incubations at in situ light intensities during 24 h combined with cell-specific secondary ion mass spectrometry showed an average net N2-fixation rate of 55 fmol N cell(-1) day(-1). Dark net N2-fixation rates over a course of 12 h were 20% of those measured in light. C-fixation, but not N2-fixation, was inhibited by high ambient light intensities during daytime. Consequently, the C:N fixation ratio varied substantially over the diel cycle. C- and N2-fixation rates were comparable to those reported for Aphanizomenon sp. in August at 19°C, using the same methods. High respiration rates (23% of gross photosynthesis) were measured with (14)C-incubations and O2-microsensors, and presumably reflect the energy needed for high N2-fixation rates. Hence, Aphanizomenon sp. is an important contributor to N2-fixation at low in situ temperatures in the early growth season.

Characterization of a lytic cyanophage that infects the bloom-forming cyanobacterium Aphanizomenon flos-aquae.

Vb-AphaS-CL131 is a novel cyanosiphovirus that infects harmful Aphanizomenon flos-aquae. This cyanophage has an isometric head, 97 nm in diameter and a long, flexible non-contractile tail, 361 nm long. With a genome size of ~120 kb, it is the second largest cyanosiphovirus isolated to date. The latent period was estimated to be ~36 h and a single infected cell produces, on average, 218 infectious cyanophages. Cyanophage infection significantly suppresses host biomass production and alters population phenotype.

First report of cylindrospermopsin production by two cyanobacteria (Dolichospermum mendotae and Chrysosporum ovalisporum) in Lake Iznik, Turkey.

Cylindrospermopsin (CYN) is a cytotoxic alkaloid produced by cyanobacteria. The distribution of this toxin is expanding around the world and the number of cyanobacteria species producing this toxin is also increasing. CYN was detected for the first time in Turkey during the summer months of 2013. The responsible species were identified as Dolichospermum (Anabaena) mendotae and Chrysosporum (Aphanizomenon) ovalisporum. The D. mendotae increased in May, however, C. ovalisporum formed a prolonged bloom in August. CYN concentrations were measured by LC-MS/MS and ranged from 0.12 µg·mg⁻¹ to 4.92 µg·mg⁻¹ as dry weight, respectively. Both species were the only cyanobacteria actively growing and CYN production was attributed solely to these species. Despite CYN production by C. ovalisporum being a well-known phenomenon, to our knowledge, this is the first report of CYN found in D. mendotae bloom.

Survey of cyanobacterial toxins in Czech water reservoirs--the first observation of neurotoxic saxitoxins.

The environmental occurrence and concentrations of cyanobacterial toxins (cyanotoxins) were investigated in the Czech Republic. Concentrations of microcystins (MCs), cylindrospermopsin (CYN) or saxitoxins (STXs) were determined immunochemically by ELISA assays in 30 water samples collected from the surface layers of 19 reservoirs during the summer season of 2010. MCs were detected in 18 reservoirs and 83 % of samples, with median and maximal concentration being 1.5 and 18.6 µg/L, respectively. The high frequency of MC occurrence coincided with prevalence of cyanobacterium Microcystis sp., which was detected in 87 % samples, followed by Dolichospermum (Anabaena) sp. observed in 33 % samples. CYN was detected by ELISA only in one sample at a concentration of 1.2 µg/L. STXs presence was indicated for the first time in Czech water reservoirs when the toxins were found at low concentrations (0.03-0.04 µg/L) in two samples (7 %) collected from two different reservoirs, where STXs co-occurred with MCs and eventually also with CYN. In both STX-positive samples, the phytoplankton community was dominated by Microcystis sp., but Dolichospermum sp. and/or Aphanizomenon sp. were also present as putative producers of STX and/or CYN. Cyanotoxins commonly occurred in Czech water reservoirs, and MCs frequently at concentrations possibly associated with human health risks. MCs were the most prevalent and abundant cyanotoxins, but also other cyanotoxins were detected, though sporadically. Further research and regulatory monitoring of cyanotoxins other than MCs is therefore required.

Aphanizomenon gracile (Nostocales), a cylindrospermopsin-producing cyanobacterium in Polish lakes.

The cyanobacterial cytotoxin cylindrospermopsin (CYN) has become increasingly common in fresh waters worldwide. It was originally isolated from Cylindrospermopsis raciborskii in Australia; however, in European waters, its occurrence is associated with other cyanobacterial species belonging to the genera Aphanizomenon and Anabaena. Moreover, cylindrospermopsin-producing strains of widely distributed C. raciborskii have not yet been observed in European waters. The aims of this work were to assess the occurrence of CYN in lakes of western Poland and to identify the CYN producers. The ELISA tests, high-performance liquid chromatography (HPLC)-DAD, and HPLC-mass spectrometry (MS)/MS were conducted to assess the occurrence of CYN in 36 lakes. The cyrJ, cyrA, and pks genes were amplified to identify toxigenic genotypes of cyanobacteria that are capable of producing CYN. The toxicity and toxigenicity of the C. raciborskii and Aphanizomenon gracile strains isolated from the studied lakes were examined. Overall, CYN was detected in 13 lakes using HPLC-MS/MS, and its concentrations varied from trace levels to 3.0 µg L(-1). CYN was widely observed in lakes of western Poland during the whole summer under different environmental conditions. Mineral forms of nutrients and temperature were related to CYN production. The molecular studies confirmed the presence of toxigenic cyanobacterial populations in all of the samples where CYN was detected. The toxicity and toxigenicity analyses of isolated cyanobacteria strains revealed that A. gracile was the major producer of CYN.

Zebrafish neurotoxicity from aphantoxins--cyanobacterial paralytic shellfish poisons (PSPs) from Aphanizomenon flos-aquae DC-1.

Aphanizomenon flos-aquae (A. flos-aquae), a cyanobacterium frequently encountered in water blooms worldwide, is source of neurotoxins known as PSPs or aphantoxins that present a major threat to the environment and to human health. Although the molecular mechanism of PSP action is well known, many unresolved questions remain concerning its mechanisms of toxicity. Aphantoxins purified from a natural isolate of A. flos-aquae DC-1 were analyzed by high-performance liquid chromatography (HPLC), the major component toxins were the gonyautoxins1 and 5 (GTX1 and GTX5, 34.04% and 21.28%, respectively) and the neosaxitoxin (neoSTX, 12.77%). The LD50 of the aphantoxin preparation was determined to be 11.33 µg/kg (7.75 µg saxitoxin equivalents (STXeq) per kg) following intraperitoneal injection of zebrafish (Danio rerio). To address the neurotoxicology of the aphantoxin preparation, zebrafish were injected with low and high sublethal doses of A. flos-aquae DC-1 toxins 7.73 and 9.28 µg /kg (5.3 and 6.4 µg STXeq/kg, respectively) and brain tissues were analyzed by electron microscopy and RT-PCR at different timepoints postinjection. Low-dose aphantoxin exposure was associated with chromatin condensation, cell-membrane blebbing, and the appearance of apoptotic bodies. High-dose exposure was associated with cytoplasmic vacuolization, mitochondrial swelling, and expansion of the endoplasmic reticulum. At early timepoints (3 h) many cells exhibited characteristic features of both apoptosis and necrosis. At later timepoints apoptosis appeared to predominate in the low-dose group, whereas necrosis predominated in the high-dose group. RT-PCR revealed that mRNA levels of the apoptosis-related genes encoding p53, Bax, caspase-3, and c-Jun were upregulated after aphantoxin exposure, but there was no evidence of DNA laddering; apoptosis could take place by pathways independent of DNA fragmentation. These results demonstrate that aphantoxin exposure can cause cell death in zebrafish brain tissue, with low doses inducing apoptosis and higher doses inducing necrosis.

A CARD-FISH protocol for the identification and enumeration of cyanobacterial akinetes in lake sediments.

Akinetes are the dormant cells of Nostocales (cyanobacteria) that enable the organisms to survive harsh environmental conditions while resting in bottom sediments. The germination of akinetes assists the dispersal and persistence of the species. The assessment of the akinete pool in lake sediments is essential to predict the bloom formation of the Nostocales population. We present here the implementation of an improved catalysed reporter deposition (CARD)-fluorescence in situ hybridization (FISH) protocol to assist the identification and quantification of akinetes in sediment samples. Several 16S rRNA gene oligonucleotide probes were evaluated for labelling akinetes of various species of Anabaena, Aphanizomenon and Cylindrospermopsis. Akinetes of all the taxa studied were successfully labelled and could be easily detected by their bright fluorescence signal. The probes' specificity was tested with 32 strains of different taxa. All six Cylindrospermopsis raciborskii strains were labelled with a specific probe for its 16S rRNA gene. A more general probe labelled 73% of the Anabaena and Aphanizomenon strains. The counting data of field samples obtained with CARD-FISH and the regular light microscopy approach did not differ significantly, confirming the suitability of both methods. The CARD-FISH approach was found to be less time-consuming because of better visibility of akinetes.

Preliminary molecular identification of cylindrospermopsin-producing Cyanobacteria in two Polish lakes (Central Europe).

The presence of toxigenic cyanobacteria capable of biosynthesis of cylindrospermopsin (CYN) was measured in 24 water samples collected from the lakes Bytynskie (BY) and Bninskie (BN) in the Western Poland. The study also covered analysis of toxigenicity and production of CYN by the culture of Cylindrospermopsis raciborskii isolated from BY. The cyrJ gene associated with CYN production was identified in 22 water samples collected in the summer seasons of 2006 and 2007. The presence of CYN was confirmed in 16 samples. The homology searches revealed that amplified sequences of four water samples, which were selected from among all the samples, displayed a strong 99% homology to cyrJ gene of Aphanizomenon sp. 10E6. The culture of C. raciborskii did not contain the cyrJ gene nor the CYN. The specificity of C. raciborskii was confirmed by application of a fragment of the rpoC1. These first genetic analyses have shown that Aphanizomenon seems to be the main cyanobacterial genus responsible for the production of CYN in the Polish lakes. The lack of toxigenicity of the isolated C. raciborskii suggests that it is possible that this invasive species does not demonstrate toxigenic activity in Polish water bodies.

Forecasting of cyanobacterial density in Torrão reservoir using artificial neural networks.

The ability of general regression neural networks (GRNN) to forecast the density of cyanobacteria in the Torrão reservoir (Tâmega river, Portugal), in a period of 15 days, based on three years of collected physical and chemical data, was assessed. Several models were developed and 176 were selected based on their correlation values for the verification series. A time lag of 11 was used, equivalent to one sample (periods of 15 days in the summer and 30 days in the winter). Several combinations of the series were used. Input and output data collected from three depths of the reservoir were applied (surface, euphotic zone limit and bottom). The model that presented a higher average correlation value presented the correlations 0.991; 0.843; 0.978 for training, verification and test series. This model had the three series independent in time: first test series, then verification series and, finally, training series. Only six input variables were considered significant to the performance of this model: ammonia, phosphates, dissolved oxygen, water temperature, pH and water evaporation, physical and chemical parameters referring to the three depths of the reservoir. These variables are common to the next four best models produced and, although these included other input variables, their performance was not better than the selected best model.

First report of anatoxin-a-producing cyanobacterium Aphanizomenon issatschenkoi in northeastern Germany.

The neurotoxin anatoxin-a (ATX), has been detected in several northeast German lakes during the last two decades, but no ATX producers have been identified in German water bodies so far. In 2007 and 2008, we analyzed phytoplankton composition and ATX concentration in Lake Stolpsee (NE Germany) in order to identify ATX producers. Sixty-one Aphanizomenon spp. strains were isolated, morphologically and phylogenetically characterized, and tested for ATX production potential by liquid chromatography-tandem mass spectrometry (LC-MS/MS). New primers were specifically designed to identify a fragment of a polyketide synthase gene putatively involved in ATX synthesis and tested on all 61 Aphanizomenon spp. strains from L. Stolpsee and 92 non-ATX-producing Aphanizomenon spp., Anabaena spp. and Anabaenopsis spp. strains from German lakes Langersee, Melangsee and Scharmützelsee. As demonstrated by LC-MS/MS, ATX concentrations in L. Stolpsee were undetectable in 2007 and ranged from 0.01 to 0.12 microg l(-1) in 2008. Fifty-nine of the 61 strains isolated were classified as Aphanizomenon gracile and two as Aphanizomenon issatschenkoi. One A. issatschenkoi strain was found to produce ATX at concentrations of 2354+/-273 microg g(-1) fresh weight, whereas the other A. issatschenkoi strain and A. gracile strains tested negative. The polyketide synthase gene putatively involved in ATX biosynthesis was found in the ATX-producing A. issatschenkoi strain from L. Stolpsee but not in the non-ATX-producing Aphanizomenon spp., Anabaena spp. and Anabaenopsis spp. strains from lakes Stolpsee, Langersee, Melangsee, and Scharmützelsee. This study is the first confirming A. issatschenkoi as an ATX producer in German water bodies.

Paralytic shellfish poisoning toxin-producing cyanobacterium Aphanizomenon gracile in northeast Germany.

Neurotoxic paralytic shellfish poisoning (PSP) toxins, anatoxin-a (ATX), and hepatotoxic cylindrospermopsin (CYN) have been detected in several lakes in northeast Germany during the last 2 decades. They are produced worldwide by members of the nostocalean genera Anabaena, Cylindrospermopsis, and Aphanizomenon. Although no additional sources of PSP toxins and ATX have been identified in German water bodies to date, the observed CYN concentrations cannot be produced solely by Aphanizomenon flos-aquae, the only known CYN producer in Germany. Therefore, we attempted to identify PSP toxin, ATX, and CYN producers by isolating and characterizing 92 Anabaena, Aphanizomenon, and Anabaenopsis strains from five lakes in northeast Germany. In a polyphasic approach, all strains were morphologically and phylogenetically classified and then tested for PSP toxins, ATX, and CYN by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and enzyme-linked immunosorbent assay (ELISA) and screened for the presence of PSP toxin- and CYN-encoding gene fragments. As demonstrated by ELISA and LC-MS, 14 Aphanizomenon gracile strains from Lakes Melang and Scharmützel produced four PSP toxin variants (gonyautoxin 5 [GTX5], decarbamoylsaxitoxin [dcSTX], saxitoxin [STX], and neosaxitoxin [NEO]). GTX5 was the most prevalent PSP toxin variant among the seven strains from Lake Scharmützel, and NEO was the most prevalent among the seven strains from Lake Melang. The sxtA gene, which is part of the saxitoxin gene cluster, was found in the 14 PSP toxin-producing A. gracile strains and in 11 non-PSP toxin-producing Aphanizomenon issatschenkoi, A. flos-aquae, Anabaena planktonica, and Anabaenopsis elenkinii strains. ATX and CYN were not detected in any of the isolated strains. This study is the first confirming the role of A. gracile as a PSP toxin producer in German water bodies.

Investigation of toxin content in Cylindrospermopsis raciborski (Woloszynska) Seenaya and Subba Raju and Aphanizomenon ovalisporum (Forti) strains isolated from shallow lakes of Hungary.

Cylindrospermopsin (CYN) is an alkaloid type cytotoxic metabolite produced by several cyanobacterial species, which caused human illnesses. The occurrence of CYN has been mostly associated with tropical and subtropical cyanobacteria, but recently it is appearing in several countries, all over the world. We analyzed CYN concentration and polyketide synthase/peptide synthetase (PKS /PS) genes, important parts of the gene cluster responsible for the CYN biosynthesis, in 14 isolated/collected Cylindrospermopsis raciborskii and Aphanizomenon ovalisporum strains originated mostly from Hungary. CYN and PKS /PS genes were detected in Aphanizomenon ovalisporum strains isolated from Spain (of our isolation) and isolated in Israel (IL C-164), but the Hungarian isolate from the hyposaline Lake Szelidi had a lack of production capacity. In the Hungarian samples of C. raciborskii, we found no CYN and PKS /PS genes content comparing to CYN producer C. raciborskii AQS originated from Australia.

Inhibition of gap-junctional intercellular communication and activation of mitogen-activated protein kinases by cyanobacterial extracts--indications of novel tumor-promoting cyanotoxins?

Toxicity and liver tumor promotion of cyanotoxins microcystins have been extensively studied. However, recent studies document that other metabolites present in the complex cyanobacterial water blooms may also have adverse health effects. In this study we used rat liver epithelial stem-like cells (WB-F344) to examine the effects of cyanobacterial extracts on two established markers of tumor promotion, inhibition of gap-junctional intercellular communication (GJIC) and activation of mitogen-activated protein kinases (MAPKs) - ERK1/2. Extracts of cyanobacteria (laboratory cultures of Microcystis aeruginosa and Aphanizomenon flos-aquae and water blooms dominated by these species) inhibited GJIC and activated MAPKs in a dose-dependent manner (effective concentrations ranging 0.5-5mgd.w./mL). Effects were independent of the microcystin content and the strongest responses were elicited by the extracts of Aphanizomenon sp. Neither pure microcystin-LR nor cylindrospermopsin inhibited GJIC or activated MAPKs. Modulations of GJIC and MAPKs appeared to be specific to cyanobacterial extracts since extracts from green alga Chlamydomonas reinhardtii, heterotrophic bacterium Klebsiella terrigena, and isolated bacterial lipopolysaccharides had no comparable effects. Our study provides the first evidence on the existence of unknown cyanobacterial toxic metabolites that affect in vitro biomarkers of tumor promotion, i.e. inhibition of GJIC and activation of MAPKs.

First occurrence of cylindrospermopsin in freshwater in France.

Eleven waterbodies in Western France dominated by cyanobacteria of the genera Aphanizomenon and Anabaena were analyzed in September 2006 for microcystins (MC) and cylindrospermopsin (CYN). CYN was detected for the first time in France in four of them in the presence of Aphanizomenon flos-aquae and in the presence of Anabaena planctonica in the other. The intracellular concentrations of CYN measured by LC-MS/MS ranged between 1.55 and 1.95 microg/L. The occurrence of CYN represents an additional health hazard to MC especially because Aphanizomenon flos-aquae is the third most common species in freshwaters in France.

Occurrence of the cyanobacterial toxin cylindrospermopsin in northeast Germany.

The frequent occurrence of the cyanobacterial toxin cylindrospermopsin (CYN) in the (sub)tropics has been largely associated with cyanobacteria of the order Nostocales of tropical origin, in particular Cylindrospermopsis raciborskii. C. raciborskii is currently observed to spread northwards into temperate climatic zones. In addition, further cyanobacteria of the order Nostocales typically inhabiting water bodies in temperate regions are being identified as CYN-producers. Therefore, data on the distribution of CYN in temperate regions are necessary for a first assessment of potential risks due to CYN in water used for drinking and recreation. A total of 127 lakes situated in the north-eastern part of Germany were investigated in 2004 for the presence of the toxin CYN and the phytoplankton composition. The toxin could be detected in half of the lakes (n = 63) and in half of 165 samples (n = 88). Concentrations reached up to 73.2 microg CYN/g DW. CYN thus proved more widely distributed than previously demonstrated. The analyses of phytoplankton data suggest Aphanizomenon sp. and Anabaena sp. as important CYN producers in Germany, and confirm recent findings of Aphanizomenon flos-aquae as CYN-producing species frequently inhabiting water bodies in temperate climatic regions. The data shown here suggest that CYN may be an important cyanobacterial toxin in German water bodies and that further data are needed to assess this.

Occurrence of toxin-producing cyanobacteria blooms in a Brazilian semiarid reservoir.

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.

Analysis of paralytic shellfish toxins in Aphanizomenon DC-1 from Lake Dianchi, China.

Lake Dianchi is in Yunnan Province in southwestern China. In recent years, significant cyanobacterial blooms have occurred in this lake nearly every year because of eutrophication. Monitoring data for the past 5 years acquired by our research group showed that phytoplankton composition alternated between species of Microcystis sp. during warm seasons and those of Aphanizomenon sp. during cool seasons. In March 2003, when phytoplankton composition was highly dominated by Aphanizomenon sp., samples were taken from the lake for toxin detection and immediate strain isolation. A mouse bioassay with extracts from the lyophilized field material showed obvious intoxication from paralytic shellfish poisons (PSPs), and all mice died within 30 min. Further analysis of both field and isolated algal strain Aphanizomenon DC-1 by the postcolumn HPLC-FLD method confirmed its PSP-producing ability. The analogues found in the extracts from the field material were neoSTX, dcSTX, and dcGTX3, with contents of 2.279, 1.135, and 0.547 ng/mg DW, respectively. Under laboratory culture condition, toxin content in the Aphanizomenon strain DC-1 varied greatly during different growth phases, with two peaks: in the early-exponential and late-stationary growth phases. When the culture grew at a relatively high rate during the mid- to late-exponential growth phase, toxin content declined gradually. Moreover, the types of toxin in the DC-1 strain varied greatly during a single culture cycle. The HPLC results showed that dcSTX was the only toxin isomer detected throughout the culture period, and its level remained stable. On the other hand, dcGTX2 and GTX4 were the major toxins during the early-exponential and stationary phases, respectively. This article presents the first data on the identification and detection of paralytic shellfish toxins from cyanobacteria in Lake Dianchi. As far as we know, this is also the first report of this type of toxin in inland water bodies in China. Our study indicates the threat associated with PSP toxins in Lake Dianchi and suggests that necessary measures and programs for control are urgently needed to prevent the spread of toxic cyanobacterial blooms.

Occurrence of toxin-producing cyanobacteria blooms in a Brazilian semiarid reservoir

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.

First report on cylindrospermopsin producing Aphanizomenon flos-aquae (Cyanobacteria) isolated from two German lakes.

Three single-filament isolates of Aphanizomenon flos-aquae from two German lakes were found to produce remarkable amounts of the cyanobacterial hepatotoxin cylindrospermopsin (CYN). CYN-synthesis of the strains were evidenced both by LC-MS/MS analysis and detection of PCR products of gene fragments which are implicated in the biosynthesis of the toxin. The strains contain CYN in the range of 2.3-6.6 mg g(-1) of cellular dry weight. To our knowledge this is the first report of CYN in A. flos-aquae.