Anabaena Circinalis Research Articles

Influence of environmental parameters on toxic cyanobacterial bloom occurrence in a Lake of Bangladesh

Increased nutrients have led cyanobacteria to become dominant in many ponds, lakes and reservoirs in many countries of the world. The occurrence and abundance of cyanobacterial population were monitored in a lake (known as Ishakha Lake) at Bangladesh Agricultural University campus, Mymensingh, Bangladesh. The hydrographic parameters such as water temperature, pH, chlorophyll a and nutrients (NO3–N and PO4–P) were recorded to find out their relationship with the cyanobacterial bloom formation. During the study period five species of cyanobacteria namely, Microcystis aeruginosa Kutz., M. wesenbergii Kom., M. botrys Teli., M. viridis (A. Br.) Lemm. and Anabaena circinalis Rabenh., were identified and among them M. aeruginosa was the dominant species during the bloom period. At the peak period of bloom, the highest cell density of M. aeruginosa was 1550 × 103 cells ml−1 which comprised 97.45 % among the blue-green algae and 96.84 % to the total phytoplankton. The initiation and persistence of natural bloom of cyanobacteria, especially Microcystis spp. was found to be controlled by relatively high temperature (>25.00 °C) and nutrients, especially high NO3–N (3.80 mg l−1) concentration. Temperature and NO3–N showed positive correlation with cyanobacterial cells abundance which were r = 0.62 and r = 0.92. Therefore, it could be said that temperature and NO3–N made a favorable circumstance to form cyanobacterial bloom in as Ishakha Lake. The Enzyme-linked Immunosorbent Assay revealed that the concentration of MCs 37,460.00 pg ml−1 at the peak period of bloom.

Proteogenomics of a saxitoxin-producing and non-toxic strain of Anabaena circinalis (cyanobacteria) in response to extracellular NaCl and phosphate depletion.

In Australia, saxitoxin production is strain dependent within the bloom-forming freshwater cyanobacterium Anabaena circinalis. Freshwater cyanobacteria are exposed to rapid fluctuations in environmental nutrient concentrations, and their adaption is vital for competition, succession and dominance. Two elements of environmental significance, phosphorus and sodium chloride, are proposed to play a role in bloom development and saxitoxin biosynthesis respectively. The aim of our study was to comparatively analyse the model saxitoxin-producing A. circinalis AWQC131C and non-toxic A. circinalis AWQC310F at the genomic level and proteomic level, in response to phosphate depletion and increased extracellular NaCl. When challenged, photosynthesis, carbon/nitrogen metabolisms, transcription/translation, oxidative stress and nutrient transport functional categories demonstrated the largest changes in protein abundance. In response to increased NaCl, SxtC, a protein conserved in all known saxitoxin biosynthetic pathways, was downregulated. Additionally, toxin quantification revealed a decrease in total saxitoxin and decarbomoyl-gonyautoxin2/3 content in response to the NaCl treatment. In response to phosphate depletion, the toxic and non-toxic strain displayed similar proteomic profiles, although the toxic strain did not alter the abundance of as many proteins as the non-toxic strain. These findings have important implications for the future, since response and adaption mechanisms are directly related to in situ dominance of cyanobacteria.

Relationship between a Dense Population of Cyanobacteria and Odorous Compounds in the North Han River System in 2014 and 2015

To evaluate the relationship between dynamics of cyanobacteria and odorous compounds, a monthly monitoring of water quality and phytoplankton were conducted at the three serial lakes (Lake Ui-am, Lake Cheong-pyeong and Lake Pal-dang) in the North Han River for 11 times from May 2014 to March 2015. In the three serial lakes, phytoplankton communities showed that seasonal changes in Bacillariophyceae- Cyanophyceae-Bacillariophyceae. Anabaena and Pseudanabaena were dominant species in August and September 2014. At the same time the odors (Geosmin, 2-MIB) were also detected with high concentration. Relationship between environmental factors and cyanobacterial abundance showed a significant correlation with Anabaena circinalis and geosmin (r=0.983, p<0.01). In the case of Pseudanabaena limnetica showed a significant correlation of total nitrogen (r=0.685, p<0.01) and NO3-N (r=0.723, p<0.01). In addition, similarly Pseudanabaena limnetica and 2-MIB (r=0.717, p<0.01) was high. The odorous compounds appeared in the North Han River water were considered to be a direct relationship with cyanobacteria.

Elevated Na(+) and pH influence the production and transport of saxitoxin in the cyanobacteria Anabaena circinalis AWQC131C and Cylindrospermopsis raciborskii T3.

Saxitoxins (STX), neurotoxic alkaloids, fall under the umbrella of paralytic shellfish toxins produced by marine dinoflagellates and freshwater cyanobacteria. The genes responsible for the production of STX have been proposed, but factors that influence their expression and induce toxin efflux remain unclear. Here we characterize the putative STX NorM-like MATE transporters SxtF and SxtM. Complementation of the antibiotic-sensitive strain Escherichia coli KAM32 with these transporters decreased fluoroquinolone sensitivity, indicating that while becoming evolutionary specialized for STX transport these transporters retain relaxed specificity typical of this class. The transcriptional response of STX biosynthesis (sxtA) along with that of the STX transporters (sxtM and sxtF from Cylindrospermopsis raciborskii T3, and sxtM from Anabaena circinalis AWQC131C) were assessed in response to ionic stress. These data, coupled with a measure of toxin intracellular to extracellular ratios, provide an insight into the physiology of STX export. Cylindrospermopsis raciborskii and Anabaena circinalis exhibited opposing responses under conditions of ionic stress. High Na(+) (10 mM) induced moderate alterations of transcription and STX localization, whereas high pH (pH 9) stimulated the greatest physiological response. Saxitoxin production and cellular localization are responsive to ionic strength, indicating a role of this molecule in the maintenance of cellular homeostasis.

Use of lactic acid bacteria as a biological agent against the cyanobacterium Anabaena flos-aquae

In the present study, we assessed whether lactic acid bacteria (LAB) with antimicrobial activity could be used to effectively control Anabaena flos-aquae growth. In our screening of cyanobacteriacidal bacteria from 14 LAB strains belonging to 11 species, we selected six candidate strains that could lyse 90 % or more A. flos-aquae cells compared with a control. Of those, Lactobacillus paraplantarum KCTC 5045T had the strongest cyanobacteriacidal activity showing complete lysis of cyanobacterial cells at the initial densities of ≥104 cells mL−1. A host range assay revealed that L. paraplantarum strongly inhibited A. flos-aquae, Anabaena crassa, Stephanodiscus hantzschii, and Peridinium bipes but weakly inhibited or stimulated the growth of Scenedesmus actus, Pediastrum sp., Cyclotella meneghiniana, Coelastrum reticulatum, Chlamydomonas sp., and Microcystis aeruginosa. In the microcosm experiment using natural freshwater including abundant phytoplankton assemblage, moreover, the LAB under inoculation of about 105 cells mL−1 could completely terminate the co-growth of A. flos-aquae, A. crassa, Anabaena circinalis, and other Anabaena spp. (over 104 cells mL−1) without a secondary bloom by another algal and cyanobacterial species. Our observation revealed that the cyanobacteriacidal bacterium releases two or more extracellular compounds possessing cyanobacteriacidal activity without cell-to-cell contact when the host cyanobacterium necessarily exits in surrounding water. Property study of cyanobacteriacidal substance revealed the release of heat stable and hydrophobic chemical substances that do not appear to be protein and peptide compound. Taken together, our results indicate that LAB may be a potential bio-agent for future use in controlling freshwater Anabaena blooms without causing the problem of pathogenicity if there is no secondary bloom by a resistant species to this bacterium.

Phytoplankton community structure and water quality assessment of Hejiang River, a branch of Xijiang River, Pearl River drainage basin

为了解珠江流域西江支流贺江浮游藻类的分布并评价其水质情况,于2013年丰水期和枯水期对贺江的浮游藻类群落结构进行调查和分析,结果表明:调查期间共检出浮游藻类7门130种,其中丰水期7门63种,枯水期5门103种,浮游藻类群落组成以绿藻门、硅藻门和蓝藻门为主,丰水期绿藻门居多,硅藻门次之,藻细胞丰度平均值为2.13×10⁶cells/L;枯水期硅藻门最多,藻细胞丰度平均值为3.71×10⁶cells/L;优势种主要有水华微囊藻、卷曲鱼腥藻、小颤藻、啮蚀隐藻、短小舟形藻、变异直链藻、颗粒直链藻、四尾栅藻、集星藻、小球衣藻和小球藻.RDA分析表明,影响贺江浮游藻类群落分布的主要环境因子是氮、磷营养盐,综合营养状态指数显示贺江处于中营养水平.;To study the distribution of phytoplankton and evaluate water quality of Hejiang River, a branch of Xijiang River, Pearl River drainage basin, the community structure of phytoplankton was investigated and analyzed in wet and dry seasons in 2013.The results showed that a total of 130 species belonging to seven phyla of phytoplankton was identified.Including 63 species of seven phyla in wet season and 103 species of five phyla in dry season, phytoplankton community structure in Hejiang River was represented by Chlorophyta, Bacillariophyta and Cyanophyta.Chlorophyta was dominant in wet season, followed by Bacillariophyta.The mean value of phytoplankton density was 2.13×10⁶ cells/L.Bacillariophyta dominated the phytoplankton in dry season, and the mean value of phytoplankton density was 3.71×10⁶cells/L.The dominant species were Microcystis flos-aquae, Anabaena circinalis, Oscillatoria tenuis, Cryptomonas erosa, Navicula exigua, Melosira varians, Melosira granulata, Scenedesmus quadricauda, Actinastrum hantzschii, Chlamydomonas microsphaera and Chlorella valgaris.Based on RDA analysis, nitrogen and phosphorus were important environmental factors that affected the distribution of phytoplankton in Hejiang River.The river was classified as mesotrophic according to comprehensive trophic state index.

The response of phycobiliproteins to light qualities in Anabaena circinalis

S. K. Ojit, Th. Indrama , O. Gunapati , S. O. Avijeet , S. A. Subhalaxmi , Ch. Silvia, D. W. Indira, Kh. Romi , Sh. Minerva, D. A. Thadoi, O. N. Tiwari , G. D. Sharma Freshwater Cyanobacterial and Microalgal Repository Microbial Resources Division, Institute of Bioresources and Sustainable Development (A National Institute of DBT, Govt. of India) Takyelpat, Imphal-795001, Manipur, INDIA. Department of Life Science and Bio-informatics Hargobind Khurana School of Life Sciences, Assam University, Silchar-788011, Assam, INDIA.

Effect of external pH on cyanobacterial phycobiliproteins production and ammonium excretion

The response of phycobiliproteins to light qualities in Anabaena circinalis S. K. Ojit, Th. Indrama, O. Gunapati, S. O. Avijeet, S. A. Subhalaxmi, Ch. Silvia, D. W. Indira, Kh. Romi, Sh. Minerva, D. A. Thadoi, O. N. Tiwari, G. D. Sharma

북한강 수역에서 분리한 남조류 Anabaena circinalis 휴면포자 발아에 대한 환경요인의 영향

북한강 수역에서 분리한 남조류 Anabaena circinalis 휴면포자 발아에 대한 환경요인의 영향

The effect of pH on the release of metabolites by cyanobacteria in conventional water treatment processes

Cyanobacteria and their metabolites are recognised as serious water quality issues for water suppliers around the world. Water shortages not only increase the risk of the proliferation of cyanobacteria but also necessitate the development of more effective treatment regimes. Conventional water treatment processes are considered an effective initial barrier in removing cyanobacterial cells intact and without damage. However, the cells can be exposed to a range of pH conditions during these processes. The impact of various pH conditions typical of the water treatment processes was evaluated on common bloom species, Microcystis aeruginosa, Cylindrospermopsis raciborskii and Anabaena circinalis. By using cyanobacterial metabolite analysis and cell viability assays, it was shown that low pH stress (pH below 5), which can occur during coagulation upon the application of metal hydroxide coagulants, occurs quickly and results in considerable cell lysis and metabolite release. It is demonstrated that it is critical to keep the pH of water above 5 (locally) at all times in order to reduce the risk of water contamination with problem metabolites.

The seasonal and spatial variations of phytoplankton community and their correlation with environmental factors in a large eutrophic Chinese lake (Lake Chaohu)

The seasonal and spatial variations of phytoplankton community and their correlation with environmental factors, as well as the applicability of phytoplankton to serve as biological water quality indicator in Lake Chaohu are investigated in the present study. 97 phytoplankton species were identified, in which 35.1% of Cyanophyta and 37.1% of Chlorophyta. In terms of the community composition at the annual average level and the spatial distribution, Cyanophyta was absolutely dominant (more than 99.4% of the total). The main dominant species in Lake Chaohu were Microcystis viridis, Microcystis flos-aquae, and Anabaena circinalis, all belonging to Cyanophyta. The average phytoplankton cell density of the dominant species showed substantial seasonal differences. In Lake Chaohu, the M. flos-aquae was dominant in spring and summer; while the M. viridis and the A. circinalis were dominant in autumn and in winter, respectively. The canonical correspondence analysis (CCA) showed that the water temperature (T), oxidation reduction potential (ORP), dissolved oxygen (DO) and orthophosphate (PO43−-P) were the environmental factors having the greatest influence on the phytoplankton community composition in Lake Chaohu, whereas T, ORP, total suspended solids (TSS) and total nitrogen (TN) were the most important environmental factors in the inflow and outflow rivers. The average species number of phytoplankton was lowest, and the average cell density of phytoplankton was highest in summer, which corresponded to the worst water quality, as indicated by physical and chemical indicators, TSS, DO, chemical oxygen demand (COD) and total phosphorus (TP); while, in winter, the average species number of phytoplankton was largest, and the average cell density of phytoplankton was lowest, which corresponded to the best water quality, as indicated by TSS, DO, COD and TP. This implied that the species number and cell density of phytoplankton could serve as biological water quality indicators, which would give overall descriptions of water quality by combining with the physical and chemical indicators.

Lysogenic infection in sub-tropical freshwater cyanobacteria cultures and natural blooms

Lysogeny has been reported for a few freshwater cyanobacteria cultures, but it is unknown how prevalent it is in freshwater cyanobacteria in situ. Here we tested for lysogeny in (a) cultures of eight Australian species of subtropical freshwater cyanobacteria; (b) seven strains of one species: Cylindrospermopsis raciborskii; and (c) six cyanobacterial blooms in drinking water reservoirs in South East Queensland, Australia. Lysogenic infection in the cyanobacteria was induced through mitomycin C addition. By measuring the decline in host cell numbers and the concomitant increase in cyanophages over the course of the experiment, we observed lysogenic infection in five of the eight species of cyanobacteria (i.e. Nodularia spumigena, Anabaena circinalis, Anabaenopsis arnoldii, Aphanizomenon ovalisporum, Microcystis botrys, Microcystis aeruginosa, C. raciborskii and Anabaena spp., and in four of the seven strains of C. raciborskii) but only in two of the six natural cyanobacteria blooms. Lysogeny dominated laboratory culture strains whereas in natural blooms of cyanobacteria few species were lysogenic (i.e. not mitomycin C inducible). Thus, lysogenic laboratory cultures may not necessarily reflect the genetics nor the physiology of a natural cyanobacterial population, and more information on both forms is needed to understand better how cyanobacteria behave and exist in their natural habitat.

Synthesis and identification of proposed biosynthetic intermediates of saxitoxin in the cyanobacterium Anabaena circinalis (TA04) and the dinoflagellate Alexandrium tamarense (Axat-2)

Here, we describe the synthesis of the genetically predicted biosynthetic intermediates of the neurotoxin saxitoxin (STX) (1), 2, 6 and 7, and identification of 2 and 6 in toxin-producing microorganisms. This is the first chemical evidence supporting the genetically predicted biosynthetic route toward 1.

Effects of hydrology and river management on the distribution, abundance and persistence of cyanobacterial blooms in the Murray River, Australia

Major cyanobacterial blooms (biovolume>4mm3L−1) occurred in the main water reservoirs on the upper Murray River, Australia during February and March 2010. Cyanobacterial-infested water was released and contaminated rivers downstream. River flow velocities were sufficiently high that in-stream bloom development was unlikely. The location has a temperate climate but experienced drought in 2010, causing river flows that were well below the long-term median values. This coupled with very low bed gradients meant turbulence was insufficient to destroy the cyanobacteria in-stream. Blooms in the upper 500km of the Murray and Edward Rivers persisted for 5 weeks, but in the mid and lower Murray blooms were confined to a small package of water that moved progressively downstream for another 650km. Anabaena circinalis was the dominant species present, confirmed by 16S rRNA gene sequencing, but other potentially toxic species were also present in smaller amounts. Saxitoxin (sxtA), microcystin (mcyE) and cylindrospermopsin (aoaA) biosynthesis genes were also detected, although water sample analysis rarely detected these toxins. River water temperature and nutrient concentrations were optimal for bloom survival. The operational design of weirs and retention times within weir pools, as well as tributary inflows to and diversions from the Murray River all influenced the distribution and persistence of the blooms. Similar flow, water quality and river regulation factors were underlying causes of another bloom in these rivers in 2009. Global climate change is likely to promote future blooms in this and other lowland rivers.

Overwintering populations of Anabaena, Aphanizomenon and Microcystis as potential inocula for summer blooms

Overwintering cyanobacterial populations of Nostocales and Microcystis were investigated in six freshwater reservoirs in Northwestern Spain during two consecutive winters. Surface sediments hosted 10–10 akinetes mL and 10–10 Microcystis colonies mL. Sediments from deeper areas close to dam accumulated 2-fold (Microcystis) and 11-fold (akinetes) greater concentrations than those at the shallower upstream areas. Anabaena spp. and Microcystis aeruginosa dominated the sediment pool, with minor amounts of akinetes of Aphanizomenon (Aph. flos-aquae, Aph. gracile) and benthic Nostocales (Cylindrospermum, Nostoc and Trichormus). Our study confirms the dual benthic-pelagic overwintering of Anabaena, Aphanizomenon and Microcystis, found in the pelagial at 7.5–9.88C. This study also provides an insight into the little known annual cycle of potential cyanotoxin-producers Aph. gracile and Anabaena circinalis. Our estimates show that: (i) only a small fraction (,1%) of the sediment pool of akinetes and Microcystis was resupended in the bottom water during winter which, however, may be sufficient inocula to build up the summer maxima under realistic in situ growth rates; and (ii) the time required for the development of summer populations is mainly driven by growth rates, and therefore by the environmental conditions faced by the inoculum, with a lower influence (although greater for Microcystis than for Nostocales) of the inoculum size.

Measurement of cyanobacteria using in-vivo fluoroscopy – Effect of cyanobacterial species, pigments, and colonies

The effect of instrument calibration range, algal growth phase, chlorophyll-a and turbidity interference and colony size, on the measurement of phycocyanin by in-vivo fluoroscopy (IVF) was investigated. The cyanobacterial species Microcystis aeruginosa PCC 7820, Anabaena circinalis and Planktothricoides raciborskii were used to investigate variation in phycocyanin content in the different cyanobacteria and growth phases. The green alga, Chodatella sp., and Kaolin particles were used as the sources of chlorophyll-a and turbidity respectively to determine how these factors can impact on phycocyanin measurements. Another cyanobacterium, M. aeruginosa PCC 7005, which forms large colonies, was used to investigate the relationships between colony size and phycocyanin concentration measured using IVF. Results showed that chlorophyll-a, turbidity, and the colonial status of the cyanobacteria significantly interfered with the measurement of phycocyanin fluorescence. Models were developed to compensate for the effect of chlorophyll-a, turbidity and colony size on the measurement. The models were successfully used to correct phycocyanin probe data collected from several reservoirs in Taiwan to establish good correlation between measurements made using the phycocyanin probe and microscopic cell counts.

Earthy odor compounds production and loss in three cyanobacterial cultures

Geosmin and 2-methylisoborneol (MIB) related odor events caused by cyanobacteria have been a very common problem to water supply. This paper investigated the effects of temperature (18 and 25 °C) and light intensity (10 and 100 μmol photons m−2 s−1) on the production behaviors of earthy odor compounds by three odorous cyanobacteria, i.e., the geosmin-producing planktonic Anabaena circinalis (Ana 318), geosmin-producing benthic Phormidium amoenum (Pho 012) and MIB-producing benthic Phormidium sp. (Pho 689). At the same time, the effects of biodegradation and volatilization on the fates of the released odor compounds in water were also evaluated. The combination of high temperature (25 °C) and light intensity (100 μmol photons m−2 s−1) favored the growth of the three cyanobacteria and the production of chl-a and odor compounds. However, higher chl-a and odor yields (average odor compounds per cell) were achieved for the two benthic cyanobacteria at the temperature of 18 °C. Most of geosmin was included within the cells for Ana 318 (95–99%) and Pho 012 (85–60%), while only 20–40% MIB was bound to the cells for Pho 689. The half-life times of MIB and geosmin due to volatilization varied between 18.8 and 35.4 days, while 8 out of 10 samples exhibited a half-life time (t1/2) for geosmin biodegradation shorter than 1 day (0.38–15.0 h), showing that biodegradation could affect the fate of geosmin significantly in aquatic environments. In comparison, biodegradation of MIB was much slower (t1/2: 122–2166 h). Denaturing gradient gel electrophoresis (DGGE) analysis showed that Pseudomonas- and Sphingomonas-like bacteria coexisted with cyanobacteria in the cultures, and may have played an important role in geosmin/MIB biodegradation. The result of this study will be helpful for better understanding and managing the earthy odor problems caused by cyanobacteria in water supply.

Seasonal Dynamics of Nutrient Loading and Chlorophyll A in a Northern Prairies Reservoir, Saskatchewan, Canada

Harmful algae blooms have become an increasing concern in context with the safety of water resources around the globe; however, little is known about the dynamics and specific causes of such blooms in the prairie ecozone in North America. The aim of this study was to research the nitrogen (N) and phosphorous (P) content and nutrient limitation (defined as N and P limitation) of growth of cyanobacteria in a northern prairies reservoir (Lake Diefenbaker [LD], SK, Canada). A combination of concentration balance analysis for N and P, controlled bioassays with the natural consortium of phytoplankton or defined monocultures of cyanobacteria, and satellite imagery was applied to address this aim. The current trophic status of Lake Diefenbaker is one of moderate eutrophication. Primary production in the lake is P-limited, and N did not represent a limiting factor for algal production. There was no significant increase in TP con- centrations between the upper and lower portions of the reservoir, indicating that most of the phosphorus in LD comes from upstream sites in Alberta. Anabaena circinalis, a species that has the potential to seriously degrade lake ecosys- tems, was identified as the predominant cyanobacteria in LD. Together with the fact that TP influxes into the reservoir primarily originate from upstream sources, these results suggest the need for remedial measures in the upstream reach of the South Saskatchewan River. Satellite imaging represented a promising approach in support of monitoring for po- tential algal blooms in LD; however, due to limited sensitivity and issues associated with atmosphere interference this methodology should only be used in combination with in situ water quality monitoring. In summary, while this study indicated that Lake Diefenbaker is potentially at risk with cyanobacteria blooms (some of which such as Anabena sp. that can produce toxins) during late summer and fall, development of clear causal relationships and risk assessment strategies is currently limited due to lack of monitoring data and programs.

Impact of sonication at 20 kHz on Microcystis aeruginosa, Anabaena circinalis and Chlorella sp.

Blooms of toxic cyanobacteria such as Microcystis aeruginosa periodically occur within wastewater treatment lagoons in the warmer months, and may consequently cause contamination of downstream water and outages of the supply of recycled wastewater. Lab-scale sonication (20 kHz) was conducted on suspensions of M. aeruginosa isolated from a wastewater treatment lagoon, and two other algal strains, Anabaena circinalis and Chlorella sp., to investigate cell reduction, growth inhibition, release of microcystin and sonication efficiency in controlling the growth of the M. aeruginosa. For M. aeruginosa, for all sonication intensities and exposure times trialled, sonication led to an immediate reduction in the population, the highest reduction rate occurring within the initial 5 min. Sonication for 5 min at 0.32 W/mL, or for a longer exposure time (>10 min) at a lower power intensity (0.043 W/mL), led to an immediate increase in microcystin level in the treated suspensions. However, prolonged exposure (>10 min) to sonication at higher power intensities reduced the microcystin concentration significantly. Under the same sonication conditions, the order of decreasing growth inhibition of the three algal species was: A. circinalis > M. aeruginosa > Chlorella sp., demonstrating sonication has the potential to selectively remove/deactivate harmful cyanobacteria from the algal communities in wastewater treatment lagoons.

Novel cytotoxicity associated with Anabaena circinalis 131C

The production of secondary metabolites by cyanobacteria is extensively varied. Anabaena spp. have been shown to produce the toxins saxitoxin, anatoxin-a, anatoxin-a(s), cylindrospermopsin and microcystin. In this study we show cytotoxicity associated with Anabaena circinalis 131C that could not be attributed to its high saxitoxin content. Analytical, ELISA and enzymatic methods excluded the presence of other known cyanobacterial toxins leading to the suggestion of novel toxicity.