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• Five strains of each species maintained growth for 10 days under phosphorus depleted conditions. • The intraspecific variation among strains of each species was more pronounced than the interspecific variation. • The results emphasize the fragility of generalizing about the ecophysiology of a species based on only a few strains. Phosphorus loading plays an important role in the occurrence of cyanobacterial blooms and understanding how this nutrient affects the physiology of cyanobacteria is imperative to manage these phenomena. Microcystis aeruginosa and Raphidiopsis raciborskii are cyanobacterial species that form potentially toxic blooms in freshwater ecosystems worldwide. Blooms comprise numerous strains with high trait variability, which can contribute to the widespread distribution of these species. Here, we explored the intraspecific variability in response to phosphorus depleted conditions (P-) testing five strains of each species. Strains could be differentiated by cell volume or genetic profiles except for those of the same species, sampling location and date, though these presented differences in their response to (P-). Although differently affected by (P-) over 10 days, all strains were able to grow and maintain photosynthetic activity. For most M. aeruginosa and R. raciborskii strains growth rates were not significantly different comparing (P+) and (P-) conditions. After ten days in (P-), only one M. aeruginosa strain and two R. raciborskii strains showed reduction in biovolume yield as compared to (P+) but in most strains chlorophyll- a concentrations were lower in (P-) than in (P+). Reduced photosystem II efficiency was found for only one R. raciborskii strain while all M. aeruginosa strains were affected. Only two M. aeruginosa and one R. raciborskii strain increased alkaline phosphatase activity under (P-) as compared to (P+). Variation in P-uptake was also observed but comparison among strains yielded homogeneous groups comprised of representatives of both species. Comparing the response of each species as a whole, the (P-) condition affected growth rate, biovolume yield and chlorophyll yield. However, these parameters revealed variation among strains of the same species to the extent that differences between M. aeruginosa and R. raciborskii were not significant. Taken together, these results do not support the idea that R. raciborskii , as a species, can withstand phosphorus limitation better than M. aeruginosa and also point that the level of intraspecific variation may preclude generalizations based on studies that use only one or few strains. [ABSTRACT FROM AUTHOR]

Toxic cyanobacterial blooms are a water quality issue worldwide whose incidence and severity are predicted to increase due to climate change and eutrophication. Argentina is not an exception to this trend, since those massive proliferations have increased in the last two decades as a consequence of water quality changes due to human activities. This work presents a thorough search and analysis of published literature on the occurrence of cyanobacterial blooms and cyanotoxins in Argentina. We retrieved 241 bloom events (1944–2014) covering 63 impacted water bodies, used either for recreational activities and/or drinking water supply. The highest incidence was concentrated in the central and eastern areas of the country (Chaco-Pampean Plain and Peripampean Sierras), the most densely populated regions, also highly impacted by agro-industrial activities. Intense blooms of Microcystis, Dolichospermum and Cylindrospermopsis species represent a potential hazard for both human beings and wild–life through oral ingestion and/or direct contact, although quantitative and systematic registers to estimate the extent of occurrence are still missing. Elevated microcystins concentrations, together with the presence of blooms of potential saxitoxin or anatoxin-a producers emphasize the need to increase monitoring of these toxins in drinking water supplies and recreational areas. The data presented are valuable for promoting the generation and implementation of guideline values and risk management frameworks at a national and regional scale. [ABSTRACT FROM AUTHOR]

An early warning scheme is proposed that runs ensembles of inferential models for predicting the cyanobacterial population dynamics and cyanotoxin concentrations in drinking water reservoirs on a diel basis driven by in situ sonde water quality data. When the 10- to 30-day-ahead predicted concentrations of cyanobacteria cells or cyanotoxins exceed pre-defined limit values, an early warning automatically activates an action plan considering in-lake control, e.g. intermittent mixing and ad hoc water treatment in water works, respectively. Case studies of the sub-tropical Lake Wivenhoe (Australia) and the Mediterranean Vaal Reservoir (South Africa) demonstrate that ensembles of inferential models developed by the hybrid evolutionary algorithm HEA are capable of up to 30 days forecasts of cyanobacteria and cyanotoxins using data collected in situ . The resulting models for Dolicospermum circinale displayed validity for up to 10 days ahead, whilst concentrations of Cylindrospermopsis raciborskii and microcystins were successfully predicted up to 30 days ahead. Implementing the proposed scheme for drinking water reservoirs enhances current water quality monitoring practices by solely utilising in situ monitoring data, in addition to cyanobacteria and cyanotoxin measurements. Access to routinely measured cyanotoxin data allows for development of models that predict explicitly cyanotoxin concentrations that avoid to inadvertently model and predict non-toxic cyanobacterial strains. [ABSTRACT FROM AUTHOR]

Temperate and tropical shallow lakes differ in several fundamental aspects with respect to management of eutrophication. High altitude tropical shallow lakes are a special case, showing similarities with temperate and tropical lakes. We studied the ecology of the eutrophic high-altitude tropical lake Yahuarcocha in the Ecuadorian Andes and evaluated the potential of biomanipulation to control eutrophication. With a toxin-producing Cylindrospermopsis bloom, low Secchi depth and low submerged macrophyte cover, Yahuarcocha is clearly in a turbid ecosystem state. Relatively low nutrient concentrations should theoretically allow for a shift to a clear water state through biomanipulation. Top-down control of phytoplankton by zooplankton, however, is complicated by the (1) absence of predatory fish, (2) fish community dominated by small poecelid species, (3) lack of a refuge for zooplankton from fish predation within the macrophytes, and (4) persistent, grazing resistant bloom of the cyanobacterium Cylindrospermopsis . In these aspects, lake Yahuarcocha is more similar to tropical shallow lakes, probably because water temperature is high relative to the mean air temperature and because of the absence of a cold season. The fish and macrophyte communities consisted almost entirely of exotic species. The exotic fish species probably stabilized the turbid state in the lake. [ABSTRACT FROM AUTHOR]

We tested the hypothesis that a combination of coagulant and ballast could be efficient for removal of positively buoyant harmful cyanobacteria in shallow tropical waterbodies, and will not promote the release of cyanotoxins. This laboratory study examined the efficacy of coagulants [polyaluminium chloride (PAC) and chitosan (made of shrimp shells)] alone, and combined with ballast (lanthanum modified bentonite, red soil or gravel) to remove the natural populations of cyanobacteria collected from a shallow eutrophic urban reservoir with alternating blooms of Cylindrospermopsis and Microcystis . PAC combined with ballast was effective in settling blooms dominated by Microcystis or Cylindrospermopsis. Contrary to our expectation, chitosan combined with ballast was only effective in settling Cylindrospermopsis -dominated blooms at low pH, whereas at pH ≥ 8 no effective flocculation and settling could be evoked. Chitosan also had a detrimental effect on Cylindrospermopsis causing the release of saxitoxins. In contrast, no detrimental effect on Microcystis was observed and all coagulant-ballast treatments were effective in not only settling the Microcystis dominated bloom, but also lowering dissolved microcystin concentrations. Our data show that the best procedure for biomass reduction also depends on the dominant species. [ABSTRACT FROM AUTHOR]

Dolichospermum flos-aquae and Cylindrospermopsis raciborskii are two cyanobacteria species which cause harmful blooms around the world. Both these species share the capacity to fix atmospheric nitrogen in heterocytes (cell where fixation occurs). While Dolichospermum can express heterocytes at rather regular intervals across the filament, Cylindrospermopsis can only express heterocytes at the end of the filament. The aim of this study was to experimentally assess the role of heterocyte position in the eco-physiological responses of these bloom forming cyanobacteria. Replicated monocultures of each species were grown at different eutrophication scenarios (limiting and sufficient nitrogen and phosphorus concentrations, in factorial design). Dolichospermum reached high biomass regardless of the nitrogen (and phosphorus) provided, suggesting that this species could bloom in situations with and without nitrogen limitation. In contrast, Cylindrospermopsis reached high biomass only when nitrogen supply was high; its biomass was 15-20 times lower when relying on nitrogen fixation. Hence, despite its ability to fix nitrogen, blooms of Cylindrospermopsis would be expected only under high total nitrogen availability. In Dolichospermum heterocytes occurred only in the scenarios without supplied nitrogen while in Cylindrospermopsis heterocytes occurred regardless of nitrogen availability. Yet, in both species nitrogen fixation occurred (heterocytes were functional) only when nitrogen was limiting, and nitrogen fixation increased significantly at higher phosphorus concentration. Finally, in the absence of supplied nitrogen, filament length in Dolichospermum was the longest, while filaments in Cylindrospermopsis were the shortest (up to 13 times shorter than at nitrogen sufficiency). Therefore, heterocyte expression in Dolichospermum , and filament length in Cylindrospermopsis seem good proxies of nitrogen fixation. The eco-physiological responses recorded here help understand the distribution of these species along nutrient gradients in nature. [ABSTRACT FROM AUTHOR]

The cyanobacterial genera Raphidiopsis and Cylindrospermopsis morphologically resembled each other and are difficult to distinguish, especially when heterocytes do not form in Cylindrospermopsis species. The phylogeny based on multiple gene loci sequences in previous studies cannot divide the strains of these two genera into separate clusters. In the present study, four gene loci 16S rRNA, ITS-L, cpc BA-IGS and rpoC1 , sequenced from many Chinese strains (44 Cylindrospermopsis strains and 16 Raphidiopsis strains), were analyzed to infer the phylogenetic relationship between the two genera. According to the 16S rRNA, cpc BA-IGS and rpoC1 gene phylogeny, Cylindrospermopsis and Raphidiopsis strains are intermixed and divide into two or three groups. By contrast, the ITS-L analysis implied that they respectively form two separate and unique clusters. A fragment of 7 bp (RAGAAACT) in ITS-L was conserved for Raphidiopsis strains, which could be distinguished from Cylindrospermopsis strains. A pair of primers targeting the ITS-L fragment specific to Raphidiopsis strains were designed and further verified. [ABSTRACT FROM AUTHOR]

The development of cyanobacterial blooms in inland aquatic ecosystems is greatly promoted by nutrient availability, especially nitrogen and phosphorous. When blooms are dominated by toxigenic species the harmful effects of nutrient loading becomes particularly relevant. Among toxic species, Cylindrospermopsis raciborskii found in South American ecosystems is characterized by the production of saxitoxin and analogs (Paralytic Shellfish Poisoning, PSP), for which the factors that trigger their production have not been elucidated. In this study, the effect of nitrate availability on the relative transcript abundance of two genes ( sxtU and sxtI ), both involved in different steps of PSP biosynthetic pathway, was addressed in C. raciborskii MVCC19 by qPCR. The relative transcript abundance of both genes significantly increased from the beginning to the end of growth, independent of nitrate availability in the culture medium. Differences between the genes in terms of the levels of relative expression were also found, implying that during growth in nitrate-rich or nitrate-deprived conditions C. raciborskii MVCC19 has the ability to produce different kind of PSP molecules. The presence of nifH transcripts in the nitrogen-depleted treatment confirmed that in the absence of nitrate C. raciborskii fixed atmospheric N 2 . Moreover, after transferring filaments to nitrate-rich conditions the synthesis of nifH mRNA continued for few hours, suggesting that cell adjustments enabling the utilization of soluble nitrogen sources are not immediate. Our results show that biosynthesis of saxitoxin and analogs in C. raciborskii is not related to nitrate availability, but rather is linked to cyanobacteria growth rate. [ABSTRACT FROM AUTHOR]

The hypothesis that cyanobacteria can be controlled by commercially available ultrasound transducers was tested in laboratory experiments with cultures of the cyanobacteria Anabaena sp., Cylindrospermopsis raciborskii and Microcystis aeruginosa and the green alga Scenedesmus obliquus that were grown in the absence or presence of ultrasound (mix of 20, 28 and 44 kHz). The Scenedesmus experiment also included a treatment with the zooplankton grazer Daphnia magna . Chlorophyll- a and biovolume-based growth of Anabaena was significantly lower in ultrasound exposed cultures than in controls. Particle based growth rates were higher in ultrasound treatments. Filaments were significantly shorter in ultrasound exposed cultures reflecting filament breakage. Photosystem II efficiency was not affected by ultrasound. In Cylindrospermopsis chlorophyll- a based growth rates and photosystem II efficiencies were similar in controls and ultrasound treatments, but biovolume-based growth was significantly lower in ultrasound exposed cultures compared to controls. Despite biovolume growth rates of the filamentous cyanobacteria were reduced in ultrasound treatments compared to controls, growth remained positive implying still a population increase. In Microcystis and Scenedesmus growth rates were similar in controls and ultrasound treatments. Hence, no effect of ultrasound on these phytoplankton species was found. Ultrasound should not be viewed “environmental friendly” as it killed all Daphnia within 15 min, releasing Scenedesmus from grazing control in the cultures. Based on our experiments and critical literature review, we conclude that there is no music in controlling cyanobacteria in situ with the commercially available ultrasound transducers we have tested. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Highlights: [•] The dialysis membrane allowed both analogues of cylindrospermopsin to be quantified. [•] Production of both analogues of cylindrospermopsins is a constitutive process. [•] The deoxycylindrospermopsin to cylindrospermopsin ratio was strain specific. [•] Deoxycylindrospermopsin increased in stationary phase in both strains. [•] Dissolved cylindrospermopsins are primarily a result of cell lysis. [Copyright &y& Elsevier]

Abstract: Longitudinal heterogeneity in reservoirs is especially related to increase in sedimentation and water transparency along the river/dam axis. Consequently, primary production tends to reach higher values in intermediate regions where there is a balance between the availability of the main resources (light and nutrients) suitable for phytoplankton growth. Many factors such as reservoir morphometry, retention time, thermal stratification and geographical location can affect the boundaries between these regions. The tropical Funil Reservoir (Brazil), despite a low retention time, has experienced severe eutrophication in recent decades, with persistent cyanobacteria blooms. During the course of 1 year, samples were collected at four stations along the reservoir (fluvial, intermediate and lentic compartments) to evaluate if spatial heterogeneity could affect the occurrence and distribution of these blooms along the reservoir. Although the reservoir has a short annual retention time (mean 41.5 days), the typical zonation pattern was observed for the main abiotic variables and phytoplankton abundance. However, higher biomass occurred in the lentic compartment rather than in the intermediate zone. Despite the peculiar heterogeneity in total biomass, the phytoplankton composition and seasonal variability were very similar along the entire reservoir, with a few marked differences only in the fluvial zone. Phytoplankton total biomass in Funil Reservoir was high, even in periods of lower seasonal retention time (around 15 days), and was especially related to high input of nutrients. Moreover, retention time directly affects the spatial heterogeneity of phytoplankton biomass, since strong variability was only observed during the cold–dry season, corresponding to periods of longer retention time (around 80 days). While high availability of nutrients promoted high cyanobacterial biomass in the entire system, the few periods of heterogeneous spatiality seemed to be related to changes in retention time. [Copyright &y& Elsevier]

Abstract: The potentially toxic cyanobacterium Cylindrospermopsis raciborskii (Wołoszyńska) Seenya et Subba Raju, originally described as a tropical-subtropical species, is increasingly found in temperate regions and its range is expanding. Climate change is hypothesised to be a factor in this expansion. We studied the effects of dissolved inorganic carbon (DIC) and pH on growth and photosynthesis of this species. We prepared six treatments in a continuous culture (turbidostat) grown at high light, two at low light, and eight in batch cultures grown under low light, by manipulating pH, and CO2 to assess the effect, if any, of these parameters on the growth rate, inorganic carbon acquisition and photosynthetic parameters of C. raciborskii. When the turbidostats were grown at 100 μmol photons (PAR) m−2 s−1, concentration and pH had a positive effect on growth rate; the specific growth rate in 6 mM , for example, was twice what it was in 0.6 mM (0.84 ± 0.10 and 0.44 ± 0.04 d−1 respectively). Growth was lower in turbidostats grown at 20 μmol photons (PAR) m−2 s−1. Isotope disequilibrium experiments showed that the contribution of to DIC acquisition is proportionately greater at the higher light. The maximum relative electron transport rate (rETRmax) was significantly higher at the higher light, while the slope of the linear portion of the rETRmax versus irradiance curve (α) was unchanged. In low light batch cultures, increasing concentration and pH had a negative effect on growth, while CO2 concentration had a small, positive effect. This species of cyanobacterium has an efficient CCM and under ideal growing conditions gets most of its carbon from . It may, therefore, be at a competitive disadvantage in a high CO2 world. [Copyright &y& Elsevier]

Abstract: Cylindrospermopsis raciborskii is a tropical invasive, toxin-producing, filamentous-heterocystous, N2-fixing cyanobacterium that has recently expanded its range in temperate waterways. Because it is capable of exploiting low salinity (oligohaline) waters experiencing nutrient enrichment, it opens up brackish eutrophying systems to potential invasion. We examined the susceptibility of oligohaline (historically 0–3.5 salinity) Currituck Sound (CS), North Carolina to C. raciborskii proliferation during 2007–2008. This component of the Albemarle-Pamlico Sound estuarine system is experiencing incipient eutrophication. We addressed the following questions: (1) Is C. raciborskii currently present in CS, and (2) what conditions favor its growth and expansion? In 2007, C. raciborskii was confirmed by microscopy, diagnostic photopigment and molecular analyses, which further revealed its genetic potential to produce the cyanotoxin cylindrospermopsin. In 2008, CS salinity had risen due to a persistent drought, and C. raciborskii was no longer microscopically observed. The potential for C. raciborskii to grow in CS was assessed using in situ nutrient addition bioassays. Primary productivity, nitrogen fixation (nitrogenase activity) rates and chlorophyll a measurements demonstrated that C. raciborskii could grow in CS water, and dissolved inorganic nitrogen (nitrate and ammonium) additions increased its growth potential. Salinity was a key factor influencing C. raciborskii growth, with elevated salinity (8.4) significantly limiting biomass accumulation. Interestingly, nitrogen enrichment enabled C. raciborskii to better withstand elevated salinities and increased its competitive success in the CS phytoplankton community. Emphasis should be placed on controlling nutrient, particularly nitrogen, enrichment in order to prevent the expansion of C. raciborskii in this and other nutrient-sensitive oligohaline ecosystems. [Copyright &y& Elsevier]

Abstract: We evaluated the temporal and spatial variability of cyanotoxins, water chemistry, and cyanobacteria communities in two lakes of different trophic status. Bear Lake is a hypereutrophic system that flows into mesotrophic Muskegon Lake. Total microcystins (MC) in Bear Lake (mean, 1.66μg/L) were composed of multiple structural analogs: 43% MC-LR, 50% MC-RR, and 7% MC-YR. Total microcystins in Muskegon Lake (mean, 0.52μg/L) consisted of MC-LR (76%), MC-RR (14%), MC-YR (6%), and MC-LA (3%). The lakes were dominated by the cyanobacteria Microcystis spp., which accounted for 75% of phytoplankton biovolume in Bear Lake and >90% in Muskegon Lake. Total microcystin concentration was positively correlated with cyanobacteria biovolume and turbidity (Muskegon Lake) and total phosphorus (Bear Lake), while negatively correlated with ammonia (Bear Lake) and nitrate (both lakes). The relationships between microcystins and environmental factors differed between lakes, despite hydrologic connectivity, suggesting that local conditions have a greater influence on toxin production than regional effects. Cylindrospermopsis raciborskii was found in both systems; however, the assemblage does not appear to be capable of producing cylindrospermopsin due to the absence of the PKS gene. Although the Bear Lake discharge appears to be the source of C. raciborskii, the physical/chemical properties of Muskegon Lake (lower turbidity and temperature, higher nitrate) may constrain the growth of this invasive species. Thus, local conditions in each lake are important in determining which species are capable of maintaining a viable population. [Copyright &y& Elsevier]

Abstract: A multi-gene analysis was performed to investigate the phylogenetic relationship between the cyanobacterial genera Cylindrospermopsis and Raphidiopsis. The phylogeny based on the concatenated sequences of seven gene loci including psbA, 16S rDNA, rbcL, rbcS, rpoC1, cpcB, and ITS1 between 16S and 23S rDNA, indicated that 12 strains of C. raciborskii, 6 strains of R. mediterranea, and 3 strains of R. curvata were clustered into two distinct groups, named as Clade A and Clade B, respectively. Clade A was composed of only strains of C. raciborskii; however, in Clade B, 3 sub-groups were found: 2 well supported sub-groups as termed B1 for R. mediterranea and B2 for R. curvata and R. brookii, and B3 for the remaining strains of C. raciborskii, thus suggesting that Cylindrospermopsis and Raphidiopsis might be congeneric. Additionally, these results also suggested that the traditionally defined C. raciborskii is paraphyletic, and Clade A and Clade B deserved some taxonomic reconsideration, either as separate genera or as separate species within the same genus. [Copyright &y& Elsevier]

Abstract: Cylindrospermopsis raciborskii occurs predominantly in tropical to subtropical freshwaters but appears to be spreading to temperate regions. After the hurricanes of 2005, a bloom of this organism took place in Lake Dauterive and Lake Fausse Pointe in Louisiana. The cyanobacterium dominated the phytoplankton community for three months. Of the three known morphotypes (straight, coiled and spiral) only coiled and spiral were found. In June 2006, 60% of the organisms were of the spiral morphotype but the relative abundance of this morphotype decreased dramatically within the month of June. However, the average density for both morphotypes remained the same until September. Densities (up to 160,000 cells/mL) significantly exceeded the threshold for toxicity. Because the sampled region offers optimal light and nutrient conditions, it is likely that C. raciborskii has been established in this region and future blooms can be expected. Therefore, a monitoring program should be implemented. [ABSTRACT FROM AUTHOR]

Bioassays using Daphnia pulex and Moina micrura were designed to detect cyanobacterial neurotoxins in raw water samples. Phytoplankton and cyanotoxins from seston were analyzed during 15 months in a eutrophic reservoir. Effective time to immobilize 50% of the exposed individuals (ET50) was adopted as the endpoint. Paralysis of swimming movements was observed between ∼0.5–3 h of exposure to lake water containing toxic cyanobacteria, followed by an almost complete recovery of the swimming activity within 24 h after being placed in control water. The same effects were observed in bioassays with a saxitoxin-producer strain of Cylindrospermopsis raciborskii isolated from the reservoir. Regression analysis showed significant relationships between ET50 vs. cell density, biomass and saxitoxins content, suggesting that the paralysis of Daphnia in lake water samples was caused by saxitoxins found in C. raciborskii. Daphnia bioassay was found to be a sensitive method for detecting fast-acting neurotoxins in natural samples, with important advantages over mouse bioassays. [Copyright &y& Elsevier]

Abstract: Cyanobacteria produce a diverse array of toxic or otherwise bioactive compounds that pose growing threats to human and environmental health. We utilized the zebrafish (Danio rerio) embryo, as a model of vertebrate development, to investigate the inhibition of development pathways (i.e. developmental toxicity) by the cyanobacterial toxin, cylindrospermopsin (CYN), as well as extracts from various isolates of Cylindrospermopsis raciborskii and Aphanizomenon ovalisporum. CYN was toxic only when injected directly into embryos, but not by direct immersion at doses up to 50μg/ml. Despite the dose dependency of toxicity observed following injection of CYN, no consistent patterns of developmental defects were observed, suggesting that toxic effects of CYN may not target specific developmental pathways. In contrast, direct immersion of embryos in all of the extracts resulted in both increased mortality and reproducible, consistent, developmental dysfunctions. Interestingly, there was no correlation of developmental toxicity observed for these extracts with the presence of CYN or with previously reported toxicity for these strains. These results suggest that CYN is lethal to zebrafish embryos, but apparently inhibits no specific developmental pathways, whereas other apparent metabolites from C. raciborskii and A. ovalisporum seem to reproducibly inhibit development in the zebrafish model. Continued investigation of these apparent, unknown metabolites is needed. [Copyright &y& Elsevier]

We report the first documented observation of the potentially toxic cyanobacterium Cylindrospermopsis in Lake Erie and Sandusky Bay in 2005 (0.043-1.326 mg L-1 wet weight, 16-1,942 trichomes mL-1) and quantify the physical and chemical parameters and the cyanobacterial community composition contemporaneous to its occurrence. We hypothesize that the high temperature, low light intensity, and high nutrient content of Sandusky Bay, a shallow, drowned river mouth along the southwestern shore of Lake Erie, provides an ideal habitat for Cylindrospermopsis. This is consistent with published laboratory and field studies that show these physical and chemical conditions facilitate Cylindrospermopsis growth. Using multivariate statistics, we found that Cylindrospermopsis biomass correlated with high temperatures and shallow depths, conditions often found in Sandusky Bay. Light climate and nutrient concentrations were not associated with Cylindrospermopsis biomass, most likely because the light climate did not systematically change during the season and because nutrients exceeded demand. We propose that Cylindrospermopsis will increase in importance in Lake Erie, as previous research on elimate change in the Great Lakes region predicts future higher water temperatures and lower water levels. [ABSTRACT FROM AUTHOR]

Abstract: Cylindrospermopsin (cyn) is a cyanobacterial toxin implicated in human and wildlife poisonings. We have completed studies investigating the potential of purified cyn to induce developmental toxicity in mammals. The teratology study involved intraperitoneal injections (8.0–128μgkg−1) on gestational days (GD) 8–12 with subsequent examination of term fetuses for viability, weight and morphological anomalies. Cyn was lethal to a significant portion of the dams receiving ⩾32μgkg−1. Surviving pregnant females were killed and fetuses removed for examination. Analysis indicates no adverse effects on litter size, fetal weight, or incidence of anomalies. Subsequently, 50μgkg−1 cyn was administered on GD 8–12 or 13–17. Animals were allowed to give birth and litters monitored for growth and viability. A reduction in litter size occurred in treated groups. Avg. pup wt. was only affected in the GD 13–17 group. GD 13–17 dams did not exhibit the toxicity noted in the GD 8–12 group but gave birth significantly earlier than controls. There was a significant number of dead GD 13–17 pups and incidences of blood in the gastrointestinal tract and hematomas in the tips of the tails in survivors. Pups were cross-fostered to control mothers in litters of 10. On postnatal days (PND) 5–6 there were no significant differences in weight gain or viability in GD 8–12 litters, while GD 13–17 litters had significantly reduced weight gain and viability. GD 13–17 exposed male pups still weighed significantly less than the controls after 15 months. [Copyright &y& Elsevier]

Abstract: Cyanobacterial biovolume is used as a guide to the public health risk from these organisms for users of potable and recreational waters. Most routine surveillance programs preserve phytoplankton samples before analysis. We tested the effect of Lugol''s Iodine, a common preservative, on the cell biovolume of four common freshwater cyanobacteria, Microcystis aeruginosa, Anabaena circinalis, Cylindrospermopsis raciborskii and Aphanocapsa incerta. Linear dimensions and cell area were measured with an image analyser. All four species shrank after preservation. The magnitude of shrinkage varied with species and preservation time but was not affected by Lugol''s concentration. The maximum shrinkage in each species was a 30–40% reduction compared to the live cell biovolume. These results suggest shrinkage can be a greater source of uncertainty in estimating the biovolume of toxigenic cyanobacteria in aquatic environments than natural variability in the cell dimensions, instrument precision or cell counting. Standardised cyanobacterial biovolume lists based on agreed geometric shapes and formulae would improve the value of this information for public health risk assessment. [Copyright &y& Elsevier]

Cylindrospermopsin (CYN) is a toxic alkaloid produced by several genera of freshwater cyanobacteria. This compound has been implicated in outbreaks of human sickness and the death of domestic and wild animals. Given that several of the cyanobacterial genera known to produce CYN are common components of the phytoplankton of freshwaters including aquaculture facilities, we studied the accumulation of CYN in the freshwater mussel (swan mussel) Anodonta cygnea.Anodonta were exposed to CYN-producing cultures of the cyanobacterium Cylindrospermopsis raciborskii for 16 days and were found to accumulate the toxin to concentrations up to 2.52 μg g tissue dry weight−1. There was considerable variation in the concentrations of CYN detected in different parts of the body. At the end of a 2-week accumulation period the distribution of CYN in the body of Anodonta was as follows: haemolymph (68.1%), viscera (23.3%), foot and gonad (7.7%) and mantle (0.9%). No CYN was detected in the gills or adductor muscle of any animals. Following a 2-week depuration period, approximately 50% of the toxin remained in the tissues. Based on the recently derived guideline value for CYN in human drinking water (1 μg l−1) and the concentrations of this compound in animal tissues reported here, there is a clear need for the increased monitoring of this compound in organisms grown for human and animal consumption. [Copyright &y& Elsevier]

The Artemia salina bioassay was successfully applied to the analysis of the hepatotoxic cyanobacterial alkaloid and protein synthesis inhibitor, cylindrospermopsin. A dose-dependent response in mortality was observed for purified cylindrospermopsin and LC50 values decreased with time from 8.1 to 0.71 μg ml−1, between 24 and 72 h, respectively. Cylindrospermopsin was slightly less potent than microcystin-LR, with similar LC50 values on a gravimetric basis, but was more toxic to A. salina than the protein synthesis inhibitors, cycloheximide, chloramphenicol and tetracycline. Cylindrospermopsin-containing strains of the cyanobacterium Cylindrospermopsis raciborskii were found to be toxic to A. salina and the LC50 concentration for these strains over time was greater than the LC50 for purified cylindrospermopsin, with the exception of C. raciborskii strain CR1. [Copyright &y& Elsevier]

• Toxic cyanobacterium Raphidiopsis raciborskii was found blooming in a coastal lake whose water is used for human consumption. • The toxic biomass is transported downstream reaching coastal and estuarine waters. • R. raciborskii strains can survive, grow and increase the production of saxitoxins at salinities up to 6. • Saxitoxins of limnic origin can reach coastal ecosystems and accumulate in marine shellfish, causing poisoning. Raphidiopsis raciborskii (formerly Cylindrospermopsis raciborskii) is a freshwater cyanobacterium potentially producing saxitoxins (STX) and cylindrospermopsin. Its ecophysiological versatility enables it to form blooms in the most diverse types of environments, from tropical to temperate, and from relatively pristine to polluted. In Peri Lake, located in the subtropical south of Brazil, growing populations of STX-producing R. raciborskii have been detected since 1994, posing risks to the use of its waters that supply a population of about 100,000 inhabitants. Despite the existence of a monitoring system for the presence and toxicity of cyanobacteria in Peri Lake water, no assessment has been made in the coastal region, downstream of outflowing lake water, thereby potentially making available a toxic biomass to natural and cultivated shellfish populations in the salt water ecosystem. To address this problem, the present study evaluated environmental variables and STX concentration by profiling the outflowing waters between Peri Lake and the adjacent coastal zone. Laboratory experiments were carried out with three strains of R. raciborskii in order to confirm the effect of salinity on STX production and verify if Perna Perna mussels fed with R. raciborskii cultures would absorb and accumulate STX. Results showed that environmental concentrations of STX reach high levels (up to 6.31 µg L−1 STX eq.), especially in the warmer months, reaching the coastal zone. In laboratory tests, it was found that the strains tolerate salinities between 4 and 6 and that salinity influences the production of STX. In addition, mussels fed with R. raciborskii effectively absorb and accumulate STX, even in typically marine salinities (22 to 30), suggesting that R. raciborskii biomass remains available and toxic despite salinity shock. These results draw attention to the ecological and health risk associated with R. raciborskii blooms, both in the lake environment and in the adjacent marine environment, calling attention to the need to improve the monitoring and management systems for water and shellfish toxicity in the region of interest, as well as other places where toxic cyanobacteria of limnic origin can reach the coastal zone. [ABSTRACT FROM AUTHOR]

• Invasive nostocalean cyanobacteria have been found in temperate region, nakdong River, korea. • A low quantity of invasive nostocalean cyanobacteria occurred from spring to winter. • Three genera, four species, and twenty-four strains of invasive nostocalean cyanobacteria were isolated from the nakdong river. • Neurotoxin anatoxin-a was verified in the nakdong river cuspidothrix issatschenkoi isolates. The extent and frequency of harmful cyanobacterial blooms are increasing, owing to the climate change caused by global warming, and some harmful filamentous cyanobacteria that were first reported in the tropics are spreading to temperate regions, such as North America, Europe, and Northeast Asia. Although these exotic invasive cyanobacteria have a high toxigenic potential, they are not targeted in management plans in many countries. This study analyzed the occurrence of and potential toxin and off-flavor secondary metabolite production by invasive nostocalean cyanobacteria in the Nakdong River in Korea, which is a temperate region. The occurrence of four species belonging to three genera of cyanobacteria was confirmed in the Nakdong River. The quantities of cyanobacteria in the Nakdong River were mostly low, fewer than 1,000 cells mL−1. Twenty-four strains belonging to four species in three genera of cyanobacteria were isolated from the Nakdong River. Analysis revealed no off-flavor secondary metabolite production by any of the isolates, and those belonging to Cylindrospermopsis raciborskii, Sphaerospermopsis aphanizomenoides, and S. reniformis were identified as nontoxic strains. However, anatoxin-a production was observed in two of the eleven isolates of Cuspidothrix issatschenkoi. Given the sites and the timing of its occurrence, C. issatschenkoi had the highest potential for toxin production among the invasive nostocalean cyanobacteria appearing in the Nakdong River. [ABSTRACT FROM AUTHOR]

A 2 year field study in two shallow, polytrophic lakes (Langer See and Melangsee) in Brandenburg revealed the importance of environmental factors in controlling the population dynamics of various cyanobacterial species which do not form layers or aggregations. The species belonged to the toxin producing genera Cylindrospermopsis, Planktothrix, Aphanizomenon and Anabaena, and to the nontoxic members of Limnothrix and Pseudanabaena. In German waters, Cylindrospermopsis raciborskii is a neophyte, and exhibits a comparatively low temperature requirement of about 17 °C for germination and growth. The nutrient concentrations were comparable in both the lakes, and did not change measurably during the summer succession. The dissolved nitrogen fractions were well below 50 μg l–1 with total depletion of nitrate. Soluble reactive phosphate concentrations never fell below 3 μg l–1 throughout the summer season. The light attenuation factors (Kd) of 3–5.8 m–1 indicate high self-shading. However, under calm weather conditions, the cyanobacteria were not concentrated in near surface layers and the species composition was relatively uniform in the vertical. In mid-summer, the diazotrophic Nostocales were replaced by Oscillatoriales. Reduced light availability caused by mixing and self-shading is considered to be the main factor causing the summer decline of Nostocales. By means of two weather stations, more frequent, deeper and longer lasting mixing events could be observed in Langer See than in the more shallow, but wind protected Melangsee. The success of Planktothrix agardhii may be due to the more turbulent mixing regime in Langer See. The algal association, S of Reynolds (Reynolds, C.S., 1997), should be modified, since the different species grouped together in S have different responses to turbulent mixing. [Copyright &y& Elsevier]