Growth of microalgae and cyanobacteria consortium in a photobioreactor treating liquid anaerobic digestate from vegetable waste.

This research examines the biological treatment of undiluted vegetable waste digestate conducted in a bubble column photobioreactor. Initially, the bioreactor containing 3N-BBM medium was inoculated with Microglena sp., Tetradesmus obliquus, and Desmodesmus subspicatus mixture with a density of 1.0 × 104 cells/mL and the consortium was cultivated for 30 days. Then, the bioreactor was semi-continuously fed with liquid digestate with hydraulic retention time (HRT) of 30 days, and the treatment process was continued for the next 15 weeks. The change in the microalgal and cyanobacterial species domination was measured in regular intervals using cell counting with droplet method on a microscope slide. At the end of the experiment, Desmonostoc sp. cyanobacteria (identified with 16S ribosomal RNA genetical analysis) as well as Tetradesmus obliquus green algae along with Rhodanobacteraceae and Planococcaceae bacteria (determined with V3-V4 16sRNA metagenomic studies) dominated the microbial community in the photobioreactor. The experiment demonstrated high treatment efficiency, since nitrogen and soluble COD were removed by 89.3 ± 0.5% and 91.2 ± 1.6%, respectively, whereas for phosphates, 72.8 ± 2.1% removal rate was achieved.

Cyanobacterial cell-wall components as emerging environmental toxicants - detection and holistic monitoring by cellular signaling biosensors.

Cyanobacterial blooms constitute a recognized danger to aquatic environment and public health not only due to presence of main group of cyanotoxins, such as microcystins, cylindrospermopsin or anatoxin-a, but also other emerging bioactivities. An innovative approach identifying such bioactivities is the application of cellular biosensors based on reporter genes which detect the impact of cyanobacterial cells and components on actual human cells in a physiological-like setting. In the present study biosensor cell lines detecting four different types of bioactivities (ARE - oxidative stress, NFKBRE - immunomodulatory pathogen-associated molecular patterns, AHRE - persistent organic pollutants, GRE - endocrine disruptors) were exposed to concentrated cyanobacterial cells from 21 environmental bloom samples and from eight cultures (Microcystis aeruginosa, Aphanizomenon flos-aquae, Planktothrix agardhii and Raphidiopsis raciborskii). The AHRE and GRE biosensors did not detect any relevant bioactivity. In turn, ARE biosensors were significantly activated by bloom samples from Jeziorsko (180-250%) and Sulejów (250-400%) reservoirs with the highest cyanobacterial biomass, while activation by cultures was weak/undetectable. The same biosensors were stimulated by microcystin-LR (250%) and anatoxin-a (150%). The NFKBRE biosensors were activated to varying extent (140-650%) by most bloom and culture samples, pointing to potential immunomodulatory toxic effects on humans. Lipopolysaccharide and lipoproteins were identified as responsible for NFKBRE activation (probably via pattern recognition receptors), while peptidoglycan had no bioactivity in this assay. Thus, the holistic approach to sample analysis with the application of cellular biosensors geared towards 4 separate pathways/bioactivities was validated for identification of novel bioactivities in organisms with recognized public health significance (e.g. this study is the first to describe cyanobacterial lipoproteins as potential environmental immunomodulators). Moreover, the ability of cellular biosensors to be activated by intact cyanobacterial cells from blooms provides proof of concept of their direct application for environmental monitoring, especially comparison of potential threats without need for chemical analysis and identification of toxicants.

Oxidative Stress, Programmed Cell Death and Microcystin Release in Microcystis aeruginosa in Response to Daphnia Grazers.

There is increasing evidence that programmed cell death (PCD) in cyanobacteria is triggered by oxidative stress and that it contributes to the survival of the cyanobacterial population such as Microcystis aeruginosa. At the same time, microcystins (MCs) released during cell lysis have been implicated in colony formation (enabled by the release of polysaccharides) in M. aeruginosa - a strategy that allows the effect of a stressor, including grazing to be avoided or decreased. This experimental research has explored whether extracts of Daphnia magna and Daphnia cucullata (corresponding to 5, 25, 50, and 100 individuals per liter) reveal the effect on the growth, intracellular reactive oxygen species (ROS) content, lipid peroxidation, PCD, MC-LR release, and bound exopolysaccharide (EPS) level in M. aeruginosa during 7 days of exposure. As demonstrated, extracts of both daphnids induced dose-dependent growth inhibition, increase in ROS levels, lipid peroxidation, and PCD. Moreover, the release of MC-LR and an increase in the bound EPS fraction were observed in treated cultures. Generally, the greatest effects were observed under the influence of D. magna extracts. The study indicates that grazer presence can potentially trigger a series of events in the Microcystis population, with cells undergoing oxidative stress-induced PCD associated with MC release, which in turn increases EPS production by intact cells. As argued, this strategy is likely to have evolved in response to abiotic stressors, since both PCD and synthesis of MC in cyanobacteria predate the metazoan lineage. Nevertheless, it may still provide a benefit for the survival of the MC-producing M. aeruginosa population under grazer pressure.

In Vitro Toxicological Screening of Stable and Senescing Cultures of Aphanizomenon, Planktothrix, and Raphidiopsis.

Toxicity of cyanobacteria is the subject of ongoing research, and a number of toxic metabolites have been described, their biosynthesis pathways have been elucidated, and the mechanism of their action has been established. However, several knowledge gaps still exist, e.g., some strains produce hitherto unknown toxic compounds, while the exact dynamics of exerted toxicity during cyanobacterial growth still requires further exploration. Therefore, the present study investigated the toxicity of extracts of nine freshwater strains of Aphanizomenon gracile, an Aphanizomenon sp. strain isolated from the Baltic Sea, a freshwater strain of Planktothrix agardhii, and two strains of Raphidiopsis raciborskii obtained from 25- and 70-day-old cultures. An in vitro experimental model based on Cyprinus carpio hepatocytes (oxidative stress markers, DNA fragmentation, and serine/threonine protein activity) and brain homogenate (cholinesterase activity) was employed. The studied extracts demonstrated toxicity to fish cells, and in general, all examined extracts altered at least one or more of considered parameters, indicating that they possess, to some degree, toxic potency. Although the time from which the extracts were obtained had a significant importance for the response of fish cells, we observed strong variability between the different strains and species. In some strains, extracts that originated from 25-day-old cultures triggered more harmful effects on fish cells compared to those obtained from 70-day-old cultures, whereas in other strains, we observed the opposite effect or a lack of a significant change. Our study revealed that there was no clear or common pattern regarding the degree of cyanobacterial bloom toxicity at a given stage of development. This means that young cyanobacterial blooms that are just forming can pose an equally toxic threat to aquatic vertebrates and ecosystem functioning as those that are stable or old with a tendency to collapse. This might be largely due to a high variability of strains in the bloom.

Comprehensive approach to restoring urban recreational reservoirs. Part 2 - Use of zooplankton as indicators for the ecological quality assessment.

The presented research is part of the LIFE project ("EH-REK" LIFE08 ENV/PL/000517) on innovative restoration methods for small urban impoundments in the city of Lódz (Poland). The objective was to evaluate the usefulness of zooplankton as a biological quality element, when assessing the effectiveness of restoration efforts in three urban reservoirs and a one pond. The fifth unrestored pond was used as an example of the progressive eutrophication of an urban ecosystem. Studies were conducted during two periods: before (2010-2012) and after (2013-2016) restoration. A selection of zooplankton indices, including the rotifer trophic state index (TSIROT), was used. The influence of the supplying river resulted in the negligible responses of biological parameters to the restoration efforts in the Upper Arturówek (UA) reservoir, which is the first in cascade of reservoirs. However, clear symptoms of water quality improvements were observed in the other two reservoirs (the Middle Arturówek, MA; the Lower Arturówek, LA) and in the Bzura-17 (B17) pond. After restoration, the contribution of species indicative of high trophic levels decreased in these ecosystems. The TSIROT was strongly positively correlated with the trophic state index based on chlorophyll a, and both parameters significantly decreased in the MA, LA and B17. In the unrestored pond (B11), the successive increase in the concentrations of chemical parameters indicated progressing eutrophication. Interestingly, since 2013, the TSIROT values clearly decreased in B11, but the strong negative correlation between ammonium concentration and rotifer density indicated that the reduced TSIROT values didn't result from improvements in water quality; rather, they resulted from the increases in pollution and the associated harmful impacts on Rotifera. In conclusion, the TSIROT can be a useful tool for assessing the ecological quality of small urban ecosystems; however, the use of biological indices must be supported by also monitoring physicochemical parameters.

A report of Cylindrospermopsis raciborskii and other cyanobacteria in the water reservoirs of power plants in Ukraine.

The occurrence of cyanobacteria in freshwaters attracts much attention due to its associated health threats and ecological implications. Yet data on the composition of cyanobacteria taxa and toxigenicity in some regions is still scarce. Here, we explored the occurrence of cyanobacteria and cyanotoxins in three locations in Ukraine (reservoir for Kasperivtsi Hydrothermal Power Plant and outflowing River Seret, and cooling pond of Khmelnytsky Atomic Power Plant) in summer 2017. Cyanobacteria were a dominant fraction at all stations. A number of potent-toxin producers were identified including Cylindrospermopsis raciborskii, Aphanizomenon gracile, Dolichospermum flos-aquae, and Planktothrix agardhii. Screening for the presence of dissolved and particulate content of microcystins (-LR, -YR, and -RR), cylindrospermopsin, and anatoxin-a yielded negative results. The studied waters displayed no toxicity in human platelets in vitro. Further toxicological and ecological studies are necessary to evaluate the potential presence of cyanotoxin producers in Ukraine.

Restoration of a shady urban pond - The pros and cons.

The Bzura-7 pond (Lódz, Poland) is a typical shallow and shady urban reservoir situated on the Bzura River that is exposed to pollutants introduced mainly by internal loads and the supply from the catchment. In 2010-2012, the following characteristics were observed in the pond: a high allochthonous input of organic matter, high concentration of ammonium, low concentration of dissolved oxygen and low diversity of zooplankton, dominated mainly by Daphnia spp. From January to June 2013, restoration measures were performed, including sediment removal, increasing light access to the pond and construction of a sequential sedimentation-biofiltration system (SSBS). The aim of the present study was to investigate how the water quality in the Bzura-7 pond was affected by the restoration process, which included reducing pollutant inflows and enhancing habitat potential, thus increasing the diversity of this ecosystem. Restoration efforts improved the chemical and physical parameters of the water. The oxygen concentration increased, and the concentrations of TN and ammonium significantly decreased. Despite the increase in pond lighting, the growth of cyanobacteria was limited. However, we observed increased abundance of green algae and diatoms but less than adequate changes in the zooplankton community structures. Although we observed a significant increase in the zooplankton species richness after restoration, this increase was related to the small-bodied groups of zooplankton, rotifers and bosminiids, characteristic of eutrophic ecosystems. In addition, a planktivorous fish - sunbleak (Leucaspius delineatus) - was identified as an unintended side effect of the restoration effort. Further conservation efforts in the Bzura-7 pond and monitoring of results are still needed.

Application of cellular biosensors for detection of atypical toxic bioactivity in microcystin-containing cyanobacterial extracts.

Despite the focus of most ecotoxicological studies on cyanobacteria on a select group of cyanotoxins, especially microcystins, a growing body of evidence points to the involvement of other cyanobacterial metabolites in deleterious health effects. In the present study, original, self-developed reporter gene-based cellular biosensors, detecting activation of the main human xenobiotic stress response pathways, PXR and NFkappaB, were applied to detect novel potentially toxic bioactivities in extracts from freshwater microcystin-producing cyanobacterial blooms. Crude and purified extracts from cyanobacteria containing varying levels of microcystins, and standard microcystin-LR were tested. Two cellular biosensor types applied in this study, called NHRTOX (detecting PXR activation) and OXIBIOS (detecting NFkappaB activation), successfully detected potentially toxic or immunomodulating bioactivities in cyanobacterial extracts. The level of biosensor activation was comparable to control cognate environmental toxins. Despite the fact that extracts were derived from microcystin-producing cyanobacterial blooms and contained active microcystins, biosensor-detected bioactivities were shown to be unrelated to microcystin levels. Experimental results suggest the involvement of environmental toxins (causing a response in NHRTOX) and lipopolysaccharides (LPS) or other cell wall components (causing a response in OXIBIOS) in the potentially harmful bioactivity of investigated extracts. These results demonstrate the need for further identification of cyanobacterial metabolites other than commonly studied cyanotoxins as sources of health risk, show the usefulness of cellular biosensors for this purpose and suggest a novel, more holistic approach to environmental monitoring.

Response of Daphnia's antioxidant system to spatial heterogeneity in Cyanobacteria concentrations in a lowland reservoir.

Many species and clones of Daphnia inhabit ecosystems with permanent algal blooms, and they can develop tolerance to cyanobacterial toxins. In the current study, we examined the spatial differences in the response of Daphnia longispina to the toxic Microcystis aeruginosa in a lowland eutrophic dam reservoir between June (before blooms) and September (during blooms). The reservoir showed a distinct spatial pattern in cyanobacteria abundance resulting from the wind direction: the station closest to the dam was characterised by persistently high Microcystis biomass, whereas the upstream stations had a significantly lower biomass of Microcystis. Microcystin concentrations were closely correlated with the cyanobacteria abundance (r = 0.93). The density of daphniids did not differ among the stations. The main objective of this study was to investigate how the distribution of toxic Microcystis blooms affects the antioxidant system of Daphnia. We examined catalase (CAT) activity, the level of the low molecular weight antioxidant glutathione (GSH), glutathione S-transferase (GST) activity and oxidative stress parameters, such as lipid peroxidation (LPO). We found that the higher the abundance (and toxicity) of the cyanobacteria, the lower the values of the antioxidant parameters. The CAT activity and LPO level were always significantly lower at the station with the highest M. aeruginosa biomass, which indicated the low oxidative stress of D. longispina at the site with the potentially high toxic thread. However, the low concentration of GSH and the highest activity of GST indicated the occurrence of detoxification processes at this site. These results demonstrate that daphniids that have coexisted with a high biomass of toxic cyanobacteria have effective mechanisms that protect them against the toxic effects of microcystins. We also conclude that Daphnia's resistance capacity to Microcystis toxins may differ within an ecosystem, depending on the bloom's spatial distribution.

Role of environmental factors and toxic genotypes in the regulation of microcystins-producing cyanobacterial blooms.

The aim of this study was to understand: (1) how environmental conditions can contribute to formation of Microcystis-dominated blooms in lowland, dam reservoirs in temperate climate-with the use of quantitative molecular monitoring, and (2) what is the role of toxic Microcystis genotypes in the bloom functioning. Monitoring of the Sulejow Reservoir in 2009 and 2010 in two sites Tresta (TR) and Bronislawow BR), which have different morphometry, showed that physicochemical conditions were always favorable for cyanobacterial bloom formation. In 2009, the average biomass of cyanobacteria reached 13 mg L(-1) (TR) and 8 mg L(-1) (BR), and in the second year, it decreased to approximately 1 mg L(-1) (TR and BR). In turns, the mean number of toxic Microcystis genotypes in the total Microcystis reached 1% in 2009, both in TR and BR, and in 2010, the number increased to 70% in TR and 14 % in BR. Despite significant differences in the biomass of cyanobacteria in 2009 and 2010, the mean microcystins (MCs) concentration and toxicity stayed at a similar level of approximately 1 µg L(-1). Statistical analysis indicated that water retention time was a factor that provided a significant difference between the two monitoring seasons and was considered a driver of the changes occurring in the Sulejow Reservoir. Hydrologic differences, which occurred between two studied years due to heavy flooding in Poland in 2010, influenced the decrease in number of Microcystis biomass by causing water disturbances and by lowering water temperature. Statistical analysis showed that Microcystis aeruginosa biomass and 16S rRNA gene copy number representing Microcystis genotypes in both years of monitoring could be predicted on the basis of total and dissolved phosphorus concentrations and water temperature. In present study, the number of mcyA gene copies representing toxic Microcystis genotypes could be predicted based on the biomass of M. aeruginosa. Moreover, MCs toxicity and concentration could be predicted on the basic of mcyA gene copy number and M. aeruginosa (biomass, 16S rRNA), respectively. Present findings may indicate that Microcystis can regulate the number of toxic genotypes, and in this way adjust the whole bloom to be able to produce MCs at the level which is necessary for its maintenance in the Sulejow Reservoir under stressful hydrological conditions.

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.

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.

Perennial toxigenic Planktothrix agardhii bloom in selected lakes of Western Poland.

The presence of toxigenic blooms dominated by filamentous cyanobacterium Planktothrix agardhii with estimation of microcystins (MCs) concentration and toxicity was measured in two lakes: Bytynskie and Lubosinskie situated in Western Poland. Investigations were carried out in summer, autumn, and winter of 2007/2008 and early spring of 2008. In both lakes, a domination of P. agardhii in relation to the total cyanobacterial biomass oscillated, throughout the year, almost on the same level between 75 and 99%. The PCR analysis of mcyE gene indicated a presence of toxigenic strains in all collected samples. In addition, the result of semiquantification of mcyE gene band showed that both lakes seem to have variable, throughout the seasons, toxigenic potential with the highest density of mcyE gene in spring. Two separate methods were used: protein phosphatase inhibition assay for estimation of MCs toxicity (biological activity) and high-performance liquid chromatography for determination of MCs concentration (quantity). The highest seasonal MCs toxicity (15.8 µg/L Bytynskie and 21.9 µg/L Lubosinskie) and concentration (34.6 µg/L Bytynskie and 52.2 µg/L Lubosinskie) were determined in autumn and indicated on a Second Alert Level, according to WHO guidelines for bathing water. The results showed the ability of toxigenic strains of cyanobacteria dominated by P. agardhii to remain and produce MCs during the whole year. This was confirmed by significant correlations between P. agardhii biomass and MCs concentrations in both lakes (r = 0.84, Bninskie and r = 0.79, Lubosinskie; P < 0.05).

Establishment of an Alert Level Framework for cyanobacteria in drinking water resources by using the Algae Online Analyser for monitoring cyanobacterial chlorophyll a.

The Algae Online Analyser (AOA) fluorometer simultaneously distinguishes four different phytoplankton groups by their specific fluorescence spectra and thus allows for real-time in-situ chlorophyll a measurements per algal group. This AOA was used for monitoring cyanobacterial chlorophyll a in the drinking water at the Bronislawow Bay abstraction point in Sulejow Reservoir (Poland). The main goal of this research was to develop an early warning method for the detection of cyanobacterial biovolume in the source water, in order to establish an Alert Level Framework for the drinking water abstraction point in Sulejow Reservoir. A positive correlation between cyanobacterial biovolume, as determined by conventional methods, and cyanobacterial chlorophyll a, as measured by the AOA, was found (p<0.05). The results of this study were used to determine threshold values for the Alert Level Framework, based on cyanobacterial chlorophyll a concentrations in the source water of Sulejow Reservoir. The presented threshold values are determined specifically for this abstraction point, but the principles can be applied to other locations.

First report of the cyanobacterial toxin cylindrospermopsin in the shallow, eutrophic lakes of western Poland.

Cyanobacterial dominance in eutrophic lakes causes water quality problems due to the production of toxins harmful to humans and animals, as well as a number of odorous compounds. Cylindrospermopsin (CYN) is a potent cytotoxic cyanobacterial metabolite involved in triggering illness in humans. The occurrence of CYN has been mostly associated with tropical and subtropical cyanobacteria. We analyzed CYN concentration and phytoplankton assemblages of three lakes located in western Poland during the summers of 2006 and 2007. CYN was detected in 46% of our samples using the HPLC and LC-MS/MS methods. CYN concentrations were in the range of 0.16-1.8 microg L(-1) and exceeded the drinking water guideline value of 1 microgL(-1) in two samples. This is the first report of CYN occurrence in this part of Europe and provides further evidence that this toxin is common not only in subtropical and tropical regions. The lakes were dominated by Planktothrix agardhii but the occurrence of the CYN investigated here might be associated with the invasive species Cylindrospermopsis raciborskii and/or native Aphanizomenon gracile.

Biomonitoring of cyanobacterial blooms in Polish water reservoir and the cytotoxicity and genotoxicity of selected cyanobacterial extracts.

OBJECTIVES: Water pollution with toxic cyanobacterial blooms is a worldwide problem. Cyanobacteria species that mainly produce microcystins predominate in Polish water reservoirs. MATERIALS AND METHODS: In our study, cyanobacterial blooms were monitored during summer of 2004 in the Sulejów reservoir. The concentration of microcystins in water and cyanobacterial cells were determined using liquid chromatography and immunobiotests, while the biological activity of microcystic cyanobacterial extracts was assessed using bacterial tests (SOS Chromotest, UMU test), the comet assay and micronucleus test with human lymphocytes. RESULTS: It was revealed that cyanobacterial bloom was most intensive in mid August and lasted until the end of September. Microcystis aeruginosa and Aphanizomenon flos-aquae dominated in the blooms. The highest concentration of microcystins in cyanobacterial cells was also observed at that time. The concentration of microcystins in water did not exceed 1 microg/l. All cyanobacterial extracts showed weak genotoxicity only for Escherichia coli PQ37. The cyanobacterial extracts prepared at the beginning of September were most toxic to human lymphocytes, the effective microcystin extracts (EC50) concentration was about two or three times lower compared to the other extracts. The level of DNA damage in lymphocytes after short exposure to microcystic extracts (3 and 6 h) was significantly higher than respective levels after longer exposure. The microcystins of cyanobacterial blooms induced a slight increase in micronuclei frequencies in human lymphocytes. CONCLUSION: Phytoplankton biomass and the genotoxicity of massive cyanobacterial blooms should be assessed for eucariotic cells in the Sulejów reservoir to avoid the hazard induced by cyanobacterial blooms.

Detection and monitoring toxigenicity of cyanobacteria by application of molecular methods.

The aim of this study was early genetic identification of microcystin-producing cyanobacteria and monitoring their toxigenicity by determining toxin concentrations in three Polish lakes throughout the summer of 2004. The assessment of cyanobacterial blooms was carried out in shallow, eutrophic water bodies: Lake Jeziorak, Lake Bninskie, and Sulejow Reservoir. Samples for DNA, phycological, and toxin analyses were collected from July till October. Molecular analysis of the 16S rRNA region was used to detect cyanobacteria in water samples. The microscopic analysis was performed to investigate seasonal variation of phytoplankton. Cyanobacteria, with domination by Microcystis, Planktothrix, and Planktolyngbya were detected during the whole monitoring period in Sulejow Reservoir, Lake Bninskie, and Lake Jeziorak, respectively. The presence and identification of toxic strains in water bodies was studied by PCR amplification of mcy genes in the microcystis synthesis pathway. The presence of the mcyA, mcyB, mcyD, and mcyE genes in water samples indicated the genetic potential to produce microcystins. Toxicity of water samples and microcystin concentrations were established by PPIA and HPLC, respectively. The maximum concentration of microcystins was 11.13 microg/L and 4.67 microg/L in samples dominated by P. agardhii and M. aeruginosa, respectively. Molecular analysis showed that toxigenic strains of cyanobacteria occurred in the three lakes throughout the summer season.

Summer changes in cyanobacterial bloom composition and microcystin concentration in eutrophic Czech reservoirs.

In mid-July and August 2003 and 2004, 18 reservoirs in the Czech Republic were sampled for phytoplankton species composition and concentration of intracellular microcystins (MCs). As a consequence of high nutrient loading, most of the reservoirs experienced cyanobacterial blooms of various intensities, with the prevalence of cyanobacteria increasing markedly in August, along with a conspicuous shift in species composition toward dominance of Microcystis spp. Microcystins were detected in 90% of the samples, and their amount also increased considerably in August, reflecting the cyanobacterial biomass. In Microcystis-dominated samples, a significantly higher amount of MCs (p < 0.001) occurred than in samples in which other taxa prevailed. Microcystins were positively correlated with chlorophyll a and cyanobacterial biovolume (p < 0.05, R2 = 0.61 and 0.66, respectively), with the strongest correlation found for Microcystis spp. biovolume (p < 0.001, R2 = 0.87). This taxon was the most important producer of MCs in Czech reservoirs. The main structural variants of MCs were MC-LR, MC-RR, and MC-YR. This study's data also indicate that the relative share of MC variants (MC-LR and MC-RR) varies considerably with time, most likely as a consequence of different species and strain compositions during the summer. This study clearly demonstrates a high prevalence of MC-producing cyanobacteria in Czech reservoirs. Therefore, regular monitoring of these reservoirs is highly desirable in an effort to minimize potential health risks to the human population.

Hepatotoxic cyanobacterial blooms in the lakes of northern Poland.

The lakes of northern Poland are among the recreational sites most valued by Polish and German holiday makers. Given the socioeconomic importance of these lakes, water quality should be maintained at high levels for such intensive recreational purposes. In 2002 studies of species composition, biomass, and toxin production by phytoplankton and the attendant physicochemical variables were performed in order to assess the risk of cyanobacterial blooms in selected northern lakes: Lakes Jeziorak, Jagodne, Szymoneckie, Szymon, Taltowisko, Siecino, and Trzesiecko. The research showed that total phosphorus (0.1 mg P/L) and total nitrogen (1.5 mg N/L) in the studied lakes almost exceeded the permissible limits for eutrophication of water bodies. Most phytoplankton samples were taken in late summer, when cyanobacteria were expected to reach their highest biomass. At the time of sampling most of the lakes were dominated by oscillatorialean and nostocalean species. Average chlorophyll-a concentration was higher than 10 microg/L in almost all the lakes studied, which corresponded with an average microcystin concentration in the range of 4-5 microg/L. The main microcystins in the analyzed samples were dmMC-RR, MC-RR, MC-YR, and MC-LR. The results demonstrated a potential for intensive cyanobacterial blooms to appear during the summer in northern Polish lakes. The levels of cyanobacteria found in the lakes investigated indicated that toxicity had reached the first-alert level according to World Health Organization recommendations. If microcystin-producing cyanobacteria dominate, with a microcystin concentration of 2-4 microg/L, symptoms of toxicity can appear in the swimmers most sensitive to exposure. Analysis of cyanobacterial assemblages in northern Polish lakes also indicated a significant presence of Aphanizomenon species including a Scandinavian species, A. skujae (Skuja) Kom.-Legn. & Cronb. Future investigations of Polish lakes also should assess neurotoxins and study the biology of their producers. This study was the first attempt to evaluate the potential danger of toxic cyanobacterial blooms in the lakes of northern Poland.

Measurement of phycocyanin fluorescence as an online early warning system for cyanobacteria in reservoir intake water.

Cyanobacterial blooms in drinking water reservoirs may cause a variety of water quality problems, including those of taste and odor, and can compromise the water supply destined for human consumption. In response to this problem an online monitoring tool for analyzing the cyanobacterial concentration in intake water is of practical value. This study demonstrated a positive correlation between phycocyanin fluorescence and cyanobacterial biomass during Microcystis aeruginosa blooms in a lowland drinking water reservoir, using online detection. The highest correlation coefficients were found for a cyanobacterial biomass concentration below 15 mg freshweight/L, indicating that this method can be an effective early warning system. Rapid changes in fluorescence were observed when wind drift moved higher cyanobacterial concentrations into the water intake, indicating that fluorescence could be employed as a quick warning for changed requirements for plant operations.