Rapid in situ assessment of high-resolution spatial and temporal distribution of cyanobacterial blooms using fishery echosounder

Cyanobacterial blooms are increasing in frequency, magnitude, and duration globally because of enhanced eutrophication and climate change. Thus, comprehensive investigation and systematic monitoring of the spatial and temporal distribution of cyanobacteria in aquatic environments are urgently needed to better understand bloom development and complex interactions within a dynamic environment. Various methods have been used to investigate the distribution of cyanobacteria, however, none of them can provide high-resolution data for the three-dimensional spatial structure of the bloom and its dynamics in real time. In the present study, we investigated the applicability of a high-frequency (200 kHz) fishery echosounder, a type widely used in fisheries acoustics, to detect and estimate the cyanobacterial genus Microcystis bloom distribution and biomass in a shallow lake (Sulejów Reservoir, Poland). Verification of the usefulness of in situ acoustic quantification of bloom-forming cyanobacteria was based on a comparison of acoustic estimates of cyanobacterial biomass with the ground truth-that is, fluorometric measurements and chlorophyll a concentrations. We compared the acoustic estimates with other methods for continuous measurements along 10 predetermined parallel transects and point samples at 14 stations situated on the transects. In vertical hydroacoustic measurements at night, we observed that cyanobacterial biomass was highest in the uppermost layer and diminished continuously with depth. For both horizontal and vertical continuous measurements, we found significant positive correlations between acoustic and fluorometric estimates of cyanobacterial biomass. The traditional point samples measurements, however, did not agree equally well with the acoustic estimates, especially for vertical beam. We argue that the point measurements have more stochastic character and less adequately describe dynamic changes in the cyanobacteria distribution than continuous acoustic estimates. More studies are required to explore the cyanobacteria distribution patterns under different biological, physical, and meteorological conditions.

The ecohydrological approach, SWAT modelling, and multi-stakeholder engagement - A system solution to diffuse pollution in the Pilica basin, Poland

The reduction of diffused nutrient pollution from agriculture is one of the defining challenges of our time, demanding system solutions. A nitrogen and phosphorus (N&P) reduction strategy at the catchment scale is the most realistic and effective long-term approach to eutrophication management. In this study, a voluntary programme for the reduction of diffuse pollution was developed for the Pilica catchment and the Sulejów Reservoir in Poland. The Action Plan was based on the ecohydrological approach, which strives to use ecosystem processes as a management tool. One fundamental element of the Plan was a SWAT model, used to estimate N&P emissions and to determine the priority areas in the catchment. Strong cooperation between water managers, interdisciplinary researchers, and stakeholders helped to catalyse the capacity-building process of public participation, through dialogical interaction including a critical exchange of knowledge. Finally, a list of selected spatially-targeted mitigation measures was generated based on the modelling results and following measure acceptance by stakeholders. The key assumption in the creation of the measure list was that ecohydrological nature-based solutions (NBS) should be used complementarily to good agricultural practices. Such an approach has contributed to a faster achievement of 'good ecological status' of water bodies.

Long-Term Patterns in the Population Dynamics of Daphnia longispina, Leptodora kindtii and Cyanobacteria in a Shallow Reservoir: A Self-Organising Map (SOM) Approach

The recognition of long-term patterns in the seasonal dynamics of Daphnia longispina, Leptodora kindtii and cyanobacteria is dependent upon their interactions, the water temperature and the hydrological conditions, which were all investigated between 1999 and 2008 in the lowland Sulejow Reservoir. The biomass of cyanobacteria, densities of D. longispina and L. kindtii, concentration of chlorophyll a and water temperature were assessed weekly from April to October at three sampling stations along the longitudinal reservoir axis. The retention time was calculated using data on the actual water inflow and reservoir volume. A self-organising map (SOM) was used due to high interannual variability in the studied parameters and their often non-linear relationships. Classification of the SOM output neurons into three clusters that grouped the sampling terms with similar biotic states allowed identification of the crucial abiotic factors responsible for the seasonal sequence of events: cluster CL-ExSp (extreme/spring) corresponded to hydrologically unstable cold periods (mostly spring) with extreme values and highly variable abiotic factors, which made abiotic control of the biota dominant; cluster CL-StSm (stable/summer) was associated with ordinary late spring and summer and was characterised by stable non-extreme abiotic conditions, which made biotic interactions more important; and the cluster CL-ExSm (extreme/summer), was associated with late spring/summer and characterised by thermal or hydrological extremes, which weakened the role of biotic factors. The significance of the differences between the SOM sub-clusters was verified by Kruskal-Wallis and post-hoc Dunn tests. The importance of the temperature and hydrological regimes as the key plankton-regulating factors in the dam reservoir, as shown by the SOM, was confirmed by the results of canonical correlation analyses (CCA) of each cluster. The demonstrated significance of hydrology in seasonal plankton dynamics complements the widely accepted pattern proposed by the plankton succession model for lakes, the PEG (Plankton Ecology Group), and may be useful for the formulation of management decisions in dam reservoirs.

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.

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 Bronisławow 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.

Application of a microbiotests battery for complete toxicity assessment of rivers

Acute hazard classification based on selected microbiotests was proposed to assess and compare the toxicity of rivers including surface-water, sediment and soil from floodplains. No direct relationship between the classification of pollution for surface-water based on physical-chemical parameters and proposed acute hazard classification based on organisms' sensitivity was observed. The quality of water according to hazard classification was better than in the mandatory classification of pollution, with the domination of Class II (slight acute hazard). The samples of sediment and soil were more toxic and represented Class II or Class III (acute hazard). The results indicated a need to complete the mandatory monitoring of surface-water in rivers with biological monitoring with toxicity assessment of rivers including water, sediment and soil from floodplains based on acute hazard classification. This integral approach enables a complete evaluation of the toxicity of aquatic life together with an estimation of negative changes in river systems.

Diurnal variations in the photosynthesis-respiration activity of a cyanobacterial bloom in a freshwater dam reservoir: an isotopic study

The stable isotopic analyses of molecular oxygen dissolved in water (delta18O(DO)) and dissolved inorganic carbon (delta13C(DIC)), supplemented with basic chemical measurements, have been carried out on a diurnal basis to better understand the dynamics of photosynthesis and respiration in freshwater systems. Our observations have been carried out in a lowland dam reservoir, the Sulejow Lake (central Poland), during the summer cyanobacterial bloom. All data obtained, isotopic, hydrochemical, and biological, show a high mutual consistency. Namely, the lowest delta18O(DO) values, obtained at 10:00 and 14:00 (16.0 and 15.5 per thousand, respectively), correspond to the highest amount of cyanobacterial cells observed (66 and 63 mg dm(-3), respectively), whereas the minimum delta13C(DIC) (-10.6 per thousand) obtained at 22:00 corresponds to the maximum content of organic matter (110 mg dm(-3)). This evidence suggests that isotopic assays of delta18O(DO) and delta13C(DIC) are a reliable tool for the quantitative study of biochemical processes in freshwater systems.

Assessing drinking water treatment systems for safety against cyanotoxin breakthrough using maximum tolerable values

For assessing the safety of drinking water supplies suffering cyanobacterial blooms in their water source, a methodology is proposed which relates the performance of their current treatment train to the quality of the raw water. The approach considers that different treatment trains can remove algal toxins with different efficiency. Maximum Tolerable (MT-) values of the raw water expressed by cell counts or by biovolumes of cyanobacteria were calculated. Three MT-categories were identified by colours; high risk (red), moderate risk (yellow) and no risk (green). Two treatment facilities using a conventional (1) and polishing train (2) were assessed using this methodology. For most of the time during an algal bloom the water quality could be classified as yellow which means short term higher toxin levels in comparison to the guide line in clear water were found. However, the red classification, indicating a high risk for drinking water quality was never reached. The model proposed can be understood as supplement of the common alert level framework, ALF-concept (Chorus and Bartram, Situation Assessment, Planning and Management. London and New York: E & FN Spon. 1999; House et al., Management Strategies for Toxic Blue Green Algae: Literature Review. Australia: CRC for Water Quality and Treatment. 2004).

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.

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.

Elimination of microcystins by water treatment processes-examples from Sulejow Reservoir, Poland

Eutrophication is a serious problem in Polish freshwaters. Mass occurrences of toxic cyanobacteria in reservoirs cause problems in the production of safe drinking water and the diversity of produced toxins complicates monitoring of freshwaters. The aim of this study was to estimate the efficiency of water treatment processes in the removal of microcystins (MCs), cyanobacterial hepatotoxins. Elimination of microcystins was studied at two waterworks, which supply drinking water to the city of Lodz from Sulejow Reservoir. The consecutive steps of pre-oxidation, coagulation, sand filtration, ozonation and chlorination used in the water treatment showed effective elimination of microcystins in water from Sulejow Reservoir in 2002 and 2003. The highest total concentration of microcystin (variants MC-RR, MC-YR, MC-LR) amounted to 6.7 microgl(-1) in raw water and was detected on the 13th of August 2002. In 2003 the water utility decided to increase the contribution of ground water in the production of drinking water. This resulted in a decrease of microcystin in water during and after the treatment process. The current management strategy of the waterworks company includes mixing of surface water and ground water, which reduces the hazards caused by toxic cyanobacterial blooms in the reservoir.