The German Federal Environmental Agency (Umweltbundesamt – UBA) operates an experimental field on... more The German Federal Environmental Agency (Umweltbundesamt – UBA) operates an experimental field on the southern outskirts of Berlin for the investigation of special aspects of environmental hygiene. One part of the field consists of a storage pond with subsequent bank filtration, artificial recharge and slow sand filtration where experiments on the behavior of hazardous substances during bank filtration, artificial recharge or slow sand filtration can be carried out on a field scale without any adverse environmental impacts under nearly natural conditions. Experiments on the elimination of cyanobacteria and their toxins are currently being conducted in the plant as part of the research project of the KompetenzZentrum Wasser Berlin (KWB) named Natural and Artificial Systems for Recharge and Infiltration (NASRI).
ABSTRACT After installation of phosphorus elimination plants at the inflows of the eutrophic Lake... more ABSTRACT After installation of phosphorus elimination plants at the inflows of the eutrophic Lake Tegel and Schlachtensee, phosphorus (P) loading declined by a factor of 40 and 100, respectively. This resulted in a pronounced reduction of phosphorus concentrations in the lake water, followed by a decline of chlorophyll-a concentrations. However, for many years P release from sediments due to mineralization and desorption of sedimentary P continued. In Schlachtensee, the presence of nitrate above the sediment suppresses P release, because the Fe/P ratio is sufficient to provide enough aerobic sorption capacity. In Lake Tegel, some P release occurs even under aerobic conditions because of the low aerobic P sorption capacity of the sediments. There, nitrate could moderate the P release peaks which occur when the Fe-P cycle at the sediment water interface is disturbed by precipitation of iron sulfide after reduction of sulfate during times of high mineralization intensity. The potentially mobile P pool in the sediments of both lakes is rather small, indicating that the P release could subside after sufficient reduction of the external P load in Lake Tegel and the disruption of the internal P cycle in Schlachtensee.
Toxicon : official journal of the International Society on Toxinology, 2003
Cylindrospermopsis raciborskii, a freshwater cyanobacterium of tropical origin, is not only incre... more Cylindrospermopsis raciborskii, a freshwater cyanobacterium of tropical origin, is not only increasingly found in (sub) tropical water bodies, but also in temperate regions. Since this species may produce potent toxins such as cylindrospermopsin (CYN) and paralytic shellfish poisons, its massive occurrence in water bodies used as drinking water sources or for recreation is of major concern. The proliferation of C. raciborskii in German water bodies has been documented for the past decade. We investigated the occurrence of CYN in field populations and isolates of C. raciborskii from two lakes, and assessed the toxicity of culture isolates using the mouse bioassay, primary rat hepatocytes and human derived cell lines. We show for the first time the occurrence of CYN in German water bodies. None of seven isolates of C. raciborskii contained CYN, however, all isolates were toxic to primary rat hepatocytes, human hepatoblastoma (HEP-G2) and human colon adenocarcinoma (CACO-2) cells. Meth...
Three single-filament isolates of Aphanizomenon flos-aquae from two German lakes were found to pr... more Three single-filament isolates of Aphanizomenon flos-aquae from two German lakes were found to produce remarkable amounts of the cyanobacterial hepatotoxin cylindrospermopsin (CYN). CYN-synthesis of the strains were evidenced both by LC-MS/MS analysis and detection of PCR products of gene fragments which are implicated in the biosynthesis of the toxin. The strains contain CYN in the range of 2.3-6.6 mg g K1 of cellular dry weight. To our knowledge this is the first report of CYN in A. flos-aquae. q
In Bangladesh the exposure of millions of inhabitants to water from (shallow) tube wells contamin... more In Bangladesh the exposure of millions of inhabitants to water from (shallow) tube wells contaminated with high geogenic loads of arsenic is a major concern. As an alternative to the costly drilling of deep wells, the return to the use of surface water as a source of drinking water is considered. In addition to the well-known hazards of water borne infectious diseases associated with the use of surface water, recently the potential public health implications of toxic cyanobacteria have been recognized. As a first step towards a risk assessment for cyanotoxins in Bangladesh surface waters, seston samples of 79 ponds were analysed in late summer 2002 for the presence of cyanobacteria and microcystins (MCYST), the most frequently detected cyanobacterial toxins worldwide. Microcystins could be detected in 39 ponds, mostly together with varying abundance of potentially microcystin-producing genera such as Microcystis, Planktothrix and Anabaena. Total microcystin concentrations ranged bet...
For management of cyanobacterial hazards to human health, a basic understanding of the properties... more For management of cyanobacterial hazards to human health, a basic understanding of the properties, the behaviour in natural ecosystems, and the environmental conditions which support the growth of certain species is helpful. This chapter provides information on how cyanobacteria are structured and the abilities which they posses that support their proliferation in aquatic ecosystems.
International Journal of Hygiene and Environmental Health, 2014
To protect groundwater as a drinking water resource from microbiological contamination, protectio... more To protect groundwater as a drinking water resource from microbiological contamination, protection zones are installed. While travelling through these zones, concentrations of potential pathogens should decline to levels that pose no risks to human health. Removal of viruses during subsurface passage is influenced by physicochemical conditions, such as oxygen concentration, which also affects virus survival. The aim of our study was to evaluate the effect of redox conditions on the removal of viruses during sand filtration. Experiments in glass columns filled with medium-grained sand were conducted to investigate virus removal in the presence and absence of dissolved oxygen. Bacteriophages MS2 and PhiX174, as surrogates for human enteric viruses were spiked in pulsed or in continuous mode and pumped through the columns at a filter velocity of about 1 m/d. Virus breakthrough curves were analyzed by calculating total viral elimination and fitted using one-dimensional transport models (CXTFIT and HYDRUS-1D). While short-term experiments with pulsed virus application showed only small differences with regard to virus removal under oxic and anoxic conditions, a long-term experiment with continuous dosing revealed a clearly lower elimination of viruses under anoxic conditions. These findings suggest that less inactivation and less adsorption of viruses in anoxic environments affect their removal. Therefore, in risk assessment studies aimed to secure drinking water resources from viral contamination and optimization of protection zones, the oxic and anoxic conditions in the subsurface should also be considered.
After reduction of the external phosphorus load by phosphorus elimination plants, Lake Tegel and ... more After reduction of the external phosphorus load by phosphorus elimination plants, Lake Tegel and Schlachtensee in Berlin underwent a significant trophic improvement. The phosphorus elimination plants work by precipitation/coagulation/flocculation--sedimentation--post precipitation--filtration. The external load was reduced by one to two orders of magnitude down to 10-20 mgg PL(-1). The inlake phosphorus concentration followed. The development of algae and cyanobacteria was reduced substantially below a threshold value of about 50 microg PL(-1) clearly due to phosphorus limitation. In Lake Tegel, the external load reduction of the main inflow was counteracted partially by the external load of the second main inflow by the River Havel and the internal load. This has to be managed further in future.
Three single-filament isolates of Aphanizomenon flos-aquae from two German lakes were found to pr... more Three single-filament isolates of Aphanizomenon flos-aquae from two German lakes were found to produce remarkable amounts of the cyanobacterial hepatotoxin cylindrospermopsin (CYN). CYN-synthesis of the strains were evidenced both by LC-MS/MS analysis and detection of PCR products of gene fragments which are implicated in the biosynthesis of the toxin. The strains contain CYN in the range of 2.3-6.6 mg g K1 of cellular dry weight. To our knowledge this is the first report of CYN in A. flos-aquae. q
Cylindrospermopsin (CYN) is a potent hepatotoxin produced by different cyanobacteria of the order... more Cylindrospermopsin (CYN) is a potent hepatotoxin produced by different cyanobacteria of the order Nostocales. Questions of major concern are: which species produce CYN, which are the seasonal patterns of CYN dynamics and how are they regulated? Therefore, we studied for the first time the seasonal dynamics of particulate and dissolved CYN concentrations, cyanobacterial abundance and environmental factors in two German lakes over 2 years. Total CYN reached maximum concentrations of 0.34 and 1.80 mg L À1 in Melangsee and Langer See, respectively. In both lakes, maxima of the dissolved CYN fraction occurred later in the season than those of the particulate fraction, and it reached higher concentrations. This indicates that CYN is poorly decomposed and accumulates in the water. The cyanobacterial community in both lakes included several potentially CYNproducing species that did not correlate with CYN concentrations. Significant correlations between the particulate CYN concentrations and species biovolume were only found for Aphanizomenon gracile (r s ¼ 0.803) in Langer See indicating that this species is a CYN producer. Different correlations of CYN with abiotic factors in the two lakes indicate the presence of further undetected CYN producers as well as different regulation mechanisms of their dynamics and the variability of CYN.
Recent results show that cylindrospermopsin is more frequent and widespread in surface waters tha... more Recent results show that cylindrospermopsin is more frequent and widespread in surface waters than previously assumed. Studies on the fate of CYN in sediments are lacking, but this is important if these resources are used for drinking-water production via sediment passage. Therefore, the aim of our study was to determine a) CYN retention in two sandy sediments as a function of flow rate, CYN concentration, the presence of DOM and the content of fines (1% and 4%, respectively) and b) the influence of sediment preconditioning and DOM composition of the water (aquatic DOM versus DOM released from lysed cells) on CYN degradation. Retention of CYN proved negligible under the investigated conditions. Degradation in virgin sediments showed the highest lag phases (20 days). Preconditioned sediments showed no lag phase. The presence of aquatic DOM yielded highest degradation rates (k 1 ¼ 0.46 and 0.49 day À1 ) without a lag phase. Readily available organic carbon sources were preferentially metabolized and hence induced a lag phase. Thus, the presence and composition of DOM in the water proved important for both CYN degradation rates in preconditioned sediments and for the lag phase. Cylindrospermopsin degradation took place solely in the sediment and not in the water body.
Microcystis is a well-known cyanobacterial genus frequently producing hepatotoxins named microcys... more Microcystis is a well-known cyanobacterial genus frequently producing hepatotoxins named microcystins. Toxin production is encoded by microcystin genes (mcy). This study aims (i) to relate the mcy occurrence in individual colonies to the presence of microcystin, (ii) to assess whether morphological characteristics (morphospecies) are related to the occurrence of mcy genes, and (iii) to test whether there are geographical variations in morphospecies specificity and abundance of mcy genes. Individual colonies of nine different European countries were analysed by (1) morphological characteristics, (2) PCR to amplify a gene region within mcyA and mcyB indicative for microcystin biosynthesis, (3) matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) to detect microcystins. Almost one hundred percent of the colonies predicted to produce microcystins by PCR analysis were found to contain microcystins. A high similarity in microcystin variants in the different colonies selected from lakes across Europe was demonstrated. The different morphospecies varied in the frequency with which they contained mcy genes. Most colonies (>75%) of M. aeruginosa and M. botrys contained the mcy genes, whereas ≤20% of the colonies identified as M. ichthyoblabe and M. viridis gave a PCR product of the mcy genes. No colonies of M. wesenbergii gave a PCR product of either mcy gene. In addition, a positive relationship was found between the size of the colony and the frequency of those containing the mcy genes. It is concluded that the analysis of morphospecies is indicative for microcystin production, although the quantitative analysis of microcystin concentrations in water remains indispensable for hazard control.
Two previously highly eutrophic lakes, Lake Tegel and Schlachtensee in Berlin, Germany, were subj... more Two previously highly eutrophic lakes, Lake Tegel and Schlachtensee in Berlin, Germany, were subjected to similar external but different internal restoration measures during the last 20–25 years. External phosphorus (P) load was reduced in both lakes by P-stripping their main inflows using P-elimination plants; internal P load was treated by aeration in Lake Tegel and by hypolimnetic withdrawal in Schlachtensee. Loads before and after treatment are compared with the targets using the Vollenweider model and a modified One-Box model. The results indicate that external load reduction was the main cause of the pronounced lake water quality improvements. The hypolimnetic withdrawal in Schlachtensee was effective only in the initial years. No significant positive effect can be identified for the aeration of Lake Tegel.
The lake number was used to describe the mixing condition for three consecutive years (1992)(1993... more The lake number was used to describe the mixing condition for three consecutive years (1992)(1993)(1994) in Lake Tegel, Berlin, and compared to the successions of diatoms, dinoflagellates and cyanobacteria, the main phytoplankton groups in the lake, as well as to diversity and similarity indices. Using both diversity and similarity indices in juxtaposition provides an indication of the growth type of prevailing species (r-or K-strategists) and the degree of competition in the aqua-ecological system.
A novel C18 lipid, containing a 10-membered lactone, mueggelone (1), was isolated from a field-co... more A novel C18 lipid, containing a 10-membered lactone, mueggelone (1), was isolated from a field-collected sample of Aphanizomenon flos-aquae, together with the known compound lupenyl acetate (3). Both structures were secured using extensive spectroscopic analysis (1D and 2D NMR, MS, IR). Biological activity assessment of both compounds indicated them to have significant inhibitory effects on fish embryo larval development.
This paper summarises the outcomes of the 13 th Workshop of the International Association of Phyt... more This paper summarises the outcomes of the 13 th Workshop of the International Association of Phytoplankton Taxonomy and Ecology (IAP). The authors mostly addressed their contributions on the following topics: the effect of trophic state on the attainment of a steady-state; the establishment of equilibria in deep and shallow lakes; the role of spatial heterogeneity, disturbance, and stress in the establishment of equilibrium assemblages; the mechanisms leading to the steady state; the frequency and longevity of equilibrium phases, and the role of morphological and physiological plasticity of phytoplankton in maintaining the (apparently) same populations under different environmental conditions. The composition of steady-state assemblages is compared to that of phytoplankton functional groups (coda). Those functional associations recognised as steady-state assemblages appear to be strongly K-determined in many instances.
The influence of light and temperature on the cylindrospermopsin (CYN) production of two Aphanizo... more The influence of light and temperature on the cylindrospermopsin (CYN) production of two Aphanizomenon flos-aquae strains, isolated from North-eastern German lakes, was investigated with semi-continuously growing cultures. A light gradient from 10 to 60 mE m À2 s À1 in combination with temperatures of 16, 20, and 25 8C was tested.
The German Federal Environmental Agency (Umweltbundesamt – UBA) operates an experimental field on... more The German Federal Environmental Agency (Umweltbundesamt – UBA) operates an experimental field on the southern outskirts of Berlin for the investigation of special aspects of environmental hygiene. One part of the field consists of a storage pond with subsequent bank filtration, artificial recharge and slow sand filtration where experiments on the behavior of hazardous substances during bank filtration, artificial recharge or slow sand filtration can be carried out on a field scale without any adverse environmental impacts under nearly natural conditions. Experiments on the elimination of cyanobacteria and their toxins are currently being conducted in the plant as part of the research project of the KompetenzZentrum Wasser Berlin (KWB) named Natural and Artificial Systems for Recharge and Infiltration (NASRI).
ABSTRACT After installation of phosphorus elimination plants at the inflows of the eutrophic Lake... more ABSTRACT After installation of phosphorus elimination plants at the inflows of the eutrophic Lake Tegel and Schlachtensee, phosphorus (P) loading declined by a factor of 40 and 100, respectively. This resulted in a pronounced reduction of phosphorus concentrations in the lake water, followed by a decline of chlorophyll-a concentrations. However, for many years P release from sediments due to mineralization and desorption of sedimentary P continued. In Schlachtensee, the presence of nitrate above the sediment suppresses P release, because the Fe/P ratio is sufficient to provide enough aerobic sorption capacity. In Lake Tegel, some P release occurs even under aerobic conditions because of the low aerobic P sorption capacity of the sediments. There, nitrate could moderate the P release peaks which occur when the Fe-P cycle at the sediment water interface is disturbed by precipitation of iron sulfide after reduction of sulfate during times of high mineralization intensity. The potentially mobile P pool in the sediments of both lakes is rather small, indicating that the P release could subside after sufficient reduction of the external P load in Lake Tegel and the disruption of the internal P cycle in Schlachtensee.
Toxicon : official journal of the International Society on Toxinology, 2003
Cylindrospermopsis raciborskii, a freshwater cyanobacterium of tropical origin, is not only incre... more Cylindrospermopsis raciborskii, a freshwater cyanobacterium of tropical origin, is not only increasingly found in (sub) tropical water bodies, but also in temperate regions. Since this species may produce potent toxins such as cylindrospermopsin (CYN) and paralytic shellfish poisons, its massive occurrence in water bodies used as drinking water sources or for recreation is of major concern. The proliferation of C. raciborskii in German water bodies has been documented for the past decade. We investigated the occurrence of CYN in field populations and isolates of C. raciborskii from two lakes, and assessed the toxicity of culture isolates using the mouse bioassay, primary rat hepatocytes and human derived cell lines. We show for the first time the occurrence of CYN in German water bodies. None of seven isolates of C. raciborskii contained CYN, however, all isolates were toxic to primary rat hepatocytes, human hepatoblastoma (HEP-G2) and human colon adenocarcinoma (CACO-2) cells. Meth...
Three single-filament isolates of Aphanizomenon flos-aquae from two German lakes were found to pr... more Three single-filament isolates of Aphanizomenon flos-aquae from two German lakes were found to produce remarkable amounts of the cyanobacterial hepatotoxin cylindrospermopsin (CYN). CYN-synthesis of the strains were evidenced both by LC-MS/MS analysis and detection of PCR products of gene fragments which are implicated in the biosynthesis of the toxin. The strains contain CYN in the range of 2.3-6.6 mg g K1 of cellular dry weight. To our knowledge this is the first report of CYN in A. flos-aquae. q
In Bangladesh the exposure of millions of inhabitants to water from (shallow) tube wells contamin... more In Bangladesh the exposure of millions of inhabitants to water from (shallow) tube wells contaminated with high geogenic loads of arsenic is a major concern. As an alternative to the costly drilling of deep wells, the return to the use of surface water as a source of drinking water is considered. In addition to the well-known hazards of water borne infectious diseases associated with the use of surface water, recently the potential public health implications of toxic cyanobacteria have been recognized. As a first step towards a risk assessment for cyanotoxins in Bangladesh surface waters, seston samples of 79 ponds were analysed in late summer 2002 for the presence of cyanobacteria and microcystins (MCYST), the most frequently detected cyanobacterial toxins worldwide. Microcystins could be detected in 39 ponds, mostly together with varying abundance of potentially microcystin-producing genera such as Microcystis, Planktothrix and Anabaena. Total microcystin concentrations ranged bet...
For management of cyanobacterial hazards to human health, a basic understanding of the properties... more For management of cyanobacterial hazards to human health, a basic understanding of the properties, the behaviour in natural ecosystems, and the environmental conditions which support the growth of certain species is helpful. This chapter provides information on how cyanobacteria are structured and the abilities which they posses that support their proliferation in aquatic ecosystems.
International Journal of Hygiene and Environmental Health, 2014
To protect groundwater as a drinking water resource from microbiological contamination, protectio... more To protect groundwater as a drinking water resource from microbiological contamination, protection zones are installed. While travelling through these zones, concentrations of potential pathogens should decline to levels that pose no risks to human health. Removal of viruses during subsurface passage is influenced by physicochemical conditions, such as oxygen concentration, which also affects virus survival. The aim of our study was to evaluate the effect of redox conditions on the removal of viruses during sand filtration. Experiments in glass columns filled with medium-grained sand were conducted to investigate virus removal in the presence and absence of dissolved oxygen. Bacteriophages MS2 and PhiX174, as surrogates for human enteric viruses were spiked in pulsed or in continuous mode and pumped through the columns at a filter velocity of about 1 m/d. Virus breakthrough curves were analyzed by calculating total viral elimination and fitted using one-dimensional transport models (CXTFIT and HYDRUS-1D). While short-term experiments with pulsed virus application showed only small differences with regard to virus removal under oxic and anoxic conditions, a long-term experiment with continuous dosing revealed a clearly lower elimination of viruses under anoxic conditions. These findings suggest that less inactivation and less adsorption of viruses in anoxic environments affect their removal. Therefore, in risk assessment studies aimed to secure drinking water resources from viral contamination and optimization of protection zones, the oxic and anoxic conditions in the subsurface should also be considered.
After reduction of the external phosphorus load by phosphorus elimination plants, Lake Tegel and ... more After reduction of the external phosphorus load by phosphorus elimination plants, Lake Tegel and Schlachtensee in Berlin underwent a significant trophic improvement. The phosphorus elimination plants work by precipitation/coagulation/flocculation--sedimentation--post precipitation--filtration. The external load was reduced by one to two orders of magnitude down to 10-20 mgg PL(-1). The inlake phosphorus concentration followed. The development of algae and cyanobacteria was reduced substantially below a threshold value of about 50 microg PL(-1) clearly due to phosphorus limitation. In Lake Tegel, the external load reduction of the main inflow was counteracted partially by the external load of the second main inflow by the River Havel and the internal load. This has to be managed further in future.
Three single-filament isolates of Aphanizomenon flos-aquae from two German lakes were found to pr... more Three single-filament isolates of Aphanizomenon flos-aquae from two German lakes were found to produce remarkable amounts of the cyanobacterial hepatotoxin cylindrospermopsin (CYN). CYN-synthesis of the strains were evidenced both by LC-MS/MS analysis and detection of PCR products of gene fragments which are implicated in the biosynthesis of the toxin. The strains contain CYN in the range of 2.3-6.6 mg g K1 of cellular dry weight. To our knowledge this is the first report of CYN in A. flos-aquae. q
Cylindrospermopsin (CYN) is a potent hepatotoxin produced by different cyanobacteria of the order... more Cylindrospermopsin (CYN) is a potent hepatotoxin produced by different cyanobacteria of the order Nostocales. Questions of major concern are: which species produce CYN, which are the seasonal patterns of CYN dynamics and how are they regulated? Therefore, we studied for the first time the seasonal dynamics of particulate and dissolved CYN concentrations, cyanobacterial abundance and environmental factors in two German lakes over 2 years. Total CYN reached maximum concentrations of 0.34 and 1.80 mg L À1 in Melangsee and Langer See, respectively. In both lakes, maxima of the dissolved CYN fraction occurred later in the season than those of the particulate fraction, and it reached higher concentrations. This indicates that CYN is poorly decomposed and accumulates in the water. The cyanobacterial community in both lakes included several potentially CYNproducing species that did not correlate with CYN concentrations. Significant correlations between the particulate CYN concentrations and species biovolume were only found for Aphanizomenon gracile (r s ¼ 0.803) in Langer See indicating that this species is a CYN producer. Different correlations of CYN with abiotic factors in the two lakes indicate the presence of further undetected CYN producers as well as different regulation mechanisms of their dynamics and the variability of CYN.
Recent results show that cylindrospermopsin is more frequent and widespread in surface waters tha... more Recent results show that cylindrospermopsin is more frequent and widespread in surface waters than previously assumed. Studies on the fate of CYN in sediments are lacking, but this is important if these resources are used for drinking-water production via sediment passage. Therefore, the aim of our study was to determine a) CYN retention in two sandy sediments as a function of flow rate, CYN concentration, the presence of DOM and the content of fines (1% and 4%, respectively) and b) the influence of sediment preconditioning and DOM composition of the water (aquatic DOM versus DOM released from lysed cells) on CYN degradation. Retention of CYN proved negligible under the investigated conditions. Degradation in virgin sediments showed the highest lag phases (20 days). Preconditioned sediments showed no lag phase. The presence of aquatic DOM yielded highest degradation rates (k 1 ¼ 0.46 and 0.49 day À1 ) without a lag phase. Readily available organic carbon sources were preferentially metabolized and hence induced a lag phase. Thus, the presence and composition of DOM in the water proved important for both CYN degradation rates in preconditioned sediments and for the lag phase. Cylindrospermopsin degradation took place solely in the sediment and not in the water body.
Microcystis is a well-known cyanobacterial genus frequently producing hepatotoxins named microcys... more Microcystis is a well-known cyanobacterial genus frequently producing hepatotoxins named microcystins. Toxin production is encoded by microcystin genes (mcy). This study aims (i) to relate the mcy occurrence in individual colonies to the presence of microcystin, (ii) to assess whether morphological characteristics (morphospecies) are related to the occurrence of mcy genes, and (iii) to test whether there are geographical variations in morphospecies specificity and abundance of mcy genes. Individual colonies of nine different European countries were analysed by (1) morphological characteristics, (2) PCR to amplify a gene region within mcyA and mcyB indicative for microcystin biosynthesis, (3) matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) to detect microcystins. Almost one hundred percent of the colonies predicted to produce microcystins by PCR analysis were found to contain microcystins. A high similarity in microcystin variants in the different colonies selected from lakes across Europe was demonstrated. The different morphospecies varied in the frequency with which they contained mcy genes. Most colonies (>75%) of M. aeruginosa and M. botrys contained the mcy genes, whereas ≤20% of the colonies identified as M. ichthyoblabe and M. viridis gave a PCR product of the mcy genes. No colonies of M. wesenbergii gave a PCR product of either mcy gene. In addition, a positive relationship was found between the size of the colony and the frequency of those containing the mcy genes. It is concluded that the analysis of morphospecies is indicative for microcystin production, although the quantitative analysis of microcystin concentrations in water remains indispensable for hazard control.
Two previously highly eutrophic lakes, Lake Tegel and Schlachtensee in Berlin, Germany, were subj... more Two previously highly eutrophic lakes, Lake Tegel and Schlachtensee in Berlin, Germany, were subjected to similar external but different internal restoration measures during the last 20–25 years. External phosphorus (P) load was reduced in both lakes by P-stripping their main inflows using P-elimination plants; internal P load was treated by aeration in Lake Tegel and by hypolimnetic withdrawal in Schlachtensee. Loads before and after treatment are compared with the targets using the Vollenweider model and a modified One-Box model. The results indicate that external load reduction was the main cause of the pronounced lake water quality improvements. The hypolimnetic withdrawal in Schlachtensee was effective only in the initial years. No significant positive effect can be identified for the aeration of Lake Tegel.
The lake number was used to describe the mixing condition for three consecutive years (1992)(1993... more The lake number was used to describe the mixing condition for three consecutive years (1992)(1993)(1994) in Lake Tegel, Berlin, and compared to the successions of diatoms, dinoflagellates and cyanobacteria, the main phytoplankton groups in the lake, as well as to diversity and similarity indices. Using both diversity and similarity indices in juxtaposition provides an indication of the growth type of prevailing species (r-or K-strategists) and the degree of competition in the aqua-ecological system.
A novel C18 lipid, containing a 10-membered lactone, mueggelone (1), was isolated from a field-co... more A novel C18 lipid, containing a 10-membered lactone, mueggelone (1), was isolated from a field-collected sample of Aphanizomenon flos-aquae, together with the known compound lupenyl acetate (3). Both structures were secured using extensive spectroscopic analysis (1D and 2D NMR, MS, IR). Biological activity assessment of both compounds indicated them to have significant inhibitory effects on fish embryo larval development.
This paper summarises the outcomes of the 13 th Workshop of the International Association of Phyt... more This paper summarises the outcomes of the 13 th Workshop of the International Association of Phytoplankton Taxonomy and Ecology (IAP). The authors mostly addressed their contributions on the following topics: the effect of trophic state on the attainment of a steady-state; the establishment of equilibria in deep and shallow lakes; the role of spatial heterogeneity, disturbance, and stress in the establishment of equilibrium assemblages; the mechanisms leading to the steady state; the frequency and longevity of equilibrium phases, and the role of morphological and physiological plasticity of phytoplankton in maintaining the (apparently) same populations under different environmental conditions. The composition of steady-state assemblages is compared to that of phytoplankton functional groups (coda). Those functional associations recognised as steady-state assemblages appear to be strongly K-determined in many instances.
The influence of light and temperature on the cylindrospermopsin (CYN) production of two Aphanizo... more The influence of light and temperature on the cylindrospermopsin (CYN) production of two Aphanizomenon flos-aquae strains, isolated from North-eastern German lakes, was investigated with semi-continuously growing cultures. A light gradient from 10 to 60 mE m À2 s À1 in combination with temperatures of 16, 20, and 25 8C was tested.
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