Occurrence of the hepatotoxic cyanobacterium Nodularia spumigena in the Baltic Sea and structure of the toxin

Water blooms formed by potentially toxic species of cyanobacteria are a common phenomenon in the Baltic Sea in late summer. Twenty-five cyanobacterial bloom samples were collected from open and coastal waters of the Baltic Sea during 1985 to 1987, and their toxicity was determined by mouse bioassay. All of 5 bloom samples from the southern Baltic Sea, 6 of 6 from the open northern Baltic Sea (Gulf of Finland), and 7 of 14 Finnish coastal samples were found to contain hepatotoxic cyanobacteria. Nodularia spumigena and Aphanizomenon flos-aquae occurred together in high amounts in blooms from the open-sea areas. In addition, coastal samples contained the species Anabaena lemmermannii, Microcystis aeruginosa, and Oscillatoria agardhii. Eighteen hepatotoxic N. spumigena cultures were isolated from water bloom and open-sea water samples. High-pressure liquid chromatographic analysis of both hepatotoxic bloom samples and Nodularia strains showed a single toxic fraction. The toxin concentrations of the blooms were less than or equal to 2.4 mg/g of freeze-dried material, and those of laboratory-grown cultures were 2.5 to 8.0 mg/g of freeze-dried cells. A single toxin was isolated from three N. spumigena-containing bloom samples and three N. spumigena laboratory isolates. Amino acid analysis and low- and high-resolution fast-atom bombardment mass spectroscopy indicated that the toxin from all of the sources was a cyclic pentapeptide (molecular weight, 824) containing glutamic acid, beta-methylaspartic acid, arginine, N-methyldehydrobutyrine, and 3-amino-9-methoxy-2,6,8-trimethyl-10-phenyl-4,6-decadienoic acid.(ABSTRACT TRUNCATED AT 250 WORDS)     

Occurrence of the hepatotoxic cyanobacterium Nodularia spumigena in the Baltic Sea and structure of the toxin.

Water blooms formed by potentially toxic species of cyanobacteria are a common phenomenon in the Baltic Sea in late summer. Twenty-five cyanobacterial bloom samples were collected from open and coastal waters of the Baltic Sea during 1985 to 1987, and their toxicity was determined by mouse bioassay. All of 5 bloom samples from the southern Baltic Sea, 6 of 6 from the open northern Baltic Sea (Gulf of Finland), and 7 of 14 Finnish coastal samples were found to contain hepatotoxic cyanobacteria. Nodularia spumigena and Aphanizomenon flos-aquae occurred together in high amounts in blooms from the open-sea areas. In addition, coastal samples contained the species Anabaena lemmermannii, Microcystis aeruginosa, and Oscillatoria agardhii. Eighteen hepatotoxic N. spumigena cultures were isolated from water bloom and open-sea water samples. High-pressure liquid chromatographic analysis of both hepatotoxic bloom samples and Nodularia strains showed a single toxic fraction. The toxin concentrations of the blooms were less than or equal to 2.4 mg/g of freeze-dried material, and those of laboratory-grown cultures were 2.5 to 8.0 mg/g of freeze-dried cells. A single toxin was isolated from three N. spumigena-containing bloom samples and three N. spumigena laboratory isolates. Amino acid analysis and low- and high-resolution fast-atom bombardment mass spectroscopy indicated that the toxin from all of the sources was a cyclic pentapeptide (molecular weight, 824) containing glutamic acid, beta-methylaspartic acid, arginine, N-methyldehydrobutyrine, and 3-amino-9-methoxy-2,6,8-trimethyl-10-phenyl-4,6-decadienoic acid.(ABSTRACT TRUNCATED AT 250 WORDS)     

Competitive exclusion of Cyanobacterial species in the Great Salt Lake

The Great Salt Lake is separated into different salinity regimes by rail and vehicular causeways. Cyanobacterial distributions map salinity, with Aphanothece halophytica proliferating in the highly saline northern arm (27% saline), while Nodularia spumigena occurs in the less saline south (6–10%). We sought to test if cyanobacterial species abundant in the north are competitively excluded from the south, and if southern species are excluded by the high salinity of the north. Autoclaved samples from the north and south sides of each causeway were inoculated with water from each area. Aphanothece, Oscillatoria, Phormidium, and Nodularia were identified in the culture flasks using comparative differential interference contrast, fluorescence, and scanning electron microscopy. Aphanothece halophytica occurred in all inocula, but is suppressed in the presence of Nodularia spumigena. N. spumigena was found only in inocula from the less saline waters in the south, and apparently cannot survive the extremely hypersaline waters of the northern arm. These data suggest that both biotic and abiotic factors influence cyanobacterial distributions in the Great Salt Lake.     

A Fuzzy Logic Model to Describe the Cyanobacteria Nodularia spumigena Blooms in the Gulf of Finland, Baltic Sea

A fuzzy logic model to describe the seasonal evolution of Nodularia spumigena blooms in the Gulf of Finland was built and calibrated on the basis of monitoring data. The model includes three phosphate sources: excess phosphate after the annual spring bloom and parameterised phosphate transport to the upper mixed layer by turbulent mixing and upwelling events. Surface layer temperature and wind mixing form the physical conditions controlling the growth of N. spumigena. Model simulations revealed that phosphate input caused by turbulent mixing and upwelling have to be taken into account to achieve the best fit with observed data. Testing the fuzzy model for early prediction of maximum N. spumigena biomass about a month before the usual occurrence of blooms, gave good results. The potential use of the model for prediction of bloom risk at a certain location along the Estonian or Finnish coast was tested. The bloom transport velocities used in the fuzzy model were pre-calculated by a 3D numerical circulation model for different wind regimes.     

Phosphatase activities in relation to phosphorus nutrition in Nodularia spumigena (Cyanobacteriaceae)

Alkaline phosphatase activities were examined in blooms of Nodularia spumigena Mertens in the Peel-Harvey estuarine system, Western Australia. Variations in phosphatase activity occurred geographically and diurnally, as well as over the duration of a bloom. These variations were well correlated with differences in the phosphorus nutritional status of the Nodularia. In the laboratory, Nodularia phosphatase production was inversely proportional to cellular phosphorus, but not to external soluble reactive phosphorus.     

Reduction of cyanobacterial toxins through coprophagy in Mytilus edulis

An experiment was conducted to follow the fate of the cyanobacterial toxin, nodularin, produced by Nodularia spumigena through ingestion by Mytilus edulis and re-ingestion of faecal material (coprophagy). Mussels were fed with cultures of N. spumigena, and the faeces that were produced were fed to other mussels not previously exposed to N. spumigena. Concentrations of nodularin were measured in the food (N. spumigena), the mussels and in the faeces in order to make a toxin budget. High concentrations of nodularin were found in the mussels and their faeces after 48 h incubation with N. spumigena. When the toxic faeces were fed to new mussels, the toxin content of faeces was reduced from 95 μg nod g⁻¹ dry weight (DW) to 1 μg nod g⁻¹ DW through the process of coprophagy. Hence, when toxic faeces were fed to mussels, the nodularin concentration of the resulting faecal material was reduced by 99%. Pseudofaeces were produced when the mussels were grazing on N. spumigena, but not when grazing on faeces. The pseudofaeces contained high concentrations of nodularin and apparently intact N. spumigena cells. However, these cells were growth-inhibited and their potential contribution to seeding a bloom is probably limited. Our data indicate that a large fraction of ingested nodularin in M. edulis is egested with the faeces, and that the concentration of nodularin in the faeces is reduced when faeces are re-ingested.     

Intraspecific variation in the response of the cyanobacterium Nodularia spumigena to moderate UV-B radiation

Floating and nodularin-producing strains of Nodularia spumigena from the Baltic Sea are regarded as belonging to one species. However, intraspecific variation in the response of N. spumigena to environmental factors has been commonly overlooked. As blooms of N. spumigena occur in late summer, a period with strong light and stable water-column stratification, the cells can be expected to also be exposed to ultraviolet-B radiation (UV-B, 280–320 nm). The UV-B tolerance of four different strains of N. spumigena, isolated from the Baltic Sea, was investigated in the laboratory for 8 days, by measuring photosynthesis, growth and pigment composition. Variables included maximum quantum yield of photosynthesis (F_v/F_m, PAM fluorometry), growth rate (cell counts) and photosynthetic pigments, as well as mycosporine-like amino acids (HPLC). Intraspecific differences regardless of treatment were found for cell dimension, growth rate, F_v/F_m and pigment concentrations. UV-B related effects differed between strains. By Day 8 one of the four strains showed a lower F_v/F_m when treated with UV-B; in another strain the growth rate and cell numbers were lower. In three strains, UV-B exposure resulted in higher cell concentrations of carotenoids and chlorophyll a. In all strains, the concentrations of total mycosporine-like amino acids were 60–130% higher in the UV-B treated samples compared with samples shielded from UV-B. Although strain-specific differences in UV-B tolerance were observed, it is concluded that N. spumigena is a species that is not generally negatively affected by moderate levels of UV-B radiation.     

Abiotic factors influencing cyanobacterial bloom development in the Gulf of Finland (Baltic Sea)

Blooms of cyanobacteria are a recurrent phenomenon in the Baltic Sea, including the Gulf of Finland. The spatial extension, duration, intensity and species composition of these blooms varies widely between years. Alg@line data collected regularly from ferries as well as weather service and marine monitoring data from 1997 to 2005 are analysed to determine the main abiotic factors influencing the intensity and species composition of cyanobacterial blooms in the Gulf of Finland. It is demonstrated that the development of the Nodularia spumigena Mertens bloom is highly dependent on weather conditions such as photosynthetically active radiation and water temperature. Nutrient conditions, especially the surplus of phosphorus (according to Redfield ratio) related to the pre-bloom upwelling events in the Gulf, affect the intensity of Aphanizomenon sp. (L.) Ralfs blooms. Differences in bloom timing and duration indicate that, if the preconditions (like nutrient ratio/concentration and weather conditions) for bloom formation are favourable, then the Aphanizomenon bloom starts earlier, the overall bloom period is longer and the Nodularia peak might appear in a wider time window. Handling editor: K. Martens     

Occurrence of cyanobacterial blooms in the baltic sea in relation to environmental conditions

Cyanobacterial blooms occur regularly in summer in central parts of the Baltic Sea. They are mainly composed of Aphanizomenon sp. and Nodularia spumigena. Both species have almost similar ecological requirements and can roughly be considered a uniform functional group. In order to identify factors that might favour bloom development, water quality data from monitoring programmes were compared with bloom distribution. A salinity from 3.8 to 11.5 PSU proved important for the spatial distribution of the bloom development. The bloom's onset was triggered by temperatures approximating 16°C provided that global radiation was > 120 W/m² (daily mean) and wind speed was < 6 m/s. Nutrient concentrations decreased immediately before the bloom. The bloom's development ceased with poor weather conditions characterized by low irradiation or high wind speed.     

Occurrence and toxicity of an Anabaena bloom in a tropical reservoir (Southeast Brazil)

Potentially toxic cyanobacterial blooms are becoming common in the Brazilian reservoirs in all regions of the country. During October 2004, a dense bloom of cyanobacteria occurred in the Monjolinho Reservoir (São Carlos, São Paulo State, Brazil) and a significant amount of cyanobacterial material accumulated on the water surface. Phytoplankton analysis showed that the main species in this bloom were Anabaena circinalis and Anabaena spiroides. Cladoceran (Ceriodaphnia dubia and Ceriodaphnia silvestrii) and mouse bioassays were performed to detect toxic products in extracts of the natural samples collected at the three different dates during in short period. To prepare the extracts, freeze-dried cells were dispersed in distilled water and subjected to repeated freeze/thaw cycles and sonication and centrifuging processes. Crude extracts were toxic both to cladocerans (LC₅₀ 94–406 mg freeze-dried cells L⁻¹) and mice (indicative LD₅₀ 297–445 mg freeze-dried cells kg⁻¹) and the toxicity of the bloom increased for cladocerans during the occurrence of the bloom. Toxin analysis by ELISA revealed that microcystin (MC) was found in the water of the reservoir (concentrations ranging from 28 to 45 μg L⁻¹). In addition, microcystin was also found in freeze-dried cyanobacteria cells with concentrations ranging from 138 to 223 μg g⁻¹. On the other hand, neurotoxins (saxitoxin and gonyautoxin) were not detected in any of the natural samples by HPLC. Signs of toxicity in mice did not indicate whether the bloom samples were predominantly hepatotoxic or neurotoxic. It is known that natural Anabaena blooms can contain other toxic compounds besides microcystins and neurotoxins such as lipopolysaccharides or other toxins not identified or known. Methods of detecting cyanotoxins used in this study were insufficient to clarify the toxicological features of Anabaena bloom and indicated that other methods should be investigated.     

Estimating nodularin content of cyanobacterial blooms from abundance of Nodularia spumigena and its characteristic pigments—a case study from the Baltic entrance area

The presence of toxin-producing cyanobacteria is of concern for the management of recreational waters. The abundance of toxic cyanobacteria and environmental concentrations of their toxins may fluctuate substantially within a short time emphasising the need for rapid methods to estimate toxin concentrations in the water. During late June-early September 2002 the abundance, biomass and characteristic pigments of Nodularia spumigena Mertens and the hepatotoxin nodularin produced by N. spumigena were analysed in water samples collected from the Baltic entrance area. Significant relationships were found between cell-bound concentrations of nodularin and the abundance and biomass of N. spumigena with a relationship of approximately 1 pg nodularin per Nodularia-cell. It is suggested that simple counts of Nodularia under the microscope may be used as a rapid on-site technique to estimate potential nodularin concentrations in recreational waters. Comparison with data from Australia shows that cell-bound concentration of nodularin per Nodularia-cell differs between geographically distant areas and therefore such relationships should be established for individual areas. The carotenoids echinenone, canthaxanthin and a cis-canthaxanthin-like caroteniod, identified from a laboratory culture of N. spumigena isolated from the Baltic Sea, were also significantly correlated with concentrations of cell-bound nodularin. However, Aphanizomenon and Anabaena, two genera commonly co-occurring with Nodularia, also contain these pigments and thus the significant correlations obtained presumably originate from Nodularia being the dominant cyanobacterium in all samples collected in 2002.     

Mortality of dogs associated with a mass development of Nodularia spumigena (Cyanophyceae) in a brackish lake at the German North Sea coast

Mortality of two dogs, after exposure to water of a brackishlake on the German North Sea coast in 1990, is considered tobe caused by a toxic Nodularia spumigena Mertens bloom.     

Occurrence of saxitoxins and an anatoxin-a(s)-like anticholinesterase in a Brazilian drinking water supply

Blooms of toxic cyanobacteria are very common in Brazilian waterbodies, as a consequence of eutrophication processes. Our investigations were focused on the detection of neurotoxins during a cyanobacterial bloom in Tapacurá reservoir, which serves as a water supply for Recife city in northeastern Brazil. We also investigated the possible presence of neurotoxins in strains of Anabaena spiroides isolated from this environment. Samples were collected from March to May 2002 at the water surface and close to the dam. Limnological parameters (conductivity, pH, inorganic nutrients) and cyanobacterial abundance were measured. The samples were assayed for toxicity by mouse bioassay and acetylcholinesterase-inhibiting activity by a colorimetric method; saxitoxins (paralytic shellfish poisons) were quantified by a HPLC-FLD postcolumn derivatization method. The dominant cyanobacteria during the bloom were found to be A. spiroides, Pseudanabaena sp., Cylindrospermopsis raciborskii and Microcystis aeruginosa. The mouse bioassays showed the presence of neurotoxins during both A. spiroides and C. raciborskii dominance, whereas anticholinesterase activity was only observed during periods of A. spiroides dominance. The A. spiroides strains isolated during the study also exhibited an acetylcholinesterase inhibitor. HPLC-FLD chromatograms of bloom material extracts revealed the presence of saxitoxin, neosaxitoxin and dc-saxitoxin, probably produced by C. raciborskii.     

Morphology,phylogeny, growth rate and nodularin production of Nodularia spumigena from Brazil

Blooms of the toxic cyanobacterium Nodularia spumigena occur in various locations worldwide, but have not been observed in Brazil until recently. Three Nodularia strains were isolated from summer blooms in experimental shrimp production ponds of Penaeus vannamei in Rio Grande, in southern Brazil; these strains were characterized by morphology, phylogeny, growth rate and toxicity. The strains were identified as N. spumigena based on the size of vegetative cells, heterocytes and akinetes under a light microscope and based on the number of gas vesicles per μm² under a transmission electron microscope. The 16S rRNA gene sequences of the three strains showed high identity (> 99%) with N. spumigena sequences available on the NCBI database but were grouped closer in the phylogenetic tree with N. spumigena strains from Australia and USA than those from the Baltic Sea. The growth rate in batch culture varied between 0.2 and 0.6 μ?d^?1 based on cell density, optical density and chlorophyll-a content. The three strains produced the hepatotoxin nodularin (ELISA plate kit) with similar toxicity values (4.8–4.9?µg?l^?1). We conclude that the three isolated strains are N. spumigena with similar rates of growth and nodularin production. The presence of N. spumigena now represents a potential problem in aquaculture and estuarine environments in Brazil.     

Nitrogen fixation patterns displayed by cyanobacterial consortia in Alchichica crater-lake, Mexico

Alchichica is a saline crater-lake located in Mexico. Tufa grows on its periphery and a wind-driven Nodularia cf. spumigena bloom occurs annually. Fixation rates were assayed by the acetylene reduction method. Here, we describe the patterns of nitrogen fixation on two tufa forms before, during and after the bloom, as well as those from the planktonic cyanobacteria. We also analyzed the effect of ultraviolet radiation (under 390 nm) on the nitrogen fixation rates. Tufa showed light-stimulated nitrogen fixation, while N. cf. spumigena peaks in early morning and midnight. Both tufa forms diminished their nitrogen fixation rates after the planktonic bloom. UV radiation affected negatively nitrogen fixation rates in all forms.     

Sedimentation of Nodularia spumigena and distribution of nodularin in the food web during transport of a cyanobacterial bloom from the Baltic Sea to the Kattegat

Nodularia spumigena is a toxic cyanobacteria that blooms in the Baltic Sea every year. In the brackish water of the Baltic Sea, its toxin, nodularin, mainly affects the biota in the surface water due to the natural buoyancy of this species. However, the fate of the toxin is unknown, once the cyanobacteria bloom enters the more saline waters of the Kattegat. In order to investigate this knowledge gap, a bloom of N. spumigena was followed during its passage, carried by surface currents, from the Baltic Sea into the Kattegat area, through the Öresund strait. N. spumigena cells showed an increased cell concentration through the water column during the passage of the bloom (up to 130 10³ cells ml⁻¹), and cells (4.2 10³ cells ml⁻¹) could be found down to 20 m depth, below a pycnocline. Sedimentation trap samples from below the pycnocline (10–12 m depth) also showed an increased sedimentation of N. spumigena filaments during the passage of the bloom. The toxin nodularin was detected both in water samples (0.3–6.0 μg l⁻¹), samples of sedimenting material (a toxin accumulation rate of 20 μg m^-2 day⁻¹), zooplankton (up to 0.1 ng ind.⁻¹ in copepods), blue mussels (70–230 μg kg⁻¹ DW), pelagic and benthic fish (herring (1.0–3.4 μg kg⁻¹ DW in herring muscle or liver) and flounder (1.3-6.2 μg kg⁻¹ DW in muscle, and 11.7-26.3 μg kg⁻¹ DW in liver). A laboratory experiment showed that N. spumigena filaments developed a decreased buoyancy at increased salinities and that they were even sinking with a rate of up to 1,7 m day⁻¹ at the highest salinity (32 PSU). This has implications for the fate of brackish water cyanobacterial blooms, when these reach more saline waters. It can be speculated that a significant part of the blooms content of nodularin will reach benthic organisms in this situation, compared to blooms decaying in brackish water, where most of the bloom is considered to be decomposed in the surface waters.     

Benthic fauna affects recruitment from sediments of the harmful cyanobacterium Nodularia spumigena

Physical disturbance and feeding by macrofauna in the sediment can potentially affect bloom initiation of phytoplankton species that have benthic stages in their life cycle. In this experimental study, we investigated how different species of macrozoobenthos can affect the recruitment of Nodularia spumigena from the sediment to the water column. N. spumigena is a toxic, nitrogen-fixing filamentous cyanobacterium, which forms large summer blooms in the Baltic Sea. Benthic recruitment from resting stages (akinetes) and vegetative cells deposited on the seafloor have long been suspected to initiate the blooms. We found that, depending on species-specific traits, deposit-feeding macrofauna (an amphipod, Monoporeia affinis, a bivalve, Macoma balthica and an invasive polychaete, Marenzelleria cf. arctia) has the potential to either reduce or facilitate recruitment of this cyanobacterium. Shorter filament length in treatments with fauna than in the treatment without indicates feeding on or mechanical destruction of N. spumigena by the animals. Our results show the importance of an often overlooked aspect of phytoplankton bloom initiation, the role of macrozoobenthos.     

Relationship of cellular phosphorus in the cyanobacterium Nodularia to phosphorus availability in the Peel-Harvey Estuarine System

A laboratory-determined critical concentration of phosphorus in the cyanobacterium Nodularia spumigena was used to assess the phosphorus sufficiency of field populations in the Peel-Harvey Estuarine System, Western Australia. Nutrient addition bioassays indicated that phosphorus was the limiting nutrient. Since river flow, and thus phosphorus input, to the estuary ceases 1–2 months before the onset of Nodularia blooms, the phosphorus contained in these blooms was derived from sediment release and nutrient recycling. A progressive increase in the mean cellular phosphorus concentration of Nodularia from 1981 to 1983 indicated that sediments were releasing a greater amount of phophorus each year. Although evidence suggests that the biomass of recent Nodularia blooms is now limited by physical factors, the additional phosphorus contained in each bloom will increase the supply of phosphorus to other organisms. Cellular phosphorus concentrations in Nodularia appeared to be correlated with river phosphorus loadings in the Peel Inlet but not in the Harvey Estuary.     

Toxic and noxious phytoplankton in Big Glory Bay,Stewart Island,New Zealand

Diurnal vertical profile sampling of the water column, during a fish killing bloom of the raphidophycean alga Heterosigma akashiwo, revealed a phytoplankton population otherwise composed almost entirely of a variety of dinoflagellates. Of these Glenodinium danicum, Dinophysis acuta, Polykrikos schwartzii, Ceratium furca and Gyrodinium spirale were predominant. The distribution of the major species within the phytoplankton were documented and evidence of synchronous vertical migration of H. akashiwo, G. danicum and P. schwartzii was observed. Extracts of shellfish obtained during the bloom and tested by mouse bioassay showed no PSP toxicity but a marginal degree of DSP toxicity. During a subsequent one year phytoplankton monitoring programme another potentially noxious species (Chaetoceros convolutus) appeared and the seasonal reoccurrence of species present during the bloom (e.g. H. akashiwo) was observed. Important year to year differences in the summer phytoplankton (diatom versus flagellate dominated populations) were apparent and analysis of climate data showed that these differences related to different weather conditions prevailing during the two summer periods sampled. The data suggest the fish killing bloom was giving a chance to develop by a prolonged period of warm, calm weather (during which several heavy rainfall events occurred) leading to stable hydrographic conditions (i.e. stratification) and an increase in the retention time of water within the bay.     

Effects of Cyanobacteria on Survival and Reproduction of the Littoral Crustacean Gammarus zaddachi (Amphipoda)

Toxic cyanobacteria can have harmful or fatal impacts on aquatic organisms. In the archipelagos of the northern Baltic Sea, the open sea blooms often drift into littoral areas, where they decompose and release toxins and other chemical compounds in the water. However, the effects of cyanobacteria on the littoral organisms have not previously been investigated. We studied the effects of three cyanobacteria species (toxic Nodularia spumigena, non-toxic N. sphaerocarpa and non-toxic Aphanizomenon flos-aquae) and purified dissolved nodularin (produced by N. spumigena) on a common littoral amphipod Gammarus zaddachi. Nodularin was transferred to eggs, juveniles and adults of G. zaddachi, but no significant negative effects of dissolved nodularin were detected on adults, eggs or juveniles. However, survival of adults decreased by the exposure to toxic N. spumigena cells. The egg hatching rate and juvenile survival were not affected when exposed to the three cyanobacteria species. In contrast, a weak decrease in the egg production and an increased abortion of embryos from the brood pouch of females was observed, the later indicating a failure in parental care. Further, a decrease in grazing rate on the filamentous green alga Enteromorpha intestinalis was observed. The results suggest that toxic cyanobacteria blooms are not extremely fatal, but may have, in high concentrations, negative effects on the adult survival, fecundity, and feeding behaviour of gammarids inhabiting the littoral zone.