Effects of salinity and source of inocula on germination of Anabaena akinetes from a tidally influenced lake

1. Sedimentary akinetes (resting stages) may represent significant potential inocula for nuisance blooms of cyanobacteria. We studied the effects of salinity and sediment source on the germination and subsequent growth of Anabaena flos‐aquae akinetes from a shallow, tidally influenced lake. 2. Surface sediments collected from littoral and open‐water sites were used as inocula to culture A. flos‐aquae akinetes in four salinities (0.1, 2.2, 4.4 and 6.5) over 22 days. Akinete germination and development was followed by counting developmental stages every second day. 3. Filament growth, but not akinete germination, was inhibited by salinity and there were significantly fewer filaments at 6.5 than at 0.1 and 2.2. Cultures inoculated with littoral sediment had more akinetes, germlings and filaments than those inoculated with open‐water sediment. 4. Sediment is a potential source of inocula for Anabaena blooms in the lake, which potentially could develop solely from this source because germination and subsequent filament growth do not depend on the existence of an initial pelagic Anabaena population.     

Daphnia vertical distribution and the presence of toxic cyanobacteria

Daphnia can alter its vertical position in the water column in response to chemical cues from predators. In this study we tested the hypothesis that a Daphnia pulex clone with little evolutionary exposure to cyanobacteria would move away from patches of cyanobacteria (Anabaena affinis and A. flos-aquae) which contain potent endotoxins. Daphnia was censused at 2 h intervals for 6 h in laboratory columns in which there was a steep vertical gradient of cyanobacteria. Data were analyzed by repeated-measures ANOVA. Control (no Anabaena) and experimental columns showed no significant differences in Daphnia distributions. Daphnia in experimental columns frequently moved into areas with dense concentrations of Anabaena and stayed there for long periods of time. Our results show that this D. pulex clone does not exhibit a rapid (within 6 h) avoidance response to toxic Anabaena.     

Toxic cyanobacteria (blue-green algae) in Finnish fresh and coastal waters

A survey of the occurrence of toxic blooms of cyanobacteria in Finnish fresh and coastal waters was made during 1985 and 1986. Toxicity of the freeze-dried water bloom samples was tested by mouse-bioassay (i.p.). Forty-four per cent (83/188) of the bloom samples were found to be lethally toxic. Hepatotoxic blooms (54) were almost twice as common as neurotoxic ones (29). Anabaena was the most frequently found genus in toxic and non-toxic blooms and it was present in all neurotoxic samples. Statistical associations were found between hepatotoxicity and incidence of Microcystis aeruginosa, M. viridis, M. wesenbergii, Anabaena flos-aquae and Anabaena spiroides. Neurotoxicity was statistically associated with Anabaena lemmermannii, Anabaena flos-aquae and Gomphosphaeria naegeliana. Isolation of strains of cyanobacteria confirmed the occurrence of hepatotoxic and neurotoxic strains of Anabaena, as well as hepatotoxic strains of Microcystis and Oscillatoria species.Toxic blooms caused cattle poisonings at three different lakes during the study period. Toxic blooms also occurred in drinking water sources. Our study shows that toxic cyanobacteria are more common in Finnish lakes than would be expected on the basis of animal poisonings. The results of this study show the existence of toxic cyanobacteria in Finnish water supplies and the need for their continued study as agents of water based disease.     

EMASCULATION EFFECTS ON THE STAMEN FILAMENT OF NIGELLA HTSPANICA AND THEIR PARTIAL REVERSAL BY GIBBERELLIC ACID

Anther removal from stamens whose filaments are 1–3 mm long restricts filament elongation to approximately 60% of the normal length. Removal of one-third to one-half of the anthers affects only the antherless filaments and does not appear to inhibit the growth of the other organs of the flower. Filament growth inhibition induced by anther removal involves both an inhibition of epidermal cell elongation along the length of the filament and also an inhibition of cell division. There is no evidence that the inhibition of filament growth is a response to damage caused by anther removal. Rather, it is suggested that anther removal severs a normal hormonal relationship existing between the anther and the developing filament. The application of gibberellic acid (GA₃) in lanolin paste stimulated the elongation of the antherless filaments to achieve an average of 87% of the filament length of adjacent intact stamens. The closer a filament is to having attained its final number of cells before anther removal, the closer does its length come to reaching the final length of filaments in intact stamens. The elongation of these antherless filaments with the application of GA₃ was accompanied by elongation of the epidermal cells of the filament to normal, or in some cases greater than normal, lengths. There is no evidence that GA₃ application affected the inhibition of epidermal cell devision induced by anther removal. The results of this study support the suggestion of Plack that emasculation-induced inhibition in the growth of floral organs and its reversal by GA₃ is a general phenomenon.     

Diurnal changes in the vertical distribution of phytoplankton in hypertrophic Lake Kasumigaura,Japan

The daily vertical migration of five species;Microcystis aeruginosa (Kütz.) Trevis,Anabaena spiroides Klebahn f.crassa (L.) Elenkin,Aphanizomenon flos-aquae (L.) Ralfs,Melosira granulata (E). Ralfs, andCoscinodiscus lacustris Grun. was studied using a close-interval water sampler on a calm summer day in Lake Kasumigaura. Many colonies ofMicrocystis were observed at the middle of the water column (approx. 1.5 m depth) in the afternoon, and at the surface in the early morning.Anabaena occurred mostly in the upper layer whileAphanizomenon tended to be uniformly distributed. The difference in migration patterns suggests thatMicrocystis is superior toAnabaena andAphanizomenon in obtaining both light and nutrients from this lake. Among diatoms,Melosira remained at the bottom of the water column throughout day and night, but Coscinodiscus was uniformly distributed.     

Temperature dependence of filament length of Anabaena spiroides Klebahn var. crassa Lemm.

Temperature dependence of filament length ofAnabaena spiroides Klebahn var.crassa Lemm. was examined for a strain isolated from Lake Kasumigaura, Japan. The length of the algal filaments is shown to have good correspondence with the thermal master reaction of cell multiplication.     

ROLE OF GROWTH SUBSTANCES IN THE FILAMENT GROWTH OF FUCHSIA HYBRIDA CV “BRILLIANT”

Filaments of Fuchsia hybrida cv “Brilliant” double in length within 24 hr after bud opening. Filament growth characterized by fresh wt increase and cell elongation was significantly inhibited in vitro by l-aminocyclopropane-l-carboxylic acid (ACC) but was not promoted by any growth regulator tested. Ions of Co²⁺ blocked the inhibitive effects of ACC in vitro suggesting that ethylene produced from ACC is the growth inhibiting substance. Ethylene levels surrounding the filaments within the closed bud decreased during development, and premature opening of the sepals which released the ethylene into the atmosphere resulted in rapid filament growth. The ACC levels were found to be much higher in the anthers than the filaments. This suggests that ethylene produced from floral organs other than filaments regulates filament elongation in Fuchsia. This is the first report of filament growth which cannot be promoted by application of growth regulators but which is inhibited by ethylene.     

Fungal infection for cyanobacterium <Emphasis Type="Italic">Anabaena smithii</Emphasis> by two chytrids in eutrophic region of large reservoir Lake Shumarinai,Hokkaido, Japan

Fungal infection of the filamentous cyanobacterium Anabaena smithii was observed in Lake Shumarinai in 2004–2006. Two fungal species were found to parasitize the specialized cells of A. smithii. These fungi might not correspond to the chytrid species that the previous studies reported as the parasites for Anabaena species. One fungus showed selective attachment to the akinete (akinete type). The filaments parasitized by this fungus increased in August 2004 and October 2006, when akinete and filament densities also increased. The maximum percentage of parasitized filaments was 3.2% of all filaments in October 2006. The other fungus was usually attached to the heterocyst (heterocyst type). The filaments parasitized by this fungus increased in October from 2004 to 2006. The maximum percentage of parasitized filaments was 20.6% in October 2004. The biomass of A. smithii was not suppressed by akinete-type fungus because of the low percentage of parasitized filaments. The heterocyst-type fungus might disturb the nitrogen fixation, but its effect was negligible due to a high concentration of available nitrogen for planktonic algae in Lake Shumarinai.     

THE ROLES OF AUXIN,ETHYLENE, AND ACID GROWTH IN FILAMENT ELONGATION IN GAILLARDIA GRANDIFLORA (ASTERACEAE)

Filament elongation and the role of auxin in this process in Gaillardia grandiflora was investigated. Filament elongation in vivo occurred just prior to anthesis and was accompanied by cell elongation and fresh weight increase. Filaments isolated and exposed to auxin in vitro grew more rapidly than controls and their growth was comparable to that of filaments in vivo. Furthermore, the natural auxin content of disc flowers (determined by double-standard isotope dilution analyses) increased just prior to anthesis and filament elongation. These results imply that auxin controls filament elongation. Applied ethylene slightly promoted filament elongation in vitro, and ethylene production of the flowers (determined by gas chromatography) slightly increased prior to filament growth. Fusicoccin and acidic buffers also stimulated elongation of isolated filaments. Thus, the role of auxin in controlling filament elongation in Gaillardia may involve stimulation of ethylene biosynthesis and acid growth.     

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.     

Electron microscopy as a quantitative method for investigating tau fibrillization

Fibrillization of tau protein is a hallmark lesion in Alzheimer's disease. To clarify the utility of electron microscopy as a quantitative assay for tau fibrillization in vitro, the interaction between synthetic tau filaments and carbon/formvar-coated grids was characterized in detail. Filament adsorption onto grids was hyperbolic when analyzed as a function of time or bulk protein concentration, with no evidence for competitive displacement or elution from other components in the reaction mixture. Filament length measurements were linear with filament concentration so long as the concentration of total tau protein in the sample was held constant, suggesting that measurement of filament lengths was accurate under these conditions. Furthermore, exponential filament length distributions were not significantly affected by adsorption time or filament concentration, suggesting that preferential binding among filaments of differing lengths was minimal. However, monomeric tau protein was found to be a strong competitor of filament adsorption, indicating that comparison of filament length measurements at different bulk tau concentrations should be interpreted with caution.     

A survey of toxicity of cyanobacterial blooms in Lake Ladoga and adjacent water bodies

Twentyfive cyanobacterial blooms in Lake Ladoga and adjacent water bodies were studied in the summer of 1990–1992. Toxicity of the water bloom material for mice was detected in 9 cases. The maximal tolerable doses (MTD) of the material extracted from biomass varied within 3–30 mg kg^–1 mouse body weight; 50% lethal doses (LD₅₀) were within 45–125 mg kg^–1. Toxic water blooms were registered in Karelian lakes and in the Neva Bay, Gulf of Finland. Cyanobacterial samples collected on the eastern coast of Lake Ladoga proved to be non-toxic. The species identified in toxic bloom material included Anabaena circinalis, A. flos-aquae, A. lemmermannii, Anabaena sp., Aphanizomenonflos-aquae, Gloeotrichia echinulata, G. pisum, Microcystis aeruginosa and Oscillatoria sp. These data suggest that toxic forms of cyanobacteria are widespread in Karelian lakes belonging to the drainage basin of Lake Ladoga.     

Sodium transport in filamentous nitrogen fixing cyanobacteria

Two filamentous, nitrogen fixing cyanobacteria were examined for their salt tolerance and sodium (Na⁺) transport.Anabaena torulosa, a saline form, grew efficiently and fixed nitrogen even at 150 mM salt (NaCl) concentration while,Anabaena L-31, a fresh water cyanobacterium, failed to grow beyond 35 mM NaCl.Anabaena torulosa showed a rapidly saturating kinetics of Na⁺ transport with a high affinity for Na⁺ (K _m, 0.3 mM).Anabaena L-31 had a much lower affinity for Na⁺ (K_m, 2.8 mM) thanAnabaena torulosa and the pattern of uptake was somewhat different. BothAnabaena spp. exhibited an active Na⁺ extrusion which seems to be mediated by a Na⁺-K⁺ ATPase and aided by oxidative phosphorylation.Anabaena L-31 was found to retain much more intracellular Na⁺ thanAnabaena torulosa. The results suggest that the saline form tolerates high Na⁺ concentrations by curtailing its influx and also by an efficient Na⁺ extrusion, although these alone may not entirely account for its success in saline environment.     

Effect of Anabaena flos-aquae on the abilities of Daphnia and Keratella to feed and reproduce on unicellular algae

SUMMARY.

• 1 This study tests the hypothesis that the filamentous cyanobacterium, Anabaena flos-aquae, inhibits Daphnia's ability to feed and reproduce on unicellular algae more than it does Keratella's. Double-label radiotracer experiments using whole and sonieally disrupted Anabaena filaments showed that even low concentrations of Anabaena (5 × 10³ cells ml^?1) inhibited the abilities of Daphnia pulex and D. galeata mendotae to feed on Chlamydomonas and that this inhibition was due to both mechanical interference with feeding and increased food availability. A single-label radiotracer experiment showed that Anabaena (5 × 10³ and 2 × 10⁴ cells ml^?l) reduced the abilities of neonate, juvenile, and adult D. pulex to feed on Chlamydomonas but had a much more pronounced effect on adults.
• 2 Single-label radiotracer experiments using screened (25 μm mesh) and unscreened suspensions of whole Anabaena filaments showed that only very high concentrations of Anabaena (10⁵ cells ml^?1) reduced the ability of Keratella cochlearis to feed on Cryptomonas and that this inhibition probably was due to mechanical interference with feeding, since Keratella ate Anabaena extremely inefficiently - especially when single cells and short filaments were removed by screening.
• 3 Experiments comparing the survivorship and fecundity of individuals fed Anabaena, Chlamydomonas, or no food showed that the Anabaena was not toxic to either Keratella or D. galeata mendotae, was not utilized by Keratella, and was utilized by Daphnia, although not as well as Chlamydomonas was.
• 4 Anabaena (5 × 10³ or 10⁴ cells ml^?1) did not affect, or slightly increased, the population growth rate (r_m) of K. cochlearis on Cryptomonas, while it substantially increased that of D. pulex, Duphnia's ability to utilize Anabaena probably more than offset its reduced ability to feed on Cryptomonas. The presence of cyanobacterial filaments in natural plankton communities could adversely affect Daphnia and decrease its ability to competitively suppress Keratella and other rotifers if the filaments were of little nutritional value to the Daphnia, greatly interfered

     

Effect of temperature on growth of the cyanobacterium Aphanizomenon flos-aquae in Lake Biwa and Lake Yogo

The water bloom‐forming cyanobacterium Aphanizomenon flos‐aquae Ralfs ex Bornet et Flahault (Nos‐tocales, Cyanophyceae) appeared in Lake Biwa and Lake Yogo in 1999 for the first time. The morphological characteristics were described using natural samples. In contrast to the other water bloom‐forming cyanobacteria such as Microcystis and Anabaena in Lake Biwa and Lake Yogo, the small summer population of A. flos‐aquae is apt to grow in winter, suggesting the low temperature preference or tolerance of this species. In order to clarify the effect of temperature on the growth, culture experiments were conducted using an axenic strain isolated from Lake Biwa. The strain could grow at above 8°C with an optimum temperature ranging from 23 to 29°C, and survived even at 5°C for at least 25days under low light conditions. Although these results confirmed the ability of the bloom formation during late autumn and winter, it is still unclear why the Aphanizomenon bloom occurred at temperatures of ca 10°C in December and not immediately after the disappearance of Microcystis and/or Anabaena bloom during autumn.     

A comparative study of nitrogen fixation by the Anabaena-Azolla symbiosis and free-living populations of Anabaena spp. in Lake Ngahawa,New Zealand

Summary The symbiotic fern Azolla filiculoides var. rubra, which contains a blue-green nitrogen fixing alga Anabaena azollae, fixed 164 Kg N·ha^-1·ann^-1 in the littoral zone of a small eutrophic lake. Associated planktonic Anabaena spp. blooms, dominated by Anabaena spiroides, fixed 29.5Kg N·ha^-1·ann^-1. Nitrogen fixation in both organisms was not obviously related to ambient dissolved inorganic nitrogen levels. By comparing ¹⁵N–N₂ and acetylene reduction techniques, we determined a ratio of 3 moles C₂H₂ reduced to 1 mole of N₂ fixed. Combining this with results from one diurnal investigation, it was estimated that 24% of the total daily fixation by Azolla occurred at night. Highest nitrogen fixation rates in Azolla occurred when plant density was lowest. Nitrogen fixation by planktonic Anabaena spp. generally paralleled changes in biomass. Frond breakage due to wind caused a decrease in Azolla nitrogen fixation and growth which was followed by a bloom of planktonic Anabaena spp. A second Anabaena spp. bloom was instrumental in the summer decline of Azolla. Maximum growth and nitrogen fixation of both organisms did not occur simultaneously. If physical disruption to the Azolla mat does not occur, it is likely that growth of the population would continue throughout the year.This work was completed at the Department of Scientific and Industrial Research, Freshwater Section, PO Box 415, Taupo, New Zealand, with partial assistance of N.S.F. Grant BMS-74-20745 to C.R. Goldman     

Succession of cable bacteria and electric currents in marine sediment

Filamentous Desulfobulbaceae have been reported to conduct electrons over centimetre-long distances, thereby coupling oxygen reduction at the surface of marine sediment to sulphide oxidation in sub-surface layers. To understand how these ‘cable bacteria'' establish and sustain electric conductivity, we followed a population for 53 days after exposing sulphidic sediment with initially no detectable filaments to oxygen. After 10 days, cable bacteria and electric currents were established throughout the top 15 mm of the sediment, and after 21 days the filament density peaked with a total length of 2 km cm⁻². Cells elongated and divided at all depths with doubling times over the first 10 days of <20 h. Active, oriented movement must have occurred to explain the separation of O₂ and H₂S by 15 mm. Filament diameters varied from 0.4–1.7 μm, with a general increase over time and depth, and yet they shared 16S rRNA sequence identity of >98%. Comparison of the increase in biovolume and electric current density suggested high cellular growth efficiency. While the vertical expansion of filaments continued over time and reached 30 mm, the electric current density and biomass declined after 13 and 21 days, respectively. This might reflect a breakdown of short filaments as their solid sulphide sources became depleted in the top layers of the anoxic zone. In conclusion, cable bacteria combine rapid and efficient growth with oriented movement to establish and exploit the spatially separated half-reactions of sulphide oxidation and oxygen consumption.     

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.     

Seasonal succession of phytoplankton in Lake Yogo over 2 years: effect of artificial manipulation

We studied the seasonal variation in concentrations of nutrients and phytoplankton in Lake Yogo for 2 years, from May 2000 to May 2002, in order to clarify the seasonal succession of phytoplankton and the effect of various manipulations on it. It was revealed that in spite of the installation of aeration systems and the pumping of mesotrophic water from Lake Biwa during the summer season, the trophic state of Lake Yogo overall has not improved during the past few decades. However, the pumping of water from Lake Biwa did affect the concentrations of nutrients and the periods of cyanobacterial bloom during the summer. The pumping period was different in each year, and the cyanobacterial bloom occurred during the period without pumping in both years. The aeration destratification was not strong enough to prevent cyanobacterial blooms. Cyanobacteria and Bacillariophyceae contributed most to the phytoplankton biomass in both years. Aphanizomenon, Anabaena, and Microcystis were the main genera among cyanobacteria. The bloom of Aphanizomenon or Anabaena occurred early in the summer, and was then replaced by Microcystis. Aphanizomenon was almost always present, and often formed bloom even in winter. The seasonal succession of Bacillariophyceae was almost the same in both years and was well categorized: winter-growing species such as Aulacoseira pusilla (F. Meister) Tuji et Houki and species of Thalassiosiraceae, spring-growing species such as Asterionella formosa Hassall, Fragilaria crotonensis Kitton, and Synedra cf. acus, and fall-growing species such as Aulacoseira ambigua (Grunow) Simonsen, and Aulacoseira granulata (Ehrenb.) Simonsen.     

Occurrence of anatoxin-a(s) during a bloom of <Emphasis Type="Italic">Anabaena crassa</Emphasis> in a water-supply reservoir in southern Brazil

Cyanobacterial blooms and the accompanying production of cyanotoxins are a serious global problem. Toxic blooms of Anabaena species are common in lagoons and reservoirs of southern Brazil. Worldwide, species of the genus Anabaena produce the majority of the known hepatotoxins (microcystins) and neurotoxins [anatoxin-a, anatoxin-a(s), and saxitoxins]. This report links a bloom of Anabaena crassa in the Faxinal Reservoir, the main water supply for the city of Caxias do Sul (400,000 inhabitants) in southern Brazil, to the occurrence of anatoxin-a(s) in the water. During the bloom period, the reservoir was strongly stratified, with higher temperatures and a deep anoxic hypolimnion. Two methods for sample concentration (direct and complete extraction) were tested, and direct extraction of samples proved to be more efficient. Water samples collected during the bloom showed 9% acetylcholinesterase inhibition at 50 mg mL⁻¹, corresponding to 0.61 μg of anatoxin-a(s) per gram of lyophilized powder. At these concentrations, symptoms of neurotoxicity and mortality were not observed in tests with Swiss albino mice. Although the concentrations of anatoxin-a(s) in the Faxinal Reservoir were low, these results are important because this is the first record of the toxin for A. crassa. Furthermore, this cyanotoxin is not yet included in Brazilian legislation for drinking-water monitoring, because of the lack of information about toxicity levels and risk calculation for oral doses. The data presented here contribute to the basis for the future inclusion of this toxin in Brazilian legislation for drinking-water quality control, and for the development of analytical methods for this toxin.