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1.
Seasonal changes in the photosynthesis and primary productionof Microcystis aeruginosa Kütz. were investigated in LakeKasumigaura during 19811982. Microcystis always showeda light-saturated photosynthesis-light curve. Both Pmax andthe initial slope of the photosynthesis-light curve of Microcystisin early summer were very high, so it was concluded that Microcystisutilized both low and high light intensities efficiently. ThePmax of Microcystis was found to be a function of the watertemperature except in August and September. The linear regressionon the temperature-Pmax relationship discontinued at 11°C,where the Pmax value dropped; Microcystis did not photosynthesizebelow 4°C. The initial slope of the curve was also descendingbelow 11°C. It is suggested that Microcystis changes itsphysiological properties below 11°C. The highest value ofgross production calculated for M. aeruginosa was 5.4 gC m2d1 in July; the annual gross production was estimatedto be 300 gC m2year1 (i.e., 40% of the total primaryproduction in this lake). 相似文献
2.
Sedimentation of phytoplankton populations dominated by Microcystis in a shallow lake 总被引:1,自引:0,他引:1
The sedimentary flux of phytoplankton was measured using sedimenttraps in a shallow hypertrophic lake (Lake Kasumigaura), whereMicrocystis bloomed, from June to November 1983 The sedimenttraps were set at 0.5, 1.5 and 3.0 m depth in Takahamairi Bay(3.5 m depth). Microcystis spp. (including M.aerugmosa and M.viridis)in the traps were rare until early August, but increased thereafter.Sinking rates of Microcystis were 0.0045, 0.020 and 0.24 m day1in JuneAugust, September and October respectively, whichwere far lower than those of Melosira (0.21.7 m day1)and Syncdra (0.21.0 m day1). The total sedimentaryfluxes of POC and that of algal carbon during the study periodwere 283.2 and 96.7 gC m2 which were 59.5% and 20.3%of the gross primary production (475.8 gC m2) respectively.The sedimentary flux of living algae measured by algal countswas large in June but small in August and September. On theother hand, the flux of detritus obtained by subtracting totalalgal carbon from POC was small in June and July but large inAugust and September. Therefore diatoms, which appeared mostlyin June, tended to sink as live algae, while Microcystis sankas detritus after being decomposed or consumed in the waterIt was concluded from the results of carbon budget calculationsand the respiration rate of the 1- to 20-µm fraction thatthe activity of decomposers or consumers increased greatly inthe short period at the end of the bloom of Microcystis. 相似文献
3.
During cyanobacterial blooms, processes influencing the population dynamics of blooming species remain partially unexplained. To provide new information, we performed a high-frequency monitoring – every 2 days at six sampling points – of a Microcystis aeruginosa population blooming in a shallow lake. At each sampling date, there was no spatial heterogeneity in the ITS genotypic composition of the population and in the proportion of potentially microcystin- producing (mcyB+) cells, whereas high variations were recorded in cell abundances. In contrast, when looking at the temporal evolution of these parameters, the ITS genotypic composition of the population and in a lesser extent the percentage of mcyB+ cells displayed high variations during the growth phase of the bloom, but not during the plateau phase or the subsequent decline. This suggests that during the development of the bloom, there was no directional selection leading to the dominance of a restricted number of genotypes and that a balancing selection process permitted the maintenance of a high genetic diversity in the Microcystis population. Finally, no relationship was found between these variations occurring in the Microcystis population and those recorded for several environmental parameters, suggesting that many factors and processes interacting together might be involved in these variations. 相似文献
4.
V. I. Kolmakov 《Microbiology》2006,75(2):115-118
Methods for prevention of mass development of the cyanobacterium Microcystis aeruginosa Kutz emend. Elenk. in continental water bodies and industrial water supply systems are reviewed. The physicochemical, chemical, and biological methods for prevention of M. aeruginosa development in water bodies and water supply systems are considered; examples of successful inhibition of M. aeruginosa growth in laboratory experiments are demonstrated. The scientific problems are outlined that are to be solved for perfecting techniques for prevention of M. aeruginosa mass development in open water bodies and in closed water supply systems. 相似文献
5.
Kolmakov VI 《Mikrobiologiia》2006,75(2):149-153
Methods for prevention of mass development of the cyanobacterium Microcystis aeruginosa Kutz emend. Elenk. in continental water bodies and industrial water supply systems are reviewed. The physicochemical, chemical, and biological methods for prevention of M. aeruginosa development in water bodies and water supply systems are considered; examples of successful inhibition of M. aeruginosa growth in laboratory experiments are demonstrated. The scientific problems are outlined that are to be solved for perfecting techniques for prevention of M. aeruginosa mass development in open water bodies and in closed water supply systems. 相似文献
6.
7.
Hyperscums are crusted buoyant mats of densely packed cyanobacteria, often decimeters thick, that persist for periods of weeks to months at the same site. In Hartbeespoort Dam, a hypertrophic lake in South Africa, hyperscums of the cyanobacterium Microcystis aeruginosa that cover more than a hectare and contain up to 2 tons of chlorophyll a typically form in winter and persist for 2–3 months. This paper reports on the environmental conditions that favour hyperscum formation.Reynolds & Walsby (1975) postulated that cyanobacterial bloom formation depended on the coincidence of three preconditions: a pre-existing population, a significant proportion of the organisms having positive buoyancy, and turbulent mixing that is too weak to overcome the tendency of the cells to float. This model of bloom formation is evaluated in the context of hyperscums, based on a case-study from Hartbeespoort Dam. We examine the occurrence of hyperscums and the dynamics of their formation and breakdown in relation to diurnal and seasonal changes in the wind regime and in relation to the population dynamics and buoyancy of Microcystis. We conclude that Reynolds and Walsby's preconditions are essential but not sufficient to explain hyperscum formation. The additional preconditions are prolonged low speed wind regime, suitable lake morphometry, large cyanobacterial standing crops, and high insolation. The rare co-occurrence of these conditions make hyperscums an uncommon phenomenon, but with increasing eutrophication worldwide the frequency and distribution of hyperscum occurrence are likely to increase. 相似文献
8.
Overwintering of Microcystis in Lake Mendota 总被引:5,自引:0,他引:5
SUMMARY. Microcystis , an important bloom-forming blue-green alga in Lake Mendota, Wisconsin, was found to accumulate at the lake bottom and overwinter there. Microcystis collected from winter sediments were photosynthetically active, showing temperature and light optima similar to summer and autumn populations. Sediments incubated under in situ conditions in the laboratory maintained photosynthetic activity for at least four months. Such a maintenance ability may be part of an overall strategy by Microcystis populations to ensure a suitable inoculum for the following growth season. 相似文献
9.
SUMMARY. 1. This paper examines the structural, physical and chemical characteristics of cyanobacterial hyperscums (floating scums of densely packed eyanobacteria. measuring decimetres in thickness, that are covered by a dry crust of photo-oxidized cells) from hypertrophic Hartbeespoort Dam, South Africa. 2. The hyperscum community was a cyanobacterial-baclcrial association, in which the cyanobacterium Microcystis aeruginosa comprised 98% of the biovolumc, with cell concentrations exceeding 109 ml?1. 3. The buoyancy mechanism of M. aeruginosa and evaporation at the surface led to increasing compaction of the colonies with declining distance from the surface, and the formation of three distinct, but continuous layers: a 1–2 mm dry surface crust (water content: 14%, chlorophyll a concentration: 3 g l?1), a 5–10 mm compact layer just below the crust (77% water, 1 g l?1 chlorophyll a), and a less compact layer (96% water, 200–500 mg l?1 chlorophyll a) from about 1 cm depth to the bottom, comprising the bulk of the hyperscum. 4. The crust attenuated all the incident light and reduced free gas exchange. Beneath it continuously dark anaerobic, highly reduced conditions prevailed. As the hyperscum aged over 3 months in 1984, at 10 cm depth the pH gradually declined from 6.6 to 5.9, interstitial water ammonia-N concentrations increased from 0.45 to 119 mg l?1, soluble reactive phosphorus from 2.8 to 83.3 mg l?1, and dissolved organic carbon reached a maximum of 460 mg l?1. At any point in time these concentrations declined gradually with increasing depth within the hyperscum, and declined dramatically beneath the hyperscum. Similar patterns were recorded in another hyperscum in 1986. 5. The chemical and temperature depth profiles indicated that free water movement took place around and under the hyperscum, but within it water movement was restricted to diffusion. 6. Gas bubbles composed of 28% methane. 19% CO2, 53% N2, and traces of H2 trapped within the hyperscum, and the presence of volatile fatty acids in the interstitial water were indicative of anaerobic decomposition processes mediated by fermenting and methanogenic bacteria, and N:P ratios below 1.5 in the interstitial water suggested that nitrogen was lost as gas, possibly through denitrification. 7. We hypothesize that the major sites of decay of M. aeruginosa were the crust and the compact layer beneath it, while deeper within the hyperscum this cyanobacterium could survive prolonged periods of dark anaerobic conditions. This hypothesis requires confirmation. 相似文献
10.
A method for the Cryopreservation of Microcystis aeruginosa f. aeruginosa is described. For the five strains tested, dimethyl sulfoxide (DMSO) (3% v/v) was the only effective cryoprotectant for freezing to, and thawing from -196°C and allowed the successful recovery (>50%) of all the strains. The viability of frozen material was independent of the period of storage in liquid nitrogen. The strain NIES-44 (National Institute for Environmental Studies) had a recovery level of greater than 90% at 3–10% (v/v) DMSO in both two step and rapid cooling methods. The other three strains, NIES-87, 88 and 89 had greater than 60% of viability after freeze/thawing in presence of both 3% and 5% DMSO concentrations. On the other hand, the strain NIES-90 showed approximately 50% of viability in only 3% DMSO solution after two step cooling to and thawing from -196°C. This strain was damaged by greater than 4% DMSO and by rapid cooling to -196°C. It was found that cold shock injury and the cytotoxicity of DMSO were different at a strain level. 相似文献
11.
Nitrate- and phosphate-limited conditions had no effect on toxin production by Microcystis aeruginosa. In contrast, iron-limited conditions influenced toxin production by M. aeruginosa, and iron uptake was light dependent. A model for production of toxin by M. aeruginosa is proposed. 相似文献
12.
It is proposed that surface scums of densely packed planktoniccyanobacteria (blue-green algae) which exist for weeks to months,measure several decimeters in thickness and are covered by acrust of photo-oxidized cells, be called hyperscums. Hyperscumsof Microcystis aeruginosa formed during prolonged periods ofcalm weather in wind-protected sites in a hypertrophic lakesubject to low wind speeds (Hart beespoort Dam, South Africa).A hyperscum that extended over 12 hectares and persistedfor 103 days during winter 1983 was studied. Chlorophyll a concentrationsranged from 100 to 300 mg l2 Microcystis cell concentrationsreached 1.76x109 cells ml1 or 116 cm3l1. The hyperscumenvironment was anoxic, aphotic, with a fluctuating temperatureregime and low pH values. The densely packed Microcystis cellssurvived these conditions for more than 2 months. This was shownby comparing the potential photosynthetic capacity of Microcystisfrom the hyperscum with that of Microcystis from the main basinof the lake. However, after 3 months the hyperscum algae losttheir photosynthetic capacity and decomposition processes prevailed.The hyperscum gradually shrank in size until a storm causedits complete disintegration. 相似文献
13.
A toxic substance contained in the blue-green alga Microcystis aeruginosa was purified and partially characterized. Toxic algal cells were collected from a highly eutrophic lake in Japan, and the toxin was purified by homogenization, ultrafiltration, gel filtration, and ion-exchange chromatography. The final preparation gave a single peak on high-performance liquid chromatography. The toxicity was somewhat less than that reported for other toxins from this alga. The water extract of 6.7 mg (dry weight) of cells and 72 microgram of the purified protein was required to kill a mouse (1 mouse unit). The main amino acids of the toxin were glutamic acid, asparatic acid, alanine, glycine, arginine, and leucine. The molecular weight of the toxin was 2,950 as determined by high-performance liquid chromatography. 相似文献
14.
Resuspension in a shallow eutrophic lake 总被引:11,自引:7,他引:11
The frequency and the importance of wind-induced resuspension were studied in the shallow, eutrophic Lake Arresø, Denmark (41 km2, mean depth 3 m). During storm events in autumn 1988 lake water samples were collected every 2–8 hours by an automatic sampler at a mid-lake station. The concentration of suspended solids and Tot-P was found to increase markedly. During storms up to 2 cm of the superficial sediment was resuspended, and the concentration of resuspended solids in the water column rose to 140 mg l–1. The resuspended particles had a relatively high settling velocity and on average, a relatively short residence time in the water column of 7 hours.A model which describes the concentration of resuspended solids as a function of wind velocity and of settling velocity of the resuspended particles is presented. Using additional wind velocity data from a nearby meteorological station, the model has been used to calculate the frequency of resuspension events and concentration of resuspended solids for the period from May to November 1988.These calculations show that resuspension occurred about 50% of the time. Average flux of suspended solids from the sediment to the water was 300 g m–2 d–1 and during 50% of the time lake water concentration of suspended solids was more than 32 mg l–1. A relationship between concentration of suspended solids and Secchi-depth is presented. Because of resuspension, Secchi-depth in Lake Arresø is reduced to 0.5 m.Resuspension also had a marked effect on Tot-P concentration in the lake water, and P input to the lake water being totally dominated by resuspension events. 相似文献
15.
通过混合培养和添加过滤液两种方式观察铜绿微囊藻和惠氏微囊藻的生长曲线,探讨两种微囊藻之间的化感作用。结果表明:在混合培养条件下,两者能够形成相互抑制作用;当两者起始藻密度高于0.5×106cells.mL-1、混合比为1:1时,惠氏微囊藻的生长因化感作用而受到显著抑制(P<0.05),同时惠氏微囊藻也会对铜绿微囊藻产生一定的胁迫作用;处于对数生长期的铜绿微囊藻过滤液能抑制惠氏微囊藻的生长,且惠氏微囊藻起始藻密度低于0.5×106cells.mL-1,连续滴加该过滤液后,其生长受到极显著抑制(P<0.01)。 相似文献
16.
Ming Li Wei Zhu Xiaoxuan Dai Man Xiao Gloria Appiah-Sefah Philip Nti Nkrumah 《Aquatic Ecology》2014,48(2):207-217
Microcystis was cultured under standard conditions in BG-11 and M-11 media. Using results of an analysis of RNA and total organic carbon (TOC) content, a significant logarithmic relationship between Microcystis growth rate and the RNA/TOC ratio was described to measure the growth rate. Colonial Microcystis samples collected in a shallow, hypertrophic lake (Lake Taihu, China) during May–November 2012 were divided into six size classes (<75, 75–100, 100–150, 150–300, 300–500, and >500 μm), and the RNA/TOC ratio of each class was analyzed to evaluate differences in growth. The growth rate of colonies in the 150–300-μm size class was highest from May to August, but the growth rate increased along with the increase in colony size from September to November. Our results also indicated that water temperature did not change the relationship between growth rate and colony size, but the growth rate of larger colonies was higher than the growth rate of smaller colonies at conditions of low total nitrogen, low total dissolved phosphorus concentration, and high light intensity. Taken together, these results suggest that large colonial Microcystis possess an advantage that is a consequence of this faster growth at lower nutrient concentrations and high light intensities. 相似文献
17.
Toxicity of a unialgal culture of Microcystis aeruginosa 总被引:39,自引:0,他引:39
18.
Hydrodynamics-driven plankton community in a shallow lake 总被引:4,自引:0,他引:4
19.
Resuspension of inorganic sediments in a very shallow Swedish lake is studied using settling sediment traps and measurements of suspended matter. Theoretical aspects of resuspension dynamics is discussed emphasizing special shallow lake aspects. Bottom shear stress distribution is computed for different wind conditions. 相似文献
20.
Microcystin production by Microcystis aeruginosa in a phosphorus-limited chemostat 总被引:13,自引:0,他引:13
The production of microcystins (MC) from Microcystis aeruginosa UTEX 2388 was investigated in a P-limited continuous culture. MC (MC-LR, MC-RR, and MC-YR) from lyophilized M. aeruginosa were extracted with 5% acetic acid, purified by a Sep-Pak C(18) cartridge, and then analyzed by high-performance liquid chromatography with a UV detector and Nucleosil C(18) reverse-phase column. The specific growth rate (mu) of M. aeruginosa was within the range of 0.1 to 0.8/day and was a function of the cellular P content under a P limitation. The N/P atomic ratio of steady-state cells in a P-limited medium varied from 24 to 15 with an increasing mu. The MC-LR and MC-RR contents on a dry weight basis were highest at mu of 0.1/day at 339 and 774 microg g(-1), respectively, while MC-YR was not detected. The MC content of M. aeruginosa was higher at a lower mu, whereas the MC-producing rate was linearly proportional to mu. The C fixation rate at an ambient irradiance (160 microeinsteins m(-2) s(-1)) increased with mu. The ratios of the MC-producing rate to the C fixation rate were higher at a lower mu. Accordingly, the growth of M. aeruginosa was reduced under a P limitation due to a low C fixation rate, whereas the MC content was higher. Consequently, increases in the MC content per dry weight along with the production of the more toxic form, MC-LR, were observed under more P-limited conditions. 相似文献