The effect of mercury on the growth rate of Fragilaria crotonensis kitton and Asterionella formosa Hass.

Hydrobiologia ◽  
1976 ◽  
Vol 49 (2) ◽  
pp. 111-116 ◽  
Author(s):  
Terry Tompkins ◽  
Dean W. Blinn
Keyword(s):  
Growth Rate ◽  
Asterionella Formosa ◽  
Fragilaria Crotonensis

Sorption of Cadmium and its Effect on Growth and the Utilization of Inorganic Carbon and Phosphorus of Two Freshwater Diatoms

1979 ◽  
Vol 36 (5) ◽  
pp. 579-586 ◽  
Author(s):  
H. Lee Conway ◽  
Susan C. Williams
Keyword(s):  
Growth Rate ◽  
Inorganic Carbon ◽  
Cadmium Toxicity ◽  
Cadmium Concentration ◽  
Cadmium Content ◽  
Site Location ◽  
Key Words Cadmium ◽  
Asterionella Formosa ◽  
Freshwater Diatoms ◽  
Fragilaria Crotonensis

Cadmium was rapidly sorbed by Asterionella formosa and Fragilaria crotonensis during the first 5–10 min of exposure (0.05 to ~9 μg Cd∙L−1), followed by a hyperbolic increase in the cellular cadmium content as a function of time. Results obtained from experiments conducted in the light and dark, experiments using live and dead populations, and cellular site location studies imply that the sorption of cadmium by A. formosa is partially an active process, but for F. crotonensis it appears to be passive. Populations of A. formosa exhibited a corresponding decrease in the growth rate as the ambient cadmium concentration was increased from ~2 to ~9 μg∙L−1. In contrast, the growth rate of F. crotonensis was unaffected at levels ranging from ~0.05 to ~9 μg Cd∙L−1. The utilization of inorganic carbon by A. formosa was unaffected at ~4 μg Cd∙L−1, but reduced 45% at ~9 μg Cd∙L−1. The utilization rates of carbon and phosphorus by F. crotonensis were reduced at the lower cadmium concentrations and enhanced at the highest. Key words: cadmium, toxicity, sorption, diatom, Asterionella formosa, Fragilaria crotonensis

Resource requirements of Asterionella formosa and Fragilaria crotonensis in oligotrophic alpine lakes: implications for recent phytoplankton community reorganizations

2005 ◽  
Vol 62 (7) ◽  
pp. 1681-1689 ◽  
Author(s):  
Jasmine E Saros ◽  
Timothy J Michel ◽  
Sebastian J Interlandi ◽  
Alexander P Wolfe
Keyword(s):  
Phytoplankton Community ◽  
Alpine Lakes ◽  
N Deposition ◽  
Mountain Range ◽  
P Availability ◽  
Asterionella Formosa ◽  
Resource Requirements ◽  
Fragilaria Crotonensis ◽  
N Enrichment ◽  
Enrichment Experiments

A widespread increase in the relative abundances of Asterionella formosa and Fragilaria crotonensis has occurred in oligotrophic alpine lakes across the western United States. Previous investigations have suggested that enhanced atmospheric nitrogen (N) deposition is driving these shifts in diatom community structure; however, little information is available on N requirements of these taxa. We examined the distributions of these two taxa in relation to a variety of physicochemical parameters in a suite of lakes situated in the Beartooth Mountain Range (Montana–Wyoming, USA). We also conducted a series of nutrient enrichment experiments to assess the response of these taxa to changes in N, phosphorus (P), and silica (Si) supply. The distributions of both taxa were positively correlated with C:P, N:P, and Si:P seston ratios, revealing that these taxa are abundant when P availability is very low and the supply of N and Si are moderate to high. In the enrichment experiments, both taxa responded strongly to N additions, whereas P or Si enrichment alone had no effect. While these two taxa are indicative of P enrichment in temperate lakes, our results indicate that in these oligotrophic alpine lakes, N enrichment is driving their recent increase.

scholarly journals Differential Effects of the Allelochemical Juglone on Growth of Harmful and Non-Target Freshwater Algae

2020 ◽  
Vol 10 (8) ◽  
pp. 2873 ◽  
Author(s):  
Myung-Hwan Park ◽  
Keonhee Kim ◽  
Soon-Jin Hwang
Keyword(s):  
Green Algae ◽  
Algal Species ◽  
Allelopathic Effect ◽  
Freshwater Algae ◽  
Nuisance Algae ◽  
Asterionella Formosa ◽  
Fragilaria Crotonensis ◽  
Synedra Acus ◽  
Stephanodiscus Hantzschii ◽  
Algicidal Effects

Allelopathy has been applied to control nuisance algae in aquatic systems, but the effects of allelochemicals on the broad spectrum of algae are not well understood. We investigate algicidal effects of the allelochemical juglone on the bloom-forming, harmful algae Microcystis aeruginosa and Stephanodiscus hantzschii, and on several non-target algal species including cyanobacteria (Anabaena flos–aquae, Oscillatoria curviceps, and Phormidium subfuscum), diatoms (Asterionella formosa, Fragilaria crotonensis, and Synedra acus), and green algae (Chlorella vulgaris, Scenedesmus ecornis, and Scenedesmus quadricauda), in laboratory and field enclosure bioassays. Under three treatment concentrations (0.01, 0.1, and 1 mg L−1) of juglone, Microcystis cell density is significantly reduced by 35–93%. Concentrations of 0.1 and 1 mg L−1 inhibits Stephanodiscus growth almost equally (66% and 75%, respectively). To contrast, juglone produces a stimulatory allelopathic effect on three green algae, and other tested diatoms showed hormesis. Overall, the cyanobacteria are more sensitive to juglone than the green algae and diatoms. These results indicate that the allelopathic effects of juglone on microalgae vary depending on their characteristic cellular morphology and anatomy.

Recent trophic changes in Kootenay Lake, British Columbia, as recorded by fossil diatoms

1983 ◽  
Vol 61 (7) ◽  
pp. 1983-1992 ◽  
Author(s):  
G. L. Ennis ◽  
T. G. Northcote ◽  
J. G. Stockner
Keyword(s):  
Drainage Basin ◽  
Sediment Cores ◽  
Phosphate Fertilizer ◽  
Phosphorus Loading ◽  
Diatom Species ◽  
Asterionella Formosa ◽  
Trophic Changes ◽  
Fragilaria Crotonensis ◽  
Kootenay Lake ◽  
Fossil Diatoms

Short sediment cores (ca. 40 cm long) were collected from three locations within Kootenay Lake, B.C., and the occurrence of diatoms within the cores was recorded and analyzed. This analysis of fossil diatoms in the sediments of Kootenay Lake has provided evidence for environmental change as a result of man's activities in the drainage basin. Changes to the trophic status of the lake are related to operation of a phosphate fertilizer plant (beginning in 1953) on the major southern inlet river and to more recent water regulation on both the southern and northern major inlet rivers. Diatom numbers and volumes at the deeper core depths were lowest. Diatom species in the deeper core depths consisted of an assemblage of oligotrophic and eutrophic indicators corresponding to high (but not critically high) phosphorus loading to the lake. Above the 5-cm depth, numbers increased and peaked at the 3-cm depth in samples nearest the south end of the lake. At other locations within the lake, where sedimentation rates were lower, numbers peaked in the top centimetre of sediment. Concomitant with increased phosphorus loading diatom species indicative of oligotrophic conditions such as Cyclotella ocellata declined, while eutrophic indicators including Cyclotella glomerata, Melosira granulata v. angustissima, Stephanodiscus spp., Asterionella formosa, and Fragilaria crotonensis increased. Asterionella formosa and Fragilaria crotonensis showed highest abundances in the top 2 cm of the core. These species, which form a major component of the spring and fall diatom blooms, were responding to both increased nutrients and improved light conditions resulting from decreased freshet turbidity. The Araphidineae/Centrales ratio was not useful in classifying trophic changes in Kootenay Lake since numbers of centric diatoms did not decline with nutrient enrichments (although there was a dominance shift from oligotrophic centrics to eutrophic centrics). Shannon–Wiener diversity values remained high throughout the recent history of the lake.

The threshold energy for atom displacement in fcc metals

1990 ◽  
Vol 48 (4) ◽  
pp. 530-531
Author(s):  
Wilfried Sigle ◽  
Matthias Hohenstein ◽  
Alfred Seeger
Keyword(s):  
Growth Rate ◽  
Elevated Temperatures ◽  
Threshold Energy ◽  
Dislocation Loops ◽  
Absolute Minimum ◽  
Voltage Electron ◽  
Atom Displacement ◽  
Electron Microscopes ◽  
Fcc Metal

Prolonged electron irradiation of metals at elevated temperatures usually leads to the formation of large interstitial-type dislocation loops. The growth rate of the loops is proportional to the total cross-section for atom displacement,which is implicitly connected with the threshold energy for atom displacement, Ed . Thus, by measuring the growth rate as a function of the electron energy and the orientation of the specimen with respect to the electron beam, the anisotropy of Ed can be determined rather precisely. We have performed such experiments in situ in high-voltage electron microscopes on Ag and Au at 473K as a function of the orientation and on Au as a function of temperature at several fixed orientations.Whereas in Ag minima of Ed are found close to <100>,<110>, and <210> (13-18eV), (Fig.1) atom displacement in Au requires least energy along <100>(15-19eV) (Fig.2). Au is thus the first fcc metal in which the absolute minimum of the threshold energy has been established not to lie in or close to the <110> direction.

Saturation mechanism and generated viscosity in gravito-turbulent accretion disks

2020 ◽  
Vol 640 ◽  
pp. A53
Author(s):  
L. Löhnert ◽  
S. Krätschmer ◽  
A. G. Peeters
Keyword(s):  
Growth Rate ◽  
Numerical Simulations ◽  
Accretion Disks ◽  
Gravitational Instability ◽  
Turbulent Viscosity ◽  
Radial Distance ◽  
Maximum Growth ◽  
Wave Number ◽  
Radiative Cooling ◽  
Mixing Length

Here, we address the turbulent dynamics of the gravitational instability in accretion disks, retaining both radiative cooling and irradiation. Due to radiative cooling, the disk is unstable for all values of the Toomre parameter, and an accurate estimate of the maximum growth rate is derived analytically. A detailed study of the turbulent spectra shows a rapid decay with an azimuthal wave number stronger than ky−3, whereas the spectrum is more broad in the radial direction and shows a scaling in the range kx−3 to kx−2. The radial component of the radial velocity profile consists of a superposition of shocks of different heights, and is similar to that found in Burgers’ turbulence. Assuming saturation occurs through nonlinear wave steepening leading to shock formation, we developed a mixing-length model in which the typical length scale is related to the average radial distance between shocks. Furthermore, since the numerical simulations show that linear drive is necessary in order to sustain turbulence, we used the growth rate of the most unstable mode to estimate the typical timescale. The mixing-length model that was obtained agrees well with numerical simulations. The model gives an analytic expression for the turbulent viscosity as a function of the Toomre parameter and cooling time. It predicts that relevant values of α = 10−3 can be obtained in disks that have a Toomre parameter as high as Q ≈ 10.

TEMPERATURE DEPENDENCE OF THE CRYSTAL GROWTH RATE IN POLAR GLACIERS

1987 ◽  
Vol 48 (C1) ◽  
pp. C1-661-C1-662 ◽  
Author(s):  
J. R. PETIT ◽  
P. DUVAL ◽  
C. LORIUS
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Temperature Dependence ◽  
Crystal Growth Rate
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