Phosphate Uptake Rates of Phytoplankton Assemblages Grown at Different Dilution Rates in Semicontinuous Culture

1986 ◽  
Vol 43 (8) ◽  
pp. 1474-1481 ◽  
Author(s):  
C. A. Suttle ◽  
P. J. Harrison
Keyword(s):  
Dilution Rate ◽  
Uptake Rate ◽  
Time Course ◽  
Phytoplankton Community ◽  
Phytoplankton Assemblages ◽  
Uptake Rates ◽  
Maximum Uptake Rate ◽  
Synechococcus Sp ◽  
The Relationship ◽  
Natural Phytoplankton

We studied the effects of pulsed nutrient supplies on the physiology of natural phytoplankton assemblages. A natural phytoplankton community, from an oligotrophic lake, was grown at several dilution rates from 0.1 to 1.5∙d−1 in P-limited semicontinuous cultures. Particulate C:P and N:P ratios (by atoms) were approximately 300:1 and 50:1, respectively, at the lowest dilution rate and 40:1 and 7:1, respectively, at the highest dilution rate. This demonstrates that a range of P-limited conditions can be established using the semicontinuous culturing technique. The time-course of uptake, in response to a saturating addition of phosphate, revealed that there was a short lag before maximum rates of uptake were observed at all but the highest dilution rate, and that maximum uptake rates over the first 30 min of incubation were higher at intermediate dilution rates. Subsequent to the maximum uptake rate occurring, the relationship between uptake rate and time was species dependent. In Oscillatoria sp. dominated cultures the uptake rates declined with increasing cellular P, and the rates of these declines increased with dilution rate; in Synechococcus sp. dominated cultures the uptake rates remained constant and were independent of cellular P.

scholarly journals Characteristics of Different Size Phytoplankton for Primary Production and Biochemical Compositions in the Western East/Japan Sea

2020 ◽  
Vol 11 ◽  
Author(s):  
Jae Joong Kang ◽  
Hyo Keun Jang ◽  
Jae-Hyun Lim ◽  
Dabin Lee ◽  
Jae Hyung Lee ◽  
...  
Keyword(s):  
Primary Production ◽  
Uptake Rate ◽  
Phytoplankton Community ◽  
Japan Sea ◽  
Trophic Levels ◽  
Total Carbon ◽  
Carbon Uptake ◽  
Uptake Rates ◽  
Small Phytoplankton ◽  
Biochemical Compositions

The current phytoplankton community structure is expected to change, with small phytoplankton becoming dominant under ongoing warming conditions. To understand and evaluate the ecological roles of small phytoplankton in terms of food quantity and quality, the carbon uptake rates and intracellular biochemical compositions (i.e., carbohydrates, CHO; proteins, PRT; and lipids, LIP) of phytoplankton of different sizes were analyzed and compared in two different regions of the western East/Japan Sea (EJS): the Ulleung Basin (UB) and northwestern East/Japan Sea (NES). The average carbon uptake rate by the whole phytoplankton community in the UB (79.0 ± 12.2 mg C m–2 h–1) was approximately two times higher than that in the NES (40.7 ± 2.2 mg C m–2 h–1), although the average chlorophyll a (chl a) concentration was similar between the UB (31.0 ± 8.4 mg chl a m–2) and NES (28.4 ± 7.9 mg chl a m–2). The main reasons for the large difference in the carbon uptake rates are believed to be water temperature, which affects metabolic activity and growth rate, and the difference in euphotic depths. The contributions of small phytoplankton to the total carbon uptake rate were not significantly different between the regions studied. However, the rate of decrease in the total carbon uptake with increasing contributions from small phytoplankton was substantially higher in the UB than in the NES. This result suggests that compared to other regions in the EJS, the primary production in the UB could decrease rapidly under ongoing climate change. The calorific contents calculated based on biochemical compositions were similar between the small (1.01 ± 0.33 Kcal m–3) and large (1.14 ± 0.36 Kcal m–3) phytoplankton in the UB, whereas the biochemical contents were higher in the large phytoplankton (1.88 ± 0.54 Kcal m–3) than in the small phytoplankton (1.06 ± 0.18 Kcal m–3) in the NES. The calorific values per unit of chl a were higher for the large phytoplankton than for the small phytoplankton in both regions, which suggests that large phytoplankton could provide a more energy efficient food source to organisms in higher trophic levels in the western EJS.

scholarly journals Fish-mediated nutrient recycling and the trophic cascade in lakes

2001 ◽  
Vol 58 (10) ◽  
pp. 1924-1931 ◽  
Author(s):  
José Luiz Attayde ◽  
Lars-Anders Hansson
Keyword(s):  
Phytoplankton Community ◽  
Nutrient Recycling ◽  
Effect Sizes ◽  
Zooplankton Grazing ◽  
Relative Importance ◽  
Phytoplankton Community Structure ◽  
Phytoplankton Assemblages ◽  
Nutrient Excretion ◽  
Positive Effects ◽  
Natural Phytoplankton

The effects of planktivorous fish on phytoplankton through nutrient recycling and zooplankton herbivory were experimentally separated and their relative importance quantified in a eutrophic humic lake. Natural phytoplankton assemblages were incubated in nutrient-permeable chambers placed inside enclosures with or without fish. Outside these chambers, phytoplankton were exposed to zooplankton herbivory and to nutrient recycling by fish and zooplankton, whereas inside the chambers, phytoplankton were exposed only to nutrient recycling by these consumers. Our results show that fish had significant positive effects on cyanobacteria, cryptomonads, and chlorophytes inside the chambers, indicating that fish-mediated nutrient recycling had significant effects on these phytoplankton groups. However, our results also indicate that changes in zooplankton grazing induced by fish were an important mechanism by which fish affected all phytoplankton groups except cyanobacteria. Comparison of effect sizes revealed that the effects on cyanobacteria and chlorophytes through nutrient recycling were stronger than those through zooplankton grazing. Moreover, most of the fish-mediated nutrient recycling effects were due to increased nutrient recycling by zooplankton rather than direct nutrient excretion by fish. In conclusion, we provide experimental evidence supporting the hypothesis that fish-mediated nutrient recycling is an important mechanism affecting phytoplankton community structure and favoring cyanobacteria dominance in lakes.

Uptake of ammonium by four species of macroalgae in Port Phillip Bay, Victoria, Australia

1999 ◽  
Vol 50 (6) ◽  
pp. 515 ◽  
Author(s):  
Stuart J. Campbell
Keyword(s):  
Competitive Advantage ◽  
Nutrient Uptake ◽  
Uptake Rate ◽  
Undaria Pinnatifida ◽  
Ammonium Uptake ◽  
N Availability ◽  
Low Concentrations ◽  
Uptake Rates ◽  
Maximum Uptake Rate ◽  
Saturation Rate

The uptake rates of ammonium were determined for three species of native macroalgae and an exotic macroalga from Port Phillip Bay. All species exhibited rate-saturated mechanisms of uptake described by Michaelis–Menten uptake kinetics. At the highest concentration examined (28.6 µmol NH4-N) Hincksia sordida had a higher rate of uptake (435 µmol NH4 -N g dry wt–1 h–1) than Ulva sp. (108 µmol NH4-N g dry wt–1 h–1) or Polysiphonia decipiens (53 µmol NH4 -N g dry wt–1 h–1). Maximum surge uptake rate was highest for H. sordida and lowest for P. decipiens (802 and 57 µmol NH4 -N g dry wt–1 h–1 respectively). The introduced phaeophyte Undaria pinnatifida had an intermediate capacity for ammonium uptake which was dependent on blade maturity. Differences in the ratio of maximum uptake rate to half-saturation rate between surge and assimilation uptake phases suggest a propensity for some species to take up ammonium at low concentrations. The relationships between nutrient uptake and growth among species would afford mature U. pinnatifida, H. sordida and Ulva sp. a competitive advantage for ammonium uptake in winter during high N availability, whereas P. decipiens would be able to exploit low N concentrations in spring and summer.

Computer Simulation of the Responses of Human Motoneurons to Composite 1A EPSPS: Effects of Background Firing Rate

1997 ◽  
Vol 77 (1) ◽  
pp. 405-420 ◽  
Author(s):  
Kelvin E. Jones ◽  
Parveen Bawa
Keyword(s):  
Computer Simulation ◽  
Firing Rate ◽  
Time Course ◽  
Current Model ◽  
Response Probability ◽  
Muscle Spindles ◽  
Excitatory Postsynaptic Potential ◽  
Biophysical Properties ◽  
Rhythmic Firing ◽  
The Relationship

Jones, Kelvin E. and Parveen Bawa. Computer simulation of the responses of human motoneurons to composite 1A EPSPS: effects of background firing rate. J. Neurophysiol. 77: 405–420, 1997. Two compartmental models of spinal alpha motoneurons were constructed to explore the relationship between background firing rate and response to an excitatory input. The results of these simulations were compared with previous results obtained from human motoneurons and discussed in relation to the current model for repetitively firing human motoneurons. The morphologies and cable parameters of the models were based on two type-identified cat motoneurons previously reported in the literature. Each model included five voltage-dependent channels that were modeled using Hodgkin-Huxley formalism. These included fast Na+ and K+ channels in the initial segment and fast Na+ and K+ channels as well as a slow K+ channel in the soma compartment. The density and rate factors for the slow K+ channel were varied until the models could reproduce single spike AHP parameters for type-identified motoneurons in the cat. Excitatory synaptic conductances were distributed along the equivalent dendrites with the same density described for la synapses from muscle spindles to type-identified cat motoneurons. Simultaneous activation of all synapses on the dendrite resulted in a large compound excitatory postsynaptic potential (EPSP). Brief depolarizing pulses injected into a compartment of the equivalent dendrite resulted in pulse potentials (PPs), which resembled the compound EPSPs. The effects of compound EPSPs and PPs on firing probability of the two motoneuron models were examined during rhythmic firing. Peristimulus time histograms, constructed between the stimulus and the spikes of the model motoneuron, showed excitatory peaks whose integrated time course approximated the time course of the underlying EPSP or PP as has been shown in cat motoneurons. The excitatory peaks were quantified in terms of response probability, and the relationship between background firing rate and response probability was explored. As in real human motoneurons, the models exhibited an inverse relationship between response probability and background firing rate. The biophysical properties responsible for the relationship between response probability and firing rate included the shapes of the membrane voltage trajectories between spikes and nonlinear changes in PP amplitude during the interspike interval at different firing rates. The results from these simulations suggest that the relationship between response probability and background firing rate is an intrinsic feature of motoneurons. The similarity of the results from the models, which were based on the properties of cat motoneurons, and those from human motoneurons suggests that the biophysical properties governing rhythmic firing in human motoneurons are similar to those of the cat.

Inhibition of carbon fixation as a function of zinc uptake in natural phytoplankton assemblages

1979 ◽  
Vol 59 (4) ◽  
pp. 937-949 ◽  
Author(s):  
Anthony G. Davies ◽  
Jillian A. Sleep
Keyword(s):  
Carbon Fixation ◽  
Natural Populations ◽  
Plant Cells ◽  
Toxic Metal ◽  
Vitamin B ◽  
Phytoplankton Assemblages ◽  
Metal Contents ◽  
Rate Limiting ◽  
Natural Phytoplankton

There is now a substantial body of evidence that the growth rates of phytoplankton in culture are more closely related to the cellular levels of the rate-limiting constituent, be it a nutrient, micronutrient or toxic metal, than to the concentrations in the supporting medium; nitrate, Caperon (1968); phosphate, Fuhs (1969); silicate, Paasche (1973); vitamin B12, Droop (1968); iron, Davies (1970); mercury, Davies (1974); cadmium, Davies (1978a). This has suggested the requirement for a technique which would allow the determination of comparable relationships for natural populations of phytoplankton - how, for instance, their carbon fixation rates depend upon the metal contents of the plant cells. Although the effects of metals upon carbon fixation in phytoplankton assemblages from several different sea areas have already been examined (Knauer & Martin, 1972; Patin et al. 1974; Zingmark & Miller, 1975; Ibragim & Patin, 1976) no data seem to have been obtained on the levels of the metals present in the phytoplankton at the time of the measurements.

Potassium depletion improves myocardial potassium uptake in vivo

2004 ◽  
Vol 287 (1) ◽  
pp. C135-C141 ◽  
Author(s):  
Henning Bundgaard
Keyword(s):  
Uptake Rate ◽  
High Plasma ◽  
Potassium Depletion ◽  
Uptake Capacity ◽  
K Uptake ◽  
Impulse Generation ◽  
Uptake Rates ◽  
Clinical Interest ◽  
A Minor

Potassium depletion (KD) is a very common clinical entity often associated with adverse cardiac effects. KD is generally considered to reduce muscular Na-K-ATPase density and secondarily reduce K uptake capacity. In KD rats we evaluated myocardial Na-K-ATPase density, ion content, and myocardial K reuptake. KD for 2 wk reduced plasma K to 1.8 ± 0.1 vs. 3.5 ± 0.2 mM in controls ( P < 0.01, n = 7), myocardial K to 80 ± 1 vs. 86 ± 1 μmol/g wet wt ( P < 0.05, n = 7), increased Mg, and induced a tendency to increased Na. Myocardial Na-K-ATPase α2-subunit abundance was reduced by ∼30%, whereas increases in α1- and K-dependent pNPPase activity of 24% ( n = 6) and 13% ( n = 6), respectively, were seen. This indicates an overall upregulation of the myocardial Na-K pump pool. KD rats tolerated a higher intravenous KCl dose. KCl infusion until animals died increased myocardial K by 34% in KD rats and 18% in controls ( P < 0.05, n = 6 for both) but did not induce different net K uptake rates between groups. However, clamping plasma K at ∼5.5 mM by KCl infusion caused a higher net K uptake rate in KD rats (0.22 ± 0.04 vs. 0.10 ± 0.03 μmol·g wet wt−1·min−1; P < 0.05, n = 8). In conclusion, a minor KD-induced decrease in myocardial K increased Na-K pump density and in vivo increased K tolerance and net myocardial K uptake rate during K repletion. Thus the heart is protected from major K losses and accumulates considerable amounts of K during exposure to high plasma K. This is of clinical interest, because a therapeutically induced rise in myocardial K may affect contractility and impulse generation-propagation and may attenuate increased myocardial Na, the hallmark of heart failure.

scholarly journals Excessive Pressure in Multichambered Cuffs Used for Sequential Compression Therapy

2002 ◽  
Vol 82 (10) ◽  
pp. 1000-1008 ◽  
Author(s):  
Patrick Segers ◽  
Jean-Paul Belgrado ◽  
Andre Leduc ◽  
Olivier Leduc ◽  
Pascal Verdonck
Keyword(s):  
Time Course ◽  
Compression Therapy ◽  
Lymphatic Drainage ◽  
Chamber Pressure ◽  
Excessive Pressure ◽  
Ellipsoidal Model ◽  
Order Of Magnitude ◽  
Pneumatic Compression Devices ◽  
Target Pressure ◽  
The Relationship

Abstract Background and Purpose. Pneumatic compression devices, used as part of the therapeutic strategy for lymphatic drainage, often have cuffs with multiple chambers that are inflated sequentially. The purpose of this study was to investigate (1) the relationship between cuff chamber pressure (Pchamber) and the pressure on the cuff-skin interface (Pinterface) and (2) the mechanical interaction of cuff chambers and consequences for device control. Subjects and Methods. In this study, we used 3 cylindrical (60-, 80-, and 100-mm-diameter) model limbs and 1 ellipsoidal model of the arm to test a commercially available pressure controller using “target pressures,” indicated by the controller, of 30, 60, 80, and 100 mm Hg. We studied the time course of Pchamber and Pinterface during the inflation sequence and the effect of local curvature on Pinterface. Results. Our data indicated that, overall, Pinterface is of the same order of magnitude as Pchamber. There was some effect of model diameter and shape, with the smaller curvatures yielding the highest Pinterface. Cuff chamber interaction led to Pchamber and Pinterface values in the most distal (first inflated) chamber that were up to 80% higher than the target pressure. For the 80-mm cylindrical model, for instance, pressure in this chamber reached 54, 98, 121, and 141 mm Hg, respectively, instead of the 30, 60, 80, and 100 mm Hg indicated by the controller. Discussion and Conclusion. The discrepancy between the target pressure, indicated by the controller, and the pressure measured inside the cuff chambers undermines the therapeutic control and efficacy of the pneumatic compression devices. Because the measured pressures were far beyond the pressure level indicated by the controller, it is recommended that pneumatic compression devices be used at much lower target pressures (&lt;30 mm Hg) than those applied in clinical practice.

The relationship between crop yield (or mean plant weight) of lettuce and plant density, length of growing period, and initial plant weight

1976 ◽  
Vol 86 (1) ◽  
pp. 83-91 ◽  
Author(s):  
M. A. Scaife ◽  
D. Jones
Keyword(s):  
Time Course ◽  
Plant Density ◽  
Unit Area ◽  
Subterranean Clover ◽  
Plant Weight ◽  
Relative Growth ◽  
Growing Period ◽  
Lettuce Growth ◽  
Log Linear ◽  
The Relationship

SUMMARYLettuce obeys the Shinozaki–Kira relationship in which the reciprocal of plant weight is linearly related to plant density. The intercept (a) represents the reciprocal of the weight of an isolated plant and the slope (b) represents the reciprocal of yield/unit area at high densities (the ‘ceiling yield’). This work examines the time course of (a) and (b) in an ‘ideal environment’ in which water and nutrients are non-limiting, and the light/temperature regime is constant.Two pot experiments are described: the first showed that the growth of isolated lettuces follows a logistic expression, which can therefore be substituted for a–1 in the Shinozaki-Kira equation. It was then hypothesized that b–1, the ‘ceiling yield’ would be constant over time. This was confirmed by the second experiment, giving the equationw–1t = w–10 e1–kt × w–1max × bd,in which wt is mean plant weight at time t, w0 and wmax are the initial and final weights of isolated plants, k is the early relative growth rate of such plants, b–1 is the constant ceiling yield, and d is the plant density.Two examples of the use of the equation are given: one shows how it predicts the interaction between seed size and plant density within a species (subterranean clover): the other illustrates how it can be used to explain why lettuce growth appears to be log-linear against time whereas cereal growth is more nearly just linear.

Estimation of the rate of appearance in the non-steady state with a two-compartment model

1992 ◽  
Vol 263 (2) ◽  
pp. E400-E415 ◽  
Author(s):  
A. Mari
Keyword(s):  
Steady State ◽  
Time Course ◽  
Specific Activity ◽  
Glucose Production ◽  
Compartment Model ◽  
New Method ◽  
Two Compartment Model ◽  
Glucose Clamp Technique ◽  
Glucose Output ◽  
The Relationship

A simple tracer-based method for calculating the rate of appearance of endogenous substances in the non-steady state, free from the inconsistencies of Steele's equation, is still lacking. This paper presents a method based on a two-compartment model by which the rate of appearance can be calculated with only a modest increase in complexity over Steele's approach. An equation is developed where the rate of appearance is expressed as a sum of three terms: a steady-state term, a term for the first compartment, and a term for the second compartment. The formula employs three parameters and makes the relationship between rate of appearance and specific activity changes explicit. An equation is also provided for estimating the error of the method in each individual run. The algorithm can be implemented with a spreadsheet on a personal computer. Simulated and experimental data obtained by the hyperinsulinemic euglycemic glucose clamp technique were used as a test. The accuracy with which the time course of glucose production could be reconstructed was clearly better than that using Steele's equation. Marked negative values for endogenous glucose output were calculated with Steele's equation but not with the new method. The characteristics of generality, simplicity, and accuracy and the availability of an error estimate make this new method suitable for routine application to non-steady-state tracer analysis.

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