Assessment of Phosphorus Limitation in an Oligotrophic Lake Using Radiophosphorus Uptake Kinetics

1983 ◽  
Vol 40 (6) ◽  
pp. 817-821 ◽  
Author(s):  
Patricia Chow-Fraser ◽  
Hamish C. Duthie
Keyword(s):  
Analytical Methods ◽  
Kinetic Data ◽  
Phosphorus Limitation ◽  
P Uptake ◽  
Phytoplankton Growth ◽  
Uptake Kinetics ◽  
Uptake Kinetic ◽  
P Limitation ◽  
Ultraoligotrophic Lake ◽  
Tracer Experiments

We used 32P uptake kinetics as a means of assessing periods of P limitation to phytoplankton growth in an ultraoligotrophic lake. Tracer experiments, conducted biweekly and weekly in 1975 and 1976, respectively, yielded information regarding the availability of phosphorus over the sampling seasons. Analytical measurements of ambient phosphorus concentrations were not as informative as uptake kinetic data in the assessment of phosphorus demands in the lake. Whereas analytical methods identified probable periods of P limitation at the end of summer, radiophosphorus data indicated that P limitation was prevalent throughout most of the summer.

Phosphorus Kinetics in Lake Superior: Light Intensity and Phosphate Uptake in Algae

1981 ◽  
Vol 38 (2) ◽  
pp. 224-232 ◽  
Author(s):  
C. Nalewajko ◽  
K. Lee ◽  
H. Shear
Keyword(s):  
Management Strategy ◽  
Phosphorus Content ◽  
Lake Superior ◽  
Chlorella Pyrenoidosa ◽  
Phosphorus Limitation ◽  
P Uptake ◽  
Uptake Kinetics ◽  
Low Light ◽  
Light Levels ◽  
Uptake Rates

Epilimnetic phytoplankton in Lake Superior in September, 1979, had low Ik values (75–190 μE∙m−2∙s−1), low N/P ratios (8 to 13:1) and 32PO4–P uptake kinetics that were not consistent with a state of extreme phosphorus limitation. Parallel laboratory experiments with Chlorella pyrenoidosa indicated that phosphorus content per cell was higher and uptake rates of phosphate were lower in cells grown under low light (57 μE∙m−2∙s−1) than those under high light (340 μE∙m−2∙s−1). Maximum 32PO4 uptake occurred at about 50–60 μE∙m−2∙s−1 in both cultures indicating 32PO4 uptake kinetics are light dependent at very low light levels, below or close to their Ik values. It appears that light and not phosphorus limited phytoplankton growth in Lake Superior at the time of our experiments. Antecedent solar radiation prior to our experiments coupled with complete mixing of the top 20–25 m of the Lake possibly resulted in a low light-adapted phytoplankton population. We suggest that phosphorus control need not be the correct management strategy to maintain oligotrophy in Lake Superior. Key words: phosphorus, kinetics, light, primary production, mixing, management

The effects of intensity on V̇O2 kinetics during incremental free swimming

2015 ◽  
Vol 40 (9) ◽  
pp. 918-923 ◽  
Author(s):  
Kelly de Jesus ◽  
Ana Sousa ◽  
Karla de Jesus ◽  
João Ribeiro ◽  
Leandro Machado ◽  
...  
Keyword(s):  
Oxygen Uptake ◽  
Slow Component ◽  
Metabolic Stress ◽  
Relevant Information ◽  
Oxygen Uptake Kinetics ◽  
Uptake Kinetics ◽  
Uptake Kinetic ◽  
Performance Diagnosis ◽  
Incremental Protocol ◽  
And Training

Swimming and training are carried out with wide variability in distances and intensities. However, oxygen uptake kinetics for the intensities seen in swimming has not been reported. The purpose of this study was to assess and compare the oxygen uptake kinetics throughout low-moderate to severe intensities during incremental swimming exercise. We hypothesized that the oxygen uptake kinetic parameters would be affected by swimming intensity. Twenty male trained swimmers completed an incremental protocol of seven 200-m crawl swims to exhaustion (0.05 m·s−1 increments and 30-s intervals). Oxygen uptake was continuously measured by a portable gas analyzer connected to a respiratory snorkel and valve system. Oxygen uptake kinetics was assessed using a double exponential regression model that yielded both fast and slow components of the response of oxygen uptake to exercise. From low-moderate to severe swimming intensities changes occurred for the first and second oxygen uptake amplitudes (P ≤ 0.04), time constants (P = 0.01), and time delays (P ≤ 0.02). At the heavy and severe intensities, a notable oxygen uptake slow component (>255 mL·min−1) occurred in all swimmers. Oxygen uptake kinetics whilst swimming at different intensities offers relevant information regarding cardiorespiratory and metabolic stress that might be useful for appropriate performance diagnosis and training prescription.

scholarly journals On the potential vegetation feedbacks that enhance phosphorus availability – insights from a process-based model linking geological and ecological timescales

2014 ◽  
Vol 11 (13) ◽  
pp. 3661-3683 ◽  
Author(s):  
C. Buendía ◽  
S. Arens ◽  
T. Hickler ◽  
S. I. Higgins ◽  
P. Porada ◽  
...  
Keyword(s):  
Biomass Production ◽  
Primary Productivity ◽  
Chemical Weathering ◽  
Production Efficiency ◽  
Root Exudation ◽  
Terrestrial Ecosystems ◽  
Global Scale ◽  
P Uptake ◽  
P Availability ◽  
P Limitation

Abstract. In old and heavily weathered soils, the availability of P might be so small that the primary production of plants is limited. However, plants have evolved several mechanisms to actively take up P from the soil or mine it to overcome this limitation. These mechanisms involve the active uptake of P mediated by mycorrhiza, biotic de-occlusion through root clusters, and the biotic enhancement of weathering through root exudation. The objective of this paper is to investigate how and where these processes contribute to alleviate P limitation on primary productivity. To do so, we propose a process-based model accounting for the major processes of the carbon, water, and P cycles including chemical weathering at the global scale. Implementing P limitation on biomass synthesis allows the assessment of the efficiencies of biomass production across different ecosystems. We use simulation experiments to assess the relative importance of the different uptake mechanisms to alleviate P limitation on biomass production. We find that active P uptake is an essential mechanism for sustaining P availability on long timescales, whereas biotic de-occlusion might serve as a buffer on timescales shorter than 10 000 yr. Although active P uptake is essential for reducing P losses by leaching, humid lowland soils reach P limitation after around 100 000 yr of soil evolution. Given the generalized modelling framework, our model results compare reasonably with observed or independently estimated patterns and ranges of P concentrations in soils and vegetation. Furthermore, our simulations suggest that P limitation might be an important driver of biomass production efficiency (the fraction of the gross primary productivity used for biomass growth), and that vegetation on old soils has a smaller biomass production rate when P becomes limiting. With this study, we provide a theoretical basis for investigating the responses of terrestrial ecosystems to P availability linking geological and ecological timescales under different environmental settings.

Carbon flux response and recovery to drought years in a hemi-boreal peat bog between different vegetation types

2020 ◽  
Author(s):  
Chris R Taylor ◽  
Ben Keane ◽  
Iain Hartley ◽  
Gareth Phoenix
Keyword(s):  
Carbon Dioxide ◽  
Nutrient Availability ◽  
Anthropogenic Activities ◽  
Terrestrial Ecosystems ◽  
Phosphorus Limitation ◽  
Atmospheric Concentration ◽  
Ecosystem Responses ◽  
N Limitation ◽  
Plant Soil ◽  
P Limitation

<p>Terrestrial ecosystems absorb 30% of anthropogenic carbon dioxide (CO<sub>2</sub>) emissions, slowing its rising atmospheric concentration and substantially inhibiting climate change. This uptake is believed to be due to elevated CO<sub>2</sub> (eCO<sub>2</sub>) stimulating plant photosynthesis and growth, thus increasing carbon (C) storage in plants and soil organic matter. However, nitrogen (N) limitation can reduce ecosystem C uptake capacity under eCO<sub>2</sub> by as much as 50%. Phosphorus (P) limitation in ecosystems is almost as common as N-limitation and is increasing due to ongoing deposition of N from anthropogenic activities. Despite this, we do not know how P-limited ecosystems will respond to eCO<sub>2</sub>, constituting a major gap in our understanding of how large areas of the biosphere will impact atmospheric CO<sub>2</sub> over the coming decades.</p><p>In the first study conducted into the effect of eCO<sub>2</sub> on P-limited ecosystems with manipulated nutrient availability, the Phosphorus Limitation And ecosystem responses to Carbon dioxide Enrichment project (PLACE), investigates the effects of eCO<sub>2</sub> on C cycling in grasslands, which are a critical global C store. Turf mesocosms from P-limited acidic and limestone grasslands, where N and P inputs have been manipulated for 20 years (control, low N (3.5 g m<sup>-2</sup> y<sup>-1</sup>), high N (14 g m<sup>-2</sup> y<sup>-1</sup>), and P (3.5 g m<sup>-2</sup> y<sup>-1</sup>)), have been exposed to either ambient or eCO<sub>2</sub> (600 ppm) in a miniFACE (mini Free Air Carbon Enrichment) system. Long-term P addition has alleviated P limitation while N additions have exacerbated it. The two contrasting grasslands contain different amounts of organic versus mineral P in their soils and, thus, plants may have to use contrasting strategies to acquire the additional P they need to increase growth rates under elevated CO<sub>2</sub>.</p><p>We present data from the first two growing seasons, including above and below ground productivity, and C, N and P cycling through plant, soil and microbial pools. Aboveground harvest data from the second year have shown eCO<sub>2</sub> has only increased biomass production in the limestone grassland (by 17%; p< 0.0001), and not in the acid grassland. There was also a significant effect of nutrient treatment (p< 0.001) with biomass increasing under P and HN, indicating some co-NP limitation. Stable isotope tracing, using the fumigation CO<sub>2</sub> signal has shown the fate of newly assimilated C and its contribution to gaseous C flux to the atmosphere in the form of methane (CH<sub>4</sub>) and respired CO<sub>2</sub>.  In summary, our first two years of eCO<sub>2</sub> treatment suggests that productivity of limestone and acidic grassland respond differently and that these responses depend on nutrient availability, indicating the complexity of predicting P-limited ecosystem responses as atmospheric CO<sub>2 </sub>continues to rise.</p>

scholarly journals Kinetics of solvolysis in water of four secondary alkyl nitrates

1982 ◽  
Vol 60 (13) ◽  
pp. 1780-1785 ◽  
Author(s):  
Ross Elmore Robertson ◽  
Kalvelil Matthew Koshy ◽  
Adrianne Annessa ◽  
Jan N. Ong ◽  
John Marshall William Scott ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Rate Constant ◽  
Analytical Methods ◽  
Kinetic Data ◽  
Activation Parameters ◽  
Single Step ◽  
Alkyl Nitrates ◽  
Two Stage ◽  
Kinetics Of ◽  
Single Step Reaction

Kinetic data are reported for the solvolysis in water of propane-2-nitrate, butane-2-nitrate, cyclopentyl nitrate, and cyclohexyl nitrate. In each case, the dependence of rate constant on temperature is analysed in terms of two mechanisms for the solvolytic reaction. First it is assumed that the rate constant describes a single step reaction, the analysis leading to estimates of the heat capacity of activation ΔCp≠. Three different analytical methods are discussed in this regard. Second it is assumed that the rate constant describes a two stage mechanism, the first stage being reversible. In this case the explanation of the ΔCp≠ term calculated according to the first mechanism is quite different. We comment on the alternative explanations of trends in activation parameters.

scholarly journals High temperature decreases the PIC / POC ratio and increases phosphorus requirements in <i>Coccolithus pelagicus</i> (Haptophyta)

2014 ◽  
Vol 11 (1) ◽  
pp. 1021-1051 ◽  
Author(s):  
A. C. Gerecht ◽  
L. Šupraha ◽  
B. Edvardsen ◽  
I. Probert ◽  
J. Henderiks
Keyword(s):  
Elevated Temperature ◽  
Growth Rates ◽  
Exponential Growth ◽  
Phosphorus Limitation ◽  
Photic Zone ◽  
P Limitation ◽  
P Content ◽  
Phytoplankton Communities ◽  
Global Biogeochemical Cycles ◽  
Coccolithus Pelagicus

Abstract. Rising ocean temperatures will likely increase stratification of the water column and reduce nutrient input into the photic zone. This will increase the likelihood of nutrient limitation in marine microalgae, leading to changes in the abundance and composition of phytoplankton communities, which in turn will affect global biogeochemical cycles. Calcifying algae, such as coccolithophores, influence the carbon cycle by fixing CO2 into particulate organic carbon (POC) through photosynthesis and into particulate inorganic carbon (PIC) through calcification. As calcification produces a net release of CO2, the ratio of PIC / POC determines whether coccolithophores act as a source (PIC / POC > 1) or a sink (PIC / POC < 1) of atmospheric CO2. We studied the effect of phosphorus (P-) limitation and temperature stress on the physiology and PIC / POC ratios of two subspecies of Coccolithus pelagicus. This large and heavily calcified species (PIC / POC generally > 1.5) is a major contributor to calcite export from the photic zone into deep-sea reservoirs. Phosphorus limitation did not influence exponential growth rates in either subspecies, but P-limited cells had significantly lower cellular P-content. A 5 °C temperature increase did not affect exponential growth rates either, but nearly doubled cellular P-content under both high and low phosphate availability. The PIC / POC ratios did not differ between P-limited and nutrient-replete cultures, but at elevated temperature (from 10 to 15 °C) PIC / POC ratios decreased by 40–60%. Our results suggest that elevated temperature may intensify P-limitation due to a higher P-requirement to maintain growth and POC production rates, possibly reducing abundances in a warmer ocean. Under such a scenario C. pelagicus may decrease its calcification rate relative to photosynthesis, resulting in PIC / POC ratios < 1 and favouring CO2-sequestration over release. Phosphorus limitation by itself is unlikely to cause changes in the PIC / POC ratio in this species.

scholarly journals Phosphate Acquisition Components of the Myxococcus xanthus Pho Regulon Are Regulated by both Phosphate Availability and Development

2008 ◽  
Vol 190 (6) ◽  
pp. 1997-2003 ◽  
Author(s):  
David E. Whitworth ◽  
Antony B. Holmes ◽  
Alistair G. Irvine ◽  
David A. Hodgson ◽  
David J. Scanlan
Keyword(s):  
Myxococcus Xanthus ◽  
P Uptake ◽  
P Availability ◽  
Pho Regulon ◽  
Down Regulation ◽  
Multicellular Development ◽  
P Acquisition ◽  
P Limitation ◽  
Highly Active ◽  
Low Concentrations

ABSTRACT In many organisms, phosphatase expression and phosphate (P) uptake are coordinately regulated by the Pho regulon. In Myxococcus xanthus P limitation initiates multicellular development, a process associated with changes in phosphatase expression. We sought here to characterize the link between P acquisition and development in this bacterium, an organism capable of preying upon other microorganisms as a sole nutrient source. M. xanthus seems to possess no significant internal P stores, as reducing the P concentration to less than 10 μM retarded growth within one doubling time. Pyrophosphate, polyphosphate, and glyceraldehyde-3-phosphate could support growth as sole P sources, although many other P-containing biomolecules could not (including nucleic acids and phospholipids). Several Pho regulon promoters were found to be highly active during vegetative growth, and P limitation specifically induced pstSCAB, AcPA1, and pho3 promoter activity and repressed pit expression. Enhanced pstSCAB and pho3 promoter activities in a phoP4 mutant (in the presence of high and low concentrations of P) suggested that PhoP4 acts as a repressor of these genes. However, in a phoP4 background, the activities of pstSCAB remained P regulated, suggesting that there is additional regulation by a P-sensitive factor. Initiation of multicellular development caused immediate down-regulation of Pho regulon genes and caused pstSCAB and pho3 promoter activities to become P insensitive. Hence, P acquisition components of the M. xanthus Pho regulon are regulated by both P availability and development, with developmental down-regulation overriding up-regulation by P limitation. These observations suggest that when development is initiated, subsequent changes in P availability become irrelevant to the population, which presumably has sufficient intrinsic P to ensure completion of the developmental program.

scholarly journals High temperature decreases the PIC / POC ratio and increases phosphorus requirements in <i>Coccolithus pelagicus</i> (Haptophyta)

2014 ◽  
Vol 11 (13) ◽  
pp. 3531-3545 ◽  
Author(s):  
A. C. Gerecht ◽  
L. Šupraha ◽  
B. Edvardsen ◽  
I. Probert ◽  
J. Henderiks
Keyword(s):  
High Temperature ◽  
Growth Rates ◽  
Exponential Growth ◽  
Temperature Increase ◽  
Phosphorus Limitation ◽  
Photic Zone ◽  
P Limitation ◽  
P Content ◽  
Phytoplankton Communities ◽  
Coccolithus Pelagicus

Abstract. Rising ocean temperatures will likely increase stratification of the water column and reduce nutrient input into the photic zone. This will increase the likelihood of nutrient limitation in marine microalgae, leading to changes in the abundance and composition of phytoplankton communities, which in turn will affect global biogeochemical cycles. Calcifying algae, such as coccolithophores, influence the carbon cycle by fixing CO2 into particulate organic carbon through photosynthesis (POC production) and into particulate inorganic carbon through calcification (PIC production). As calcification produces a net release of CO2, the ratio of PIC to POC production determines whether coccolithophores act as a source (high PIC / POC) or a sink (low PIC / POC) of atmospheric CO2. We studied the effect of phosphorus (P-) limitation and high temperature on the physiology and the PIC / POC ratio of two subspecies of Coccolithus pelagicus. This large and heavily calcified species is a major contributor to calcite export from the photic zone into deep-sea reservoirs. Phosphorus limitation did not influence exponential growth rates in either subspecies, but P-limited cells had significantly lower cellular P-content. One of the subspecies was subjected to a 5 °C temperature increase from 10 °C to 15 °C, which did not affect exponential growth rates either, but nearly doubled cellular P-content under both high and low phosphate availability. This temperature increase reduced the PIC / POC ratio by 40–60%, whereas the PIC / POC ratio did not differ between P-limited and nutrient-replete cultures when the subspecies were grown near their respective isolation temperature. Both P-limitation and elevated temperature significantly increased coccolith malformations. Our results suggest that a temperature increase may intensify P-limitation due to a higher P-requirement to maintain growth and POC production rates, possibly reducing abundances in a warmer ocean. Under such a scenario C. pelagicus may decrease its calcification rate relative to photosynthesis, thus favouring CO2 sequestration over release. It seems unlikely that P-limitation by itself causes changes in the PIC / POC ratio in this species.

Sign in / Sign up

Export Citation Format

Share Document