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

scholarly journals Growth and specific P-uptake rates of bacterial and phytoplanktonic communities in the Southeast Pacific (BIOSOPE cruise)

2007 ◽  
Vol 4 (6) ◽  
pp. 941-956 ◽  
Author(s):  
S. Duhamel ◽  
T. Moutin ◽  
F. Van Wambeke ◽  
B. Van Mooy ◽  
P. Rimmelin ◽  
...  
Keyword(s):  
Heterotrophic Bacteria ◽  
P Uptake ◽  
Low Light ◽  
Size Fractions ◽  
Cell Abundance ◽  
Abundance Estimate ◽  
Uptake Rates ◽  
Wide Range ◽  
Southeast Pacific ◽  
Specific Growth Rates

Abstract. Predicting heterotrophic bacteria and phytoplankton specific growth rates (μ ) is of great scientific interest. Many methods have been developed in order to assess bacterial or phytoplankton μ. One widely used method is to estimate μ from data obtained on biomass or cell abundance and rates of biomass or cell production. According to Kirchman (2002), the most appropriate approach for estimating μ is simply to divide the production rate by the biomass or cell abundance estimate. Most methods using this approach to estimate μ are based on carbon (C) incorporation rates and C biomass measurements. Nevertheless it is also possible to estimate μ using phosphate (P) data. We showed that particulate phosphate (PartP) can be used to estimate biomass and that the P uptake rate to PartP ratio can be employed to assess μ. Contrary to other methods using C, this estimator does not need conversion factors and provides an evaluation of μ for both autotrophic and heterotrophic organisms. We report values of P-based μ in three size fractions (0.2–0.6; 0.6–2 and >2 μm) along a Southeast Pacific transect, over a wide range of P-replete trophic status. P-based μ values were higher in the 0.6–2 μm fraction than in the >2 μm fraction, suggesting that picoplankton-sized cells grew faster than the larger cells, whatever the trophic regime encountered. Picoplankton-sized cells grew significantly faster in the deep chlorophyll maximum layer than in the upper part of the photic zone in the oligotrophic gyre area, suggesting that picoplankton might outcompete >2 μm cells in this particular high-nutrient, low-light environment. P-based μ attributed to free-living bacteria (0.2-0.6 μm) and picoplankton (0.6–2 μm) size-fractions were relatively low (0.11±0.07 d−1 and 0.14±0.04 d−1, respectively) in the Southeast Pacific gyre, suggesting that the microbial community turns over very slowly.

scholarly journals Growth and specific P-uptake rates of bacterial and phytoplanktonic communities in the Southeast Pacific (BIOSOPE cruise)

2007 ◽  
Vol 4 (3) ◽  
pp. 2027-2068 ◽  
Author(s):  
S. Duhamel ◽  
T. Moutin ◽  
F. Van Wambeke ◽  
B. Van Mooy ◽  
P. Rimmelin ◽  
...  
Keyword(s):  
Heterotrophic Bacteria ◽  
P Uptake ◽  
Low Light ◽  
Size Fractions ◽  
Cell Abundance ◽  
Abundance Estimate ◽  
Uptake Rates ◽  
Wide Range ◽  
Southeast Pacific ◽  
P Uptake Rates

Abstract. Predicting heterotrophic bacteria and phytoplankton growth rates (μ) is of great scientific interest. Many methods have been developed in order to assess bacterial or phytoplankton μ. One widely used method is to estimate μ from data obtained on biomass or cell abundance and rates of biomass or cell production. According to Kirchman (2002), the most appropriate approach for estimating μ is simply to divide the production rate by the biomass or cell abundance estimate. Most of the methods using this approach are expressed using carbon (C) data. Nevertheless it is also possible to estimate μ using phosphate (P) data. We showed that particulate phosphate (PartP) can be used to estimate biomass and that the phosphate uptake rate to PartP ratio can be employed to assess μ. Contrary to other methods using C, this estimator does not need conversion factors and provides an evaluation of μ for both autotrophic and heterotrophic organisms. We report values of P-based μ in three size fractions (0.2–0.6; 0.6–2 and >2 μm) along a Southeast Pacific transect, over a wide range of P-replete trophic status. P-based μ values were higher in the 0.6–2 μm fraction than in the >2 μm fraction, suggesting that picoplankton-sized cells grew faster than the larger cells, whatever the trophic regime encountered. Picoplankton-sized cells grew significantly faster in the deep chlorophyll maximum layer than in the upper part of the photic zone in the oligotrophic gyre area, suggesting that picoplankton might outcompete >2 μm cells in this particular high-nutrient, low-light environment. P-based μ attributed to free-living bacteria (0.2–0.6 μm) and picoplankton (0.6–2 μm) size-fractions were relatively low (0.11±0.07 d−1 and 0.14±0.04 d−1, respectively) in the Southeast Pacific gyre, suggesting that the microbial community turns over very slowly.

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.

Growth ofPseudotsuga menziesiiandTsuga heterophyllaseedlings along a light gradient: resource allocation and morphological acclimation

1997 ◽  
Vol 75 (9) ◽  
pp. 1424-1435 ◽  
Author(s):  
D. Mailly ◽  
J. P. Kimmins
Keyword(s):  
Leaf Morphology ◽  
Biomass Accumulation ◽  
Tsuga Heterophylla ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Low Light ◽  
Growing Seasons ◽  
Light Levels ◽  
Light Gradient ◽  
Relative Light Intensity

Silvicultural alternatives that differ in the degree of overstory removal may create shady environments that will be problematic for the regeneration of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). Gradients of light in the field were used to compare mortality, growth, and leaf morphological acclimation of two conifer species of contrasting shade tolerances: Douglas-fir and western hemlock (Tsuga heterophylla (Raf.) Sarg.). Results after two growing seasons indicated that Douglas-fir mortality occurred mainly at relative light intensity (RLI) below 20%, while western hemlock mortality was evenly distributed along the light gradient. Height, diameter, and biomass of the planted seedlings increased with increasing light for both species but at different rates, and maximum biomass accumulation always occurred in the open. Douglas-fir allocated more resources to stem biomass than western hemlock, which accumulated more foliage biomass. Increases in specific leaf area for Douglas-fir seedlings occurred at RLI ≤ 0.4 and red/far red (R/FR) ratio ≤ 0.6, which appear to be the minimal optimum light levels for growth. Conversely, western hemlock seedlings adjusted their leaf morphology in a more regular pattern, and changes were less pronounced at low light levels. These results, along with early mortality results for Douglas-fir, suggest that the most successful way to artificially regenerate this species may be by allowing at least 20% of RLI for ensuring survival and at least 40% RLI for optimum growth. Key words: light, light quality, leaf morphology, acclimation.

Photoinhibition of DCMU-Enhanced Fluorescence in Lake Ontario Phytoplankton

1987 ◽  
Vol 44 (12) ◽  
pp. 2144-2154 ◽  
Author(s):  
M. Putt ◽  
G. P. Harris ◽  
R. L. Cuhel
Keyword(s):  
Vertical Mixing ◽  
Natural Populations ◽  
Bright Light ◽  
Euphotic Zone ◽  
Lake Ontario ◽  
Enhanced Fluorescence ◽  
Low Light ◽  
Light Levels ◽  
Phosphorus Status

Measurement of 1-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) enhanced fluorescence (FDCMU) suggested that photoinhibition of photosynthesis was frequently an artifact of in situ bottle incubations in Lake Ontario phytoplankton. In a seasonal study, FDCMU of all populations was depressed by bright light in an incubator. However, when the euphotic zone did not exceed the depth of the mixed layer, vertical transport of phytoplankton into either low-light or dark regions apparently allowed reversal of photoinhibition of FDCMU. Advantages of FDCMU as a bioassay of vertical mixing include rapidity of response time, ease of measurement in the field, and insensitivity of this parameter to changes in phosphorus status of the population. Because of seasonal changes in the photoadaptive response of natural populations, the rate constants and threshold light levels required to cause the response must be determined at each use if the method is to be quantitative.

Image classification at low light levels

1986 ◽  
Vol 3 (12) ◽  
pp. 2179 ◽  
Author(s):  
Miles N. Wernick ◽  
G. Michael Morris
Keyword(s):  
Image Classification ◽  
Low Light ◽  
Light Levels
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