Decomposition: Relative Bacterial Heterotrophic Activity
275
approximates the natural substrate concentration when K t is small, as often is,
but not always, the case. Since Sn is seldom known, interpretation ofthe (K t + Sn)
value is difficult and provides only limited information about the bacterial
community.
c. To the turnover time in hours (the ordinate intercept), is the time required for
complete removal ofthe natural substrate by the microflora, assuming a constant
rate of replacement of the substrate.
3. The counts per minute (cpm) for each filter (assimilation) and corresponding filter
paper and solution of the cup (mineralization to CO 2 ) and the blanks (killed control)
are converted to disintegrations per minute (dpm) by correcting for quench and
counting efficiency. A rigorous treatment would also include an analysis of the
trapping efficiency of CO 2 ,
4. Determine the total dpm:
Idpm = (dpma - dpmba) + (dpmm - dpmbm)
where dpma = mean dpm assimilated (corrected counts of filters), dpmba = dpm of
killed control filter, dpmm = mean dpm mineralized (corrected counts of filter paper
and solution in the cup), and dpmbm = dpm of killed control filter paper in the cup.
5. Plot v in /lg/h on the ordinate versus A, using Eq. 4 to determine whether a linear
(uptake proportional to substrate concentration) or a hyperbolic (uptake velocity
approaches a saturation level) relationship occurred. Use the following definitions:
a. dpm added to the sample is known (see p. 278).
b. F = total sample dpm/dpm added.
c. t = hours of incubation.
d. A = /lg of substrate added (see p. 278).
e. Sn is assumed to be 5/lg/1 in this example.
6. Calculate t/F and plot on the ordinate against A. Draw the line of best fit (a least
square fit is preferable), and determine (Eq. 5):
EXERCISES
a. V max from the slope (1 IV max) in /lg/l/h.
b. (K t + Sn) from the x intercept, which equals - (K t + Sn).
c. T t from the y intercept in hours. Since A = 0 at this point, from Eq. 3,
Tt = K t + Sn/Vmax·
7. Calculate the ratio of mineralization (M) of the substrate to assimilation (As):
M/As = (dpmm -=-dpmbm)
(dpma - dpm ba )
and determine the percentage of the substrate mineralized to CO 2 :
OPTION 1. VERTICAL DISTRIBUTION OF ACTIVITY
1. Collect water samples from the epi-, meta-, and hypolimnion of the central area of a lake or
reservoir with a clean Van Dorn or similar nonmetallic water sampler. Place the samples into
275
approximates the natural substrate concentration when K t is small, as often is,
but not always, the case. Since Sn is seldom known, interpretation ofthe (K t + Sn)
value is difficult and provides only limited information about the bacterial
community.
c. To the turnover time in hours (the ordinate intercept), is the time required for
complete removal ofthe natural substrate by the microflora, assuming a constant
rate of replacement of the substrate.
3. The counts per minute (cpm) for each filter (assimilation) and corresponding filter
paper and solution of the cup (mineralization to CO 2 ) and the blanks (killed control)
are converted to disintegrations per minute (dpm) by correcting for quench and
counting efficiency. A rigorous treatment would also include an analysis of the
trapping efficiency of CO 2 ,
4. Determine the total dpm:
Idpm = (dpma - dpmba) + (dpmm - dpmbm)
where dpma = mean dpm assimilated (corrected counts of filters), dpmba = dpm of
killed control filter, dpmm = mean dpm mineralized (corrected counts of filter paper
and solution in the cup), and dpmbm = dpm of killed control filter paper in the cup.
5. Plot v in /lg/h on the ordinate versus A, using Eq. 4 to determine whether a linear
(uptake proportional to substrate concentration) or a hyperbolic (uptake velocity
approaches a saturation level) relationship occurred. Use the following definitions:
a. dpm added to the sample is known (see p. 278).
b. F = total sample dpm/dpm added.
c. t = hours of incubation.
d. A = /lg of substrate added (see p. 278).
e. Sn is assumed to be 5/lg/1 in this example.
6. Calculate t/F and plot on the ordinate against A. Draw the line of best fit (a least
square fit is preferable), and determine (Eq. 5):
EXERCISES
a. V max from the slope (1 IV max) in /lg/l/h.
b. (K t + Sn) from the x intercept, which equals - (K t + Sn).
c. T t from the y intercept in hours. Since A = 0 at this point, from Eq. 3,
Tt = K t + Sn/Vmax·
7. Calculate the ratio of mineralization (M) of the substrate to assimilation (As):
M/As = (dpmm -=-dpmbm)
(dpma - dpm ba )
and determine the percentage of the substrate mineralized to CO 2 :
OPTION 1. VERTICAL DISTRIBUTION OF ACTIVITY
1. Collect water samples from the epi-, meta-, and hypolimnion of the central area of a lake or
reservoir with a clean Van Dorn or similar nonmetallic water sampler. Place the samples into