Biology Labs Page 7
ECOLOGY LAB - COMPARATIVE AQUATIC ECOSYSTEM ECOLOGY
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Handout On Plankton Metabolism.
Data Sheet for light-and-dark bottle method for measuring aquatic metabolism.
SITE: Bottle Sample Percent
No. mg oxygen/L Saturation
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Initial
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24-h Clear
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24-h Dark
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SITE: Bottle Sample Percent
No. mg oxygen/L Saturation
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Initial
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24-h Clear
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24-h Dark
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SITE: Bottle Sample Percent
No. mg oxygen/L Saturation
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Initial
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24-h Clear
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24-h Dark
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Calculations of gross and net productivity and respiration rate.
To convert your metabolic rates from units of volume, mg
O2/(liter*day), to units of water surface area, g O2/(m2*day), use the
relation: 1 mg O2/liter is equal to 1 g O2/m2. To calculate the efficiency
of net production to solar radiation assume (1) solar radiation input is 3500
kcal/(m2*day), (2) 1 g O2 produced in photosynthesis has a corresponding 1 g
of organic matter produced, and (3) 1 g organic matter is equivalent to about
4 kcal energy. Remember the sun shines approximately 0.5 days per day.
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Volume rate Area rate
SITE: mg O2/(L*d) g O2/(m2*d)
Net production = Clear minus initial =
Respiration = Initial minus dark =
Gross production = Clear minus dark =
P/R ratio of the plankton community =
Efficiency of net production to solar radiation =
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Volume rate Area rate
SITE: mg O2/(L*d) g O2/(m2*d)
Net production = Clear minus initial =
Respiration = Initial minus dark =
Gross production = Clear minus dark =
P/R ratio of the plankton community =
Efficiency of net production to solar radiation =
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Volume rate Area rate
SITE: mg O2/(L*d) g O2/(m2*d)
Net production = Clear minus initial =
Respiration = Initial minus dark =
Gross production = Clear minus dark =
P/R ratio of the plankton community =
Efficiency of net production to solar radiation =
Solubility of Dissolved Oxygen in Water.
When the partial pressure of oxygen in water is the same as the partial
pressure in the atmosphere, the water is said to be "saturated", i.e. it is
at equilibrium. Below is a table for saturation in fresh water and two
nomograms, one for fresh and one for saline water. Learn how to use both to
determine saturation at a given temperature (and salinity in saline water).
Once you have calculated the concentration of oxygen at saturation, it
is a small step to convert the dissolved oxygen concentration from milligrams
per liter to percent of saturation. Percent saturation can be more or less
than 100%. The extent to which it departs from 100% reveals how far it
diverges from equilibrium with the atmosphere.
Highly productive aquatic ecosystems are seldom at saturation. In
fact, the may exceed 100% during certain times of the day and fall below 100%
on the same day.
Table. Solubility of oxygen in water at 760 mm atmospheric pressure for
fresh and saline waters.
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mg O2/L mg O2/L
Temp. (xC) Fresh Sea Temp. (xC) Fresh Sea
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0 14.6 11.06
1 14.2 10.78 16 10.0 7.90
2 13.8 10.52 17 9.7 7.76
3 13.5 10.27 18 8.5 7.62
4 13.1 10.03 19 9.4 7.49
5 12.8 9.81 20 9.2 7.37
6 12.5 9.59 21 9.0 7.24
7 12.2 9.38 22 8.8 7.12
8 11.9 9.18 23 8.7 6.99
9 11.6 8.99 24 8.5 6.87
10 11.3 8.81 25 8.4 6.74
11 11.1 8.64 26 8.2 6.63
12 10.8 8.48 27 8.1 6.52
13 10.6 8.32 28 7.9 6.41
14 10.4 8.17 29 7.8 6.30
15 10.2 8.03 30 7.6 6.19
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