Aquatic Primary Productivity
Name________________Date_____
Type in the web address:
http://www.phschool.com/science/biology_place/labbench/lab12/concepts.html
This is called the Biology Page.
Follow the interactive lab, answering the questions on this handout as you go. When you get to the Sample
Problem under Analysis of Results, print out the chart, graph after you complete it. Take the Self-Quiz next
and print that out too. Hand in the completed questions and your print outs.
Key Concepts:
“Why did fish that I kept in an aquarium over my radiator die? An aerator was producing a constant stream of
bubbles, so they should have had plenty of oxygen.” At the end of this lab you should be able to answer this
question.
Dissolved Oxygen Availability
For each of the factors listed below, write how each affects the amount of oxygen dissolved in water:
1. Temperature2. Photosynthetic activity3. Decomposition activity4. Mixing and turbulence5. SalinityIdeal Conditions for Maximum Dissolved Oxygen
1. Which environment has the greater concentration of dissolved oxygen: salt water or fresh water?
2. Which environment has the greater concentration of dissolved oxygen: warm water (31°C) or cool water (18°C)?
3. Which environment has the greater concentration of dissolved oxygen: a clear pond or a pond with a heavy algal
mat? Explain.
Primary Productivity
1. Primary Productivity2. Gross Productivity3. Net ProductivityHow can we indirectly measure Primary Productivity? (3 different ways)
 1.

2.

3.
Measuring Primary Productivity
How can primary productivity be measured in an aquatic ecosystem? To answer this question, you must first
recall the equation for photosynthesis.
Write the equation here:
Of the three ways that Primary Productivity can be measured, which method will we be using in our lab to
measure P.P.?
Sample Problem
A biology student inadvertently removed all the screens and labels from the water-sampling bottles before he
measured the amount of dissolved oxygen. When he tested the unidentified bottles, he obtained the results shown
below.
The initial oxygen reading for this water was 4 mg O2/l. Based on the results predicted by the hypothesis that light
increases productivity, enter the letter of the bottle that corresponds to each light percentage. Then complete the rest
of the table AND graph the gross and net productivity for these data.
% Light
Bottle
Gross Productivity
Net Productivity
Light Bottle-dark bottle
Light Bottle-initial bottle
0
2
10
25
65
100
Graphing
Hints
2.
1. Be sure to label both x- and y-axes on the graph. Place the independent variable on the x-axis and
the dependent variable on the y-axis. (If you're not certain what a dependent variable or an
independent variable is, check the glossary.)
Be sure to mark units correctly on the graph — the interval between 2% light and 10% light is NOT the
same as the interval between 10% and 25%!