OPTION 2
OPTION 3
Diurnal Changes in Lake Systems
327
5. Construct quartile curves (Pennak, 1943) and plot the depth of the average individual for each
of the dominant species over the sampling period.
6. Calculate the amplitude and velocity of vertical migration of the average individual of each of
the dominant species of zooplankton.
7. Compare these results with diurnal plots of temperature, irradiance, chlorophyll, and
dissolved oxygen concentrations. Three-dimensional graph paper (e.g., National 12-186
Isometric-Orthographic) is useful in illustrating these data with depth and time.
On samples and data provided by the instructor, enumerate the zooplankton and make
calculations and graphs as called for in parts 5 through 7 of Option 1.
From data presented in Table 25.2, make calculations and graphs as called for in parts 5 through
7 of Option 1.
Problems and Questions
1. Measure the diurnal changes in spectral fractions of underwater irradiance, using a
photometer with narrow-band wavelength filters (see Exercise 2). Plot these light distributions versus depth. Does a correlation exist between light distribution changes and the
diurnal migratory patterns of zooplankton?
2. Do relationships exist in your data between the vertical amplitude of migration and the
distribution of species of zooplankton and the vertical stratification of temperature and
dissolved oxygen concentrations?
3. Were significant diurnal changes in the vertical pigment distribution observed? Were these
correlated with the migratory patterns of the zooplankton?
4. Determine the in situ grazing rates of zooplankton (if equipment is available; see
Exercise 15). How do the rates of ingestion change diurnally?
5. Collect samples of the phytoplankton at the same strata over the diurnal period (see
Exercise 10). Enumerate, identify to genera, and categorize the algae into size classes (e.g., 1
to 30/lm, 30 to 60/lm, > 60 /lm in largest dimension). Compare changes in algal distribution
diurnally and zooplankton migratory behavior. Did any ofthe algal populations, especially
the blue-green algae, appear to migrate diurnally? Why?
6. What are the major disadvantages of the average individual and quartile methods of
diagramming zooplankton movement? What are the advantages?
7. Would you expect to observe similar vertical movement of live zooplankton in the
laboratory if maintained in darkness for 24 h? Why?
8. How might high-frequency sonar be used to follow the movement of zooplankton in lakes?
9. What type of sampler would be better to use in a study of the vertical migration of
zooplankton? Why?
10. What is meant by reverse migration? Nocturnal migration? Which migratory patterns are
shown by the organisms in Table 25.2?
Apparatus and Supplies
1. Zooplankton sampling devices (see Exercise 11).
2. Preservatives, bottles, and data records (see Exercise 11).
3. Instruments for measuring temperature and irradiance (Exercise 2).
OPTION 3
Diurnal Changes in Lake Systems
327
5. Construct quartile curves (Pennak, 1943) and plot the depth of the average individual for each
of the dominant species over the sampling period.
6. Calculate the amplitude and velocity of vertical migration of the average individual of each of
the dominant species of zooplankton.
7. Compare these results with diurnal plots of temperature, irradiance, chlorophyll, and
dissolved oxygen concentrations. Three-dimensional graph paper (e.g., National 12-186
Isometric-Orthographic) is useful in illustrating these data with depth and time.
On samples and data provided by the instructor, enumerate the zooplankton and make
calculations and graphs as called for in parts 5 through 7 of Option 1.
From data presented in Table 25.2, make calculations and graphs as called for in parts 5 through
7 of Option 1.
Problems and Questions
1. Measure the diurnal changes in spectral fractions of underwater irradiance, using a
photometer with narrow-band wavelength filters (see Exercise 2). Plot these light distributions versus depth. Does a correlation exist between light distribution changes and the
diurnal migratory patterns of zooplankton?
2. Do relationships exist in your data between the vertical amplitude of migration and the
distribution of species of zooplankton and the vertical stratification of temperature and
dissolved oxygen concentrations?
3. Were significant diurnal changes in the vertical pigment distribution observed? Were these
correlated with the migratory patterns of the zooplankton?
4. Determine the in situ grazing rates of zooplankton (if equipment is available; see
Exercise 15). How do the rates of ingestion change diurnally?
5. Collect samples of the phytoplankton at the same strata over the diurnal period (see
Exercise 10). Enumerate, identify to genera, and categorize the algae into size classes (e.g., 1
to 30/lm, 30 to 60/lm, > 60 /lm in largest dimension). Compare changes in algal distribution
diurnally and zooplankton migratory behavior. Did any ofthe algal populations, especially
the blue-green algae, appear to migrate diurnally? Why?
6. What are the major disadvantages of the average individual and quartile methods of
diagramming zooplankton movement? What are the advantages?
7. Would you expect to observe similar vertical movement of live zooplankton in the
laboratory if maintained in darkness for 24 h? Why?
8. How might high-frequency sonar be used to follow the movement of zooplankton in lakes?
9. What type of sampler would be better to use in a study of the vertical migration of
zooplankton? Why?
10. What is meant by reverse migration? Nocturnal migration? Which migratory patterns are
shown by the organisms in Table 25.2?
Apparatus and Supplies
1. Zooplankton sampling devices (see Exercise 11).
2. Preservatives, bottles, and data records (see Exercise 11).
3. Instruments for measuring temperature and irradiance (Exercise 2).