176
OPTION 2.
Exercise 11
6. Compare statistically the results for the various collection devices. Which one was more
efficient? Which collector provided the most representative sample?
B. Site Sampling Error
1. Using the collection device judged to be the best on the basis of the test above (part A),
obtain five separate samples from a depth of 3 m at some location on the lake.
2. Identify species and enumerate.
3. Calculate the mean, standard error of the mean, and 95'1;, confidence limits for the major
specIes.
C. Horizontal Distribution and Variability
1. Using the collection device judged to be the best on the basis of the above test (part A),
collect samples, from a depth of 3 m at five or more randomly located positions on the lake.
Move in a random sequence to each of these positions, but collect the entire sequence of
samples in as short a time as possible. Why? Alternatively, obtain samples from the same
depth at prescribed location along a transect across the lake.
2. Identify species and enumerate.
3. Compute the mean, variance, and chi-square values for the major species collected at the
various locations. Determine whether the population was distributed randomly,
contagiously, or uniformly.
4. Based on the mean values, calculate the total number of zooplankton at the 3-m depth.
Compute the 95% confidence limits. Would one station have been sufficient to quantitatively
characterize the zooplankton at the 3-m depth?
5. Answer the questions and problems following Option 2.
1. Use zooplankton samples provided by the instructor.
2. Assume that the samples were collected with a Clarke-Bumpus plankton sampler fitted with
a # 10 silk net. The device was towed through the water at a depth of 3 m for exactly 3 min.
Calibration shows that 4.11 of water/rev pass through the sampling device under these
conditions. Perform the calculations called for above in parts A-3, B, and C (Option 1).
3. Answer the following questions and problems.
Questions and Problems
1. Evaluate the various sources of error involved in collection and enumeration of zooplankton.
2. What is the effect of water movements such as Langmuir circulation on the collection
efficiency of zooplankton?
3. What do you think causes the patchy nature of zooplankton in lakes?
4. Compare the advantages and disadvantages of a towed, metered-type sampler with a
volumetric sampler.
5. Why should the Van Dorn sampler be closed immediately when sampling zooplankton
at some depth?
6. What is "back pressure" in a plankton net?
7. How should sampling procedures vary from littoral to limnetic regions and throughout a
24-h period to obtain quantitative samples?
8. Why should plankton samples be dried at temperatures less than 105'C when obtaining
OPTION 2.
Exercise 11
6. Compare statistically the results for the various collection devices. Which one was more
efficient? Which collector provided the most representative sample?
B. Site Sampling Error
1. Using the collection device judged to be the best on the basis of the test above (part A),
obtain five separate samples from a depth of 3 m at some location on the lake.
2. Identify species and enumerate.
3. Calculate the mean, standard error of the mean, and 95'1;, confidence limits for the major
specIes.
C. Horizontal Distribution and Variability
1. Using the collection device judged to be the best on the basis of the above test (part A),
collect samples, from a depth of 3 m at five or more randomly located positions on the lake.
Move in a random sequence to each of these positions, but collect the entire sequence of
samples in as short a time as possible. Why? Alternatively, obtain samples from the same
depth at prescribed location along a transect across the lake.
2. Identify species and enumerate.
3. Compute the mean, variance, and chi-square values for the major species collected at the
various locations. Determine whether the population was distributed randomly,
contagiously, or uniformly.
4. Based on the mean values, calculate the total number of zooplankton at the 3-m depth.
Compute the 95% confidence limits. Would one station have been sufficient to quantitatively
characterize the zooplankton at the 3-m depth?
5. Answer the questions and problems following Option 2.
1. Use zooplankton samples provided by the instructor.
2. Assume that the samples were collected with a Clarke-Bumpus plankton sampler fitted with
a # 10 silk net. The device was towed through the water at a depth of 3 m for exactly 3 min.
Calibration shows that 4.11 of water/rev pass through the sampling device under these
conditions. Perform the calculations called for above in parts A-3, B, and C (Option 1).
3. Answer the following questions and problems.
Questions and Problems
1. Evaluate the various sources of error involved in collection and enumeration of zooplankton.
2. What is the effect of water movements such as Langmuir circulation on the collection
efficiency of zooplankton?
3. What do you think causes the patchy nature of zooplankton in lakes?
4. Compare the advantages and disadvantages of a towed, metered-type sampler with a
volumetric sampler.
5. Why should the Van Dorn sampler be closed immediately when sampling zooplankton
at some depth?
6. What is "back pressure" in a plankton net?
7. How should sampling procedures vary from littoral to limnetic regions and throughout a
24-h period to obtain quantitative samples?
8. Why should plankton samples be dried at temperatures less than 105'C when obtaining