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Exercise 27
EXERCISES
OPTION 1. FIELD AND LABORATORY ANALYSES BY SEVERAL METHODS
1. Obtain several cores of surficial sediments from the central depression of a lake or reservoir, as
discussed earlier.
2. Divide the class into teams and perform as many of the analyses on the sediment samples as
possible. When samples at certain intervals within the sediments must be omitted, concentrate
efforts on the surface sediments and those at 5-cm intervals within the lower portion of the
core.
3. Reduce the data to summary form and present graphically.
4. Compare the results with the stratigraphy of organic matter, phosphorus, pigment degradation products, and changes in diatom and pollen distributions. Compare to historical
events that are known to have occurred in the immediate area around the lake.
5. Answer the questions following Option 4.
OPTION 2. ANALYSES ALONG GRADIENTS
1. Obtain several cores of surficial sediments from a gradient extending from the littoral zone to
the central depression of a lake. Alternatively, sample along the gradient of a reservoir from
the central depression near the dam towards the primary inlet stream or river.
2. Perform the analyses on the sediment cores as outlined in Option 1.
3. Answer the questions following Option 4.
OPTION 3. LABORATORY ANALYSES
1. Using the sediment cores provided by your instructor, perform the analyses as outlined in
Option 1.
2. Answer the questions following Option 4.
OPTION 4. OLIGOTROPHIC VERSUS EUTROPHIC LAKES
1. Collect surface cores from the central depression of a lake known to be unproductive and from
a lake that is extremely productive.
2. Perform the analyses on the sediment cores as outlined in Option 1.
3. Answer the following questions.
Questions
1. What do differences in organic matter content of sediment indicate?
2. Pigment degradation products have been used as an indicator of changes rates of
primary productivity of lakes [e.g., Wetzel (1970)]. What are some of the problems associated with such a direct interpretation?
3. How might one evaluate the proportion of organic matter or pigment degradation products
entering the sediments from allochthonous sources of the drainage basin versus those
produced autochthonously? What factors of the lake ecosystem lessen or accentuate the
proportion from allochthonous sources? [See Davis et al. (1985).]
4. The loading of a lake system with phosphorus has been correlated directly with the amount
of phosphorus deposited in the sediments. Is such a general correlation reasonable in view of
Exercise 27
EXERCISES
OPTION 1. FIELD AND LABORATORY ANALYSES BY SEVERAL METHODS
1. Obtain several cores of surficial sediments from the central depression of a lake or reservoir, as
discussed earlier.
2. Divide the class into teams and perform as many of the analyses on the sediment samples as
possible. When samples at certain intervals within the sediments must be omitted, concentrate
efforts on the surface sediments and those at 5-cm intervals within the lower portion of the
core.
3. Reduce the data to summary form and present graphically.
4. Compare the results with the stratigraphy of organic matter, phosphorus, pigment degradation products, and changes in diatom and pollen distributions. Compare to historical
events that are known to have occurred in the immediate area around the lake.
5. Answer the questions following Option 4.
OPTION 2. ANALYSES ALONG GRADIENTS
1. Obtain several cores of surficial sediments from a gradient extending from the littoral zone to
the central depression of a lake. Alternatively, sample along the gradient of a reservoir from
the central depression near the dam towards the primary inlet stream or river.
2. Perform the analyses on the sediment cores as outlined in Option 1.
3. Answer the questions following Option 4.
OPTION 3. LABORATORY ANALYSES
1. Using the sediment cores provided by your instructor, perform the analyses as outlined in
Option 1.
2. Answer the questions following Option 4.
OPTION 4. OLIGOTROPHIC VERSUS EUTROPHIC LAKES
1. Collect surface cores from the central depression of a lake known to be unproductive and from
a lake that is extremely productive.
2. Perform the analyses on the sediment cores as outlined in Option 1.
3. Answer the following questions.
Questions
1. What do differences in organic matter content of sediment indicate?
2. Pigment degradation products have been used as an indicator of changes rates of
primary productivity of lakes [e.g., Wetzel (1970)]. What are some of the problems associated with such a direct interpretation?
3. How might one evaluate the proportion of organic matter or pigment degradation products
entering the sediments from allochthonous sources of the drainage basin versus those
produced autochthonously? What factors of the lake ecosystem lessen or accentuate the
proportion from allochthonous sources? [See Davis et al. (1985).]
4. The loading of a lake system with phosphorus has been correlated directly with the amount
of phosphorus deposited in the sediments. Is such a general correlation reasonable in view of