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Exercise 26
Questions
1. What are the conditions favorable to the formation of a bacterial plate in the
chemolimnion of a meromictic lake?
2. The monimolimnion of a meromictic lake has been referred to as a "biological
desert." Is this correct? What is meant by a biological desert?
3. How is decomposition accomplished in a meromictic lake? How does this affect the
sediment record?
4. Think about the factors that initiate and maintain meromixis in lakes. Where might
you go to find a "new" meromictic lake? [See Hutchinson et al. (1970), Judd (1970),
and Walker and Likens (1975).]
BOG LAKES, BOGS, AND QUAKING BOGS
Bog lakes and bogs occur over large areas of the temperate region of the world. The
formation of bog (mire) ecosystems depends to a great extent on conditions of high
humidity and precipitation, which encourage the colonization of Sphagnum and other
mosses.
Sphagnum mosses common to bogs and bog lakes can act very effectively as cation
exchange columns. Cations such as calcium and magnesium are absorbed by the moss,
and, as a consequence, hydrogen ions and organic acids are released into the
environment (e.g., Anschutz and Gessner (1954), Clymo (1963, 1967), Burgess (1975),
and Glime et al. (1982)]. Sphagnum mosses grow in profusion around many bog lakes,
often encompassing the entire periphery with dense mats. These mats can have
profound effects on the ionic composition of precipitation and drainage water that
passes through the plants and, therefore, on the chemistry of the lake water.
The effectiveness of cationic exchange of Sphagnum can be demonstrated readily.
Collect about 40 living specimens (dead plants work also but not as well) of Sphagnum;
keep the plants moist with water from the site where the plants were collected. Measure
the pH, specific conductance, and calcium concentration of 300 ml of a calcium chloride
solution containing 1.0 meq/l (20 mgjl) calcium (see Exercises 7 and 8). Immerse the 40
plants of Sphagnum into the solution and swirl intermittently. Measure the pH, specific
conductance, and calcium concentration of the solution at 1-h intervals for several
hours.
Quaking bogs represent a particular development of bogs in relatively deep lake
basins of small area. The prolific development of Saphagnum mosses leads to rapid
accumulation of partially decomposed organic matter in the littoral areas. The dense
Sphagnum and accumulation of peat deposits can form a dense, spongy mat, which
grows all along the periphery toward the lake center, eventually encompassing the
entire surface.
Commonly, a concentric zonation of plant communities occurs landward from the
edge of the open water. Within the water there often are found certain submersed
angiosperms (certain Potamogeton and "carnivorous" Utricularia species) and floating
leaved macrophytes, such as the water lilies (Nuphar and Nymphaea). A variety of
interesting and unusual plants are common to the lake ward portion of the Sphagnum
mat: bog cotton (Eriophorum spp.), orchids, and insectivorous plants, such as the
pitcher plant (Sarracenia purpurea L.) and sundews (Drosera spp.). The flora of the mat
grades into increasing densities of sedges (especially Carex spp.), low shrubs, such as
poison sumac and the leatherleaf (Chamaedaphne), followed by the landward develop-
Exercise 26
Questions
1. What are the conditions favorable to the formation of a bacterial plate in the
chemolimnion of a meromictic lake?
2. The monimolimnion of a meromictic lake has been referred to as a "biological
desert." Is this correct? What is meant by a biological desert?
3. How is decomposition accomplished in a meromictic lake? How does this affect the
sediment record?
4. Think about the factors that initiate and maintain meromixis in lakes. Where might
you go to find a "new" meromictic lake? [See Hutchinson et al. (1970), Judd (1970),
and Walker and Likens (1975).]
BOG LAKES, BOGS, AND QUAKING BOGS
Bog lakes and bogs occur over large areas of the temperate region of the world. The
formation of bog (mire) ecosystems depends to a great extent on conditions of high
humidity and precipitation, which encourage the colonization of Sphagnum and other
mosses.
Sphagnum mosses common to bogs and bog lakes can act very effectively as cation
exchange columns. Cations such as calcium and magnesium are absorbed by the moss,
and, as a consequence, hydrogen ions and organic acids are released into the
environment (e.g., Anschutz and Gessner (1954), Clymo (1963, 1967), Burgess (1975),
and Glime et al. (1982)]. Sphagnum mosses grow in profusion around many bog lakes,
often encompassing the entire periphery with dense mats. These mats can have
profound effects on the ionic composition of precipitation and drainage water that
passes through the plants and, therefore, on the chemistry of the lake water.
The effectiveness of cationic exchange of Sphagnum can be demonstrated readily.
Collect about 40 living specimens (dead plants work also but not as well) of Sphagnum;
keep the plants moist with water from the site where the plants were collected. Measure
the pH, specific conductance, and calcium concentration of 300 ml of a calcium chloride
solution containing 1.0 meq/l (20 mgjl) calcium (see Exercises 7 and 8). Immerse the 40
plants of Sphagnum into the solution and swirl intermittently. Measure the pH, specific
conductance, and calcium concentration of the solution at 1-h intervals for several
hours.
Quaking bogs represent a particular development of bogs in relatively deep lake
basins of small area. The prolific development of Saphagnum mosses leads to rapid
accumulation of partially decomposed organic matter in the littoral areas. The dense
Sphagnum and accumulation of peat deposits can form a dense, spongy mat, which
grows all along the periphery toward the lake center, eventually encompassing the
entire surface.
Commonly, a concentric zonation of plant communities occurs landward from the
edge of the open water. Within the water there often are found certain submersed
angiosperms (certain Potamogeton and "carnivorous" Utricularia species) and floating
leaved macrophytes, such as the water lilies (Nuphar and Nymphaea). A variety of
interesting and unusual plants are common to the lake ward portion of the Sphagnum
mat: bog cotton (Eriophorum spp.), orchids, and insectivorous plants, such as the
pitcher plant (Sarracenia purpurea L.) and sundews (Drosera spp.). The flora of the mat
grades into increasing densities of sedges (especially Carex spp.), low shrubs, such as
poison sumac and the leatherleaf (Chamaedaphne), followed by the landward develop-