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Exercise 10
4. Estimate the amount of algal carbon biomass from your estimates of cellular volume.
5. Using samples provided by your instructor, determine the amount of algal pigment biomass
(chlorophylls, carotenoids) and phaeopigment concentrations from water samples of a profile
from, or within, a lake or several lakes or along a stream gradient. From replicated samples,
determine the coefficients of variance.
Questions
1. How does the vertical profile of algal species and biomass compare to the thermal stratification?
2. You may have observed a concentration of algae in the metalimnion. What factors may
have caused this?
3. When significant numbers and biomass of algae are found in the hypolimnion, what does
this indicate about their well-being and metabolic state? How might this question be
addressed better?
4. How would you rate the various methods for enumeration of algae relative to their
practicality, ease, precision, accuracy, and reliability?
5. If horizontal variations in distribution of biomass were observed between the open water,
littoral areas, and inlet areas, how might you evaluate experimentally the causal factors
regulating such a spatial pattern?
6. Is it reasonable to make a comparison of the algal species composition and biomass
between two lake ecosystems sampled at this particular time of year? Support your answer.
7. How frequently would one have to sample a freshwater ecosystem to evaluate accurately
the population dynamics ofthe phytoplankton over an annual period? Why? Which criteria
are important in regulating change?
8. How do you explain the observed differences in the ratios of active algal pigments to phaeopigment degradation products?
9. How could the observed differences in the vertical comparison of algal numbers and
pigment biomass (corrected for phaeopigments) be explained? Does the relationship
between algal volume and corrected chlorophyll concentrations improve the relationship?
to. What is the relationship between the transmission and absorption of light?
11. How would you determine the sinking rates of algae in the counting chamber? Why should
drafts be avoided when settling plankton?
12. What kind (species) of algae would you expect to find at depth in a brown-water, bog
lake? Why?
13. Why are pigment extracts stored in the dark'!
14. Why store algal samples in darkness or use amber polyethylene bottles? What is actually
happening when an algal sample is "preserved"?
15. What are the major problems in attempting to determine the volume of an algal cell?
Colony?
Apparatus and Supplies
1. Water samplers, e.g., Van Dorn water bottle.
2. 500-ml or 1-liter amber polyethylene bottles.
3. Preservatives:
a. Lugol's fixative: Dissolve to g 12 (pure iodine; caution: toxic) and 20 g KI in 200-ml
distilled water and 20 ml concentrated glacial acetic acid. Store in ground glassstoppered, darkened bottle.
b. 50% glutaraldehyde filtered through glass fiber filters of small pore size (e.g., 0.5/lm) to
remove common particulate contaminants. Caution: very toxic. Concentrated glutaraldehyde has a limited shelf-life (ca. six months).
c. Buffered formalin solution: Buffer 40% formaldehyde with sufficient sodium acetate or
hexamethylentetramine to yield a final pH of 7.5 to 8.0 in the preserved sample.
Exercise 10
4. Estimate the amount of algal carbon biomass from your estimates of cellular volume.
5. Using samples provided by your instructor, determine the amount of algal pigment biomass
(chlorophylls, carotenoids) and phaeopigment concentrations from water samples of a profile
from, or within, a lake or several lakes or along a stream gradient. From replicated samples,
determine the coefficients of variance.
Questions
1. How does the vertical profile of algal species and biomass compare to the thermal stratification?
2. You may have observed a concentration of algae in the metalimnion. What factors may
have caused this?
3. When significant numbers and biomass of algae are found in the hypolimnion, what does
this indicate about their well-being and metabolic state? How might this question be
addressed better?
4. How would you rate the various methods for enumeration of algae relative to their
practicality, ease, precision, accuracy, and reliability?
5. If horizontal variations in distribution of biomass were observed between the open water,
littoral areas, and inlet areas, how might you evaluate experimentally the causal factors
regulating such a spatial pattern?
6. Is it reasonable to make a comparison of the algal species composition and biomass
between two lake ecosystems sampled at this particular time of year? Support your answer.
7. How frequently would one have to sample a freshwater ecosystem to evaluate accurately
the population dynamics ofthe phytoplankton over an annual period? Why? Which criteria
are important in regulating change?
8. How do you explain the observed differences in the ratios of active algal pigments to phaeopigment degradation products?
9. How could the observed differences in the vertical comparison of algal numbers and
pigment biomass (corrected for phaeopigments) be explained? Does the relationship
between algal volume and corrected chlorophyll concentrations improve the relationship?
to. What is the relationship between the transmission and absorption of light?
11. How would you determine the sinking rates of algae in the counting chamber? Why should
drafts be avoided when settling plankton?
12. What kind (species) of algae would you expect to find at depth in a brown-water, bog
lake? Why?
13. Why are pigment extracts stored in the dark'!
14. Why store algal samples in darkness or use amber polyethylene bottles? What is actually
happening when an algal sample is "preserved"?
15. What are the major problems in attempting to determine the volume of an algal cell?
Colony?
Apparatus and Supplies
1. Water samplers, e.g., Van Dorn water bottle.
2. 500-ml or 1-liter amber polyethylene bottles.
3. Preservatives:
a. Lugol's fixative: Dissolve to g 12 (pure iodine; caution: toxic) and 20 g KI in 200-ml
distilled water and 20 ml concentrated glacial acetic acid. Store in ground glassstoppered, darkened bottle.
b. 50% glutaraldehyde filtered through glass fiber filters of small pore size (e.g., 0.5/lm) to
remove common particulate contaminants. Caution: very toxic. Concentrated glutaraldehyde has a limited shelf-life (ca. six months).
c. Buffered formalin solution: Buffer 40% formaldehyde with sufficient sodium acetate or
hexamethylentetramine to yield a final pH of 7.5 to 8.0 in the preserved sample.