Light and Temperature
29
compensation depth was determined to be 1 % of surface light, how much volume of water
would be available for its growth in the different lakes?
3. How would this situation change for a particular shade-adapted blue-green alga that can
survive at < 0.1 % of surface irradiance?
4. If the crustacean M ysis were to require cold temperatures ( < 10°C) and were adapted to a
strictly blue photoenvironment, would this organism likely survive in the lake conditions
you observed?
5. Compare the Secchi disc transparencies using several colored discs to vertical extinction
coefficients within several spectral ranges as determined with an underwater photometer
with narrow-band spectral filters. Compare your results with those of Stepanek (1959) and
Elster and Stepanek (1967). The spectral analysis of paint often is available from paint
manufacturers.
6. Why do clean lakes appear blue on a clear day?
7. Which wavelengths are the most important in heating the surface waters of a lake? What
percentage of the total spectrum is found at these wavelengths?
8. What wavelengths penetrate most deeply in a dystrophic bog lake heavily stained with large
concentrations of dissolved organic compounds?
9. Why do aquatic plants appear green?
10. What is the "greenhouse effect"?
Apparatus and Supplies
1. Thermometers and maximum-minimum thermometers, calibrated against a standard
reference thermometer; calibrated, weighted line.
2. Reversing thermometer, if available.
3. Underwater electrical thermometer with calibrated cable of sufficient length to reach
maximum depths of lakes and streams under study.
4. Underwater photometer with various sensor units (e.g., Li-Cor, Inc., Lincoln, NE, or Kahl
Scientific Instrument Corp., EI Cajon, CAl; narrow-band spectral filters.
5. Four-n underwater photometer, if available (e.g., Li-Cor Inc., Lincoln, NE).
6. Secchi disc, 20 cm in diameter, weighted, with calibrated, nonstretchable line. White on
upper surface or divided into quadrants, painted so that two quadrants directly opposing
each other are white and the interv;:ning quadrants are black. (Little difference has been
found between either type of Secchi disc; most workers use all-white discs.) Lower surface
should be painted black.
7. Van Dorn or Kemmerer water sampler and clean polyethylene bottles.
8. Spectrophotometer, ratio-recording and scanning if available, with long pathlength cells (5
to lOcm).
9. Turbidity solutions:
a. Stock 1. 1.000 g hydrazine sulfate [(NH 2 )2· H2S04] dissolved in distilled water in a
volumetric flask to make 100m!.
b. Stock 2. 10.00 g hexamethylenetetramine [(CH2)6N4] dissolved in distilled water in a
volumetric flask to make 100 m!.
c. Standard: To a 100-ml volumetric flask, mix 5.0 ml of Stock Solution 1 with 5.0 ml of
Stock 2. Allow to stand 24 h at room temperature and then dilute to 100 ml and mix. The
turbidity of this suspension is 400 units. Store no longer than a week. A dilution of
10.00 ml of this standard to 100 ml with distilled water yields the standard turbidity
suspension of 40 units. A series of more dilute standards are then made to establish the
calibration curve.
10. Turbidimeter, if available (e.g., Kahl Scientific Instrument Co., EI Cajon, CAl.
11. Color solutions: Serial dilution from 5 to 1000 platinum color units, sealed in permanent
vials or glass ampules. 1000 Pt units = the color resulting from 2.492 g potassium hexachloroplatinate (K 2 PtCI 6 ), 2.000 g cobaltic chloride hexahydrate (CoCl l ·6H20), 200 ml
concentrated hydrochloric acid (HCl), and 800 ml distilled water.
29
compensation depth was determined to be 1 % of surface light, how much volume of water
would be available for its growth in the different lakes?
3. How would this situation change for a particular shade-adapted blue-green alga that can
survive at < 0.1 % of surface irradiance?
4. If the crustacean M ysis were to require cold temperatures ( < 10°C) and were adapted to a
strictly blue photoenvironment, would this organism likely survive in the lake conditions
you observed?
5. Compare the Secchi disc transparencies using several colored discs to vertical extinction
coefficients within several spectral ranges as determined with an underwater photometer
with narrow-band spectral filters. Compare your results with those of Stepanek (1959) and
Elster and Stepanek (1967). The spectral analysis of paint often is available from paint
manufacturers.
6. Why do clean lakes appear blue on a clear day?
7. Which wavelengths are the most important in heating the surface waters of a lake? What
percentage of the total spectrum is found at these wavelengths?
8. What wavelengths penetrate most deeply in a dystrophic bog lake heavily stained with large
concentrations of dissolved organic compounds?
9. Why do aquatic plants appear green?
10. What is the "greenhouse effect"?
Apparatus and Supplies
1. Thermometers and maximum-minimum thermometers, calibrated against a standard
reference thermometer; calibrated, weighted line.
2. Reversing thermometer, if available.
3. Underwater electrical thermometer with calibrated cable of sufficient length to reach
maximum depths of lakes and streams under study.
4. Underwater photometer with various sensor units (e.g., Li-Cor, Inc., Lincoln, NE, or Kahl
Scientific Instrument Corp., EI Cajon, CAl; narrow-band spectral filters.
5. Four-n underwater photometer, if available (e.g., Li-Cor Inc., Lincoln, NE).
6. Secchi disc, 20 cm in diameter, weighted, with calibrated, nonstretchable line. White on
upper surface or divided into quadrants, painted so that two quadrants directly opposing
each other are white and the interv;:ning quadrants are black. (Little difference has been
found between either type of Secchi disc; most workers use all-white discs.) Lower surface
should be painted black.
7. Van Dorn or Kemmerer water sampler and clean polyethylene bottles.
8. Spectrophotometer, ratio-recording and scanning if available, with long pathlength cells (5
to lOcm).
9. Turbidity solutions:
a. Stock 1. 1.000 g hydrazine sulfate [(NH 2 )2· H2S04] dissolved in distilled water in a
volumetric flask to make 100m!.
b. Stock 2. 10.00 g hexamethylenetetramine [(CH2)6N4] dissolved in distilled water in a
volumetric flask to make 100 m!.
c. Standard: To a 100-ml volumetric flask, mix 5.0 ml of Stock Solution 1 with 5.0 ml of
Stock 2. Allow to stand 24 h at room temperature and then dilute to 100 ml and mix. The
turbidity of this suspension is 400 units. Store no longer than a week. A dilution of
10.00 ml of this standard to 100 ml with distilled water yields the standard turbidity
suspension of 40 units. A series of more dilute standards are then made to establish the
calibration curve.
10. Turbidimeter, if available (e.g., Kahl Scientific Instrument Co., EI Cajon, CAl.
11. Color solutions: Serial dilution from 5 to 1000 platinum color units, sealed in permanent
vials or glass ampules. 1000 Pt units = the color resulting from 2.492 g potassium hexachloroplatinate (K 2 PtCI 6 ), 2.000 g cobaltic chloride hexahydrate (CoCl l ·6H20), 200 ml
concentrated hydrochloric acid (HCl), and 800 ml distilled water.