. The ecology of algae : a symposium held at the Pymatuning Laboratory of Field Biology on June 18 and 19, 1959 . H 6 8 10 12 m 16 18 20 22 2>4 TIME - DAY OXYGEN RELATIONS IN SURFACE WATERS Figure 7 In sewage stabilization ponds algae are im- portant for the oxygen they produce. California pilot plant studies of such ponds (Gotaas, Oswald and Golueke, 1954) showed an average yield of pounds of photosynthetic oxygen for each pound of algae produced. In spite of this benefit, the fact remains that an algal residue is left and must be disposed of. In the pond, or in other re- ceiving wate
. The ecology of algae : a symposium held at the Pymatuning Laboratory of Field Biology on June 18 and 19, 1959 . H 6 8 10 12 m 16 18 20 22 2>4 TIME - DAY OXYGEN RELATIONS IN SURFACE WATERS Figure 7 In sewage stabilization ponds algae are im- portant for the oxygen they produce. California pilot plant studies of such ponds (Gotaas, Oswald and Golueke, 1954) showed an average yield of pounds of photosynthetic oxygen for each pound of algae produced. In spite of this benefit, the fact remains that an algal residue is left and must be disposed of. In the pond, or in other re- ceiving waters, the algae continue to draw upon available oxygen for their respiration while alive and are oxidized by bacteria when dead. Experi- ence to date indicates that algae in such effluents generally die and decompose at a sufficiently slow rate that their deoxygenating influences are spread over a long stream reach and, consequently, do not produce acute oxygen depressions. In theory, however, an equitable materials balance must show not only the oxygen produced in growing the algae, but also the oxygen required to oxidize them to a stable state. In such a balance, the benefits of algal photosynthesis appear less attractive. The necessity to include in evaluations of the oxygenating benefits of algae the oxygen required to decompose them is shown strikingly by recent developments in Lake Washington (Sylvester, Edmondson and Bogan, 1956). Domestic eutrophi- cation has stimulated an increasing abundance of algae. It has been noted that oxygen consumption in the hypolimnion has increased greatly during the past 22 years because of the dropping down of in- creasing quantities of algae and organic derivatives from above. In 1933, 825 tons of oxygen were re- moved per month; in 1950 the rate was 1400 tons, and in 1955, 2190 tons. During the same period the minimum dissolved oxygen concentration near the bottom decreased from ppm. to ppm. Elsewhere in lakes, severe odor problems
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Keywords: ., bookc, bookcentury1900, booksubjectalgae, booksubjectplantecology
