Onondaga Lake, New York, portrays the result of modifying detergent 

 compounds. Following the implementation of local and state legislation in 

 1971-72 that limits the phosphorus allowed in detergents to 8.7% as P, a 

 decrease of 54% in the concentration of total inorganic phosphate occurred 

 in the Syracuse sewage treatment plant discharge to Onondaga Lake. The 

 average total inorganic phosphate concentration in the lake also decreased 

 by 57%. In the first full growth season after implementation of the law, 

 the blue-green alga Aphamizomenon was newly absent in the succession of 

 phytoplankton. 



In-Lake Treatment-- 



Once the nutrients have entered a lake, the problem of eutrophication 

 control is more complex. However, various control methods are under in- 

 vestigation. One can increase the nutrient output, immobilize the nutri- 

 ents, withdraw nutrient-rich hypolimnetic waters, or dredge to remove 

 nutrient-rich sediments. One may also treat the symptoms, such as nui- 

 sance algae, plants, and fish, by applying poisons or toxins, by harvesting, 

 or by biological grazing. 



Algicides and herbicides —Chemical treatment has been a widely used 

 method to improve the appearance and usefulness of lakes. It is intended 

 to limit specific populations of organisms, such as blue-green algae, 

 higher aquatic plants, or unwanted fish populations that become nuisances. 

 The chemicals vary in their cost, effectiveness, toxicity, and persistence. 

 In any event, the result is only temporary or "cosmetic" in that it treats 

 only the symptoms and not the cause of the problem. In addition, 

 decomposition of the target species serves to regenerate nutrients that 

 allow for continued biological development of the same or different popula- 

 tions. 



Mechanical harvesting --A method of eutrophication control that is being 

 used with decreasing frequency is the harvesting of plants or animals from 

 the lake. The product may be stumps or sunken logs as at Marion Pond, 

 Wisconsin, rough fish, or higher aquatic plants. Weed-harvesting equipment 

 is available, but attempts to develop equipment and procedures to harvest 

 algae have not been successful. Harvesting obviously removes some 

 nutrients from a body of water, but the amount of phosphorus and nitrogen 

 removed is exceedingly small. In the makeup of plants an average reported 

 value for P is 0.24% and for N is 2.3%, dry weight concentration. A re- 

 cently published report (Peterson, Smith and Malueg, 1974) on a harvesting 

 study on Lake Sallie, Minnesota, states: "Perhaps the most significant 

 conclusion to be derived from this study is that continuous harvest of 

 aquatic plants from Lake Sallie during the growing season could not offset 

 the high loading of phosphorus and nitrogen. The net-weight harvest of 

 428,000 kg of plants was successful in removing only 1.3% of the total 

 phosphorus to the lake, or 1.03% of the phosphorus contained in the water 

 volume of the lake during the fall circulation period. 



In spite of this, harvesting often can be justified on the basis of 

 aesthetic values alone. Research by the University of Wisconsin on Lake 

 Mendota indicates that one harvesting will reduce the amount or regrowth to 



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