A somewhat less specific herbivore, the grass carp or white amur, has 

 been released in numerous lakes in Arkansas, where it has apparently been 

 able to successfully control undesirable submerged weeds. Its widespread 

 introduction into this country, however, is still the subject of much 

 apprehension and study. 



Similar control programs involving crayfish, a specific weevil for 

 water hyacinth, and other insects are currently under investigation. 

 Aquatic mammals such as the manatee and other animals such as snails and 

 swans have also been tried. Although most of these animals have been some- 

 what effective on a local basis, few are effective over a broad geographic 

 range. The need to carefully consider and anticipate the total effects of 

 introduced or exotic species on the natural ecology is well known. 



Relatively little work has been done with biological control of algal 

 populations. Bacteria and viruses have been isolated that destroy blue- 

 green algae, but to date only laboratory tests have been conducted. No 

 full-scale, in-lake treatment has ever been tried in the United States. 

 The control of undesirable macrophytes with plant pathogens, mostly fungi, 

 may show some potential and is currently being evaluated on a small scale. 



Biomanipulation, or facilitating desirable interactions among different 

 segments of the whole ecosystem, has long been a desirable goal. Some 

 possibilities in this direction are under study. Attempts are being made 

 to reduce phytoplankton abundance by increasing the number of grazers by 

 either direct innoculation or by controlling the zooplankton by disease or 

 carnivorous fish introductions. Attempts to exploit the competitive or 

 inhibit ive reactions among aquatic weed species are also being studied as 

 possible control measures. 



Legislation 



Lake-restoration measures are in a very early stage of development. 

 Much of the technology is still being applied in laboratories, in experi- 

 mental ponds, or in pilot lake studies. No technique can be applied indis- 

 criminately to every problem lake; each must be studied and evaluated suffi- 

 ciently to assure that the most appropriate course of action is taken. Ob- 

 viously, a whole range of remedial methods must be made available. Public 

 Lake 92-500, the Federal Water Pollution Control Act Amendments of 1972, 

 will certainly help in this regard because it authorizes funds to support 

 state programs for lake restoration. The Congress has appropriated $4 

 million to EPA for this purpose; approximately 10% of the funds have been 

 designated for evaluation purposes. It is expected that funding will be 

 increased next year. 



To limit fertility in lakes, several states have passed laws setting 

 forth regulations affecting nutrient loading. Some of them are the 

 following: 



Minnesota has passed legislation to set effluent standards for phos- 

 phorus in municipal discharges. If the discharge enters a lake directly, 



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