PART VIII — AQUATIC ECOSYSTEMS 



A few cause-effect relations of en- 

 vironmental degradation are under- 

 stood — e.g., the cause of oxygen 

 depletion in Lake Erie and its relation 

 to the disappearance of blue pike 

 and the diminution of other fish and 

 fish-food organisms in the region of 

 the lake affected. The relation be- 

 tween excessive phosphorus and ob- 

 noxious algae blooms in Lakes Erie, 

 Ontario, and other scattered locations 

 has been established. Lake Ontario 

 is no longer suitable for lake trout 

 because the clean, rocky spawning 

 areas essential for its reproduction 

 are covered by a fibrous mat. 



Studies of the effects of chemical 

 and physical factors on biological 

 productivity and stability are in pre- 

 liminary stages for a few species. 

 Some information is being obtained 

 on the physical requirements for suc- 

 cessful incubation and hatching of 

 the alewife, the sea lamprey, and 

 some species of the whitefish family. 

 Thermal stresses and physiological 

 responses that influence alewife die- 

 off and abundance are under study. 



Problems of species interaction are 

 incompletely understood and only 

 a few are subject to adequate study 

 at present. Information on selective 

 feeding of the alewife and the result- 

 ant effects on changes in the com- 

 position of fish-food organisms gives 

 clues to possible competitive advan- 

 tages of the alewife that may explain 

 the decline of various species when 

 the alewife becomes dominant. There 

 is some evidence that more complex 

 feeding interactions and competition 

 during certain life stages of smelt, 

 deep-water ciscoes, and lake herring 

 may have contributed to the sharp 

 reduction of lake herring in certain 

 areas of Lake Superior in the absence 

 of alewives. The ability of the un- 

 checked sea-lamprey populations to 

 destroy a lake-trout population by 

 eliminating all mature trout has been 

 documented by detailed studies in 

 Lake Michigan, but the relation be- 

 tween lamprey-attack mortality of 

 lake trout and other large native spe- 

 cies is not known. Thus, the degree 



of lamprey reduction that will be 

 required to restore substantial stocks 

 of large species, as a step toward 

 restoration of a favorable balance of 

 all fish species, is still uncertain. 



Also unknown or uncertain are the 

 relations of physical, chemical, and 

 biological change to the declines of 

 native species throughout the Great 

 Lakes. These are the species or kinds 

 of species that must be rehabilitated 

 to restore the fishery productivity of 

 the Great Lakes. To prevent dete- 

 rioration of the lakes from pro- 

 gressing to the point where biological 

 and fishery restoration may be ex- 

 tremely difficult or impossible, control 

 of environmental degradation and un- 

 desirable species must be undertaken 

 before research on cause-effect rela- 

 tions of the various factors of de- 

 gradation can be completed. Never- 

 theless, the research must be initiated 

 expeditiously and pursued vigorously. 



The Need for Monitoring — A ba- 

 sic requirement for research to gain 

 a full understanding of the fishery 

 environmental deterioration of the 

 Great Lakes is a comprehensive moni- 

 toring program to measure all aspects 

 of the chemical, physical, and biologi- 

 cal environment. The present data 

 base and existing instrumentation 

 and techniques are adequate to start 

 development of a suitable monitoring 

 system. Data from monitoring are 

 needed to provide measures of the 

 long-term trends and the frequency, 

 intensity, and duration of short-term 

 fluctuations in environmental factors. 

 Particular attention should be given 

 to physical and chemical contami- 

 nants, and the measurement of 

 changes in the composition and 

 biomass of biological components of 

 the environment. Meaningful moni- 

 toring will require a full understand- 

 ing of the sources and identity of all 

 physical, chemical, and biological 

 contaminants entering the lake. 



Research Questions — Environ- 

 mental monitoring and the sources 

 and identity of contaminants will 

 provide the data that are needed to 



give clues for cause-effect relations 

 that can be investigated by specific 

 field and laboratory studies. What 

 factors contribute to failure of hatch- 

 ing or early survival of the previously 

 abundant native species that must be 

 restored? Precisely how might certain 

 chemicals, such as pesticides and 

 heavy metals, influence the physiol- 

 ogy, behavior, reproductive process, 

 or survival of various species of fish? 

 What effects would massive releases 

 of thermal wastes in various locations 

 and by various methods have on 

 eggs, fry, young, and adult fish, and 

 fish-food organisms, in different sea- 

 sons? These questions must be an- 

 swered to provide suitable guidelines 

 for maintaining the biological stabil- 

 ity and productivity that might be 

 achieved after the present environ- 

 mental degradation has been halted 

 and reversed in the most seriously 

 affected lakes. 



Even under very stringent protec- 

 tion, the Great Lakes will continue to 

 be influenced by growing urbaniza- 

 tion and industrialization within the 

 drainage. These influences will un- 

 doubtedly cause some uncontrollable 

 changes (physical and chemical con- 

 tamination, directly or indirectly re- 

 lated to pollution or modification of 

 the atmosphere) and accelerated en- 

 richment. Change may continue to 

 be too rapid for biological processes 

 to accommodate to it. Thus, research 

 will be required to determine the rate 

 of change that can be tolerated and 

 still maintain biological stability and 

 fishery productivity in the Great 

 Lakes. This information will be es- 

 sential for possible future modifica- 

 tion of the initial guidelines and 

 standards that must be enforced im- 

 mediately to "save" the Great Lakes. 



Need for Increased 

 Understanding and Action 



It has been said that, for the 

 aquatic ecologist, fish are the miner's 

 canary. The reason why some spe- 

 cies have disappeared is unknown, 

 but deterioration of water quality 



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