have looked at the impacts of those insecticides used in the spruce budworm 

 control program (Rabeni 1978; U.S. Forest Service 1976; and Gibbs 1977). Many 

 herbicides (e.g., toxaphene , inorganic sulfates, endothal, diquat, hyamine, 

 delapon, silvex, and 2,4-D) at high concentrations have toxic effects on 

 fishes (Workman and Neuhold 1963; Surber and Pickering 1962; McKee and Wolf 

 1963; Jones 1964; Cope et al. 1970; and U.S. Department of Agriculture 1968). 

 Toxicants in fish have not been a serious problem in Maine. 



Radioactivity . The exposure of plants and animals to radioactivity 

 should be avoided. Radionuclides in aquatic environments may affect fishes 

 through direct radiation from the water or accumulated sediments. 

 Radioactivity may be absorbed onto skin, through cell membranes, or ingested 

 with food and water. The major route of accumulation appears to be through 

 consumption of food organisms (mostly filter feeders) which already have high 

 concentrations of radionuclides from the waters around them. Radioactive 

 elements and compounds enter aquatic systems through natural fallout, release 

 of wastes from nuclear users, and accidental spills. Concentration and 

 accumulation of radionuclides in mussels has been documented in the vicinity 

 of a nuclear power plant in Plymouth, Massachusetts (personal communication 

 from A. E. Eipper, U.S. Fish and Wildlife Service, Newton Corner, MA.; 

 December, 1979). Radiation has not yet been a problem to the fishes of Maine. 



Nutrients . Raw materials essential to biological organisms are called 

 nutrients. Excess nitrogen (in the form of nitrates) and phosphorus (in the 

 form of phosphates) can lead to eutrophication in aquatic systems, enhancing 

 the growth of primary producers (e.g., algae). Blooms of these plants create 

 acute problems for fishes. As the bloom dies, deoxygenation occurs through 

 microbial action and creates a lethal environment for organisms requiring high 

 oxygen content. Chronic effects may include the eventual dominance of the 

 area by species more tolerant of low dissolved oxygen levels. Excess 

 quantities of nutrients are sometimes introduced through waste disposal, 

 runoff from agricultural and timber lands, and accidental spills (see chapter 

 7, "The Lacustrine System," and chapter 3, "Human Impacts on the Ecosystem"). 



pH. Freshwater systems with low buffering capacity are very sensitive to 

 changes in the pH (a measure of acidity or alkalinity) . Marine waters are 

 highly buffered by salts and carbonates, and pH is relatively uniform. Acid 

 precipitation is lowering the pH (increasing the acidity) of lakes and streams 

 in the northeastern U.S., including Maine, at an alarming rate (see chapter 3, 

 "Human Impacts on the Ecosystem"). Natural rainfall should have a pH near 

 5.7. Some species (e.g., most trout) are seriously impaired or killed at pH 

 levels below 5.0. The pH of precipitation in the northeastern U.S. now ranges 

 between 2.1 and 5.0 (Likens and Bormann 1974). Complete losses of fish 

 populations due to acidification have been reported in the Adirondacks region 

 of New York State (Schofield 1977) and Ontario, Canada (Beamish and Harvey 

 1972), and other areas. Symptoms of the acidification included poor 

 recruitment, failure of females to produce viable eggs, and high mortality or 

 abnormalities of eggs and larvae. Reactivities of certain toxic elements and 

 compounds in sediments are affected by pH. For example, aluminum, copper, and 

 mercury, are released by sediments at lower pH levels. The major causes of 

 acidification are: combustion of fossil fuels in power generation, and 

 transportation and subsequent production of sulfuric and nitric acids in the 

 atmosphere. The problem of acidification can only worsen as consumption of 

 fossil fuels increases. 



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