Turbidity . Suspended and settleable solids resulting from sewage 

 effluent may increase turbidity. Decreased light penetration into water, 

 because of particulate loads, decreases primary production. On the bottoms of 

 water bodies, particulate loads can render surfaces unavailable for attachment 

 of plants and invertebrates. 



Benthic invertebrates are affected by wastes containing settleable and 

 suspended solids. Silts and clays are a significant fraction of discharged 

 wastes. The impact of these particulates on benthic invertebrates is 

 discussed above under "Dredging." 



Eutrophication . Input of nutrients to water bodies by municipal, 

 residential, and commercial dischargers has effects similar to those described 

 under "Agricultural Impacts" above. Nutrients may accelerate the growth of 

 algae and vascular plants in lakes. The resultant increases in decomposition 

 causes more oxygen to be consumed than lakes can produce. This situation 

 speeds up eutrophication, which can result in oxygen depletion and, in extreme 

 cases, fish kills. Annabessacook Lake, Pleasant Lake, and Togus Pond (region 

 2) are examples of eutrophic lakes. 



Palustrine areas entrap nutrients in peat, thereby slowing the rate of 

 eutrophication in lakes downstream. Palustrine areas also export nutrients 

 and organic matter downstream. Excessive nutrients in a palustrine wetland 

 can accelerate plant succession. 



Since stream and river waters are in motion, sewage-derived nutrients do not 

 remain in the vicinity of the point source for long periods of time. 

 Eutrophication, therefore, is normally less severe in streams than in standing 

 water (lacustrine and palustrine systems). 



Sewage-derived nitrogen can lead to the production of excessive blooms of 

 phytoplankton in riverine, estuarine, and marine systems in the summer months 

 (Carpenter et al . 1969). The type of sewage treatment (primary or secondary) 

 influences the impact. Primary sewage is low in the form of nitrogen that is 

 readily usable by phytoplankton, but secondary sewage is high in this type of 

 nitrogen. The flushing characteristics of receiving waters is critical in 

 determining the consequences of point-source discharges of sewage. 



Heavy metals . Although coastal Maine is not as industrialized as the 

 rest of the Eastern U.S., heavy metal concentration in the estuarine suspended 

 particulates, biota, and sediments appears to be comparable in some locations 

 to that in heavily industrialized areas (personal communication from L. K. 

 Fink, University of Maine, Walpole, ME; January, 1979). Of the aquatic 

 systems, the riverine and estuarine systems are affected most by heavy metals, 

 because most waste-water point sources discharge into these systems. The 

 terrestrial, lacustrine, and palustrine systems receive most of their heavy 

 metal input from particulate air pollution. In addition, they may receive 

 inputs from landfill sites, from oil pollution, and from herbicide 

 application. Courtemanch (1977) report that the use of a copper-containing 

 herbicide to reduce algal blooms in Silver Lake (region 4) caused severe 

 disruption of benthic fauna. Heavy metals commonly are introduced through 

 industrial and municipal outfalls, dumping sites, dredging sites, agricultural 

 and urban runoff, fungicides, germicides, heating or burning of fields, mining 

 operations, and oil discharges from ships. The discharge of sewage and sewage 



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