the coastal city of Halifax, Nova Scotia, have declined in pH during the past 

 two decades due to atmospheric inputs of sulphur originating in sulphur 

 emitting-industrial plants in the Halifax area (Watt et al. 1978). The 

 changes in pH of Maine lakes are currently under further investigation by R. 

 B. Davis and S. A. Norton of the University of Maine at Orono. 



Fallout of heavy metals from the atmosphere may be a serious problem. Norton 

 and his coworkers (1978) found that zinc content in the sediments of Maine 

 lakes has doubled since the late 1800s. The authors ascribe this increase to 

 atmospheric inputs of zinc that originated in urban and industrial air 

 pollution. Whether the rate of accumulation of zinc is or will be serious has 

 not been determined yet. 



Hydrology 



Hydrologic factors affect lake productivity principally through rates of 

 flushing (the time it takes to fill a lake with ambient flow) and mixing and 

 flow patterns. Rivers and streams may carry nutrients into or out of a lake 

 and add or remove nutrients to degrees that might affect basic productivity. 

 Nutrient-laden streams enrich recipient lakes and, in extreme cases, may 

 accelerate eutrophication and cause severe oxygen depletion especially in 

 thermally-stratified lakes. Streams also may flush out pollutants from lakes. 

 These and other aspects of the hydrology of Maine lakes are discussed by Davis 

 and coworkers (1978a), and hydrology, nutrients, and eutrophication are 

 reviewed by Vollenweider and Dillon (1974) and Dillon (1975). 



The use of hydrologic models in the formulation of lake restoration plans has 

 recently been investigated by Uttormark and Hutchins (1978). Hydrologic 

 information is available for only a few lakes in the coastal zone. One of 

 these is Little Pond in region 3, where Mower (1978) calculated phosphorus 

 loadings. Hydrologic retention times were calculated for Highland Lake in 

 region 1, Brewer Lake in region 4, and Branch and Green lakes in region 5, 

 using information from nearby stream gauges (Royal, West Branch Union, and 

 Narraguagus rivers; Cowing and Scott, in preparation ) . The retention times 

 for these lakes were 1.1 to 1.4 years (range of three methods of calculation), 

 1.2 to 1.5 years, 2.0 to 2.3 years, and 1.4 to 1.6 years, respectively. The 

 significance of these flushing rates were not disclosed. Outside the coastal 

 zone, at culturally eutrophic Lake Sebasticook, Hannula (1978) modeled the 

 phosphorus cycle on the basis of hydrologic and other information to provide a 

 basis for management decisions in controlling nuisance algal blooms. He 

 concluded that substantial reduction in external P loading by "... removal of 

 known point sources will have little impact on the lake until the magnitude of 

 the summer sediment release is reduced" and he indicated that an extended fall 

 drain down would reduce "...the phosphorus pool at the top of the sediment." 



Geology 



Most lakes in coastal Maine originated during deglaciation and after marine 

 submergence (about 12,000 years ago; Stuiver and Borns 1975). Many of the 

 lake basins originated from glacial sub-ice abrasion that modified topography. 

 The three main types of lakes, with regard to basin geology, have been 

 recognized along the Maine coast (Davis et al. 1978a). Lake basins scoured 

 into the metamorphic rocks of the tightly-folded structural belt along the 



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