Lacustrine, palustrine, and riverine systems are particularly sensitive to 

 acid deposition, due to their relatively poor buffering capacities and/or low 

 flushing rates. Many freshwater systems are underlain by types of bedrock 

 that resist weathering, so that the surface waters have few dissolved ions and 

 consequently are poor buffering solutions. Acids that fall into freshwater 

 systems become partially neutralized. Areas underlain with limestone, on the 

 other hand, neutralize the acid rain quickly. There are very few limestone 

 deposits at present in coastal Maine. 



Although detailed studies have not been made of the effects of acid rain on 

 the structure, function, and diversity of freshwater systems, the general 

 effects are known. The lacustrine system has been studied in more detail than 

 the other systems, since the lower turnover rates and poor buffering 

 capacities of lacustrine systems render the effects of acidification on them 

 more obvious (Arnold et al. 1979). In general, lowland lakes, of which the 

 coastal zone has many, exhibit a higher acid-buffering capacity than high 

 altitude lakes. A study of 37 lowland lakes in 1978 (Davis et al. 1979) 

 indicated that all still maintained acid-buffering capacities. However, 32 of 

 the lakes showed decreases in pH. 



One of the more measurable effects of acid rain has been the virtual 

 elimination of fish in acidified lakes, a particularly acute problem in the 

 Adirondacks of New York and the White Mountains of New Hampshire (LaBastille 

 1979). This effect has not been observed on the Maine coast. Several 

 effects of increased acidity contribute to the decrease in fish populations, 

 including the alteration of calcium levels, which affect reproduction in fish, 

 the alteration of gill functioning, and changes in sodium and chloride levels 

 in fish blood (Mitchell 1979; and Arnold et al. 1979). Survival of fish eggs 

 and larvae is much reduced in acidified waters. 



Fish are not the only species affected by high acidity levels caused by acid 

 rain. Deleterious impacts of increased pH in water have been observed in 

 salamanders (Mitchell 1979), bacteria (Likens et al. 1979), zooplankton, 

 phytoplankton, neuston, and in the food web as a whole (Gorham 1978). 



In riverine systems in New Hampshire relatively small drainage systems are 

 more affected by acid rains than larger streams (Johnson 1979). This 

 indicates an added buffering capacity by forest vegetation and soils in the 

 larger systems, which reduces the hydrogen ion concentration (Hornbeck et al. 

 1975). The biological effects of acid precipitation in low water streams have 

 received little attention. Bender (1978) found that pH affects the species 

 composition of periphyton algae. 



The impact of acid precipitation deposition on palustrine and estuarine 

 wetlands is poorly understood. Since estuarine wetlands are buffered by the 

 bicarbonate system, most of the acid entering them in precipitation is 

 neutralized. 



Palustrine wetlands systems have not been studied but, like the lacustrine 

 systems, they generally are not buffered highly. Many of the impacts on the 

 palustrine systems can be assumed to be similar to lacustrine systems. 

 However, further study of palustrine systems is needed. Many peat lands 

 already possess low pH (well below 5.6) and have little capacity to neutralize 

 strong acids and thus may be sensitive to acid rains. 



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