Our Liviufi Resources — Huunm Influences 



419 



'Embryonic life stage "Selected species 



effects from acidification. Comparison of infor- 

 mation for 274 lakes surveyed between 1929 

 and 1934 and again between 197? and 1985 

 showed 80% of the lakes had declined in their 

 capacity to neutralize acidity (Driscoll et al. 

 1991). Surveys for fish in 1.469 Adirondack 

 lakes during 1984-87 showed 249c without fish, 

 with a high percentage (61%) of these fishless 

 lakes located in the southwestern portion of the 

 region where buffering of acid input is limited 

 by the local geology. These lakes are generally 

 small, shallow, and at relatively high elevations. 

 Although fish species demonstrated a wide 

 range of tolerance to acidity, studies found that 

 the number of species in a lake declined as pH 

 declined. Comparisons with historical informa- 

 tion demonstrated that populations of brook 

 trout (Salvelinus fontinalis), a relatively acid- 

 tolerant species, had disappeared from 44 of 

 409 lakes (11%), and acid-sensitive minnows 

 were lost from 33 of 170 lakes ( 19%) surveyed 

 (Baker etal. 1993). 



Surveys in the mid-Appalachian and mid- 

 Atlantic Coastal Plain regions indicate many 

 streams that are vulnerable to acidic deposition. 

 Acidic deposition influences an estimated 3.000 

 km (1,865 mi) of trout streams in Pennsylvania 

 (Carline et al. 1992). Of 344 streams surveyed 

 in western Virginia, nearly all (93%) are consid- 

 ered sensitive and nearly half are considered 

 extremely sensitive because of their low buffer- 

 ing capacity. Ten percent of the surveyed 

 streams in this area are acidic (Cosby et al. 

 1991). Waters farther south in the Blue Ridge 



province presently show little or no effects from 

 atmospheric acidity, but the potential for dam- 

 age exists because of their low buffering capac- 

 ity. Evidence suggests that the ability of the 

 watersheds to neutralize the acidic input is 

 declining, and future acidification of surface 

 waters is a continuing concern. 



In the extreme south. Florida has the distinc- 

 tion of having the greatest number of acidic 

 lakes of any U.S. region: however, many of the 

 fish species commonly found in these lakes are 

 tolerant of low pH levels. Other regions, such as 

 the upper Midwest and western states, have 

 waters with low buffering capacity and. 

 although exisdng information does not indicate 

 biological problems, they remain vulnerable to 

 acidity. 



Acidification of the aquatic environment can 

 also aftect veitebrate species other than tlsh. For 

 example, studies show acidic deposition can 

 aftect the diet, foraging, distribution, and repro- 

 duction of bird species that depend on the 

 aquatic environment (Table). Such indirect 

 eft'ects are often difficult to interpret, but they 

 could potentially lead to fundamental changes 

 in the ecosystem. 



Terrestrial Species 



Acidic deposition affects terrestrial wildlife 

 species by damaging habitat and by reducing or 

 contaminating food sources through uptake of 

 toxic levels of metals (Schreiber and Newman 

 1988). Species such as amphibians, which 



Figure. Effect of acid rain on 

 some aquatic species. As acidity 

 increases (and pH decreases) in 

 lal;es and streams, some species 

 are lost (gray). 



