418 



Human hifhieiues — Our Living Resources 



For further information: 



Linda C. Glaser 



National Biological Service 



National Wildlife Health Center 



6UU6 Schroeder Rd. 



Madison, WI 53711 



1991; Hart 1993); preliminary findings indicate 

 that OP and carbamate pesticides cause alter- 

 ations in behavior and physiology and could 

 affect survival in the wild. The total effect of 

 carbamate and organophosphorus pesticides to 

 wildlife is still unknown. 



References 



Gme. C.E., W.J. Fleming. D.G. Busby, and E.F. Hill. 1983. 

 Assessing hazards of organophosphate pesticides to 

 wildlife. Pages 200-220 in Transactions of the 48th North 

 American Wildlife and Natural Resources Conference. 

 The Wildlife Management Institute, Washmgton. DC. 



Grue. C.E., A. DM, Hart, and P. Mineau. 1991. Biological 

 consequences of depressed brain cholinesterase activity 

 in wildlife. Pages 151-209 in P. Mineau, ed. 

 Cholinesterase-inhibiting insecticides. Elsevier Science 

 Publishers, Amsterdam, The Netherlands. 



Hart, A. DM. 1993. Relationships between behavior and the 

 inhibition of acetylcholinesterase in birds exposed to 

 organophosphorus pesticides. Environmental Toxicology 

 and Chemistry 12:321-336. 



Hayes. W.J., Jr, and J. Wayland. 1975. Effects on wildlife. 

 Chapter 1 1 in Toxicology of pesticides. Williams and 

 Wilkins Company, Baltimore, MD. 



Ludke J.L., E.F Hili, and M.P Dieter. 1975. Cholinesterase 

 (ChE) response and related mortality among birds fed 

 ChE inhibitors. Archives of Environmental Contamina- 

 tion and Toxicology 3:1-21. 



Acidic 

 Deposition 

 ("Acid Rain") 



by 



Kent Schreiher 

 National Biological Service 



Acidic deposition, or ""acid rain,"' describes 

 any foi'm of precipitation, including rain, 

 snow, and fog. with a pH of 5.5 or below (Note: 

 pH values below 7 are acidic: vinegar has a pH 

 of 3). It often results when the acidity of normal 

 precipitation is increased by sulfates and 

 nitrates that are emitted into the atmosphere 

 from burning fossil fuels. This form of airborne 

 contamination is considered harmful, both 

 directly and indirectly, to a host of plant and 

 animal species. 



Although acid rain can fall virtually any- 

 where, ecological damages in environmentally 

 sensitive areas downwind of industrial and 

 urban emissions are a major concern. This 

 includes areas that have a reduced capacity to 

 neutralize acid inputs because of low alkalinity 

 soils and areas that contain species with a low 

 tolerance to acid conditions. To determine the 

 distribution of acidic deposition and evaluate its 

 biological effects, research and monitoring are 

 being conducted by the federal government 

 with support from states, universities, and pri- 

 vate industry. 



The national extent of the acid rain problem 

 has been estimated by sampling water from 

 3.000 lakes and 500 streams (Irving 1991 ). rep- 

 resenting more than 28,000 lakes" and 56.000 

 stream reaches with a total of 200.000 km 

 (125,000 mi). Some particularly sensitive areas. 

 such as the Adirondack Mountain region, have 

 been more intensively sampled and the biota 

 e.xamined in detail for effects from acidity. 



To identify trends in aquatic ecosystems, 

 present and historical survey data on water 

 chemistry and associated biota are compared. In 

 lakes, the chemical and biological history and 

 pH trends may be infen'ed or reconstructed in 

 some cases by e.xamining assemblages of fossil 

 diatoms and aquatic invertebrates in the sedi- 

 ment layers. In terrestrial ecosystems, vegeta- 

 tion damage is surveyed and effects of acidic 

 deposition to plants and animals are determined 

 from laboratory and field exposure experiments. 

 Natural variation in populations and the com- 

 plex interactions between acidity and other 



ecosystem components make it difficult to 

 extend many of the research findings to popula- 

 tions or communities. Acidity can also modify 

 ecosystem processes such as decomposition and 

 the flow of nutrients. Therefore, models are 

 ofien used to predict such effects by combining 

 information on individual species" effects, pop- 

 ulation distributions, and the patterns and 

 amounts of acidic deposition. 



Status and Trends 



Aquatic Species 



Research in the United States. Scandinavia, 

 and Canada has demonstrated that acidity 

 affects the physiology, reproduction, food 

 resources, and habitat of aquatic species. 

 Laboratory experiments and field surveys have 

 shown that sensitive aquatic species, ranging 

 from plankton and aquatic invertebrates at the 

 bottom of the food chain to fish at the top 

 (Figure), decrease in numbers with increased 

 acidity (i.e.. decreased pH). Some reductions in 

 sensitive species may be partially offset by 

 increases in more acid-tolerant species, result- 

 ing in little change in the total number of organ- 

 isms in the community even though the diversi- 

 ty of species may change. 



Melting snow, which accumulates the win- 

 ter's deposition of acidic materials, and 

 episodes of spring rainfall can be especially 

 damaging to sensitive streams and lakes. The 

 acidity that flushes from the surrounding land- 

 scape often enters the aquatic ecosystem at a 

 time of important reproductive activity in fish 

 and invertebrates. Acid conditions leach alu- 

 minum from the watershed soils, creating toxic 

 levels for aquatic organisms in the lakes and 

 streams that receive the runoff. Acidity also 

 increases the availability and toxicity of other 

 metals, such as mercury, that may be present in 

 the aquatic environment (Longcore et al. 1993). 



The Adirondack region of New York, one of 

 the most extensively studied areas in the United 

 States, has exhibited some of the most evident 



