VI 



PREFACE 



stability of the main energy source. Leffler, however, 

 concludes from a series of microcosm experiments that 

 "no relationships between diversity, nutrient avail- 

 ability, or system mass and ecosystem stability or 

 between ecosystem resistance and resilience stabilities 

 were demonstrated." Norse, examining the effects of 

 biological stressors and natural physicochemical stress 

 gradients on the distribution of tropical portunid crabs, 

 shows that biological stress increased as physicochemical 

 stress decreased. 



The rapid proliferation in the past few years of 

 studies of the environmental impact resulting from the 

 procurement, conversion, burning, and disposal of coal 

 is indicative of the reemerging importance of this energy 

 source in many industrial nations. Gehrs concludes from 

 a literature review of studies on organic contaminants 

 produced by conversion of coal to hydrocarbon com- 

 pounds with higher hydrogen-to-carbon ratios, that 

 toxicological investigations of individual compounds can 

 be made manageable by first grouping the compounds 

 on the basis of chemical structure and then studying 

 representative compounds. Schultz, Dumont, and Kyte 

 demonstrate that a 2% concentration of untreated 

 coal-conversion gasifier condensate decreased motility 

 and increased cell lysis in a ciliate protozoan. The 

 procurement of coal can result in acid mine pollution, 

 which has been demonstrated to reduce severely species 

 richness of invertebrate communities in Ohio streams 

 (Hummon etal.) but to have a much lesser impact on 

 Colorado streams (Ward, Canton, and Gray). 



Toxicological aspects of trace metals introduced 

 into streams by natural and anthropogenic processes 

 have received considerable attention in recent years. 

 Eisler reviews the effects of mercury on marine biota 

 and suggests more severe restrictions on the discharge of 

 mercury compounds in general and methyl mercury 

 compounds in particular. In a separate paper, Zubarik 

 and O'Connor discuss the uptake of mercury by Hudson 

 River biota. Other papers examine the effects of various 

 trace elements on survival of fish and amphibian eggs 

 (Birge), mortality of adult Pacific oysters (Harrison and 

 Rice), nitrification by aquatic, autotrophic bacteria 

 (Holm and Cox), and species diversity of zooplankton 



