A-/ 



ABYSSAL ZONE 



All of a sea, or a very deep lake below the 

 bathyal zone . The primary energy source for 

 this region lies far above in the euphotic zone ; 

 density of life depends on the amount of organic 

 material that settles from the euphotic zone . 

 (See Hadal Zone) 



ACCLIMATION 



Physiological and behavioral adjustments of an 

 organism in response to a change in environment, 

 (See Adaptation) 



ACCLIMATIZATION 



Acclimation of a particular species over 

 several generations in response to marked 

 environmental changes. 



ACUTE TOXICITY 



ACTINOMYCETES 



Any toxic effect that is produced within a 

 short period of time, usually 24-96 hours. 

 Although the effect most frequently considered 

 is mortality, the end result of acute toxicity 

 is not necessarily death. Any harmful biological 

 effect may be the result. (See Chronic Toxicity , 

 Direct Toxicity) 



Filamentous microorganisms intermediate between 

 the fungi and bacteria, although more closely 

 related to the bacteria. These organisms are 

 widely distributed in soils and are often 

 conspicuous in lake and river muds. They are 

 often associated with taste and odor problems 

 in water supplies. 



