S-5 



STRATIFICATION 

 (Density 

 Stratification) 



Arrangement of water masses into separate, 

 distinct, horizontal layers as a result of 

 differences in density; may be caused by 

 differences in temperature, dissolved or 

 suspended solids. (See Thermal Stratification , 

 Chemical Stratification) 



STRESS 



The conditions resulting from any environmental 

 change that disturbs the normal functioning of 

 an animal to such an extent that its chances 

 for survival are reduced. 



SUBLITTORAL ZONE 



The part of the shore from the lowest water 

 level to the lower boundary of plant growth; 

 transition zone from the littoral to 

 profundal bottom. 



SUBMERSED 

 (Submerged) 

 AQUATIC PLANTS 



Higher aquatic plants that grow, or are 

 adapted to grow, beneath the surface of the 

 water; e.g., pondweed, coontail, etc. 



SUBSTRATE 



The bottom material of a waterway; the base 



or substance upon which an organism is growing; 



a substance undergoing oxidation. 



SUMMER KILL 



Complete or partial kill of a fish population 

 in ponds or lakes during the warm months; 

 variously produced by excessively warm water, 

 by a depletion of dissolved oxygen, and by 

 the release of toxic substances from a decaying 

 algal bloom, or by a combination of these 

 factors. (See Winter Kill) 



