27 



but vary with time and place, with depth, and with 

 geography. Once known, however, they predict not only 

 their living environment, but the physical and nonbiological 

 factors or changes with a higher degree of accuracy than 

 can be done with mechanical instruraentSo In Santa Monica 

 Bay these assemblages or associations of organisms have 

 been found not only to differ appreciably with varying 

 distances from the ends of the outfall, but to vary in 

 kind, in organic productivity, and according to the 

 sediments they occupy. These results are expressed more 

 fully in the Analyses of samples from these faunal zones, 



A single association from shallow bottoms of Santa 

 Monica Bay may be represented by a quantitative sample 

 taken from a bottom area measuring two to four square 

 feet, in a volume of sediments measuring from one to 

 three cubic feet. Actually the samples have varied 

 considerably from these dimensions, usually in the lesser 

 directions, A sample may contain between 50 to 90 different 

 kinds of metazoan invertebrate animals, numbering from 

 500 to 1000 individuals, in various stages of growth 

 to maturity. These assemblages exist in integrated though 

 constantly changing patterns, and maintain inter- and 

 intraspecif ic stabilities over periods of time that may 

 exceed a year. Because they are believed to include 

 largely species with short life histories (less than 

 a year), there must be the constant replacement of popu- 

 lations by young individuals, many of which pass through 



