174 



Life 



Figure 151. Base of slope at north side of San Pedro Basin(lat. 33°24.4', long. 118° 13.3', 540 meters). Masses of rock 

 are partly buried in silty sediment. Note ophiuroids (brittle stars), asteroids, and other organisms encrusting rocks 

 and the mat of ophiuroid arms and worm tubes protruding from sediment surface. Bottom edge is about 2 meters 

 wide. 



treme; the cells are plated on a suitable 

 medium so that the colonies that grow can 

 be countered. 



Either growth method, dilution or plate 

 count, is beset by certain difficulties, mor- 

 tality by transfer, dependence on kind of 

 media, inabihty to distinguish growth from 

 single cells or from clusters, and growth 

 under artificial conditions. Unless the me- 

 dia are more favorable than that of the origi- 

 nal bottom sediment and unless the tempera- 

 ture of incubation is higher than that in situ, 

 the bacteria fail to grow in a reasonable 

 length of time. In other words, if any 

 growth in the laboratory is observable, the 

 conditions must have been altered. Ac- 

 cordingly, for studies of diagenesis of the 



sediments it is perhaps better to measure the 

 cumulative effects of bacterial activity dur- 

 ing thousands of years under natural condi- 

 tions than it is to note the mere growth of 

 colonies which occurs during the few weeks 

 of artificial conditions in a laboratory (Emery 

 and Rittenberg, 1952). 



Many specific types of bacteria have been 

 found in sediments off southern California 

 (ZoBell, 1946c, p. 98) and elsewhere, even 

 types that could not possibly be active in 

 the environment in which they were found. 

 Thus still another difficulty is presented by 

 bacteria: although we can measure how 

 many are viable in the laboratory, we do 

 not know how many were dormant in situ. 

 Thus we cannot form a satisfactory estimate 



