Chapter V 



— 75 



Distribution in the Sea 



experimental methods adopted appear to be erratic and therefore cannot 

 be correlated with any factor varying seasonally." Drainage from land 

 was one factor which operated intermittently at irregular intervals to 

 increase materially the bacterial population of surface water. The num- 

 ber of bacteria in surface water was also observed to be unusually high 

 during the time that herring fishing was in progress in the Clyde Sea. 

 The range of temperature variation was not sufficiently wide during the 

 year to affect the bacterial content of sea water. 



Samples of sea water have been collected from the end of the Scripps 

 Institution pier live or six times a week for bacteriological analysis, using 

 comparable procedures since January 1932. The only break in this series 

 was during 1938. Besides giving information on the seasonal distribution 

 of bacteria in sea water, the plates provided a source of cultures which 

 have been used for studies on bacterial physiology and for other purposes. 

 The monthly averages for the years are recorded in Table XX. 



Table XX. — Average plate counts on surface sea water at La Jolla, California, based upon 

 about 24 daily plate counts for each month during a ten year period: — 



The most striking feature of the monthly averages is their remarkable 

 constancy throughout the year. From Table XX it will be observed that 

 during only four months in ten years was the average plate count for the 

 month less than 100 bacteria per ml. of sea water. The monthly average 

 exceeded 1000 bacteria per ml. only eight times. The lowest plate 

 count obtained for any one day during the ten year period was on a sam- 

 ple collected October 4, 1932, which contained only 7 bacteria per ml. of 

 water. The count remained quite low during the first week in October 

 1932 to bring the average for the entire month down to 108 bacteria per 

 ml. The highest count during the ten year period was on a sample of 

 water collected on November 16, 1941. This high count of 30,700 viable 

 bacteria per ml. and other high counts on two or three following days are 

 directly attributable to a storm which stirred up the bottom and brought 

 in large quantities of seaweed from the kelp beds a few miles away. 



Many of the high counts obtained during the winter months are at- 

 tributable to the turbulence of water caused by storms. If it were permis- 

 sible to disregard the plate counts obtained on the days during and im- 

 mediately following such oceanic disturbances, the resulting averages for 

 relatively calm days would show that the abundance of bacteria in the 

 water parallels the abundance of phytoplankton more closely than any 



