Chapter III — 37 — Collecting Samples at Sea 



It is the concensus of most workers that the storage of samples at low 

 temperatures tends to minimize the changes in the quantity and quality 

 of the microbial population, but not even temperatures as low as o° C. will 

 prevent gross changes. Most investigators emphasize the importance of 

 analyzing water samples as soon as possible, since chilling samples with 

 ice has only slight advantages. According to Tanner and Schneider 

 (1935), the behavior of bacteria during storage varies greatly with dif- 

 ferent strains. Little difference was noted in the number of viable organ- 

 isms in water samples stored at 0° to 7° C. for 24 hours, but the quality of 

 the flora may have changed considerably. 



In its Standard Methods for the Examination of Water and Sewage, 

 the American Public Health Association (1936) specifies that "During 

 the period of storage, the temperature shall be kept between 6° and 10° C." 

 It warns that "Because of the rapid and often extensive changes which 

 may take place in the bacterial flora of bottled samples when stored even 

 at temperatures as low as 10° C, it is urged, as of importance, that all 

 samples be examined as promptly as possible after collection." | 



This precaution applies equally to samples of sea water and marine 

 mud. The matter is emphasized because, owing to the dififiiculties of an- 

 alyzing samples of marine materials in the field, many of the results re- 

 ported in the literature are based upon the bacteriological analysis of 

 samples which have been stored for several days or, in some cases, a few 

 weeks. Oftentimes there is no alternative except to store samples until 

 adequate laboratory facilities are available, under which conditions the 

 time and temperature of storage should be stated along with the analyti- 

 cal results. Preferably the temperature of storage should be near 0° C. 

 Many bacteria from the sea are injured by being subjected to temper- 

 atures exceeding 25° C. 



ZoBell and Feltham (1934) noted as much as 50 per cent decrease 

 in 1 2 hours in the total numbers of bacteria found in water samples, fol- 

 lowed by a many-fold increase during storage at 20° C. When plated 

 shortly after collection, 418 colonies representing 26 different types de- 

 veloped from i.o ml. of water. After storage for one day at room tem- 

 perature there were 1500 bacteria per ml. with only four types present. 



As pointed out by ZoBell and Anderson (1936a), the bacterial popu- 

 lation of samples of stored sea water may increase from initial counts of 

 hundreds per ml. to millions per ml. after a few days. Then the counts 

 may decrease to thousands or hundreds per ml., with only one or two pre- 

 dominating species remaining in water which initially contained 20 to 30 

 types of bacteria. The magnitude of the changes is primarily a function 

 of the organic content of the water. The rate of the change is primarily 

 a function of temperature, being very slow at 0° C. 



Gee (19326) found an increase of 65-fold in the bacterial population 

 of sea water from Tortugas, Florida, after eight days' storage and an 

 8-fold increase in the bacterial content of marine mud. The data in 

 Table VII are illustrative of the magnitude of the quantitative and quali- 

 tative changes in the bacterial flora of mud samples from the Pacific Ocean 

 after different periods of storage at 0° to 4° C. 



Neither the magnitude nor the rate of change in the bacterial flora of 

 mud samples is nearly as great as in samples of sea water. This is because 

 environmental conditions affecting the microbial population are not al- 

 tered as much with the storage of mud as with the storage of water 

 samples. 



