ZoBell 



3S 



Marine Microbiology 



Table VII. — Plate count of mud samples collected at Scripps Station 36E1 (32° 42.5' N. 

 and 117° 27' V^.) from a water depth of 60S meters after dijferent periods of storage at 0° to 4° C. 

 The number of dijferent types of colonies recognized on the plates is also given (from data of 

 ZoBell, igjSa): — 



Temperature changes during collection of samples: — Gazert (19066) 

 expressed concern over the harmful effects that may result from the 

 change in temperature which occurs while hauling water samples from the 

 depths of the ocean where the temperature is near 0° C. to the surface 

 through water which is considerably warmer. Since it requires several 

 minutes for the best electrically operated winches to haul up two or three 

 miles of wire rope, the temperature of deep-sea samples collected in trop- 

 ical and temperate zones may be increased several degrees before the 

 samples reach the surface. The extent of the temperature change is pri- 

 marily a function of the temperature gradient of the water, the time re- 

 quired to haul the sample to the surface, and the volume of the water 

 sample. 



Unless the temperature gradient is great and several hours are re- 

 quired to haul the sample to the surface, there is little likelihood that in- 

 creased bacterial activity will influence the number of bacteria in the 

 sample while it is being hauled to the surface. The extent to which heat- 

 sensitive species may be injured by the increased temperature during the 

 collection of samples from great depths is problematical. Since the max- 

 imum range of the surface temperature of deep water is around 25° C, 

 samples from great depths usually are surfaced before their temperature 

 reaches 20° C. Assuming that provisions can be made for preventing 

 further increases in temperature after the sample is surfaced, it is a ques- 

 tion of whether any marine bacteria are injured by such temperatures. 



ZoBell and Conn (1940) found that about 20 per cent of the bacteria 

 occurring in sea water and 30 per cent of those in deep sea mud are ren- 

 dered incapable of multiplication after being held for ten minutes at 30° C. 

 There was no evidence that any of the bacteria were injured by heating to 

 25° C. for ten minutes, but as shown by the data in Table IX on page 45, 

 somewhat more bacteria developed on plates incubated at 18° than at 

 25° C. The optimum temperature for the multiplication of most marine 

 bacteria, including those from cold bottom deposits, is 18° to 22° C. 



While all of the available data suggest that marine bacteria from the 

 deep sea are not injured by exposure to temperatures up to 20° or 25° C, 

 the data are not conclusive because most of the observations have been 

 made on samples which have been subjected to temperatures nearly this 

 high prior to or during the analysis of the samples. Only by the critical 

 examination of samples from the deep sea which have been kept cold will 



