Domain of the Marine Microbiologist 17 



Species, temperature, nutrients, and other factors. In large 

 volumes (5 gal) of natural sea water maintained in glass bottles 

 at 12 C, the bacterial generation time during the first few days 

 was found to range from ten to twenty hours. During the first 

 two days' storage at 22 C the generation time was only three to 

 six hours. But for various reasons marine bacteria are more active 

 under laboratory conditions than in situ. 



By noting the increase in the niunber of cells in microcolonies 

 developing on glass slides submerged in the sea, Kriss and Rukina 

 (28) estimated the bacterial generation time to range from 2.0 

 to 3.4 hours during the first eight hours submergence and from 

 6.8 to 18.7 hours during twenty-five hours submergence. From 

 the rate at which microcolonies grew on submerged slides, Kriss 

 and Markianovich (27) estimated the bacterial biomass in the 

 Caspian Sea to increase 13 to 80 per cent per day. Employing 

 similar techniques, Kriss and Lambina (26) estimated a daily 

 increase of 12 to 72 per cent in the bacterial biomass in Arctic 

 Ocean water near the North Pole. Assuming a steady state in 

 which bacteria die off at the same rate at which they reproduce, 

 a 12 per cent increase in bacterial biomass is equivalent to a 

 generation time of 8.3 days or about 44 generations per year; an 

 increase of 80 per cent in biomass is equivalent to a generation 

 time of 1.25 days or 292 generations per year. In some ways the 

 submerged slide technique approximates natural conditions, but 

 bacteria may develop more rapidly on such solid surfaces than 

 when free-floating in water. 



There is extreme patchiness in the abundance of bacteria 

 in the sea and probably even greater variability in their repro- 

 ductive rates. The abundance as well as the rate of reproduction 

 of bacteria is influenced by various environmental conditions— 

 especially by available organic matter which limits the bacterial 

 biomass. The net production of organic matter by photosynthetic 

 organisms in the sea ranges roughly from 0.03 to 10 gm of 

 organic carbon per square meter per day, the exact amount de- 

 pending upon season, locality, and a multiplicity of factors affect- 

 ing the growth of plants (46, 53). The mean net production by 

 phytoplankton is estimated to be from 35 to 350 grams organic 

 carbon per square meter per year, an amount equivalent to 1.2 



