The FDC values in this study ranged from 1 to 1 2% of the 

 ceils dividing (averaged 4%). not much different from values 

 reported elsewhere. Using the empirical relationship between 

 FDC and specific growth rate, u (In u = 0.81[FDC]-3.73), 

 (Hanson ef «/., 1983), for southern ocean bacterioplankton. we 

 calculated a specific growth rate of 0.58 day ', a doubling time 

 of 1.7 days. Growth rates estimated from the FDC method in 

 the Chirikov basin were generally lower than those made from 

 thymidine incorporation. A similar conclusion was made by 

 Riemann ('/ al. (1984), although Newell and Fallon (1982) 

 found lower results for thymidine incorporation compared 

 with FDC. The results shown here for thymidine incorporation 

 and FDC procedures indicate doubling times between 2 and 5 

 days. Correcting for inactive cells, bacterioplankton growth 

 rates probably range on the order of 1 to 3 days during the late 

 summer period in the Chirikov and south Bering Seas. 



In summary, bacterioplankton carbon production in the 

 Chirikov basin and the surface waters of the south Bering Sea 

 was estimated based on an average carbon content of 

 10 fentograms carbon per cell (Fuhrman & Azam, 1980). 

 From thymidine-based cell productivity estimates, 

 bacterioplankton production averaged 245 mg C m - d ' in the 

 Chirikov basin and 387 mg C m - d ' in the upper mixed layer 

 of the south Bering Sea (Table 3 ). Frequency of dividing cells- 

 based production was 2 to 5 times the thymidine-based estimates 

 (Table 3). The large difference between both estimates is 

 attributed to the relative accuracy of the theoretical conversion 

 factor and the empirically derived FDC equation. Thus, a 

 comparison of bacterioplankton production and phytopiankton 

 production in the Chirikov and south Bering Seas suggests that 

 bacterioplankton production ranges between 5 and 33% of the 

 phytopiankton production (Table 4). If we assume that the 

 average growth yield of marine bacteria is about 50% of the 

 organic matterconsumed, then bacterioplankton in these waters 

 may consume upwards to 70% of the total phytopiankton 

 production, but it is probably much less. Future bacterial 

 studies need to evaluate the incorporation of thymidine into 

 cellular components, growth kinetics, active cells, and empirical 

 relationships of thymidine incorporation and frequency of 

 dividing cells. 



The uiithors ihank the US Fish ,ind Wildlife .Service (USFWS) 

 and Division of Polar Programs (NSF) for traveUi lid shipping assistance 

 and Mr. Steven Kohl (USFWS) for logistical arrangements that 



TABLE 4 



Comparison of bacterioplankton and phytopiankton production 



(mg carbon m - h ') in the Chirikov basin and south Bering Sea. 



August 1988. Bacterioplankton production estimated from 



thymidine incorporation and frequency of dividing cells (see 



Table 3). 



Bacterioplankton Phytopiankton 

 Production Production 



Anadyr Waters 

 (0-40 meters) 



10.9-35.6 



Alaskan Coastal 

 Waters 

 (0-35 meters) 



9.3-25.9 



Bering Shelf 

 Waters 

 (0-40 meters) 



10,2-43.8 



Bering Sea 

 Waters 

 (0-30 meters) 



16.1-73.8 



175 



Percent 

 Bacterioplankton 



6-20 



209 



221 



5-21 



7-33 



9-74 



175-221 



5-^^ 



allowed the authors to participate in the Third Joint US-USSR Bering 

 & Chukchi Seas Expedition. Mr. Harold J. O'Connor (USFWS), the 

 US Project Leader, and Dr. Alia Tsyban, the USSR Project Leader, 

 represented the bilateral US-USSR Environmental Agreement under 

 Activity 02.07-2 1 1 . Dr. Terry Whitledge and Dr. Alia Tsyban acted 

 as chief scientists for the Americans and Soviets on the Soviet's RA' 

 Akadcmik Korolcv. The authors acknowledge the cooperation and 

 assistance of the captain, crew, and Soviet scientists during the 

 research cruise aboard the RA' Akademik Korolev. 



74 



