waters at all stations. Below the minimum frequency of 

 dividing cells (<4%), dividing cells again increased with depth 

 to5.1%nearthebottom(Figs. la,b). The frequency of dividing 

 cells averaged 4.4% dividing cells over the water column. The 

 specific activity of thymidine uptake, population growth rate, 

 averaged 4.04 x 10 -' moles cell ' h ' (Table 2) and showed no 

 relation to the frequency of dividing cells, cellular growth rate, 

 except at Station 86. Both indices of growth rates showed no 

 relation to temperature (data not shown). 



Alaskan Coastal water : With the exception of Station 9 1 

 where the water column was isothermal ( 10°C), ACW showed 

 a strong thermocline near 10 m (Figs. 4a,b; 5a,b). Rates of 

 thymidine incorporation along the eastern boundary of the 

 Chirikov basin averaged 1 .55 pmoles 1 ' h ' but not significantly 

 different (P = 0.05) from the rates measured along the western 

 boundary (Table 1 ). At Station 84 in the Bering Strait and 

 Station 91, thymidine incorporation varied little with depth, 

 whereas at Station 92, the highest rates occurred within the 

 thermocline. At Station 102 northeast of St. Lawrence Island, 

 thymidine incorporation increased in the high salinity bottom 

 waters (Fig. 4b). 



Rates of thymidine incorporation were related inversely 

 with temperature and positively with the index of the population 

 growth rate (Fig. 2, Table 2). Rates measured in the bottom 

 waters of the eastern Bering Straits clustered with rates measured 

 in the waters of the western boundary of the Chirikov basin 

 (AW, see Fig. 2), suggesting similar bottom waters flowing 

 through the eastern and western sides of the Bering Strait. 



Bacterial populations averaged 3.6 X 10* cells 1' (Table 1) 

 and were also similar to population densities in AW. Highest 

 densities occurred above the thermocline at Stations 92 and 

 102 and were approximately constant with depth at Stations 84 

 and 91 (Figs. 4a,b; 5a,b). Bacterial populations in ACW 

 showed no relation to temperature. 



The frequency of dividing cells in ACW averaged 0.037 

 (3.7% dividing cells) (Table 1). The highest frequency of 

 dividing cells (5.0%) occurred near the themiocline and declined 

 towards the bottom, except at Station 91 where dividing cells 

 remained constant over the water column. The specific activity 

 of the population averaged 4.85 x 10^' moles cell ' h ' 

 (Table 1 ) and was similar to the specific activity measured in 

 AW. The specific activity showed no relationship to dividing 

 cells except at Station 84 in the Bering Strait. Similar observation 

 was seen at Station 86 in the western Bering Strait. 



Bering Shelf water : Waters at Stations 89, 100, 104, and 

 1 06 characterized BSH W ( Figs. 2,3 ). Waters at Stations 89 and 

 106 nearest to the western boundary of the system typify AW 

 with bottom temperatures <2°C, whereas low-salinity ACW 

 dominates surface waters near the eastern boundary at Stations 

 100 and 104. Rates of thymidine incorporation averaged 

 1 .70 pmoles 1' h ' (Table 1 ). Highest rates in BSHW occurred 

 at Station 104, northeastof St. Lawrence Island (Fig. 3). Rates 

 were highly variable with temperature (P > 0.05) but correlated 

 significantly with the specific activity (Fig. 2, Table 2). 



Bacterioplankton populations averaged 5.2 x 10" cells 1 ' 

 (Table 1 ) and were significantly higher than the Anadyr and 

 ACWs ( ANOVA, P < 0.05). The highest densities occurred 



TABLE 1 



Vertical distribution of averaged bacterioplankton parameters from 



the three water types measured in the Chirikov basin. Units: 



N = number of samples averaged at each depth, depth = meters. 



Thymidine Incorporation = pmoles 1 ' h ', 



Bacteria = 10" cells 1 ', Specific Activity of 



thymidine incorporation = 10-' moles cell ' h '. 



05 

 10 

 15 

 20 

 25 

 30-35 



1.39 

 1.53 

 1.55 

 1.81 

 1.58 

 1.54 



3.1 

 4.4 

 3.5 

 3.9 

 3.9 

 2.3 



0.036 

 0.050 

 0.038 

 0.033 

 0.026 

 0.035 



4.66 

 3.48 

 4.69 

 4.96 

 4.82 

 6.55 



average 



1.55-0.09 3.6-0.2 0.037-0.003 4.85-0.54 



Bering Shelf Waters 



Thymidine 

 N Depth Incorp, 



Bacteria 



Freq. 



Dividing 



Specific 



Activity 



above or within the thermocline. Bacteria numbers were also 

 highly variable with temperature and specific activity 

 (Fig. 3, Table 2). 



The frequency of dividing cells averaged 0.038 (3.8% 

 dividing cells) (Table 1 ), In general, frequency of dividing cells 

 decreased from 5.1% in the surface to 2.9% below the 

 thermocline. The specific activity averaged 

 3.45 X 10^' moles cell ' h ' (Table 1 ), which was significantly 



62 



