A. 3. 2 Primary production 



The reference stations showed the normal autumnal decrease in 

 primary production, compared to unpublished Asko Laboratory data from 

 six previous years, with values at the end of November only one fourth 

 of those at the end of October (Fig. 4.3). The primary production in 

 the impacted area tended to be higher compared to values from the refer- 

 ence stations. Fluctuations were induced by changing light conditions, 

 (dotted line in Fig. 4.3), as indicated by the rather clear correlation 

 (linear regression, r = 0.45, N = 17, all stations combined) between 

 insolation and primary production per biomass (Fig. 4.3 and 4.4). Sta- 

 tion V in the most contaminated area, normally had higher primary pro- 

 duction than station IV, and the difference borders on statistical 

 significance (p = 0.06, sign test, Dixon and Massey, 1969: 335-340). 



4.3.3 Bacteria 



The total number of bacteria was higher at the contaminated sta- 

 tions than at the reference stations (Fig. 4.5). Five days after the 

 grounding there were about three times as many bacteria at stations II 

 and III (1.15 x 10 6 ml" 1 ) compared to station VI (0.35 x 10 ml" ). In 

 November, the difference was a factor of about two. Hagstrom et al. 

 (1979) reported the standard deviation of bacterial counts to be 9 ± 4%, 

 which supports the reality of the observed differences. The difference 

 in sampling strategy is unlikely to influence the results markedly, 

 since bacteria are rather uniformly distributed in the water column 

 during this time of the year (Hagstrom et al., 1979). In a comparison 

 with data from the same time of year from both station VI (1977 and 

 1978) and two stations (1977) in the more eutrophicated area north of 

 station I, the bacterial counts from the oiled area stand out as 

 unusually high (Hagstrom et al . , 1979; Larsson and Hagstrom, pers. 

 comm. ) . 



The measurements of the frequency of dividing cells (FDC) showed no 

 clear differences between stations (Table 4.1). 



67 



