1(H) 

 BaP tranformation 

 as percentage of 

 initial mass (%). 80 



ontrol 



Days 



Fig.4. 



Dynamics of BaP transformation in the in situ experiments using 

 microflore from waters of Caroline Atoll lagoon (a) and from the 

 South China Sea (b) at Station 127 (1988 data). (Initial BaP 

 concentration: A- 2 |ig/l; O- 10 ug/l;#- control) 



insight into the natural processes of BaP elimination from the 

 marine environment, we also undertook a study of the dynamics 

 involved in microbial transformation. The results obtained 

 from individual runs of each experiment yielded reasonably 

 consistent values. 



As may be seen from Fig. 4, the highest microbial 

 transformation rates were noted in experiments using microflora 

 taken from Caroline Atoll lagoon water. The series of samples 

 placed in natural conditions at a depth of 8 m contained just 

 50% of the initially introduced amount of BaP (initial 

 concentration 10 ug/1) after only 2 days; after 5 days had 

 elapsed, 97% of the initial BaP had been transformed. The rate 

 of microbial transformation of BaP in the lagoon waters was 

 high, with the curve of the degradation process close to linear. 



The rate of microbial transformation of BaP in the South 

 China Sea was much lower than for the atoll. With an initial 

 BaP concentration of 2 ng/1, only one-third of its initial mass 

 had been transformed after 5 days. However, after 7 days of the 

 experiment, the microflora from the top 0.5 m of the water 

 column was able to transform as much as 77% of the introduced 

 BaP. With a higher concentration (10 ug/1). microbial 

 transformation in the experiment produced a consistent value, 

 34% of the initial mass over the third through the fifth days of 

 the experiment where a period of decreased microfloral activity 

 occurred (Fig. 4), the incremental transformation amounting to 

 just 0.6 ug of BaP. In these tests, the total mass of the BaP 

 degraded after 7 days; at the time which the experiment was 

 terminated, the mass did not exceed 5.68 ug (56% of the initial 

 concentration). On the whole, the rate of microbial 

 transformation of BaP turned out to be not particularly dependent 

 on the initial concentration (2 and 10 Ug/1). Assuming the 

 process curve to be more or less linear for both the equatorial 

 and the tropical Pacific, we were able to estimate the average 

 rates of microbial transformation of BaP. The resulting values 

 were 1.94 ug/l/day for the waters of Caroline Atoll and 

 0.81 ug/l/day for the South China Sea. 



The abilities of marine microflora to degrade BaP are 

 therefore relatively high. In the case of the Caroline Atoll, the 

 biodegradation rates exceeded those of similar processes 

 investigated in impacted areas such as the Baltic Sea (Tsyban 

 ctal., 1985a). The results of our 1988 studies demonstrate the 

 need to consider PAH, and especially BaP. metabolism as an 

 exceedingly important process for detoxification through the 

 elimination of the pollutants in question from the highly 

 dynamic ecosystem that constitutes the tropical zones of the 

 World Ocean. 



TABLE 2 



Dynamics of benzo(a)pyrene transformation by microflora from central Pacific waters in the in situ 



experiments (October 1988). 



Region of 



Operations and 



sampling depth. 



m 



BaP concentration, ug/1 



Exposure, Initial At end of experiment 

 days Cj Control Exp. 



Microbial 

 transformation of 



BaP, in % of 

 concentration C, 



Caroline Atoll 

 Lagoon, S m 



South China Sea. 

 Station 127,0.5 m 



Same as above 



9.9 



9.9 



2.0 



2.0 



10 



9.9 



7.8 

 4.9 

 3.? 

 1.8 

 0.3 







1.71 

 1.37 

 0.46 



6.62 

 6.00 



4.32 





 22 

 51 

 65 

 82 

 97 

 



14.5 



3 1 .5 



77.0 









 33.8 



40.0 



56.8 







190 



