Methods 



Sampling 



The studies were performed on both rainwaterand seawater 

 samples taken from a variety of depths ranging from the surface 

 down to the benthic portion of the water column. Also 

 investigated were natural bacterioplankton communities in 

 surface and near-surface layers. 



Seawater samples were taken with Niskin bottles. 

 Rainwater samples were collected in vessels of surface area 

 0.5 m : mounted near the bow of the vessel. The BaP present in 

 the water was extracted from 1-1 samples by triple benzene 

 extraction. Final processing and analysis of 1 00 ml volumes of 

 benzene extract of BaP were carried out ashore upon completion 

 of the cruise. 



Seawater samples for use in the microbiological 

 experiments were taken using sterile sampling equipment 

 (a 5- 1 plastic Niskin bottle, and a 5-1 glass bottle, in the case of 

 Caroline Atoll lagoon). The water samples containing natural 

 microorganism communities were decanted into glass bottles 

 under sterile conditions. Further processing was carried out in 

 the shipboard microbiology lab. 



The In Situ Experiments to Assess the Biodegradation Potential 

 of Seawater Microflora in Relation to BaP 



The process involved in the microbial transformation of 

 BaP was studied under the conditions similar to the in situ 

 experiments. These involved placing 250-ml samples 

 containing natural microflora communities in dark glass bottles 

 of volume 0.5 1. A weighed amount of BaP dissolved in a 

 minimum quantity of acetone (0.05 ml ) was added to the bottles 

 immediately after addition of the water ( the acetone evaporated 

 within a few minutes). The transformation process was 

 simulated in runs using BaP concentrations of 2 and 10|ig/l. In 

 order to allow for abiotic factors, each experiment included a 

 control in the form of a sample of sterile water drawn from the 

 same depth and containing the same concentration of BaP. 

 Each complete pair of tests (experiment plus control) was run 

 three times. 



In order to make the conditions of the in situ experiments 

 as close as possible to natural, the series of glass vessels were 

 placed in baths with running water from the surrounding sea, 

 with the baths themselves mounted on the deck of the research 

 vessel. In the case of the Caroline Atoll, the sample-containing 

 vessels were placed in a plastic cassette placed on the bottom 

 of the lagoon (at a depth of 8 m). Exposure equaled 5-7 days, 

 depending on the seawater temperature. On completion of 

 exposure, the microbial activities were terminated by adding 

 several milliliters of concentrated hydrochloric acid to the 

 sample. The residual BaP in the experimental and control 

 samples were extracted using benzene. The final BaP 

 concentration values were determined ashore. 



Chemical Analysis 



Quantitative determinations of the residual BaP levels in 

 the seawater samples involved concentrating the resulting 

 benzene extracts down to a volume of 1 ml and then analyzing 

 them on alumina plates using thin layer chromatography with 

 heptane-benzene-acetone (100:60:6.7, by volume) as the 

 solvent system. The BaP-containing area of the adsorbent was 

 eluted with acetone, after which the BaP was transferred to 

 n-octane. 



The benzene extracts of BaP that were obtained in the 

 microbial experiments were treated without chromatographic 

 thin-layer separation. The evaporated portion of the benzene 

 extracts were eluted with 2-ml solutions of n-octane containing 

 1 x 10 7 g/ml of 1,12-benzopyrelene, which was used as an 

 internal standard. 



Quantitative determinations of BaP (in n-octane solution) 

 were made by a fluorescence-spectrum analysis method, relying 

 on the Shpolsky effect (Shpolsky et al., 1952; Fedoseeva & 

 Khesina. 1968). The analyses were performed with a DFS- 12 

 spectrograph at a temperature of -196°C using supplementary 

 standards (BaP and othercompounds). The minimum sensitivity 

 of the method for BaP was 1 x 10 '" g/ml, with error brackets 

 of 10%. 



The simulated rates for microbiological degradation were 

 determined from the difference between the initial (introduced) 

 and the final (remaining) mass of BaP in the separate reactors. 



Results and Discussion 



The first series of studies concerned the equatorial Pacific 

 (Fig. 1 ) in the rectangle bounded by 7° and 0°S and 150° and 

 1 80°W. Analysis of the findings showed that BaP levels in the 

 waters of the Line Islands/Phoenix Islands transect were 

 remarkable for their extreme purity. Benzo(a)pyrene levels in 

 the waters of the transect down to depths of 2.000 m 

 corresponded to the minimal background value of 1 ng/1 and 

 lower. Certain samples contained no detectable amount of BaP 

 whatever (Table 1 ). Thus, the average BaP level for the entire 

 water column at Station 1 17 was just 0.06, 0.018 ng/1. In the 

 majority of cases, the BaP levels did not exceed 5 ng/1. As seen 

 in Fig. 2, zones with elevated BaP levels were of a local 

 character. High levels were recorded for depths of 

 1,000-1,500 m (6.5 and 1 1.3 ng/1, respectively), with only one 

 instance (10.3 ng/1. Station 1 18) of a high concentration in the 

 top 0.5 m of the water column. It must be emphasized that the 

 peak levels recorded were a whole order of magnitude lower 

 than BaP levels in open ocean and other portions of the Pacific 

 as found in earlier studies (Izrael&Tsyban, 1989). The limited 

 occurrence and low levels of BaP buildup in seawater along the 

 Line/Phoenix transect may be attributed not only to the 

 remoteness of this geographic region from the principal human 

 sources of pollution (industrialized areas and shipping routes) 

 but also to the absence of any pronounced PAH flows in this 

 ultraoligotrophic part of the ocean. Nor does economic activity 

 in the waters of the Kiribati Republic archipelago appear to be 

 having any significant deleterious effect on this marine 

 environment. 



187 



