Sampling
Fifteen 8 years old sea trout (Salmo trutta trutta) were caught in late autumn (October and November 1995) from station No 3 (54o 23' N, 18o 57' 5" E). Weight, length and sex of each fish were determined. For each sea trout a segment of the muscle was taken from below the dorsal fin, after which the samples were frozen (–27oC).
The benthic animals were taken with drag from two sampling stations (station 1: 540 35' N, 180 40' E and station 2: 540 35' N, 180 44' E) in early spring (March 1996). Saduria entomon was grouped into length classes. The bivalves (Macoma baltica, Mya arenaria, Mytilus trossulus) were espoused for 24h in filtrated sea water, then grouped into length classes.
Tissue and shell were separated. All individuals from species Halicryptus spinulosus were similar in size and treated as one sample. Saduria entomon cultivated in aquatic system for half a year was analysed as comparable material. All samples were frozen (–27oC).
The sediment samples were taken (from stations 2 and 3 in March 1996) with a Niemistö corer, separated into 1cm slices to 10cm depth and frozen (–27oC).
Sample preparation
Muscle tissue of fish, tissues, shells and sediments were freeze-dried to complete dryness and divided into small pieces.
A portion of about 1–2 g was transferred to a glass extraction vial and Soxhlet-extracted in hexane and acetone at 180oC for 2 hours. Octachloronaphtalene was used as an internal standard and added prior to the extraction. After extraction, water was added to the extract to separate the hexane (containing the fat and lipophilic pollutants) from the acetone/water phase. Concentrated H2SO4 was added to oxidise the fat. The hexane phase was then evaporated in a vacuum centrifuge to dryness. The remaining material was dissolved in 400µl hexane and eluted with hexane/dichlorometane through a column containing two layers of silica gel to which K2CO3 and H2SO4 had been added. The eluate was then evaporated to dryness and dissolved in isooctane.
Grazyna Sapota 39
Analysis
The cleaned-up extract was analysed for persistent pollutants by capillary GC/ECD on VARIAN STAR 3400. Investi-gated substances were separated on a 30-m DB-5 quartz capillary column. Injection technique was split/splitless. H2 (1.5mlmin–1) was used as a carrier gas and N2 (50mlmin–1) as a make-up gas. The oven temperature was programmed as follows:
• Initially 15 min at 80oC
• Increase by 4oC per min to 320oC
• Hold for 15 min.
• Injection temperature—330oC
• Detection temperature—340oC
A pesticide mixture containing p,p'-DDE, p,p'-DDD, o,p'-DDT, p,p'-DDT, a-HCH, b-HCH, g-HCH and HCB was used as a standard. Clophen A 60 was used as a PCB standard. All substances were identified and quantified according to Mullin et. al. (1984) and Schultz et. al. (1989).
Dry weight and fat content (without shell) was determined for each sample. Fat content was determined in Soxhlet extraction (Ewald et. al., 1998).
Results and Discussion
The vertical distribution of the concentration of all investigated substances in sediments was very similar for both stations, but values at station 3 were higher than at station 2 (Figure 1). The highest concentration of all analysed substances was observed between the 3rd and 7thcm of sediment. The sediments from station 2 belong to very fine powdered sands and from station 3 to very fine organic powdered sands. Duinker and Hillebrand (1979) estimated that in organic sediments the amount of chlorinated hydrocarbons is much higher than in inorganic sands. In 1977 Trzosinska and Baumgartner reported that concentrations of SDDT for surface sediments from the Gulf of Gdansk varied from 14.6ng·g–1 d.w. to 29.3ng·g–1 d.w. In 1979 Andrulewicz et. al. estimated for the same area concentrations for sands:
DDE –4ng·g–1 d.w., DDD –1ng·g–1 d.w., DDT –2ng·g–1 d.w. and for mud: DDE –7ng·g–1 d.w., DDD –2ng·g–1 d.w., DDT –8ng·g–1 d.w. In 1987 Slaczka et al. gave concentrations of SDDT for sound sediments from Southern Baltic—
5ng·g–1 d.w. and for mud—20ng·g–1 d.w. In comparison to these data it could be stated that concentrations of DDT and its metabolites in the Gulf of Gdansk decrease.
Generally in all analysed samples the pattern of concentrations of investigated substances was similar. It was observed that the highest amount of DDE among DDT and its metabolites is an effect of metabolic degradation of DDT (Larsson and Okla, 1989). In analysed benthic organisms concentrations of all investigated substances increase with increase of fat content (Table 1, Figure 2, Figure 3, Figure 4, Figure 5). This statement is also valid taking into account the same species from the different stations (Figure 2, Figure 3, Figure 5). Saduria entomon cultivated in aquatic system shows lower concentrations than the same species from environment. Tooby and Durbin (1975) estimated that residue substances were rapidly eliminated from tissues when organisms were placed into clean water. In analysed benthic organisms concentrations increase with increase of size of animals. Comparison of concentrations calculated on wet weight in tissue and shells shows much higher concentrations in tissue (except Mya arenaria) (Figure 6). The highest concentrations of investigated substances were found in sea trout (Figure 4). Bremle et. al. (1995) stated that the level of fish contami-nation mainly depends on the food web. Sea trout is the fish at the top of the marine food web.
Chlorinated hydrocarbons in marine biota and sediments from the Gulf of Gdansk 40
Table 1 Fat content (in % of wet weight) in analysed species from the Gulf of Gdansk
Figure 1 Concentrations of investigated substances in stratified sediments from stations 2 and 3
Station No Species Length class [cm] Fat content [% w. w.]
1 Halicryptus spinulosus 0.78
Macoma baltica 1.0–1.5 2.55
1.6–2.0 1.72
Mya arenaria 1.0–1.5 2.40
1.6–2.0 1.27
2.1–2.5 1.74
2.6–3.0 1.68
Mytilus trossulus 2.6–3.0 2.13
3.1–3.5 2.82
Saduria entomon 1.6–2.5 9.09
2.6–3.5 8.40
3.6–4.5 5.64
4.6–5.5 5.62
5.6–6.5 5.91
6.6–7.5 5.94
2 Macoma baltica 1.0–1.5 1.56
1.6–2.0 1.59
2.1–2.5 1.74
Saduria entomon 2.6–3.5 7.31
3.6–4.5 4.63
4.6–5.5 4.58
6.6–7.5 4.35
3 Salmo trutta trutta 7.78
cultivated Saduria entomon 1.6–2.5 4.44
2.6–3.5 3.38
3.6–4.5 1.94
4.6–5.5 2.38
5.6–6.5 2.35
6.6–7.5 2.17
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Figure 2 Concentrations of investigated substances in animals from station 1
Figure 3 Concentrations of investigated substances in animals from station 2
Chlorinated hydrocarbons in marine biota and sediments from the Gulf of Gdansk 42
Figure 4 Concentrations of investigated substances in fish from station 3
Figure 5 Concentrations of investigated substances in cultivated Saduria entomon
Figure 6 Concentrations of investigated substances in tissues and shells of bivalves calculated on wet weight
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Conclusions
• The presence of all investigated substances in biota and sediments from the Gulf of Gdansk was confirmed.
• Fat content was the governing factor for the distribution of persistent pollutants.
• Persistent pollutant concentrations vary in marine biota in due to size.
• Concentrations of chlorinated hydrocarbons in cultivated Saduria entomon were lower than in Saduria entomon from the environment.
• Concentrations of persistent pollutants increase towards higher trophic levels.
• In bivalves, concentration of investigated substances were higher in tissue than in shell.
• The amount of analysed chlorinated hydrocarbons was higher in marine biota than in sediments.
Acknowledgements
The author would like to thank Per Larsson and Lennart Okla from University of Lund, Sweden, for their help and possi-bility to work in Lund’s laboratory.
Thank you to Monika Normant for cultivated Saduria entomon.
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