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Figure 2. Locations of sampling sites. 



aerobic techniques designed for cultivation of bacteria with extreme 

 sensitivity to oxygen (Hungate, 1969). Cores were sectioned into de- 

 sired intervals and subcores removed by a No. 4 cork-^borer or by a 3 ml 

 syringe with the end of the barrel cut off (50.3 mm ). The 0-3 cm in- 

 terval was used for all the oil and mousse addition experiments. For 

 these experiments an anoxic slurry was made by mixing the core section 

 with 20% (V/V) anoxic artifical seawater (ASW, Burkholder, 1963). In 

 experiments on hydrocarbon metabolism slurries of other depth intervals 

 were made in the same way. Subsamples (2.0-2.5 ml) from core sections 

 or slurries were transferred to 2 dram glass vials (Acme Vial and Glass 

 Co.) and sealed under a stream of helium. The helium was passed over 

 heated copper filings to remove any traces of oxygen. Vials were 

 sealed with 00 butyl rubber stoppers (A.H. Thomas). Unless noted be- 

 low, all isotope additions (1.0 ml) were taken from sterile anoxic 

 stock solutions with a 1 ml helium flushed glass syringe (Glaspak) . 

 Mousse, oil and hydrocarbon additions were added to vials containing 

 sediment under a flow of helium gas using a 1 ml pipet 12 hours before 

 microbial activities were assayed. Benzene and toluene were added with 

 a 5 pi syringe (Hamilton). 



Measurement of Microbial Activities 



All incubations were done at ambient temperatures (20-24°C). Com- 

 parisons between different samples were made by a two sample t test, 

 using the AN0V1 program of MSUSTAT (Lund, 1979). 



162 



