676 Marine Microbiology 



stoppers with two glass tubes on top. One was used as an inlet 

 for nitrogen to replace all oxygen present. The second one with 

 the greater diameter permitted an increase of the volume of the 

 mud which occurred during formation of gas during the incuba- 

 tion of the containers. An effluent tube was connected, which 

 passed into an empty test tube and then into a test tube filled 

 with a solution of zinc acetate. So as the mud volume expanded, 

 gases could escape and hydrogen sulfide present in the gases was 

 precipitated as zinc sulfide and could be determined. Completely 

 closed containers either broke or the contents emerged. 



Chemical Determinations 



The determination of sulfate was conducted by the usual 

 gravimetric method after precipitation with BaClc. The determin- 

 ation of the sulfides followed the titrimetric method, recom- 

 mended in the "Standard Methods for the Examination of Water, 

 Sewage and Industrial Wastes, 1955" (1). The total-sulfur was 

 determined as sulfate after oxydation to sulfate with nitric acid, 

 bromine and perchloric acid. This wet-ashing technique followed 

 the procedure recommended by Patterson (6). The iron was 

 determined colorimetrically wtih 1,10-phenanthroline (11). The 

 organic bound carbon was determined as CO2 using a wet- 

 combustion technique after removing the carbonate carbon ( 12 ) . 

 Determination of Bacterial Numbers 



The numbers of bacteria were deteiTnined using the MPN- 

 dilution technique with ¥2 oz. prescription bottles. The following 

 media were used: 



1. For the determination of the aerobes: 



5.0 g caseinhydrolysate 



0.05g K2HPO4 



trace FeP04 

 750 ml aged sea water 

 250 ml aqua dest. 

 The bottles were filled with 9 ml of medium. 



2. For the determination of the sulfate-reducing bacteria we used 

 a modified Starkey's medium: 



3.5 g sodium lactate 

 1.0 g NH4CI 

 0.5 g K2HPO4 



