682 



Marine Microbiology 



goland, Germany.* Also here we have a strong increase of the 

 sulfides and decrease of the sulfates. The incerase after fourteen 

 days was 0,540 mg/g wet sediment and in a second experiment 

 0.218 mg/g wet sediment after 28 days. The results are somewhat 

 different than those in 5a. In one experiment 19.6 per cent of the 

 foiTned hydrogen sulfide came from other sources than sulfate 

 (compared with about 50% in the Texas experiments). In the 

 second experiment the decrease of the sulfate was greater than 

 the increase of sulfides, a part of this sulfur must have gone into 

 another form. The numbers of the SOi-reducers were ten times 

 higher than in the Texas experiment. In one experiment we had a 

 very strong increase of their numbers, in the other one no in- 

 crease. That the organic bound sulfur could contribute a consider- 

 able amoimt of sulfur is shown by experiments we conducted in 

 Texas. Here we analysed algae and higher plants for their con- 



TABLE 1 



Sulfur Content of Plants Per Gram Dry Weight ln mg 



Sulfate -Sulphur Total Sulfur 



Higher plants 



Thalassia testudinum 

 (Konig) 



Diplanthera wrighti 

 (Asherson) 



Digenea simplex 

 (Wulfen) 



Algae 

 Ulva spec. 



Gracillaria-typc red algae 



Gracillaria hlodgettii 

 (Harvey) 



Red algae (unknown species) 



4.30 



29.28 



* The sediment in Helgoland consisted partly of weathered red .'^andstone. The 

 aged iron oxides of the sandstone were also not soluble in HCl and behaved in 

 the same way as pyrite. Therefore the data of the starting point was subtracted 

 from all further data of the pyrite. 



