All sulphur bacteria require sulphur compounds for their development. These are furnished as hydrogen sulphide by the decomposition of plant and animal remains in water. Such bacteria are abundant in quiet waters rich in sulphates, as described for the Danish coast and the Kiel Fiord by Warming (1875) and Engler (1883). (Braun-Blanquet 1932:203)
BRAUN-BLANQUET, Josias. 1932. Plant sociology: the study of plant communities. (Trans.: George D. Fuller; Henry S. Conard) New York: McGraw-Hill Book Company.