Abstract
An isotopic method has been developed to establish the biological production of volatile organohalogens. The marine microalgae Porphyridium purpureum and Dunaliella tertiolecta were grown in seawater medium containing NaH 13 CO 3 , and volatile organohalogens were extracted and analyzed by gas chromatography‐mass spectrometry (GC‐MS). Isotopically labeled methyl halides were formed in each microalgal culture, and the 13 CHCl 3 found in the P. purpureum culture confirmed the production of chloroform reported by Scarratt and Moore (Limnol. Oceanogr. 1999. 44: 703–707). No incorporation of 13 C into dichloromethane was observed, even though slightly increased CH 2 Cl 2 concentrations were detected in both algal cultures at the end of the incubation period.