Biological production of methyl bromide in the coastal waters of the North Sea and open ocean of the northeast Atlantic

Two separate studies in different oceanic regions provide evidence for the production of methyl bromide (CH₃Br) by the prymnesiophyte Phaeocystis. A sampling program to study the seasonal cycle of CH₃Br in a coastal area demonstrated that the seawater was supersaturated with respect to CH₃Br for over 3 months of the year. The greatest saturation was observed during a bloom of Phaeocystis. Also, in situ field measurements demonstrated that CH₃Br was supersaturated over a large region of the northeast Atlantic. A positive correlation was observed between CH₃Br and dimethylsulphoniopropionate (DMSP), indicating that there was a source common to both compounds. An accessory pigment, hexanoyloxyfucoxanthin, which indicates the presence of prymnesiophytes, also correlated positively with CH₃Br.