The influence of iron fertilization on the fluxes of methyl halides and isoprene from ocean to atmosphere in the SERIES experiment

As a part of an iron-fertilization experiment in the NE Pacific in July 2002 measurements were made of isoprene and methyl halides both within the fertilized patch and outside. Isoprene showed the response that would be expected of a gas having a source in phytoplankton: its concentration within the patch increased relative to outside, and after 10–14 days its calculated net production rate was about 6-fold higher within the patch. In contrast, the methyl halides showed no clear effect of fertilization, though the production rates of methyl iodide were appreciable. Hence there is no evidence that any of the algal groups present, such as diatoms that were stimulated by the fertilization played a significant role in the net production of methyl halides. The results are not inconsistent with a photochemical source of the gases, though light levels were attenuated by persistent cloud cover.