Seaweeds use vanadium bromoperoxidase, in the oxidation of bromide, as a defense mechanism against predators.
Your pith is only surpassed by your substance, wwh. Actually, I was thinking of methyl bromide.
To wit (from Google):
Methyl Bromide Challenge
There is no known single alternative fumigant, chemical, or other technology that can readily substitute for methyl bromide in efficacy, low cost, ease of use, wide availability, worker safety, and environmental safety below the ozone layer. Research by the U.S. Department of Agriculture (USDA) indicates that multiple alternative control measures will be required to replace the many essential uses of methyl bromide.