kelp is a "rich source of bromine and iodine"!

Da-Da!!!!
It says:
"Many marine plants, particularly kelp, are a rich source of bromine and iodine"
(that's why my cat doesn't care eating kelp?)

great text, I will read it more carefully later. It would be nice to find also some numbers, just to be aware of the proportions. But if I remember right, as Iodine is heavier than bromine, not too much quantity of bromine is required to neutralize the iodine, while a lot of Iodine is required to neutralize bromine.
Therefore: just a little amount of bromine in kelp could vanish the benefits of the presence of iodine!
Am i correct?
well, that's a finding...