Any CO2 that is in the environment is going to stay in the environment???if it spends a brief time as part of a kelp plant, as soon as the kelp dies it will turn right back into CO2???if a sea urchin eats the kelp its waste products will decompose into CO2???just as if the kelp had died a natural death???the idea that trees and other plants remove CO2 totally overlooks the fact that plants aren???