Here is a quote from the article if you can't read it.
"Much has been said about the danger of liberating spores when popping the vesicles of bubble algae. This is particularly true for members of Order Valoniaceae, but even then, the vesicles are said to be a sporulant risk only when having reached at least a third of their full size. Even if spores escape when you botch the job of vesicle-removal ('vesectomy', anyone?), those escapee spores have to run the gauntlet of herbivorous filter feeders, filtration equipment, and the wild lottery of hitting a good, unoccupied spot to settle and grow. Those spores will eventually be released anyway if you don't remove the vesicles."
I would guess that as for the emerald crabs, once they have eaten them through a cycle, they would be eating only younger, non-spore, alagae, and thus not spreading them. If they couldn't keep up though, they would be more prone to popping spore-laden bubbles. Those crabs are very surgeon-like and I doubt the amount of spore emitted by a crab eating it is anything close to that from a finger popped bubble.