Another question in relation to this...

The GSA looks to be dead sometime after it appears. It turns a very dark green, maybe even a black color after some time. If it is in fact dead, will it eventually fall off of the leaves? I tried to rub it off with my fingers but it persists. I am wondering if I am stuck with the algae on the leaves it has formed on. Is my only alternative to uproot and replant the plant tops?