I'd say don't panic. The green & black stuff on your clay pot is Algae or moss caused by dampness. The condition of the root is a liitle out of focus so I can't say for sure what is happening there.
My suggestion would be to make up a container, ( big enough to hold your pot,) of Physan 20 (mix according to directions) and soak the entire pot and plant. then scrub the pot to remove the moss & rinse. This should take care of it for a while. It will come back again depending on where the pot is positioned.
I am sure others will add to this.