i have a HUGE problem my trunk has rain water where the spare tire goes... on 1999 Pontiac Grand Am

but thats not the BIG problem it seems as though i have white mold brown fungi growing in spots in my trunk its really disgusting and i was wondering what should i do at this point???? CAN SOMEBODY PLEASE HELP ME????

Asked by for the 1999 Pontiac Grand Am
put someone in trunk w/flashlight and run water on car to determine leak and repair as nec