What are the possible causes of white spots on driftwood and how can they be treated or prevented?

White spots on driftwood can be caused by mold, fungus, or mineral deposits. To treat them, you can scrub the affected areas with a mixture of water and vinegar, or use a mild bleach solution. To prevent white spots, make sure the driftwood is properly dried and stored in a well-ventilated area to discourage mold and fungus growth.