Final answer:
Mariners and navigators must monitor FLIPS or revised charts for changes in local magnetic direction.
Step-by-step explanation:
The responsibility of monitoring FLIPS or revised charts for changes in local magnetic direction lies with mariners and navigators. They are the ones who need to pay attention to any updates in the charts, which include information about the magnetic direction. By staying informed, they can ensure accurate navigation and prevent any potential issues caused by discrepancies in magnetic direction.