The collectivity sent a small crew to rake the beach. It took 4 guys about 3 hours.
I heard that Saint Jean business owners had been complaining for a long time about the leftowver seaweed, but were told by the authorities that people who come to Saint Barth just don't care about beaches, just shopping and restaurants. I also hear that what changed their mind is that some of the well heeled new year's visitors did complain about the state of the beaches. This apparently triggered this overdue action.