Aggregating in one big chunk can be good news, if it is treated as a garbage collector and if the garbage is removed. If the plastic isn't removed, then it will be an eternal source of microplastics. I can't see how that is a good thing, unless some fish, bacteria or plant knows how to eat that plastic and make it into something harmless. I doubt that this will act like a plastic-magnet for the microplastics in the area.