Some, but much less than a similarly catastrophic failure at coal or nuclear power plant or even an offshore oil rig. I only mention that because there will be people who see this article and point and scream that wind turbines are dangerous.
Fiberglass chunks shouldnt be an issue in terms of pollution, thats what many boats use, it doesnt dissolve. The foam filling could be nasty but realistically its a drop in the bucket in terms of oceanic plastic pollution. Bathing is probably not gonna happen until the debris is recovered.
Well, I wonder if you could cut yourself when stepping into fiberglass chunks?
But yeah, since the material is most likely inert, it will probably at most be used as a sort of artificial reef by wild life. For the foam, that's probably also inert. But it likely swims on the surface, so has the same effect as plastic in the great Pacific garbage patch.