What powers from Brexit? Seriously? It is not an empowerment. The point of it was to leave the EU and as such remove any supra-national governance from the UK. So he is talking as much bollocks as you are. In order to impose a marine protection zone the government needs to impose a marine protection zone. Since such zone existed prior to our departure that is an objective fact that EU membership does not preclude such creation.
Well at least we agree on that. I am mystified why you try to find good from it but we have at last a start point.