I reckon this is work of a Russian submarine and torpedo's. The size of the bubbles mean the holes in the pipes must be very large.
Putin knows he's boned with regards to sending gas via these pipelines so he's damaged them as a statement to show he can do the same with the new norwegian under-sea pipeline about to open or any other infrastructure such as fibre optic cables and keep potential deniability as it's arguably an act of war.
They need to get diver's down there and try to find evidence and proof it was a russian torpedo, then things will ramp up.
The odd thing is; Are Russia continuing to send gas down the pipe from their end?
Unburned gas is an environmental disaster at the rate it''s being pumped out, it's an ongoing hazard for shipping but I guess Russia just want's to stir up yet more trouble.