They accelerate upwards and their bubbling metabolism will compensate. If any creatures on the surface die from inhalation of the fart then the whales become awake and feed on them immediately. Slumber resumed. It's like a background clean-up process.

Yup, the old brap n' snap. Everyone who swims around whales knows and fears this.

This is an interesting theory but it’s not at all how sperm whales eat and doesn’t fit into their dietary habits that we know of.