Yes. That is true. But I meant a smaller part. In Excession this part about the avatar of GSV Sleeper Service as it is contemplating offloading all of its cargo: "There was an extra, perhaps deeper melancholy at the thought that it would no longer be able to play host to the living things aboard; the creatures of the sea and the air and the gas-giant atmosphere, and the woman."

Previously in the same book it is implied that these "creatures of the gas-giant atmosphere" are animal level intellects. But my headcanon is that perhaps there are Culture ships with Nasqueron Dwellers or similar intelligent gas-dwellers with complex societies on-board.

You are absolutely right that The Algebraist is full of gas-dwelling creatures. But as far as I can recall while they have a "Culture" feel to them there are no direct Culture references in that book. But maybe I have missed something.