Airborne algae might possibly survive in the atmosphere if there's enough water vapour so they don't dry out and have enough material for photosynthesis. Temperature would have to be right of course in a region of the atmosphere with habitable air pressure or they would freeze or die from heat. Some 'volcanic' activity would maybe be needed in the core to eject dead organisms, to avoid that all carbon ends up in an inaccessible state. If the algae would possess a compartment with gaseous hydrogen for example, to stay buoyant enough to stay in the athmosphere, those algea might be possible. Still it would be a crazy and extremely weird ecosystem. : ) I don't see multicellular life working in Jool sadly : (