>>10103543Why do people seem to equate big ocean with big organisms?
The limiting factor on the size of animals on Earth is not gravity or habitat volume, it's food supply. Blue whales literally don't do shit except eat all day and night every day and night. Organisms that don't need to forage for food can get a lot bigger, but generally they're either plants or fungi, which can spread their biomass out over a huge area.
Europa however doesn't have an environment that allows for distributed biomass organisms; at best it has a lot of hydro-thermal vents on its ocean floor. Unlike Earth, where hundreds of watts of energy strike every surface on land for roughly 12 hours a day, Europan organisms would be limited to a comparatively tiny fraction of the sea bed where the conditions that allow chemotrophs to thrive would exist, and this small total would be broken up into thousands of tiny 'islands' separated by hundreds of kilometers of abyssal plain.
Furthermore, even the deep sea organisms on Earth that never leave their hydro-thermal vents still depend on surface life for the oxygen they need. That includes everything more complex than the bacteria that actually extract energy from chemicals in the water. If all life on the surface of Earth was wiped out instantly, the oxygen levels would start to drop and soon enough the tube worms and lobsters and blind shrimp and stuff that eat those chemotropic bacteria would suffocate and die.
Best case scenario for Europan life is not leviathan monsters, but rather bacteria-like organisms that form colonies kind of like stromatolites on Earth. It would be amazing if we found complex single celled life like eukaryote-analogs.
