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My alien species uses bioluminescence for communication. They live at the bottom of an ocean 50km deep. Since there is no light, the ecosphere is based on chemosynthesis. The losest rung of the food chain is not sunlight but is chemical energy pumped out of hydrothermal vents. To my knowledge chemosynthesis cannot produce oxygen.

Is there any way that the ocean could be saturated enough with dissolved oxygen to enable bioluminescence? By the way, the ocean is moon-wide and underneath a thick layer of ice (similar to Europa in our solar system).

Is there a compound that can come out of hydrothermal vents that can be used as energy that also produces oxygen as a byproduct? Or perhaps another way to produce oxygen in the depths of the ocean?

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  • $\begingroup$ I find it unlikely the organisms would develop bioluminescense on a planet with no light to begin with. Creatures glow to interact with other creatures that can see them. If no one has eyes there is no reason to glow. $\endgroup$
    – Daron
    Nov 19, 2022 at 18:48
  • $\begingroup$ That's true, and I've thought about that. I've come up with an evolutionary advantage to it: they use the bioluminescence to illuminate their prey, like a human holding a flashlight, except it's entirely biological. The aliens are in the shape of a koosh ball and have thousands of tiny tendrils that they use for senses and grabbing prey. But the feelers are limited. They have to physically touch their prey to locate it, and so the rudimentary eyes and bioluminescence help them to catch prey. $\endgroup$
    – isdi0
    Nov 19, 2022 at 18:51
  • $\begingroup$ In the solar system oxygen is produced by two pathways: 1. chemolysis of CO2 by UV light (Mars) and 2. radiolysis of water by particle radiation in strong magnetic fiels. The moons of Saturn and Jupiter could contain large amonts of O2 dissolved in the ice. Free O2 is more common in the solar system than most people think, it has even been detected (abundantly) in 2 comets. $\endgroup$
    – Avun Jahei
    Nov 20, 2022 at 11:18

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The ecosphere is based on chemosynthesis

you have your answer already. If the local life thrives on chemosynthesis, they have something that can act as an oxidizer instead of oxygen, and that very something can also be used to have bioluminescence. On Earth that something is usually sulfur.

The mechanism of bioluminescence requires an oxidation to release energy that is then used to excite a molecule which emits light. On Earth it has been developed by aerobic organisms using oxygen, but nothing prevents alternative, non oxygen based mechanisms to exist and being developed by other lifeforms.

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  • $\begingroup$ Can sulfur be used in place of oxygen in bioluminescence? I'm not exactly sure of the mechanisms behind bioluminescence, but I know that life on earth requires oxygen to do so. @L. Dutch $\endgroup$
    – isdi0
    Nov 19, 2022 at 18:37
  • $\begingroup$ @isdi0 Almost all eukaryotes breath oxygen through mitochondria. Some bacteria and archea also does breath directly (in fact mitochondria derives from ancient archea). Some bacteria hates oxygen and most of them are sulfur-reducting bacteria. Why no complex oxygen-hating life form emerged is a bit of a mystery, but might be explained by the fact that the air and the oceans are so full of oxygen, that oxygen-hating organisms could only thrive as being very simple unicellular forms in refugia environments, and by being so simple, they can't evolve any usefulness for bioluminescence. $\endgroup$ Nov 19, 2022 at 19:11

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