how much oxygen is there in the air pockets in underwater caves, and is it replenished somehow?
In: Biology
Often times, absolutely zero.
That’s one of the biggest dangers of exploring underwater caves, it is totally possible that you emerge into a large air pocket that hasn’t been exposed to the outside in years and contains zero oxygen so your first breath is your last. You could also emerge into a pocket full of hydrogen sulfide from decaying organic matter, again first breath is the last.
Unless the water recedes far enough that there’s a direct air connection between the air pocket and the entrance of the cave, the only way to replenish the oxygen in the air pocket is by diffusion through the water, but this is going to be a slow process.
There is oxygen in the water, and that oxygen can diffuse into the atmosphere. We obviously know the ocean is an enormous source of our oxygen creation by algea.
So yes, even if its permanently sealed even at low tide, the air would still exchange co2 and oxygen with the water.
Not suggesting to bring 200 friends in, because low surface area and minimal surface agitation will make it a slow process, but it would gravitate to resupplying with oxygen.
One thing to keep in mind is that said air pocket would be pressurized by the weight of the water above it. Our atmosphere is made up mostly of nitrogen, and at high pressures like what you might experience 100ft underwater your lungs will actually absorb more nitrogen than oxygen leading to something called nitrogen narcosis. So even if there is oxygen in an air pocket you might not even be able to breathe it.
I know it’s tempting with the current state of the world but no, you can’t go live with the fishes.
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Depends, but generally not much if there’s no way for it to replenish.
If you breathe out from a scuba set while in a completely flooded cave, air bubbles will form at the top, and will generally leech through the rock if it’s porous enough.
It all depends on whether the air does get refreshed by changes in water level, and if there’s anything else there that can consume O2 so it varies depending on the specific air pocket
An air pocket exposed to water but not any other input of gasses will come to equilibrium with the proportion of gasses dissolved in water. That’s not exactly the same as the proportions of gasses in air because they don’t all dissolve equally easily (water has more CO2 for example) but it gives you an idea. I would expect an underwater bubble to eventually go away as air diffuses out a bit more easily than in.
Of course the air pockets you see in caves won’t form spontaneously underwater so the air they actually hold probably depends on where the air is coming from.
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