@thepioden I love the idea of Ulmo ensuring the continuation of life withing the water (and I can’t believe I totally ignored that part :0) Would also explain why Cuivienen seems to take such a central place in Elvish cultural heritage/nostalgia. Personally I have a hard time imagining the Elves cultivating lifestock at the time, but it’s certainly possible (and the more I think about it the more likely it gets, after all it took a long time for Orome to find them), and I can imagine them growing some of the water-based plants you mentioned. And anything involving prehistoric megafauna is great!
@ivanaskye The chemotrophs/chemotrophic autotrophs idea and the giant funghi towers are amazing!! And of course someone noticed the hole with “if the Elves had a carnivorous diet what would the animals eat”, but tbh I just liked the notion that the Elves’ diet at the time resembled Gollum’s Idk why. I think the stasis is still less of a problem than constant winter would be, because then they have something to eat at least. But while I like the ‘nomadic Elves’ thing, I believe they actually stayed at Cuivienen for a long time until the journey to Valinor began, so I prefer the ‘Ulmo kept the ecosystems in bodies of water alive’ idea (see above). Chemosynthetic autotrophs as the bottom of the food chain make a lot of sense, though funghi can also use organic waste (not sure if that’s the right word in English, basically I mean dead things) as a food source. Those organisms wouldn’t die out at once, but they might be at an evolutionary disadvantage compared to other plants because of some other factor, so that’d explain why there’d be only a few of them around in the next Ages.
@vardasvapors yes the remnants of the Lamps being involved fits perfectly
So the solutions to the oxygen problem are: cyanobacteriae and algae thanks to Ulmo, bacteria that produce oxygen as a waste product from methane, and my own version, the oxygen from the trees in Aman “spreading” to Middle-Earth (with help from Manwe). I’m not going to pick one, it’s all headcanon material now. And of course, there are areas in which magic (Yavanna’s, Melian’s) keeps thing alive and out of stasis too – if those are proportional in size (compared to the rest of ME) and productivity to the modern rainforests (compared to rest of our world), it’s fine.
And @nipahgirl you mentioned that there would’ve been enough oxygen left over from the time of the Lamps, but (according to a timeline I found on tolkiengateway) over 14000 sun years passed between the destruction of the lamps and the creation of the Sun, and I’m fairly certain the oxygen would’ve run out in that time, so the other options would probably work better by then.

