During periods of catastrophic darkness caused by natural catastrophes such as asteroid impacts, massive volcanic eruptions, or large-scale wildfires, life on Earth survived with the help of organisms that can switch to another source of energy while they wait for sunlight to pierce the darkness once more. Contrary to common belief, phototrophic organisms did not completely die off during such periods. A study conducted by Charles Cockell of the Open University’s Centre for Earth, Planetary, Space and Astronomical Research in Milton Keynes, UK, and his team found that mixotrophs, which can use sunlight or consume dead organic matter, thrived in the darkness and even helped their light-dependent counterparts. The mixotrophs were able to switch to getting their energy from dead creatures and plants, and in doing so, they kept the nutrients turning over, which improved the conditions for phototrophic recovery when the samples were returned to light. The study shows that the photosynthetic biosphere is much more robust than generally assumed[1][2].
Citations:
[1] https://phys.org/news/2009-09-catastrophic-darkness-life-survives-asteroid.html
[2] https://www.sciencedirect.com/science/article/pii/S0262407909621898
[3] https://www.space.com/7256-life-dark-organisms-survived-asteroid-impacts.html
[4] https://www.visajourney.com/forums/topic/217329-life-in-the-dark-how-organisms-survived-asteroid-impacts/
[5] https://www.theguardian.com/environment/2018/jul/08/animals-live-dark-natural-history-museum-exhibition-london