Linked from
The 10 pages that link to Anoxia, each with the reason it gives.
PeatlandRelated: Saturated soils restrict oxygen and slow the decay of plant remains.
Lake TanganyikaRelated: Deep water below the oxygenated upper layer is largely anoxic.
SphagnumRelated: Waterlogged peat restricts oxygen, slowing the decay of dead Sphagnum.
AnaerobicRelated: It names a strict oxygen-free condition in which anaerobic processes may occur.