Eutrophication Dead Zone: Dissolved Oxygen Collapse

This simulator models a lake water column as 18 stacked depth layers, each tracking algal biomass and dissolved oxygen under a real diurnal light cycle. Raise nutrient loading and the algae's carrying capacity climbs, thickening the bloom; raise thermal stratification and the vertical diffusion coefficient at the thermocline collapses, cutting the bottom water off from surface reaeration. By day, photosynthesis can push surface oxygen above saturation; by night, respiration alone runs it back down, and sinking dead algae decompose at the lake bed, consuming oxygen there continuously. Watch a stratified, heavily-loaded lake develop a spreading hypoxic dead zone at depth — and see a storm-mixing event temporarily break the stratification and flush oxygen back down.