A lake is not a static container. It is a metabolic system that runs through nutrient-poor clear-water phases, moderate loading and over-fertilised tipping states in stages – usually over decades, sometimes over a single season. This animation walks through a cross-section of all four limnological stages.
Click a stage or let the auto-tour run. Secchi depth, bottom oxygen, chlorophyll-a and the greenhouse-gas factor respond in real time.
Eutrophication does not run linearly. As long as a lake stays in the clear range, nutrient input and self-purification balance each other. Once algal growth uses up bottom oxygen, the sediment releases stored phosphorus – accelerating the very process that triggered it. This feedback is the point at which stage transitions become faster and counteraction more expensive.
A hypertrophic lake emits on average six times the greenhouse gases of an oligotrophic lake of the same size – the difference is due above all to methane. Worldwide, freshwater lakes release an estimated 1.3 to 2.3 gigatonnes of carbon per year, around one fifth of the carbon released by fossil fuels. A lake in balance binds carbon; a hypertrophic one gives it up.
If you are responsible for a water body, a WAMO sensor package helps you see the stage transitions early enough – before algal toxins, anaerobic sludge or methane emissions limit your management options.
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