When a water body is deficient in nutrients, it is known as?

A water body poor in nutrients, with low biological productivity and clear, well oxygenated water, is described as oligotrophic.

Eutrophic waters are the opposite, being rich in nitrates and phosphates that drive dense algal and plant growth.

Mesotrophic waters occupy the middle ground, holding a moderate nutrient level and moderate productivity.

Dystrophic waters are stained brown by dissolved humic acids and hold very little oxygen or life.

Deep high altitude lakes and newly filled reservoirs are typical oligotrophic systems.

Heavy inflow of sewage or fertiliser can push a clean oligotrophic lake toward a eutrophic, algae choked state.