An excess of nutrients leads to eutrophication, the term for unchecked plant growth in a body of water. The plants consume all oxygen in the water, killing fish while creating thick mats of vegetation. The opposite problem, a dearth of nutrients, also may limit the fish and game that live off a lake.
Nitrates and phosphates from human activities often drive the nutrient cycle. But in remote lakes with few sources of natural or artificial nutrients, trace metals such as molybdenum may be the limiting factors. In such places, small variations in metal inflows could cause big changes in a lake’s biology.