Nutrients and Aquatic Vegetation Effects

After eutrophication from natural and civilizational causes is explained, the term oligotrophication is defined as the (partial) reversal of the eutrophication process under the influence of decreased nutrient inputs. Potentially limiting nutrients such as phosphorus, nitrogen, carbon, silicon, and trace metals are listed and evaluated with respect to: (1) mechanisms of nutrient limitation of primary biological productivity; (2) sources and relative abundance; and (3) regeneration and re-use in lake ecosystems. High concentrations of manganese in epilimnic waters are correlated with low abundance of blue-green algae, but manganese-resistant Cyanophyta were also found. An increase in areal loading of phosphorus of 0.1 g/m²/yr, equivalent to waste from one person per 1.2 ha (3 acres) of lake surface (0.6 ha or 1.5 acres if phosphate detergents are banned), is considered environmental impact.