How do oligotrophic, mesotrophic, and eutrophic lakes differ in biological productivity?

Lakes are categorized based on their levels of biological production, which are primarily determined by nutrient availability. These categories differ significantly in their rates of net primary production (NPP):1

• Oligotrophic lakes are characterized as unproductive. They have a poor supply of nutrients, resulting in low NPP—typically between 50 and 100 milligrams of carbon per square metre per day—and depressed secondary production. These lakes often feature high oxygen content and uniform vertical oxygen distribution.12
• Mesotrophic lakes represent an intermediate state of productivity. Their NPP ranges between 250 and 1,000 milligrams of carbon per square metre per day.1
• Eutrophic lakes are highly productive, with a good supply of nutrients. Their NPP is significantly higher, ranging from 600 to 8,000 milligrams of carbon per square metre per day, which supports high levels of secondary production. These conditions can lead to oxygen depletion at greater depths and the development of harmful algal blooms when nutrient inputs are excessive.12

While it was once theorized that lakes naturally evolve from oligotrophic to eutrophic states, modern science indicates that lake productivity primarily reflects contemporary nutrient supply processes.1