IV. Eutrophication and Lake Typology: Case Studies
Eutrophication is the process of increasing productivity in a body of water, providing a framework for classifying lakes.
- The Concept of Eutrophication
- Definition: The process of a water body becoming more productive.
- Lake Succession Model: An idealized progression where a lake evolves from oligotrophic (low productivity), to mesotrophic (medium), to eutrophic (highly productive), and finally to dystrophic (a bog stage with decreased productivity). This progression is heavily influenced by basin shape, climate, and geology, not just age.
- A Spectrum of Aquatic Environments
The following five lakes illustrate the range of trophic states found in nature.
| Lake Name | Location | Trophic State | Key Characteristics | Productivity (Growing Season) |
| Lake Vanda | Antarctica | Ultraoligotrophic | Permanently sealed under 3-4 meters of clear ice; very sparse phytoplankton. | ~1 mg C·m⁻²·hr⁻¹ |
| Lake Tahoe | CA/NV, USA | Oligotrophic | Remarkable clarity, deep euphotic zone (~100m). Threatened by cultural eutrophication from human activity. | Low intensity per unit volume |
| Castle Lake | CA, USA | Mesotrophic | Exhibits characteristics of both oligotrophic and productive lakes; develops oxygen depletion in deep water. | ~70 mg C·m⁻²·hr⁻¹ |
| Clear Lake | CA, USA | Eutrophic | Shallow, high turbidity, frequent blue-green algae blooms; photosynthetic zone limited to the upper 4 meters. | ~300 mg C·m⁻²·hr⁻¹ |
| Cedar Lake | CA, USA | Dystrophic | Shallow basin nearly filled with sediment, nearing extinction; invaded by terrestrial and higher aquatic plants. | ~6.0 mg C·m⁻²·hr⁻¹ |