Classifying the Condition of Our Lake (Trophic State)
Trophic state is a method to classify lakes and is an indicator of water quality. Common characteristics used are clarity, chlorophyll (a measure of algae present), and total phosphorus concentration. There are 4 stages of the Trophic State Method.
- Oligotrophic: Low biological productivity. Oligotrophic lakes are very low in nutrients and algae, and typically have high water clarity and a nutrient-poor inorganic substrate. Oligotrophic water bodies are capable of producing and supporting relatively small populations of living organisms (plants, fish, and wildlife). If the water body is thermally stratified, hypolimnetic (deep water) oxygen is usually abundant.
- Mesotrophic: Moderate biological productivity and moderate water clarity. A mesotrophic water body is capable of producing and supporting moderate populations of living organisms (plant, fish, and wildlife). Mesotrophic water bodies may begin to exhibit periodic algae blooms and other symptoms of increased nutrient enrichment and biological productivity.
- Eutrophic: High biologically productivity due to relatively high rates of nutrient input and nutrient-rich organic sediments. Eutrophic lakes typically exhibit periods of oxygen deficiency and reduced water clarity. Nuisance levels of macrophytes and algae may result in recreational impairments.
- Hypereutrophic: Dense growth of algae throughout summer. Dense macrophyte beds, but extent of growth may be light-limited due to dense algae and low water clarity. Summer fish kills are possible.: lakes have low nutrient content, and thus are very clear, produce few weeds, and do not support large fish populations.
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