Lake Classification - Lake George is a young, oligotrophic lake.

A lake can be classified due to its "age." Young lakes have high dissolved oxygen levels, high clarity readings, and sparse vascular plant growth. Lake George is a young lake!

Most often, lakes are classified by their trophic state. In general, trophic state refers to the biological production of plant and animal life occurring in a lake. The level of production that occurs is determined by several factors, but primarily by the phosphorus supply to the lake and the length of time water has been present in the lake.

Many different indicators are used to determine trophic state. The most common are bottom dissolved oxygen, Secchi disk clarity, vascular aquatic plant growth, and chlorophyll-a. These indicators determine if a lake is oligotrophic, mesotrophic, or eutrophic.

Image courtesy of: UW-Extension Lakes Program

Oligotrophic lakes

Lakes in this category tend to be larger, deeper lakes with clear water, rocky or sandy shorelines, low phosphorus enrichment, limited vascular plant growth, low algal growth and adequate dissolved oxygen throughout. They are low in nutrients and do not support large fish populations. Lake George is an oligotrophic lake.

Parameter
Secchi disk clarity
Phosphorus
Chlorophyll a
Level for oligotrophic lake
> 5 m
< 0.010 mg/l
< 2 ug/l

 

 

 



Mesotrophic lakes

Image courtesy of: UW-Extension Lakes Program

Lakes in this category fall between the two extremes of eutrophic and oligotrophic. They have fewer vascular plants than eutrophic lakes, but generally more than oligotrophic lakes.

Parameter
Secchi disk clarity
Phosphorus
Chlorophyll a
Level for mesotrophic lake
2-5 m
0.010-0.020 mg/l
2-8 ug/l

 

 

 



Eutrophic lakes

Image courtesy of: UW-Extension Lakes Program

Lakes in this category tend to be smaller and shallower, with murky bottoms. They have low dissolved oxygen levels, shallow clarity readings, abundant vascular aquatic plants, and high nutrient levels. They often support large fish populations, but are susceptible to oxygen depletion, mostly during summer months when organic matter decomposes.

Parameter
Secchi disk clarity
Phosphorus
Chlorophyll a
Level for eutrophic lake
< 2 m
> 0.02 mg/l
> 8 ug/l

 

 



Check out our CSLAP program reports to see why Lake George is an oligotrophic lake.

Credits: NHDES Environmental Fact Sheet BB-27 Layman's Guide for Measuring a Lake's Trophic State, New Hampshire DES: Interactive Lake Ecology

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