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A total of 15,634 lakes in the Northern Appalachians ecoregion are represented in the NLA. Of these lakes, 74% are natural and 26% are man-made.  

Trophic State and Key Stressors: The NLA uses trophic state as an important indicator of lake condition and assesses the extent of key stressors in the nation’s lakes.

• In the Northern Appalachians, 15% of lakes are rated as most disturbed based on trophic state, 15% are eutrophic, 55% are mesotrophic, and 15% are oligotrophic.
• The most widespread stressors assessed are phosphorus (31% of lakes), nitrogen (22%), and riparian vegetation cover (21%).

• Trophic State

  

• Indicator with the Highest Percentage of Lakes in the Most Disturbed Condition: Phosphorus

  

Human Use Condition: Cyanobacteria is one of three algal toxin related indicators presented in the NLA (see also chlorophyll a and microcystins).  It serves as a proxy for the presence of algal toxins.

• Pleasant Lake, located in the Northern Appalachians ecoregion, was sampled during the NLA 2012. Photo: Hilary SnookBased on cyanobacteria cell counts, 2% of lakes in the Northern Appalachians are in the most disturbed condition (i.e., pose a high risk of exposure to algal toxins).

Change from 2007 (for lakes >4 hectares)*:

• For the Northern Appalachians, the NLA reports an increase of 27% in the proportion of lakes in the most disturbed condition for phosphorus between 2007 and 2012.
• There was also a decrease of 27% in the proportion of lakes in the most disturbed condition based on the lake drawdown exposure indicator.

• Percentage of Lakes in Most Disturbed Condition for all Indicators: Northern Appalachians

  

To access more indicator graphics please visit the interactive NLA Dashboard.

* The change analysis is based on information from two points in time – 2007 and 2012.  The change in condition analysis only considers lakes 4 hectares and larger because smaller lakes were not sampled in 2007.