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National Aquatic Resource Surveys

Northern Appalachians Ecoregion - National Lakes Assessment 2012 Results

Key Results

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.  

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

National Lakes Assessment 2012 Bar Chart of the Trophic State of Lakes in the Northern Appalachians Ecoregion

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

National Lakes Assessment 2012 Bar Chart of the Condition of Total Phosphorus in the Northern Appalachians

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Photo of a lake in the Northern Appalachians ecoregion that was sampled during the National Lakes Assessment 2012Pleasant Lake, located in the Northern Appalachians ecoregion, was sampled during the NLA 2012. Photo: Hilary Snook, EPA.

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.

  • Based 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).

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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.

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

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* 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.