Northern Appalachians Ecoregion - National Lakes Assessment Results
NLA 2022 Ecoregional Results
Key Results
An estimated 20,219 lakes in the Northern Appalachians ecoregion are represented in the National Lakes Assessment (NLA). Of these lakes, 60% are natural and 40% are man-made.
The NLA uses trophic state as an important indicator of lake condition and assesses the extent of biological condition and key stressors in the nation’s lakes.
- In the Northern Appalachians, 11% of lakes are rated as hypereutrophic while 41% are eutrophic, 37% are mesotrophic and 11% are oligotrophic.
- The most widespread stressors assessed are phosphorus and nitrogen with 39% rated poor for phosphorus and 30% rated poor for nitrogen. Atrazine was also detected in 31% of lakes.
- Cyanobacteria are one-celled photosynthetic organisms that normally occur at low levels. Under eutrophic conditions, cyanobacteria can multiply. Not all cyanobacterial blooms are toxic, but some may release toxins, such as microcystins. For information about risks at specific locations, recreational water users should check with state, tribal or local governments.
- Based on microcystins, detections occurred in 39% of lakes and no lakes were above the recreational benchmark.
Change from 2017*
- For the Northern Appalachians, the NLA reports that the percent of lakes in good condition for benthic invertebrates decreased by 38 percentage points and the percent in good condition for chlorophyll a decreased by 31 percentage points between 2012 and 2017.
- The percent of lakes with microcystin detections increased by 37 percentage points.
To access more ecoregional specific information, please visit the interactive NLA Dashboard.
* The change analysis is based on information from two points in time – 2017 and 2022.
