LIBERTY TOWNSHIP, N.J. (Warren County) — Blue-green algae levels in Mountain Lake have risen slightly above the New Jersey Department of Environmental Protection’s advisory threshold, according to an update posted Friday by the Mountain Lake Community Association.
The association said the latest water samples were collected Sept. 16 and submitted to Princeton Hydro for analysis. Results confirmed the lake has been experiencing a late-season algae bloom.
Blue-green algae, also known as cyanobacteria, was measured at 80,189 cells per milliliter, slightly above the NJDEP advisory threshold of 80,000 cells per milliliter. Water clarity was measured at 3.5 feet.
The lake’s surface temperature was 74.4 degrees, which the association said was higher than average for mid-September. The lake remained well stratified.
Water down to 15 feet was well oxygenated and similar in temperature, with dissolved oxygen measured at 9.55 parts per million at the surface and the temperature gradually dropping to 72.7 degrees.
Below 15 feet, temperatures dropped to 65.4 degrees at 18 feet and 52.4 degrees at 24 feet, while dissolved oxygen fell to essentially zero. Those cold and anoxic conditions continued to the lake bottom at 36 feet, where the temperature was 46.9 degrees.
The association said those conditions are typical for Mountain Lake at this time of year.
Because of the algae results, the association advised people to avoid swimming, prevent pets from ingesting lake water and avoid consuming fish caught in the lake.
The Mountain Lake Community Association said it will continue monitoring the lake through October and provide results as they become available.
