LIBERTY TOWNSHIP, NJ (Warren County) – The Mountain Lake Lake Association (MLCA) is coordinating with the New Jersey Department of Environmental Protection (NJDEP) regarding the algae bloom occurring in Mountain Lake in Liberty Township.
The bloom was first detected by the Lake Association through meter readings taken on April 2. On the same day, NJDEP collected a sample for lab analysis. The results, posted Saturday, confirm that the lake is experiencing a significant bloom.
The cell count in the sample is 55,500 cells/mL, which is high but not unusually so for Mountain Lake, based on past results. However, the cyanotoxins (microcystins) in the sample measured 8.02 micrograms/liter, which is unusually high—this is the highest level ever recorded in Mountain Lake since regular testing began five years ago. The public health threshold for microcystins, set by NJDEP, is 2 micrograms/liter.
Based on these results, Mountain Lake is in an Advisory Status. As a result, residents are advised to prevent pets from ingesting the lake water, and fish caught in the lake should not be consumed.
Blue-green algae, also known as cyanobacteria, are naturally occurring microorganisms that have been around since the beginning of time. Low levels of cyanobacteria are generally not a concern. However, when there is excessive growth—referred to as a Harmful Algal Bloom (HAB)—cyanobacteria can produce potentially harmful toxins called cyanotoxins. At high levels, these toxins can be dangerous to humans, pets, livestock, and wildlife.
NJDEP provides detailed information about HABs on their website: https://dep.nj.gov/wms/bfbm/cyanohabs/
Moving forward, the MLCA will continue to monitor algae levels in the lake daily, working closely with NJDEP. The MLCA will use its two algae meters to track changes, and NJDEP will conduct additional sampling and analysis as needed. Updates will be shared with the community through posts like this one. The hope is that the bloom will soon subside as the lake transitions from spring turnover and stratifies, locking in the phosphorus (a key nutrient for algae) below the thermocline. However, weather conditions could significantly impact water quality in the lake.
This bloom highlights the importance of protecting the lake’s water quality. Water quality will be a major agenda item at the MLCA’s upcoming Spring Membership meeting on April 17. At that meeting, Princeton Hydro will present their newly completed Lake Management Plan for Mountain Lake, which outlines the steps the community needs to take to protect and restore the lake. The MLCA encourages everyone with an interest in the lake’s future to attend and support these efforts.
