Exploring Solutions to Combat Algal Blooms on Lake Hopatcong’s Shorelines

April 25, 2025| Community, Environment

By: Kyle Richter

A new pilot project is beginning this spring on Lake Hopatcong to reduce harmful algal blooms (HABs) in shallow, near-shore areas. HABs are overgrowths of algae that can sometimes produce toxins and make the water unsafe for people, pets, and wildlife. The project is led by Princeton Hydro, in partnership with the Lake Hopatcong Foundation, Lake Hopatcong Commission, and New Jersey Department of Environmental Protection, with funding from the U.S. Army Corps of Engineers. It focuses on testing innovative treatments to improve water quality.

Current Efforts and New Strategies

Lake Hopatcong has already seen successful efforts to manage nutrients through watershed projects that reduce runoff and deep-water treatments like aeration and nutrient inactivation to address phosphorus released from the lakebed in low-oxygen conditions. These strategies provide a strong return on investment by targeting nutrient issues across the lake. However, shallow, near-shore areas where algae form remain a challenge. This new pilot project will test treatments using algaecides, coagulants, and phosphorus-binding products to explore new methods for reducing HABs in these nutrient-rich shallow areas.

Treatment Methods

Over the spring and summer, six treatment methods will be tested in several coves and bays. Each method is designed to prevent algae growth or reduce it quickly if it appears. Here’s what to expect:

• Spring Treatments (starting the week of April 28): Two coves—Crescent and Ashley—will receive treatments placed on the lake bottom to stop algae before it forms. One will use a copper-based product, and the other will use an oxidizer (a product that breaks down algae).
• Early Summer Treatments: Two more coves will get treatments that help particles in the water clump together and sink. These treatments also use a safe, lake-approved material to trap phosphorus—a nutrient that feeds algae—and keep it locked in the lakebed.
• Late Summer Treatments: In two coves known for algae issues, the treatments will begin by killing any algae in the water, then add materials to settle and trap nutrients in the sediment below.

What to Expect

During the project, you may see small boats applying treatments in the coves. The products used are not pesticides—they are approved for use in lakes, safe when applied as directed, and specifically designed to improve water quality. Monitoring will take place throughout the season, with follow-up testing one week, one month, and one year after each treatment. While no lake-wide closures are expected, signs may be posted in treatment areas as a precaution, depending on the product used.

Future Impact

This pilot project aims to identify the most effective strategies for managing shoreline HABs, which could benefit not only Lake Hopatcong, but also other lakes across New Jersey and the Mid-Atlantic.