Minor algae bloom on Twilight Lake monitored

Bio-char, used to reduce nitrate levels, is not considered a permanent solution

Originally published to the Ocean Star on May 15, 2026

BAY HEAD — The Bay Head Environmental Commission heard updates on the water quality in Twilight Lake from Princeton Hydro senior environmental scientist and technical project manager J.P. Bell at its May 12 meeting.

Beginning in July of 2025, the town began putting bags of a substance called “bio-char” in the lake to reduce high levels of nitrates and phosphates. Bio-char is an inert carbon-based substance similar to charcoal which naturally absorbs nitrates and phosphates, both of which contribute to a phenomenon called nutrient pollution.

The Environmental Protection Agency (EPA) says nutrient pollution is caused by high levels of nitrogen and phosphorus entering the air and water, usually from a wide range of human activities. Nitrogen and phosphorus are nutrients that are natural parts of aquatic ecosystems, and both support the growth of algae and other aquatic plants, which provide food and habitat for fish, shellfish and smaller organisms that live in water.

While too much nutrient buildup may not seem like an ecological issue, the EPA says too much of these substances in the water can cause algae and algae-like bacteria to grow faster than ecosystems can handle, forming algal blooms. Algal blooms can severely reduce or eliminate oxygen in the water, reducing populations of local fish and crustaceans. Some blooms consist of cyanobacteria that mimic algae in their appearance and ecological role. They can release toxins into the water that can make people and animals sick if they touch, drink or eat contaminated fish or shellfish from the water.

Bell said Princeton Hydro was made aware of a minor seasonal bloom in Scow Ditch and explained that although the bio-char has led to a visible reduction in nutrient levels, it is not a permanent solution. Because the bags absorb nitrates and phosphates over time through natural diffusion, they will at some point in the future become saturated and will no longer naturally absorb the substances, but they are currently functioning as they are supposed to.

“We see the eye test, we know that it’s working,” he said. “We’ve seen it effective in smaller ponds and bigger ponds.”

Commission member Rick McGoey said he could not see a compelling trend in the nutrient data and saw a reduction in some samples but not in others, with Bell agreeing.

“The number of high reduction rates are not as many as a nominal reduction or a reversal where we’d see higher than 2022 data,” Bell said. “The results don’t lie, and as I said earlier, we've been working with (bio-char) a while now, not just this state but other states as well. This will help us conclude that bio-char is not the end all be all. It’s a tool in the toolkit, but not the end all be all. In my experience it needs to be used in the proper locations and proper environments to see the results.”

Bell and McGoey both agreed that bio-char has an undeniable effect on the quality of the water, but it is not powerful enough on its own to solve the problem of nutrient pollution.

Water samples from March are not currently available, samples from April have been taken for analysis, and further analysis on bio-char is expected.