Watershed Institute aids county officials in preventing toxic algae blooms at Rosedale Lake

PHOTO COURTESY OF SUSAN JACOBSEN

The Watershed Institute and Mercer County officials are teaming up to address toxic algae blooms in Rosedale Lake.

Rosedale Lake in Pennington is part of the Mercer County Park System and has been faced with the issue of toxic algae blooms since 2019. In 2019, Mercer County shut down all recreation in the lake at Rosedale Park for public safety.

“There has not been any action taken so far in regards to the lake. We are partnering with Mercer County to put in a specific feature called ‘floating wetlands,’ ” said Steve Tuorto, director of Science and Stewardship at the Watershed. “The plans that we have for the current project is being funded by the state Department of Environmental Protection (DEP).”

The cost of the wetlands would be covered under a $185,000 grant from the state DEP. The grant would also cover other county solutions implemented for the lake.

The floating wetlands would be about 1,000 square feet, fashioned into about 20-30 small wetlands that will float in the surface of Rosedale Lake. The plants and soil medium will absorb the pollutants, cleansing the water, according to the Watershed Institute.

Floating wetlands are not the only solution Mercer County is working on for the lake; other solutions include the installation of an aeration device and the use of barley bales to filter stormwater runoff.

“Barley bales are an algae control measure. The aeration device increases oxygen and also circulates the water, which are both algae prevention methods,” Tuorto said.

Solutions being discussed are all preventative measures against the algae blooms, Tuorto said.

“They need to kind of need get in before the blooms start. Nothing was done last year or currently,” he said. “Right now the plan is that floating wetlands will be put in next spring.”

Tuorto cautioned that the measures being implemented won’t fix the problem of the blooms (HABs).

“When the HABs bloom they fluctuate. They can get bigger or smaller depending on how much rain we get and how much nutrients are available,” he said.

A combination of hot weather, nutrients from fertilizers, pet waste and other sources create conditions where cyanobacteria grow too rapidly, producing toxins that are harmful to people and pets, according to the Watershed Institute.

Over the course of two years, Mercer County and the Watershed Institute will implement and gather data on solutions.

“We have met with county officials already. The county and I did get samples from the lake and send them to the DEP to get a baseline for the bloom,” Tuorto said. “As of now the plan is to put the features in place next spring.”