Reducing nitrogen the natural way: Scientists study how HCT’s Cold Brook ponds can help

May 7, 2026

Sure, the ponds at Harwich Conservation Trust’s (HCT) Robert F. Smith Cold Brook Preserve are beautiful, and they provide splendid habitat for a variety of wildlife. But these watery jewels offer other environmental benefits that may not be as apparent when you’re out birding or taking a stroll at the property.

Researchers from UMass Dartmouth’s Coastal Systems Program work in a pond at HCT’s Robert F. Smith Cold Brook Preserve. Photo by Gerry Beetham

Researchers from UMass Dartmouth’s Coastal Systems Program took samples from ponds at Harwich Conservation Trust’s (HCT) Robert F. Smith Cold Brook Preserve this week as part of a study into how the ponds can help reduce nitrogen flowing toward Saquatucket Harbor on Nantucket Sound.

Four ponds were created when HCT led an ecological restoration partnership that transformed a retired cranberry bog, and the project also included the rewilding of a mile of stream and the addition of a half-mile wheelchair accessible All Persons Trail. Cold Brook is now flowing freely through the 66-acre property for the first time in over a century.

Scientists launched small boats and donned scuba gear to retrieve the pond samples. “We’re taking sediment cores at the bottoms of these ponds and we’ll incubate them and we’ll see if there is denitrification happening in these sediments,” said Jennifer Benson, a Research Associate for the Coastal Systems Program at UMass Dartmouth’s School for Marine Science & Technology.

“If so, that’s great–that means nitrogen is being used up and released as nitrogen gas, so it’s out of the system.,” said Benson. “That would lower the amount of nitrogen that goes out into Nantucket Sound. the same thing with phosphorus.”

Getting the research boat into the water. Photo by Gerry Beetham

‘Taking up excess nutrients’

Nutrient pollution in coastal watersheds is a common byproduct of commercial and residential development. This nutrient overload can come from septic systems and the use of fertilizer.

“Plants need nutrients to grow–but when there’s an excess amount of them, that’s where we run into problems,” said Benson. “So, we really want to see if these ponds are acting as a sink and taking up excess nutrients before they go out to Saquatucket Harbor.”

Good for the environment and the bottom line

Eco-restoration projects like the one at Cold Brook can save towns significant money on costly sewer construction. To improve the health of the impaired Saquatucket Harbor, Harwich Town Meeting voters in 2017 approved $2 million for ecological restoration of the retired Cold Brook bogs upstream.

Reduced sewering results in reduced road construction disruption and reduced long-term sewer expenses for taxpayers. By restoring natural habitats and water flow as well as reducing nitrogen heading to the harbor, the HCT-Town eco-restoration partnership is estimated to save taxpayers up to $6 million according to the Town of Harwich Comprehensive Wastewater Management Plan.

Valuable data for future projects

The field lab at Cold Brook. Photo by Gerry Beetham

The phrase “nitrogen attenuation” was used frequently by the researchers at Cold Brook. It describes the natural reduction in the concentration of nitrogen compounds as they move through an environmental system. “The idea is that making these ponds will actually promote nitrogen attenuation by creating these systems where things can grow and thrive,” said Benson.

The results of the Cold Brook study may provide valuable data for similar eco-restoration efforts. “A project like this is very interesting and could be very useful for other places that are thinking about transforming retired cranberry bogs into wetlands,” said Benson.

So, the next time you’re enjoying a walk at the Cold Brook Preserve, take a moment to thank the ponds. There’s a lot of hard work going on beneath the surface that is a win for the environment, and it might even save you money!

 

Photo gallery: Ace HCT volunteer photographer Gerry Beetham captured some great pics during the pond research at Cold Brook:

Researchers from UMass Dartmouth’s Coastal Systems Program took samples from ponds at Harwich Conservation Trust's (HCT) Robert F. Smith Cold Brook Preserve this week as part of a study into how the ponds can help reduce nitrogen flowing toward Saquatucket Harbor on Nantucket Sound. Photo by Gerry Beetham
Researchers from UMass Dartmouth’s Coastal Systems Program took samples from ponds at Harwich Conservation Trust's (HCT) Robert F. Smith Cold Brook Preserve this week as part of a study into how the ponds can help reduce nitrogen flowing toward Saquatucket Harbor on Nantucket Sound. Photo by Gerry Beetham
Researchers from UMass Dartmouth’s Coastal Systems Program took samples from ponds at Harwich Conservation Trust's (HCT) Robert F. Smith Cold Brook Preserve this week as part of a study into how the ponds can help reduce nitrogen flowing toward Saquatucket Harbor on Nantucket Sound. Photo by Gerry Beetham
Researchers from UMass Dartmouth’s Coastal Systems Program took samples from ponds at Harwich Conservation Trust's (HCT) Robert F. Smith Cold Brook Preserve this week as part of a study into how the ponds can help reduce nitrogen flowing toward Saquatucket Harbor on Nantucket Sound. Photo by Gerry Beetham
Researchers from UMass Dartmouth’s Coastal Systems Program took samples from ponds at Harwich Conservation Trust's (HCT) Robert F. Smith Cold Brook Preserve this week as part of a study into how the ponds can help reduce nitrogen flowing toward Saquatucket Harbor on Nantucket Sound. Photo by Gerry Beetham
Researchers from UMass Dartmouth’s Coastal Systems Program took samples from ponds at Harwich Conservation Trust's (HCT) Robert F. Smith Cold Brook Preserve this week as part of a study into how the ponds can help reduce nitrogen flowing toward Saquatucket Harbor on Nantucket Sound. Photo by Gerry Beetham
Researchers from UMass Dartmouth’s Coastal Systems Program took samples from ponds at Harwich Conservation Trust's (HCT) Robert F. Smith Cold Brook Preserve this week as part of a study into how the ponds can help reduce nitrogen flowing toward Saquatucket Harbor on Nantucket Sound. Photo by Gerry Beetham
Researchers from UMass Dartmouth’s Coastal Systems Program took samples from ponds at Harwich Conservation Trust's (HCT) Robert F. Smith Cold Brook Preserve this week as part of a study into how the ponds can help reduce nitrogen flowing toward Saquatucket Harbor on Nantucket Sound. Photo by Gerry Beetham
Researchers from UMass Dartmouth’s Coastal Systems Program took samples from ponds at Harwich Conservation Trust's (HCT) Robert F. Smith Cold Brook Preserve this week as part of a study into how the ponds can help reduce nitrogen flowing toward Saquatucket Harbor on Nantucket Sound. Photo by Gerry Beetham
Researchers from UMass Dartmouth’s Coastal Systems Program took samples from ponds at Harwich Conservation Trust's (HCT) Robert F. Smith Cold Brook Preserve this week as part of a study into how the ponds can help reduce nitrogen flowing toward Saquatucket Harbor on Nantucket Sound. Photo by Gerry Beetham
Researchers from UMass Dartmouth’s Coastal Systems Program took samples from ponds at Harwich Conservation Trust's (HCT) Robert F. Smith Cold Brook Preserve this week as part of a study into how the ponds can help reduce nitrogen flowing toward Saquatucket Harbor on Nantucket Sound. Photo by Gerry Beetham
Researchers from UMass Dartmouth’s Coastal Systems Program took samples from ponds at Harwich Conservation Trust's (HCT) Robert F. Smith Cold Brook Preserve this week as part of a study into how the ponds can help reduce nitrogen flowing toward Saquatucket Harbor on Nantucket Sound. Photo by Gerry Beetham
Researchers from UMass Dartmouth’s Coastal Systems Program took samples from ponds at Harwich Conservation Trust's (HCT) Robert F. Smith Cold Brook Preserve this week as part of a study into how the ponds can help reduce nitrogen flowing toward Saquatucket Harbor on Nantucket Sound. Photo by Gerry Beetham
Researchers from UMass Dartmouth’s Coastal Systems Program took samples from ponds at Harwich Conservation Trust's (HCT) Robert F. Smith Cold Brook Preserve this week as part of a study into how the ponds can help reduce nitrogen flowing toward Saquatucket Harbor on Nantucket Sound. Photo by Gerry Beetham

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