‘A Vital Solution for the Ponds and for the People Who Love Them’

On a hot August afternoon, Chilmark Pond looks as inviting as ever: wind riffling across the surface, boats bobbing through the channel, birds stalking the shallows. But for the past several summers, a tricky problem has lain underneath. Toxic cyanobacteria blooms have turned the beloved pond into off-limits territory, keeping swimmers, anglers, and shellfishers away — and putting pets at particular risk. 

Warmer waters, combined with excess nitrogen and phosphorus from septic systems and fertilizers, have fueled the algae blooms, creating conditions that are harmful to people, deadly for dogs, and detrimental to the pond’s fragile ecosystem. Chilmark Pond has seen toxic blooms every summer since 2022. 

In true Vineyard fashion, however, the community has rallied to address the problem. The Chilmark Pond Foundation has been leading efforts to restore the pond’s health for the last seven years. This summer, they introduced a new tool: a solar-powered “sonic buoy,” formally known as the LG Sonic MPC-Buoy (monitor, predict, control), which is designed to track conditions and disrupt cyanobacteria before it takes over. The buoy has already been deployed in more than 100 countries, including in New York and New Jersey, but this is the first time the technology has arrived in Massachusetts. Scientists are watching closely, because if it works here, it could be “huge news” for addressing excessive nutrient problems in Island ponds and beyond.

The buoy’s origin story is as local as it gets. The Chilmark Pond Foundation itself grew out of the Chilmark Pond Association, when a group of neighbors decided to take a more active role in restoring the pond’s ecological health. “It’s very much modeled after the Great Pond Foundation,” says Amy Salzman, president of the Chilmark Pond Association and ex officio board member of the Chilmark Pond Foundation, referring to the nonprofit that pioneers science-driven pond restoration on the Island.

One member of the Association, Don Ingber  — a scientist who also happens to be Amy’s cousin through marriage — first came across the LG Sonic buoy while he was researching. “I asked him the other day, how’d you find this? He said he was Googling around,” Amy recalls. 

At about the same time, in an example of Vineyard serendipity, another lead surfaced. Charlie Shipway, who heads the Menemsha sailing program, happened to be out on a boat with the director of LG Sonic’s U.S. division, Greg Eiffert. They were chatting about pond health, and the subject of the sonic buoy came up. Shipway also looks after the electric boat of one of the Foundation’s board members, so word of the new technology quickly made its way back to the group. 

From there, the Foundation began researching the technology, holding calls with the company, and gathering references. “We made sure it wasn’t going to harm anything else we cared about in the pond,” Amy says. 

Then, the Foundation bought the buoy. The price tag: about $80,000 — all of it raised through community contributions.

“We decided to special order one — a stainless steel one because the pond is slightly salty,” Amy says. “The device we ordered from the Netherlands got stuck in JFK customs for about a month. So the company just went ahead and told us they were shipping us a standard aluminum one. So we have that.” Amy thinks the standard one will hold up fine, since that part of the pond is only slightly brackish.

After securing approvals from the Conservation Commission to put the roughly six-by-seven foot buoy in, actually getting it into the water was the next challenge.

“I sent a note to my Pond Association group and said, ‘Hey, does anyone know someone who can help us get this thing in the water?’ And within 10 minutes, Steve Ewing, who owns a dock-building company in Edgartown, said he could help. He and his son Niko and Gary Mottau from the neighborhood came — no charge whatsoever — and got the thing in for us.” 

Photos online show Ewing operating a crane as his son, Niko, guides the buoy to a boat at the shoreline, before bringing it out to the middle of the pond. Solar panels are visible on each side of the buoy, which is anchored in the Middle section of Chilmark Pond. It was deployed on July 23.

So, how does it work? When the buoy senses cyanobacteria moving upward through the water column to reach sunlight, it emits sound waves that stop them. “And it has the capacity to sort of change its tune. If the cyanobacteria starts ignoring it, it recalibrates itself,” Amy says. 

“Cyanobacteria are photosynthetic — they need light at the surface,” says Emily Reddington, biologist and executive director of the Great Pond Foundation, which is managing the buoy’s science and data. “They get nitrogen and phosphorus, their building blocks of life, at the bottom. What the buoy does is it makes them stop in the water column, so they can’t get both. And by getting them to stop, they can’t grow or bloom out of control.”

Cyanobacteria, also known as blue-green algae, are a normal part of a pond’s ecosystem, Emily notes. But when they grow out of control or bloom, they shift the ecological balance and dominate the ecosystem, creating fluorescent, paint-like slicks, mats, or scums that trigger health advisories. That’s when toxicity becomes a real risk. 

Cyanobacteria can produce cyanotoxins. When cyanobacteria bloom, the concentration of toxins in the water can become harmful or even deadly to other organisms. More cyanobacteria produce more toxins. Scientists are still exploring when and why cyanobacteria produce cyanotoxins, Emily says. 

In Chilmark Pond, two main forms of cyanobacteria blooms are typically found: mat-based and surface scums. The surface scum blooms resemble green paint, while mat-based blooms can either form on the bottom and rise to the surface as gas builds, or remain as benthic blooms — green clumps on the pond floor.  

Cyanobacteria can be confused with other, benign organisms found in ponds. “Sometimes it’s clear it’s cyanobacteria — it’s not really going to be anything else when you have a fluorescent green pond,” Emily says. “But sometimes it could just be green algae in a state of decay. That’s why we need to use tools like our fluoroprobe to distinguish it. What’s green algae versus what’s cyanobacteria? What’s the concentration? And then with microscopy, confirm it further.”

Anabena and Dolichospermum are genera of cyanobacteria found in Chilmark Pond. Under the microscope, she shows slides of Anabaena, which look like tiny coils, and Dolichospermum, which resemble strands of jewelry. 

For people, harmful exposure usually happens through skin contact and can be worsened by open wounds, which can lead to mild symptoms such as skin irritation or more severe symptoms such as infections if blooms are intense. Ingestion of blooming water can cause organ damage. For humans, this is unlikely. But unfortunately, pets and livestock are often exposed through ingestion and results are severe to deadly. 

“They’re actually attracted to cyanobacteria. If they’re lapping it or licking their fur, it can be fatal. Unfortunately, most times when dogs are exposed, they don’t survive,” Emily says.

The sonic buoy also serves as a monitoring station, collecting data every 30 minutes on dissolved oxygen, pH, temperature, chlorophyll, and other indicators of pond health. That information will help scientists assess how well the technology performs through the Vineyard’s bloom season, which typically runs May through October but can stretch later in nutrient-rich ponds. 

Chilmark Pond is not unique in battling cyanobacteria — the problem is widespread across the Vineyard, the Cape, and the Hamptons. But Chilmark Pond’s smaller size and shallower basins make it particularly vulnerable, and cyanobacteria blooms, driven by heat and excess nutrients (nitrogen and phosphorus) have been commonplace in recent years. Chilmark Pond gets hot, and because of runoff from septic systems and lawn fertilizers, it has excess nitrogen.

Whether the buoy is making a difference is still unclear. “We make our conclusions based on data, so we have to remain skeptical until we have competent evidence,” Emily says. “But we are seeing hints of hope and success.” The timing and intensity of the blooms came at a slightly different time this year, and around the buoy seemed a little less intense, she says. 

The real test will come later this fall, once the peaks and timing of the season’s blooms can be analyzed. Other factors such as cooler water temperatures and storms stirring the pond also play a role in bloom behavior. “So our job is to look with our real strong scientific skepticism and ask, if we see differences, are they because of the buoy or other factors in the environment? We really want it to work, but we need to look at the whole picture to evaluate its effectiveness,” Emily says. 

The buoy will likely stay in the pond until early November and return in April. Charlie Shipway and another Islander, Andrew Kahl, are going to handle the buoy’s removal, installation, and maintenance, Amy says.

The first year may be just the beginning. “The question is, can the buoy actually reduce the intensity of blooms? Can it disrupt them? It’s too early to tell if that’s the case. We know that sometimes this technology works best the second year,” Emily says. 

Still, scientists are watching the sonic buoy in Chilmark Pond closely. “There are a lot of pond groups eagerly looking on, not just on the Island, but elsewhere,” Emily says. “If this technology works, it’s something that is simple to deploy, relatively cost effective, and scalable for multiple ponds on the Island to tackle something very hard to tackle. It really could be a vital solution for the ponds and for the people who love them.”

Addressing the Source: Strategies for Reducing Nutrients in Chilmark Pond

Neighbors remember a time when kids swam freely in the pond. “There were times when toxicity wasn’t present — when people could fish and eat out of the pond, and I think that’s what the community wants to go back to,” Emily Reddington says. 

But while the buoy may help treat the symptom, the Foundation is also focused on what’s causing the problem. “You have to go to the source,” Emily says. “And that’s reducing the nitrogen and phosphorus that are coming into the pond … Hopefully this buoy will stop the toxicity while we do the longer-term work of identifying and stopping the nitrogen and phosphorus coming in.”

Dredging

One key initiative is dredging. Amy Salzman and the Chilmark Pond Foundation spent the last five years securing approvals for a dredging permit — the first time Chilmark Pond has ever had one. The pond is cut several times a year to exchange nutrient-rich water with cleaner ocean water. 

“The ocean is oligotrophic, which means low-nutrient water,” Emily explains. “It’s salty, clear, clean, low in nitrogen and phosphorus. If you have a good cut, you flush most of the pond’s high nitrogen and phosphorus, low-salinity water during tidal cycles, and you exchange that volume.”

With every cut, the tides also bring in sand, which gradually builds up a delta north of the barrier beach. “Over time, we’ve seen the breaches at Chilmark Pond become shorter in duration and carry a lower volume of water flow,” Emily says. “At Edgartown Great Pond, after a decade of dredging and removing the sand delta, the flushes became longer duration and [had a] higher volume of flow. And the pond rebounded. The health of the ecosystem came back. Things like submerged vegetation or eelgrass — you have to have a very healthy environment for a long time for those kinds of species to return.”

Dredging, or removing sand, makes flushes more effective, but regulatory hurdles slow the permitting process. “There’s an endangered species — the northern tiger beetle, that wasn’t documented at these habitats in the past,” Emily explains, adding that any work now requires a management plan to protect the species. “Policy often evolves slower than what the ecosystem needs to survive. So this dredging keeps the pressure from building in the system, hopefully reducing cyanobacteria, keeping fish healthy, hopefully changing the ecosystem. But if you wait five years, there’s further degradation that happens. So it’s two things struggling: the policy and the process versus the needs of the ecosystem.”

Amy says the Chilmark Pond Foundation is hoping to dredge in November and December.

Fertilizer Reduction 

Nitrogen enters the pond through groundwater and runoff. Wastewater is the largest source, followed by fertilizer, Emily says. Some neighbors have pledged to reduce or stop fertilizing, which helps reduce nutrient input across the watershed. The Abels Hill community worked with the Vineyard Conservation Society to sign a pledge to not use fertilizer. “So that’s low-hanging fruit,” Emily says. “Just choose to be gentler on your space around you.”

Addressing Wastewater 

Wastewater is trickier. Chilmark does not have a centralized wastewater treatment facility, and most homes rely on septic systems, many of which are Title 5 and not designed to remove nitrogen. “Some folks are converting to nitrogen-reducing septics … Some people have the type of tanks where it’s pumped out. But to really tackle the nitrogen, you have to replace everybody’s septic, which, in terms of cost and the capacity and infrastructure to do that on the Island, would be immense,” Emily says.

So the Foundation is exploring remediation technologies like permeable reactive barriers, “where you put a carbon source in the ground and you cultivate an environment where microbes transform harmful nitrogen into inert nitrogen gas,” Emily says. “And that’s capturing the nitrogen from many, many septics, and with one kind of technology, keeping nitrogen from getting into the pond.”

Another idea that the Foundation is looking into is taking nitrogen- and phosphorus-rich muck to rebuild wetlands — also known as thin layer replacement. “Because wetlands capture carbon, but they also capture nitrogen,” Emily says. “We’ve done some preliminary work showing that wetland plants can very specifically target wastewater nitrogen. So you add in the right native plants, and you’re not only capturing carbon and helping the planet, but you’re helping the pond through this natural filter. Yet again, nature is the best solution.”

Through research with the Marine Biological Laboratory in Woods Hole, the Chilmark Pond Foundation and Great Pond Foundation are also working to identify plants that are especially effective at pulling wastewater nitrogen out of the groundwater as it’s traveling to the pond. One example is phragmites (the native variety, not the invasive European interloper). “Hopefully we’ll have a list of plants by the end of this year that we can share with homeowners and Conservation Commission,” Amy says. “If you plant them at the edge of the pond — or anywhere on the watershed, frankly — they will help withdraw or attenuate nitrogen from the groundwater before it gets to the pond. The plants may even help pull nitrogen out of the pond.” 

Another hope is that shellfish can eventually return to Chilmark Pond. Right now, fecal coliform levels are too high for the Division of Marine Fisheries to allow shellfish aquaculture, even as a remediation strategy. But in other Island ponds, shellfish restoration has been successful. Adult shellfish can filter up to 50 gallons of water per day, removing nitrogen and phosphorus as they grow. “They use it as building blocks for their bodies,” Emily says. “So when those organisms are harvested from the pond, you’ve taken nitrogen and phosphorus out, and you’ve grown an organism. It’s a wonderful thing.” 

Still, the pond isn’t there yet. “You have to build the layers of restoration before you can have more options available in your ecosystem,” Emily says.