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A group of Water Mill homeowners are proposing a new solution to chronic algae blooms and flourishing invasive plants in Mill Pond: a system of air pumps and bacteria infusions that would dissolve muck several feet thick at the bottom of the pond.
The mechanics of the system will be explained in detail by representatives of the system’s manufacturer at a gathering this coming Saturday, December 4, sponsored by the Water Mill Citizens Advisory Committee and the Friends of Lake Nowedonah. It will be held at the Water Mill Community House at 11 a.m.
The proposal involves using a combination of some two dozen large air diffusers, each 18 inches in diameter, and the release of aerobic bacteria and enzymes to dissolve nitrogen-producing muck in the bottom of the pond. The company claims the system could dissolve up to a foot of muck from the bottom of the pond each year.
“The theory is that the nitrogen is in the muck and gets released as there is decomposition,” said Steve Abramson, a Water Mill CAC member and leader of the Friends of Lake Nowedonah, the Native American name for Mill Pond. “Certainly there is going to be some stirring up of the bottom, but there is going to be so much oxygen you won’t be able to blame the stirring for a lack of oxygen.”
In September 2008, a large fish kill struck the pond, and it has since been blamed on a sudden dearth of oxygen in its waters caused by a massive algae bloom that died off following a cold snap. The algae blooms, according to scientists who have been studying the pond for years, are fueled by influxes of nitrogen, or nitrates, through groundwater laced with farm fertilizers seeping into the pond, rainwater runoff from local roads and farm fields and, to a lesser extent, from the feces of the thousands of waterfowl that use the pond as an overwintering area. Runoff might be able to be addressed through a costly program of capturing rainwater in wells before it reaches the pond, but addressing the problems of birds and groundwater intrusion, the primary sources of the nitrates, will be much more difficult if not impossible, experts say.
The Southampton Town Trustees, who are responsible for overseeing the pond, have contracted a Massachusetts limnologist to help them come up with a solution to the pond’s problems. The lakes and ponds specialist, Lee Lyman, Ph.D., has thus far recommended treating the pond with alum, a heavy chemical compound that will sink to the bottom, where it would bind with the nitrates, theoretically trapping the nitrates and preventing them getting into the water and feeding the algae blooms.
Mr. Abramson said local residents are not convinced that dumping alum into the pond is the sort of permanent fix they are looking for. “Instead of just covering the muck, we need to get rid of it,” he said. “With alum, it’s impossible to get everything, and an anchor can get dragged along the bottom, or the coating can be breached in some way, and then you have the nitrates releasing into the water again.”
The system the residents are proposing would cost about $50,000 a year to operate, he said, which he expects would have to be raised in a partnership of public and private funding between the town and residents who live on or near the pond.
Mr. Abramson said that it’s believed that with the bottom muck reduced, invasive plants that also gobble up oxygen, like water lillies and millfoil, would be thinned out as well because they would not be able to anchor their roots without the soft bottom muck.
Another Trustees consultant, Jim Walker of Inter-Science Associates, a Southampton-based development and environmental consulting firm, has told the Trustees the only way to restore the lake to its former clarity and cleanliness is to get rid of the non-native carp and goldfish in the pond, which feed on native plant species that absorb nitrates and add oxygen to the lake. Mr. Walker has proposed using a chemical called Rotenone to wipe out all the carp in the pond, along with all the other fish left behind after the fish kill that claimed most of the larger species like bass and carp, and then restocking the pond with a balance of predator fish and grazers like carp.
The Trustees have not supported the use of the chemical, primarily because Mill Pond drains into Mecox Bay, but have made plans to hire commercial fishermen to net carp out of the pond. As of last week, however, Trustee Fred Havemeyer said they haven’t been able to find any fishermen who are willing to do the netting.
Mr. Walker said that netting carp will help but would not produce the sort of results starting from scratch would.
“If you do it very aggressively and thoroughly you might put a dent in the carp population,” he told the Trustees at a meeting on November 15. “Carp removal is a legitimate thing that has been successful in some places. Still, I think Rotenone is the way to go—it’s the correct way. The water quality will be spectacular.”
Mr. Walker said restoring the lake would take a couple of years, first reintroducing native plants and then fish species. He said that the alum regimen could take four or five years to show results in water quality.
He also raised doubts about the system the Water Mill residents are proposing, likening the effects of the air diffusers to that of three water circulators, known as Solar Bees, that were placed in the pond a few years ago with the Trustees’ permission by Mr. Abramson and other residents to address the algae problems. Some blame has been placed on the circulators for stirring up the bottom of the shallow pond and perhaps triggering or exacerbating the algae bloom that ultimately caused the die-off. Mr. Abramson said no evidence has ever shown the Solar Bees to have been at fault.
