Oyster Pond Recovers From Hazardous Algal Bloom 10-13-16

Oyster Pond Recovers From Hazardous Algal Bloom
The Falmouth Enterprise

Oyster Pond is well on its way to recovery, according to an update from the Oyster Pond Environmental Trust last week.

Last month, the Department of Public Works dredged 16 cubic yards of sediment from Trunk River to increase water flow into the pond.

The dredge was an emergency measure taken to increase the salinity of the pond, in hopes of abating a potentially hazardous blue-green cyanobacterial algal bloom. Trust leaders hoped that an increased flow would flush out the pond, as well as raise salinity levels high enough to kill the freshwater algae causing the eutrophication.

Measurements taken by trust member William B. Kerfoot showed that outflow from the pond increased from 736 to 2,600 cubic meters per day after the sediment had been removed.

Last Friday, October 7, the trust informed members that the algal bloom had nearly disappeared, due to the dredging project, increased rainfall and falling water temperatures.

A water sample taken by Mr. Kerfoot on August 24 showed 1,768 cells of algae per cubic centimeter of water, but a sample taken last Monday, October 3, had only 6 cells.

"The good news is that the algal bloom is now by and large gone," Mr. Kerfoot said this week. "The level of algae is back to the normal level that's in Oyster Pond at this time of year."

Now, he said, the pond is once again swimmable, fishable and habitable to herring and American eels. The pond is quickly losing its "pea green" color, and the waters are clear several feet deep.

"It could have been much worse. We could have had massive fish kills if it had not been for the town clearing the outflow," Mr. Kerfoot said.

Trust director Wendi B. Buesseler said that she had recently visited the weir at Oyster Pond, and said it was "full of herring fry getting ready to exit."

Although the dredge was perceived as successful, Mr. Kerfoot said that some tens of fish were killed due to lack of oxygen before the emergency measures took place.

In addition, the count of herring fry entering the pond this year will likely be inaccurate, since it was difficult for volunteers to see the fish entering the murky pond over the past several weeks.

Mr. Kerfoot also noted that the blue-green algae have not disappeared altogether; given hypereutrophic conditions, there could be a resurgence of the noxious algal bloom next summer.

"We need to correct some conditions in Oyster Pond to prevent this in the future," he said.

A part of that effort is reducing nutrient loading into Oyster Pond, he said, but another is consistently monitoring the outflow of Oyster Pond to maintain habitable salinity levels.

To that end, the trust is currently drafting a proposal for $140,000 that would go toward monitoring the outflow of Oyster Pond.

The funds would also go toward expanding an existing permit to allow the Falmouth Department of Marine and Environmental Services to dredge both Trunk River and the connected lagoon year-round at its discretion.

The department currently holds a permit that allows it to dredge Trunk River, but only on an emergency basis. The permit also does not apply to the pond between Oyster Pond and Trunk River.

Ms. Buesseler said the proposal is still in the planning stages but is a priority for the trust.

"We realize something has to be done long term to make sure the inflow and outflow of the pond is maintained," she said.

In the future, Ms. Buesseler said, the trust will seek out funding opportunities for the proposal, potentially with the Falmouth Water Quality Management Committee, Cape Cod Commission or Massachusetts Department of Environmental Protection.

From Forum

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