State officials are looking into the cause of a possible fish kill at Little Pond over the weekend.
“It was either a fish dump or a fish kill,” R. Charles Martinsen III, acting director of the Falmouth Natural Resources Department said, and the preliminary evidence suggests the latter. “There was a significant algae event mid-to-late last week, and this came on the heels of that.”
Mr. Martinsen said the town won’t know for sure until the Massachusetts Division of Marine Fisheries concludes its examination of the carcasses and an analysis of water samples taken from the pond Monday morning by DMF biologist John Sheppard.
Mr. Sheppard did not return a phone call requesting information on his analysis by this morning’s deadline.
Residents in the area got their first hint of something amiss on Saturday in the form of an odd odor. Gerald C. Potamis, the town’s wastewater superintendent, who lives in the Little Pond area, said neighbors along Amherst Avenue detected early Saturday what many of them believed at first was a natural gas-like smell “while others thought it smelled like a failed septic system or an odor of biological decay.”
Residents contacted National Grid, which checked the area and determined there were no gas leaks.
Meanwhile, residents along Maravista Avenue on the east side of Little Pond detected what seemed more distinctly like an odor of biological decay, Mr. Potamis said.
Later that day, Mr. Potamis said he was alerted by a neighbor that 16 dead fish, all of them striped bass, were lying on the shore of the pond. A horseshoe crab and an unspecified species of crab were also found dead among the fish.
“It’s unusual to see that many large fish dead like that,” Mr. Martinsen said, but he added that striped bass are known to swim into Little Pond through the inlet passing under Menauhant Road. “There have in the past been very large striped bass in the area. That’s one of those little secrets known to local fishermen.”
Both Mr. Martinsen and Mr. Potamis theorized that the fish entered the pond just before or during what is called a “low-oxygen event,” when excessive algae in a lake or pond consumes so much of the dissolved oxygen in the water that fish are unable to breathe.
Mr. Potamis added that the lack of rainfall this summer has lowered the pond’s water level, which would create conditions more conducive to a low-oxygen event, “which can happen very quickly.”
Little Pond is considered an “impaired water body,” Mr. Potamis said, that impairment the result of inadequate household wastewater management systems.
The Massachusetts Department of Environmental Protection (DEP) determined that 22.76 kilograms of nitrogen enter Little Pond every day. Nitrogen concentrations generally range from .49 milligrams per liter (mg/L) at the head of the pond to 3.18 mg/L in the lower section, while the state standard for nitrogen loading for the pond is .45 mg/L.
More than 40 percent of the nitrogen entering the pond is from nearby septic systems, and more than 30 percent is from land use-related runoff.
Past Fish Kills In Falmouth
Dead Fish Washing Up On Shores Of North Falmouth (July 2011)
Little Pond is one of six estuaries in town identified as in need of significant nitrogen loading remediation. Mr. Potamis said the Little Pond area has been identified as a prime neighborhood for sewering. A new draft of the town’s Comprehensive Wastewater Management Plan, unveiled earlier this month by the water quality management committee, projected a $320 million cost for such a project.
The original projected cost of $600 million, presented in a 2009 draft, was reduced by mixing sewering with non-traditional alternative approaches such as eco-toilets, inlet widening, permeable reactive barriers, and shellfish aquaculture—and by focusing sewering exclusively on the Falmouth Heights/Maravista Avenue area for the benefit of Little Pond.
Mr. Potamis said Little Pond is a prime candidate for inlet widening, which would allow for natural tidal activity to help cleanse the water of excess nitrogen, “but something like that needs more study” to measure the potential collateral impacts—erosion, flooding, et cetera.