From the New York Times:
ORLEANS, Mass. — Rising nitrogen levels are suffocating the vegetation and marine life in saltwater ponds and estuaries on Cape Cod, creating an environmental and infrastructure problem that, if left unchecked, will threaten the shellfishing industry, the tourist economy and the beaches that lure so many summer visitors.
More than 60 ponds and estuaries on the cape and a few elsewhere in the region have been choked by algae and seaweed. The culprit is nitrogen, much of it leaching out of septic system wastewater that runs through sandy soil into the estuaries. Faced with a federal mandate to fix their polluted waterways, Cape Cod towns have spent years creating plans to clean up the wastewater, largely through sewers and clustered septic systems.
So far, most of the efforts have been to no avail, stifled by disputes over science and over who should pay for such a sprawling and expensive public works project.
“This is the biggest environmental issue the cape has ever faced,” said Maggie Geist of the Association to Preserve Cape Cod, a nonprofit environmental group. “And for a long time it’s been a hidden problem.”
The root of the problem lies in the popularity and unchecked growth of Cape Cod over the last 30 years. Towns chose not to install sewers when the government helped subsidize them in the 1960s and ’70s, fearing that it would lead to an influx of people. Newcomers arrived anyway and sprawled out, using individual septic systems to get rid of waste.
“We’ve reached capacity for the watershed,” said Lindsey B. Counsell, executive director of Three Bays Preservation, a preservation group in Barnstable. “We’re a victim of our own geology.”
Without remediation, excess nitrogen could decimate shellfish beds and lead to widespread summer fish kills as algae, warm temperatures and cloud cover stifle oxygen in coastal waters, say officials who have examined the problem. Bays will be overtaken with seaweed that rots in the summer, a blow to property values and an environmental concern.
Here in Orleans, wastewater has been a divisive subject for years. Some residents say the town should put in place a $150 million plan that was drafted two years ago and approved at a town meeting, while others are calling for additional review before it is financed by taxpayers.
The problem is not always immediately apparent. From a distance, one saltwater pond here looks pristine, the summer sun bouncing off its placid waters and boats bobbing in the salt breeze.
“It’s deceiving,” said Gussie McKusick, who lives alongside the pond. “It looks beautiful, but it’s all dead underneath.”
Septic systems deposit wastewater, a mixture of urine and water, into a leach field. Because the cape’s soil is so sandy and porous, the wastewater eventually is deposited into bays. Even after septic systems are removed, wastewater already in the soil will still be leaking.
The nitrogen problem is most acute in protected bays and saltwater ponds on the cape’s southern side. The tides coming from Nantucket Sound are not high and forceful enough to flush out the nitrogen, which causes algae and seaweed to flourish, choking out oxygen needed by vegetative and marine species.
In Falmouth, which has long finger-shaped salt ponds, some areas have been closed to shellfishing for years because of elevated nitrogen levels, said Robert Griffin Jr., the assistant harbor master.
The algae and seaweed kill eelgrass, where prized bay scallops grow. Those scallops are gone from the ponds in Falmouth.
In August, the problem is sometimes smelled before it is seen. The algae bakes under the hot sun, creating a foul odor that may already be driving tourists away. Paul Niedzwiecki, the executive director of the Cape Cod Commission, a regional land use agency, said he had heard anecdotally that some people had left because of the smell...