Friday, July 24, 2009

Can We Save the Ponds by Eating Oysters?

Can Mussels and Oysters be used to consume Nitrogen in ponds.
Swedish experience and proposals from USA.
Diatoms and Fish are a better and simpler option.

News report from Martha's Vineyard

Can We Save the Ponds by Eating Oysters?


... a solution to the most pressing environmental problem on Martha’s Vineyard: pollution of our ponds by nitrogen which leaches out of septic systems.

And it’s a solution which is cost effective, creates jobs and is delicious.

We’re talking shellfish, folks.

See, about a decade ago, the Gullmar Fiord on the Swedish west coast had the same problem the ponds on this Island have today. That is, excessive nitrogen fueled excessive growth of algae which in turn led to what they call eutrophication of the water, essentially the removal of oxygen, which makes life untenable for other plants and animals.

Then a team lead by a marine ecologist with the Royal Swedish Academy of Sciences named Odd Lindahl, began cultivating mussels. They found they could cut the nitrogen load (i.e. the total nitrogen in the water) by 20 per cent, at a lower cost than a standard water treatment plant.

“In one year they removed 39 tons of nitrogen from the fiord,” said Rick Karney, director of the Martha’s Vineyard Shellfish Group.


“There are 933 existing residences in the Edgartown Great Pond watershed,” said Mr. Wilcox. “There’s roughly 300 more than the pond can tolerate.

“And we’re looking at a potential 749 extra residences, which could be built under existing zoning,” he said.

Edgartown is currently working to extend sewerage to enough of those currently-existing houses to reduce the nitrogen load by the 30 per cent.

“That can and will address the existing situation,” said Mr. Wilcox, adding:

“But what about future development? Every additional house is in excess of what that threshold number for nitrogen is.”

Of course, the town could just keep extending the sewer system; the town’s wastewater treatment plant has extra capacity. But that is very expensive.

“The areas they are doing now, it comes out to $10,000 to $15,000 for each house, which is actually relatively cheap,” said Mr. Wilcox, pointing out also that those properties now being done were close to the facility.

“But if you have to build a new plant, the cost could be three, four, five times that.

“Who pays that? People have batted around the idea of a nitrogen tax paid by all residents in the watershed. Maybe there could be impact fees for any new development.”


“If we don’t do something about growth, the ponds are going to suffer.”

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