For the second time in less than a month, Sengekontacket Pond has been closed to shellfishing, and will remain closed indefinitely while fisheries experts consider what to do about bacterial contamination.
Analysis of water samples taken on Monday again showed high counts of fecal coliform bacteria at all nine test sites on the pond, and state marine fisheries officers say they now will examine the prospect of a permanent regime of seasonal closures for Sengekontacket.
Mike Syslo, the senior marine fisheries biologist from the Division of Marine Fisheries on the Island, said there would be discussions about the summer closure of the pond at a meeting in New Bedford next week.
"This is becoming a chronic problem," Mr. Syslo said yesterday. "I suspect a decision's going to be taken next week about the future of the pond."
And that could well mean closing the pond to shellfishing for a part of the year, as already happens in some other ponds on Cape Cod.
The pond was previously closed after samples taken on June 5 all exceeded the state limits for coliform contamination. On that occasion some people - not including Mr. Syslo - blamed heavy recent rainfalls and spring tides for having washed contaminants into the pond.
"So we closed the pond, allowed it to sit and flush until June 19, when we took all the samples again," Mr. Syslo said. He continued:
"The results were borderline, so I talked to our head shellfish biologist, Mike Hickey, in the New Bedford office. He agreed to have the pond reopened with the provision that I resample it.
"The details are almost identical to the last time we closed it - maybe not quite as bad - but we still have five numbers of 50 or above [the maximum reading on the scale used for testing], two at 36 and two at 28."
A pond is considered unsafe for shellfishing if the coliform count exceeds 28 bacterial colonies per 100 milliliters of water.
Two factors make the test results this time more concerning. The first is that there has been almost no rainfall over the past several weeks, which debunks the runoff theory.
"It's not rain causing it," Mr. Syslo said. "The last rain before the June 19 sampling was six days prior and it was only 4/100 of an inch. For July 2 I believe it was at least 13 days since we last had any rain. From memory it was only 3/100 of an inch. I don't have the exact figures in front of me, but it was almost nothing.
"Certainly heavy rainfall is not going to help a pond like this, which is why some ponds are automatically closed after significant rain.
"But my feeling is that the problem with Sengekontacket is just that this is a shallow body of water with not a lot of circulation, warm water temperatures and a large waterfowl population."
The second important factor is that the water sampling the last two times was done by boat.
After the first closure, there were complaints that the samples were taken close to shore, in areas where droppings from waterfowl could have boosted the coliform counts.
"There is some concern among some fishermen that if you sample by boat, your samples are going to come out cleaner than if you sample from shore," Mr. Syslo said.
"But the bottom line is that most people fishing in that shallow body of water do it from shore, while standing up. Anyway, these tests were done by boat."
Before any decision is taken on seasonal closure of the pond, he said, "we will look at the historical water quality record and see how far we could stretch the season."
Rick Karney, shellfish biologist and director of the Martha's Vineyard Shellfish Group, said extreme tides might again have been a factor because they inundated the roosting areas of waterfowl on the pond and carried fecal matter into it.
"I would hope there is some effort taken to determine for sure if that's the cause," he said, adding:
"But I don't know where we would go from there. Pretty much all the species there are protected and there's not much we can do.
"This is the major recreational fishery for Oak Bluffs. One of the reasons people come to the Vineyard is that they can do a little recreational shellfishing. If we start getting a lot of closures, it's certainly going to dampen the appeal to a lot of folks."
Edgartown shellfish constable Paul Bagnall agreed. "This is bad, especially for Oak Bluffs. I think in the long term for Sengekontacket is we're going to have to live with a seasonal closure," he said.