Wild Side : Popping the cork
By Matt Pelikan
Published: December 3, 2009
Amid the usual blizzard of sales promotion, the holiday season has hit like a red-tail on a rabbit, and the Wild Side is warily eyeing the upcoming wave of joviality. But it's not Champagne that's on my mind today, it's pond water.
Earlier this fall, the culvert that connects Farm Pond with Nantucket Sound was unplugged. File photos by Steve MyrickIn Oak Bluffs, this has been a banner season for pond water. As an article in the October 22 issue of The M.V. Times recounted, an old culvert under Sea View Avenue was re-opened, enhancing the existing, tenuous connection between Farm Pond and Nantucket Sound. And a week later, The Times ran an article by Charles Shabica describing the removal of "cobbles and large boulders" clogging the culvert that connects Sunset Lake to Oak Bluffs Harbor. Now, that's the kind of cork-popping the Wild Side really appreciates.
In each case, the culvert was cleared to improve water quality in a beleaguered pond. Low points in heavily developed basins, Farm Pond and Sunset Lake both receive effluent from numerous septic systems, as well as surface runoff carrying everything from lawn fertilizer to dog poop to those oddly colored fluids that drip out of people's cars. Both ponds support unnaturally high numbers of waterfowl, which defecate enthusiastically in and around the water. And like every other body of water in our region, both ponds receive an artificially elevated "background" dose of nitrogen, arriving in the form of acid rain.
The contents of these ponds, then, comprises a mix of salt and fresh water plus a leavening of bacteria, toxins, and, especially, nutrients that stimulate algae growth. All the Island's salt ponds are similarly afflicted, to some degree; this is what civilization does to water. But Farm Pond and Sunset Lake, small and surrounded by development, get it worse than most.
In Farm Pond, the healthier of the two, something like a viable ecosystem persists. Eelgrass can be found in the pond's deeper portion, softshell clams are plentiful in bottom sediments (though currently unharvestable due to water quality), and recent surveys have documented a surprising variety of fish and invertebrates here. But Sunset Lake is, for all practical purposes, dead. A shrewd gull may glean the odd quahog. But the pond lacks the resources to sustain much animal life, and in recent summers, floating gobbets of algae have rendered Sunset Lake downright repulsive.
One solution, at least a partial one, is to move more seawater in and out of the ponds, diluting and removing nutrients and other undesirable chemicals by flushing them into the ocean. While not infinite, the ocean is vast enough to swallow a pond's worth of pollutants with little effect. But clearing the culverts has effects that go beyond better flushing. A narrow connection muffles the effect of the ocean's tidal cycle; within the pond, tides lag in both timing and height. The opened culverts should broaden tidal ranges in the pond.
In the case of the two Oak Bluffs pond, this may prove to be a mixed blessing. During storm surges, greater tidal effects may translate into increased flood risk to nearby properties. (The boulders removed from the Sunset Lake culvert hardly walked there on their own, and I suspect they were an informal retrofit to keep the pond within its shoreline during major storms.) But as natural systems, salt ponds actually thrive on periodic flooding, which brings nutrients and new populations of plants and animals onto the pond's marshy fringes.
While a vital management tool, enhanced flushing is not a panacea for Vineyard salt ponds, which derive their ecological value largely from the variable salinity that results from alternating openings and closures to the sea. As we increase our reliance on flushing to solve our pollution problems, our ponds will begin to lose their essential brackish character, effectively changing from salt ponds into ocean inlets and losing biodiversity in the process. But for Farm Pond and Sunset Lake, popping the cork was badly needed emergency care.
Oak Bluffs's capable shellfish warden, Dave Grunden, has made a personal crusade out of improving the health of Farm Pond, heading up a broad community coalition in getting the permits needed to open the old culvert. And Professor Shabica, with town assistance, deserves credit for unplugging Sunset Lake. Vision and determination can produce concrete action to mend the health of Island waters.
But improving circulation addresses the symptoms, not the causes, of pond degradation, and it does so at the cost of altering the essential nature of these delicate natural systems. Ultimately, aggressive action is needed to keep excess nutrients and bacteria out of our ponds in the first place, by means such as zoning, denitrifying septic systems, sewering, restricting fertilizer use, and managing local waterfowl populations. When the Island has committed to measures like that, the Wild Side will be willing to break out the Champagne.
