The latest invasive: a tale of two waterways
by Mary Thill
This is a story about a new creature in the Adirondacks. Instead of the usual arc of these narratives—discovery of foreign plant or animal, alarm over ecological and economic implications, quotes from aggrieved property owners—this one follows a Dickensian template of rich meets poor, of clarity and murk, and how neglect of bad neighborhoods creeps into good.
The recent arrival is the Asian clam (Corbicula fluminea). It is a pudgy little mollusk, growing not much wider in diameter than a dime, native to Asia, Africa and the Mediterranean. It is believed that Chinese immigrants imported the clam to the American West for food. It was ﬁrst recorded in the wild in 1938 and has since spread south and east to 39 states.
Beds of Corbicula as dense as 6,000 per square yard were discovered last summer on the sandy bottom of Lake George, just offshore of busy marinas, motels and beaches at the south end. The clam is short-lived but fecund, producing 2,000–4,000 offspring at a time, sometimes twice a year. The shells are unpleasant for bare feet to step on, but the bigger problem is the clam’s excrement: the Asian clam draws nutrients from both the water and the sand and concentrates them in waste that feeds nuisance algae.
The clam’s presence in Lake George is a bit of a curiosity. Its native range is tropical to temperate. Biologists thought the clam was bumping up against the northern limits of its cold tolerance. But it has evidently survived three or four winters in the southeast Adirondacks. If it reaches the Adirondack Park’s interior, Asian clam poses an additional threat: when the clams die their shells erode and calcium is released, potentially fostering zebra mussel habitat in granite-based lakes where calcium concentrations are otherwise too low to support that invasive species.
No one can say for sure how Asian clam arrived in Lake George. A few may have been dumped from a bait well or an aquarium (they are sold in pet stores). But Lake George residents do not abide newcomers in their water, no matter how they got there. Lake George has an impressive record of containing invasive species: After zebra mussels were discovered in the lake’s southern end in 1998, a coalition of private conservation groups (funded largely by the lake’s wealthy seasonal residents) and government partners organized a hand-harvesting campaign to remove them, one by one. Incredibly, it seems to have worked. No young zebra mussels have been detected since 2000. Some of those same partners also keep Eurasian watermilfoil and curlyleaf pondweed in check. Combined efforts have cost nearly four million dollars to date, not factoring a huge volunteer effort.
Over the winter, a private/public task force comprising eight organizations committed another half-million dollars to remove Asian clam, starting promptly at ice-out. Invasive species experts say “early detection” and “rapid response” are the most cost-effective—and often only—hope of managing damaging organisms. The original plan was to suction clams and the top six inches of sediment from shallows and under two dozen docks along 1,800 feet of shoreline, from Pine Point north to English Brook. Divers would smother clams farther offshore under three-quarter-inch-thick PVC mats for 45 days.
The partners wanted treatment completed before warm-weather tourists arrived. Ice-out came late, and potential contractors submitted suction bids that were beyond the budget. So the task force opted instead to lay mats on nearshore clams as well. In all, divers with Aquatic Invasive Management, based in Au Sable Forks, laid 900 seven-by-50-foot mats and weighted them with rebar; the company is now monitoring and spot-treating. If needed, suction harvest might be attempted in autumn. A new website, stoptheasianclam.info, describes the project in detail.
In Lake Tahoe, untreated Asian clams spread from a few acres to 200 acres in 10 years. Biologists from University of California Davis encouraged the Lake George task group to nip its problem in the bud. “The exciting thing is we really hope, unlike Lake Tahoe, that here we may have found them and been able to respond in a short enough period of time and with enough organizations involved, and enough groups contributing funding, that we have a real shot,” said Sandra Nierzwicki-Bauer, director of Rensselaer Polytechnic Institute’s Darrin Fresh Water Institute on Lake George, one of the task-force partners. “Our ultimate goal is to eradicate them. If we fall short of that, we are going to be very successful in managing them.”
Thomas Jefferson called Lake George “without comparison, the most beautiful water I ever saw.” It is deep, clear and cradled snugly by mountains. Half a dozen miles east the turbid brown water of the Champlain Canal is rarely called beautiful. The canal opened in 1823 to connect Lake Champlain and the Hudson River for commercial barging. It is straight as a road along most of its 60 miles and has 11 locks.
Asian clams were found in 2008 just below Lock 8 near Fort Edward, at the height of the canal. North of Lock 8 water ﬂows into Lake Champlain; south, into the Hudson. Last winter, University of Vermont researchers surveying a drained Lock 4 found dense beds of Corbicula near Stillwater, on the Hudson side. The clam was also identiﬁed downstate in the tidal Hudson in 2008; it has not yet been detected in Lake Champlain.
The clam’s presence on the doorstep of Lock 8 may ultimately have greater repercussions than its presence in Lake George. But in contrast to Lake George, there is no multiagency rapid response. There are no businesses looking to protect swimming beaches or homeowners’ groups hoping to maintain property values. Barges rarely convey bulk cargo on the canal anymore, though an estimated 1,700 recreational boats pass through in a season. It’s a low-rent, low-proﬁle water ﬂowing in limbo between New York State bureaucracies.
Biologists think zebra mussel, water chestnut, sea lamprey and other species that have been costly to contain reached Lake Champlain via the canal. It’s the path by which Asian clam will likely get there, as well as round goby, hydrilla and even Asian carp, connecting from the Great Lakes via the Erie Canal. The canal is the largest vector of nuisance aquatic organisms to Lake Champlain —and by extension of boating and ﬁshing, a pathway to the wider Adirondacks and Vermont.
Lake George may have succeeded in ridding its south end of zebra mussels, but the mollusks later entered from the north, likely hitchhiking on boats trailered from Lake Champlain, a few miles on the other side of Ticonderoga. Although Asian clam is less “sticky” than zebra mussel, which easily attaches to hulls in its free-swimming juvenile stage, the loop remains intact for a bilgewater, bait-bucket or boat-trailer repeat.
Asked about the disparity of response on Lake George and the Champlain Canal, a spokesman for the New York State Canal Corporation punted, saying, “On the question of the control or eradication of this or other invasive species, the Canal Corporation looks to the expertise and guidance of the Department of Environmental Conservation [DEC].” The DEC responded by citing the importance of education, coordination, partnerships and priorities.
No one doubts that education is the ideal: individuals must take it upon themselves to learn the issues, clean boating and ﬁshing equipment, and not dump bait or aquariums. But prevention, or at least containment, can also be accomplished by barriers at key points on manmade waterways, as engineers are discovering—perhaps too late—as they try to stop Asian carp from reaching the Great Lakes via Chicago canals.
“In the Champlain Canal the trick is: who is in charge, and who cares?” said Meg Modley, aquatic nuisance species coordinator for the Lake Champlain Basin Program. “I think the onus is put more on the state agencies, if they think it’s a high priority or not to treat Asian clam in the Champlain Canal. Whereas in Lake George you’re dealing with highly invested user groups. The lake is their backyard, it’s their jewel. You don’t have that buy-in along the Champlain Canal.”
The DEC and Canal Corporation post signs advising boaters to check gear. DEC is a partner and funder in the Lake George Asian clam task force. Both agencies have participated in discussions about invasives in the Champlain Canal. But neither is providing leadership. The Army Corps of Engineers is authorized to look into the cost of installing different types of ﬁsh and plant barriers on the canal; New York agencies have expressed support for the study, but its champion is a senator from another state, Patrick Leahy, of Vermont. Four years after Leahy secured the authorization, and a year after he secured $200,000 to pay for it, the study awaits more funds and has yet to begin.
Beﬁtting a Dickens tale, this chapter ends with a difﬁcult dilemma for an orphaned canal. Hopefully the cliffhanger will be resolved in the next.