Monday, March 28, 2011

Lake George Asian Clam Eradication Efforts

An aggressive plan has been released to attempt an eradication effort of the newest aquatic invasive species to Lake George – the Asian clam (Corbicula fluminea). An ad hoc coalition of environmental groups, scientists, and public agencies developed the Plan to Eradicate the Infestation of Invasive Species Asian Clam in Lake George, which details efforts starting after ice-out next month to try and rid the lake of the Asian clam. This plan, organized by the Lake George Asian Clam Rapid Response Task Force, details the scope of the problem in Lake George, long-term threats from this invasive, options for treatment, and details a plan that will try and eradicate this clam in the lake.
The risks to Lake George from inaction or delay are high. Lake Tahoe serves as a cautionary tale for the Lake George community. There Asian clams were discovered in a small area less than a decade ago. It was believed initially that the lake was too cold and too far north to sustain a viable population.

Today, Asian clams have spread to over 200 acres and many once beautiful bays are littered with heaps of clams and clam shells and fouled with intense algae blooms. Management efforts – Tahoe experts see no hope of ever accomplishing eradication – cost hundreds of thousands of dollars annually to simply try and contain the population.

Many scientists familiar with native mollusks and the Asian clam believe that if left unchecked it will spread to the popular nearby Shepard Park beach and Million Dollar Beach relatively soon, then spread throughout the south end, and then spread through the whole lake in a matter of years. Lake George has 4,800 acres of littoral zone, areas of depth of less than 25 feet, and much of this is viable Asian clam habitat. If no action is taken, then this clam will eventually infest the entire lake.

Lake George is defined by its stunning raw beauty and clean water – two things in increasingly short supply these days. Beyond beauty and clean water, the Lake George experience is many different things to many different people, but most would agree that heaps of clams shells in shallow water sandy areas and abundant algal blooms are not what the lake is all about. If the Asian clam is not contained, we all stand to lose a great deal.

The infestation in Lake George is the first documented in the Adirondack Park and Lake Champlain watershed. Lake George has just three aquatic invasive species, which have mostly been brought under control, including Eurasian watermilfoil (Myriophyllum spicatum), curlyleaf pondweed (Potamogeton crispus), and zebra mussels (Dreissena polymorpha). This pales in comparison with nearby waterbodies, such as Lake Champlain, which has dozens of aquatic invasive species.

But unlike the other three invasive species, the Asian clam has the capacity to seriously change water quality. It is believed that they have been in the lake for 2-3 years and have completed 4-6 reproduction cycles. Asian clams are hermaphrodites and can reproduce twice annually with one clam releasing 2,000-4,000 offspring each cycle. An individual clam can begin reproducing within 3-8 months. In addition to being prodigious reproducers, Asian clams grow rapidly, from a microscopic juvenile to the size of a dime or larger with 2-3 years. Research undertaken last fall and over the winter by the RPI Darrin Fresh Water Institute (DFWI) delineated an infestation area of 4.77 acres with high density populations and another adjacent area of 3.31 acres of possible low populations, a total area of 8.1 acres that is the focus.

As part of the population delineation last fall, 60 locations in a 10-mile shoreline area was surveyed every .25 miles from Diamond Park to Dunham’s Bay. No other Asian clams were found. It is believed that the current population is limited to the Village area.

Scientists with the Tahoe Environmental Research Center (University of California, Davis), have said the Asian clams promote so much algae growth there that they can turn some waters from blue to green. As they filter the water and consume plankton, they deposit high concentrations of nutrients with their excretions. Another significant impact of the Asian clams infestations is the “biofouling” or the impairment or degradation of intake pipes for power plants and drinking water treatment systems.

The Village and Town of Lake George take water for the public water supply not far from the infested area. The south end, the Caldwell Basin, is already the most stressed part of the lake, with significantly lower water quality than the north end. High nutrient loading already creates an annual dead zone in the lake nearby. Pollution added by an uncontrolled Asian clam infestation will further degrade an already impaired area of the lake.

The plan focuses on an eradication treatment in a 5-8 acre area in the Village Bay that extends from Pine Point north to the southern edge of the English Brook delta. The Village of Lake George public Lake Avenue Beach is part of this area. A 2.58 acre area will be suction harvested where sediment to a depth of six inches will be removed. Scientists found clams as deep as six inches. All clams in this sediment will be removed by this process.

The suction harvesting treatment area includes area along the shoreline and in front of bulkheads out to a distance of 10 feet, under over 40 docks (with 150 boat slips) and around these docks with a 15 foot buffer area, and 25 feet in front of public and private beaches. Sediment will be contained in large 500 cubic yard dewatering bags set up in the Village’s Lake Avenue Beach parking lot and in the Marin Village parking lot. Once bags are full, the sediment will be transported far from the lake to Village of Lake George or Town of Bolton areas for disposal where it will be used a fill and maintenance for athletic fields. We hope to start suction harvesting somewhere around April 9th, but it all depends on ice-out.

Suction harvesting is being deployed in areas unsuitable for benthic barrier treatment as well as to minimize disruptions for the shoreline resorts, some 700 rental units, and marinas that berth 150 boats. Suction harvesting will be followed by installation of 600 PVC benthic barriers (7’ x 50’) on the lake bottom weighted down with steel rebar. Benthic barrier has been found to be the best treatment method to kill Asian clams as it suffocates them as dissolved oxygen levels are quickly reduced.

A pilot study organized by DFWI last fall found that benthic barrier properly installed and maintained can be very effective at killing clams. A treatment time of 45 days is our objective, a period which should kill all the clams underneath the mat if it is not disrupted. The barrier will start to be installed on April 25th and needs to be completed before water temperatures warm to 59 degrees, the point at which the clams release juveniles as part its reproduction cycle. The earliest date on record for the Village waters reaching this temperature is May 11th.

Scientists will take core samples from the area that is suction harvested as well as areas outside the benthic barriers to try and locate any satellite populations. Any populations found will immediately be treated with benthic barrier, for which an additional contingency supply will be on hand.

Other treatments considered were chemical, heat or biological. The open area, public water supply, and general high value of the Lake George ecosystem eliminated chemical treatments as a viable option, though they have been used in very degraded ecosystems to treat Asian clams. A heat treatment was tried last fall and it did not work.

Biological controls require extensive study before a non-native species is introduced to an ecosystem. While a number of fish and animal species around the lake eat native clams and mussels, they are not present in high populations in the Village and it’s highly unlikely natural predation will contain the population. Last, a “do-nothing option,” for all the reasons stated earlier about the long-term threat, is not considered a viable option.

The Task Force has submitted permit applications to the Adirondack Park Agency, Department of Environmental Conservation and US Army Corp on Engineers. We anticipate receiving all necessary permits by the time of treatment. Additionally, authorizations were needed from the Office of General Services and State Historic Preservation Office (part of the historic 1758 sunken bateaux fleet is nearby).

The costs of this effort is considerable and will likely top $400,000 in direct outlays for materials and services with $100,000 on in-kind services by the local non-profits, state agencies and local municipalities. An additional $50,000 was spent on the pilot study and population delineation last fall and over the winter. Both the Town and Village of Lake George has been supportive and cooperative.

Our margin for error is small. Consider than the initial infestation, which has now reached 5-8 acres, probably came from a small group of clams in the bottom of a bait bucket, lodged on a boat trailer or engine, or was carried by construction equipment working on the resort strip.

What we do know now is that the Asian clam can not only survive, but it can seemingly flourish in Adirondack waters. The Asian clam is a new and ominous threat for lakes across the Adirondack Park. Asian clams are spread by boats making the various interdiction efforts incredibly important. Boat owners can take steps to prevent spread and infestation. Eradication of this species has not been successful in other waterbodies. It’s important not to spread Asian clams to other lakes. Here are steps to stop the spread of this voracious invasive species.

    • Inspect and remove any plants, animals, mud, and water from your boat hull, trailer or equipment.

 

  • Drain, wash, and where possible disinfect all water from boat bilges, live wells, bait buckets, anchor and anchor line, engines and other equipment (scuba gear). Small amounts of water carry early life stages that are not visible to naked eye.

 

  • Dry your boat and trailer in the sun for 5-7 days when moving between bodies of water.
  • Never move water from one body of water to another.

 

Photo: Asian clam bed in Lake Tahoe, Courtesy Brant Allen of UC Davis.

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Peter Bauer is the Executive Director of Protect the Adirondacks.

He has been working in various capacities on Adirondack Park environmental issues since the mid-1980s, including stints as the Executive Director of the Residents' Committee to Protect the Adirondacks and FUND for Lake George as well as on the staff of the Commission on the Adirondacks in the Twenty-First Century. He also worked at Adirondack Life Magazine. He served as Chair of the Town of Lake George Zoning Board of Appeals and has served on numerous advisory boards for management of the Adirondack Park and Forest Preserve.

Peter lives in Blue Mountain Lake with his wife and two children, enjoys a wide variety of outdoor recreational activities throughout the Adirondacks, and is a member of the Blue Mountain Lake volunteer fire department.

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3 Responses

  1. John Warren says: