Burping Benthic Barriers

By Sarah L. Tichonuk

“Dare I ask what is a benthic barrier, and why does it need burping?” I questioned LCMM archaeological director Adam Kane when he inquired about my schedule last week. Turns out that the bivalve mollusk known commonly as an Asian clam (Corbicula fluminea) was found in Lake George last year, and they want it out. This non-native clam is highly invasive, and is capable of self-fertilization (it’s hermaphroditic, if you want to nose into its sex life) and can generate up to 400 offspring per day. That’s a lot of hermaphrodites if you ask me.

LCMM Archaeologist Sarah Tichonuk dives in Lake George.
LCMM Archaeologist Sarah Tichonuk dives in Lake George to secure benthic mats designed to eradicate the invasive Asian clam.

Why are they bad for the lake?  They are filter feeders, and directly compete with juvenile fish for native mollusks food. Even worse, though, is their excretion (that’s poo) contains high concentrations of nutrients, and promotes rapid algae growth in the lake – an acute threat to the water quality.  But don’t take my word for it; the folks out in Lake Tahoe have been struggling with the Asian clam for years. See some of the photos from UC Davis’ Tahoe Environmental Research Center

To get rid of the little suckers, benthic barriers – essentially plastic pool lining cut into 50 x 7 foot rectangles – were placed down on the bottom of Lake George by some very cold-hearty divers in late April this year, in the hopes of suffocating the clams.  Five acres of the lake bottom are covered – that’s more than 700 mats!  These mats were installed in April, but waves and boating traffic have disturbed some of them. LCMM’s Adam Kane, Chris Sabick and I went diving last week assisted by mariner Tom Larsen to secure those mats that have shifted.

Although the Asian clam can live in waters as deep as 250 feet, the colony in Lake George is in shallow water.
Although the Asian clam can live in waters as deep as 250 feet, the colony in Lake George is in shallow water.

But burping? When a plastic mat covers something organic – say, weeds – it kills it. (That’s the whole point, right?) That decomposing organic matter off-gasses, creating bubbles under the tarps, which look very spooky underwater. One of our tasks last week was to “burp” out those bubbles so the mats lie flat on the lake bottom.

LCMM expects to return to Lake George to assist in the removal of these mats this summer. Let’s hope the benthic barriers have done their job.

The Asian clam problem in Lake George is being handled by several collaborative institutions, including the Lake George Association, the Darrin Fresh Water Institute and the FUND for Lake George with funding from the Lake Champlain Basin Program and others. Read more about the Eradication Plan from the Lake George Asian Clam Rapid Response Task Force.