On August 19th 2010, Jeremy Farrell was taking in the sun with his family on the shores of Lake George. While out in the water with his son, he spied a freshwater clam just under the surface at his feet. Having worked on many clam surveys over the years as a researcher for DFWI, he had never run into this particular fresh water species before. Jeremy immidiately snapped off a photo and sent it to Dan Marelli of Scientific Diving International, who has been studying native clams in Lake George for the past 15 years. He recieved a response almost immidiately stating that the specimen was determined to be Corbicula fluminea, or Asian Clam, an invasive species never before seen in Lake George.
Within a period of days, organizations from all around Lake George (APIPP, APA, FUND for Lake George, ISSD, LCBP, LGA, LGPC, SCIDI, NYSDEC, RPI/DFWI, LGWC, & VTDEC) organized and convened in meetings to pool their resources on how to combat the immidiate threat to Lake George's ecosystem. They established the Lake George Asian Clam Rapid Response Task Force (LGACRRTF).
Using SCUBA, an initial pilot study by DFWI researchers and collaborators found a asian clam infestation distribution of less than 3.5 ha (about 8 acres) and mapped to within a 500-m proximity to its initial discovery.
Map of Initial Survey Area Depicting Asian Clam Infestation
Benthic barrier installation was identified as a promising strategy that would be explored. To this point, only limited research existed on the effectiveness of benthic barriers for killing Asian Clams. Therefore, a study was set in motion to test the efficiency of different benthic barrier types.
In conjunction with DFWI researchers, the LGACRRTF set forth on a plan to eradicate the infestation. In early October of 2010, work was begun. The benthic mats were placed over the clams ensuring full coverage over the infestation area. The duration of deployment would also be taken into account studying mortality rates with samples from under the benthic mat being analyzed at 15 days, 30 days, and 45 days. Results would then be compared with a control area (no treatment) at each site.
Water Chemistry Samples and Clam Mortality
Over the next few months, water chemistry samples were taken by a sampling method called SCUBA point-intercept sampling, utilized specifically for this
project (see video below). Dissolved oxygen and ammonia concentrations were quantified from 9 locations under each mat type, plus three from the control areas on each of the first five treatment days, and every fifth day thereafter. All of the sampling was concluded after 45 treatment days. Clam mortality was quantified by analysis of sediment cores collected from locations near to where samples were collected for the chemical analyses. Results from the delineation mapping and this initial benthic barrier pilot study is currently under discussion, and is being used to guide a larger-scale management effort that will be carried out in this coming Spring 2011.
Footage depicting SCUBA divers using a point-intercept coring technique to collect water samples (video courtesy of Steve Resler: Innerspace Scientific Diving)