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Pacific Southwest Research Station
Tahoe Science Projects supported by SNPLMA
Emerald Bay control and management: stressors and mechanisms controlling Asian clam populations in Emerald Bay
Allison Gamble, John Reuter, and Geoff Schladow, University of California-Davis
The Asian clam (Corbicula fluminea) is an invasive aquatic species that was first reported in Lake Tahoe (CA-NV) in 2002. Since then, population densities have been measured up to 8000 m-2. In Lake Tahoe, C. fluminea are negatively impacting native species, aesthetic values of the nearshore, and are associated with accelerated growth of filamentous algal species (Cladophora glomerata, Zygnema sp.) and bacteria. The satellite Asian clam population in Emerald Bay is the focus of considerable management resources, as the population is localized enough that it has the potential to be treated/controlled in its entirety. SCUBA surveys have shown that the Asian clam population in Emerald Bay has likely increased in extent from ~3.5 acres in 2009 to ~5.5 acres in 2011. Tahoe basin agencies intend to conduct a large-scale deployment of bottom barriers in the Emerald Bay in the summer of 2012. Pilot studies there by University of California-Davis (UCD) and University of Nevada-Reno (UNR) have shown that there are mechanisms that could alter the time course of treatment effectiveness at that location relative to previous successful treatments in the main lake. Dissolved oxygen (DO) levels underneath a test barrier declined but did not reach zero. The mechanisms accounting for that observation are currently being investigated and will be addressed in the large-scale deployment. The primary goals of the proposed research are to provide science-based monitoring of the large-scale benthic barrier installation to control Asian clams in Emerald Bay, Lake Tahoe, and to provide information to lake managers that will allow them to take an adaptive approach during the deployment. The proposed research will 1) assess whether the large-scale deployment of bottom barriers in Emerald Bay will depress or eliminate Asian clam populations, 2) describe how DO and food supply drive the survival, depression or elimination of the Emerald Bay clam population under the barrier treatments and 3) determine whether augmenting bottom barriers with organic carbon can further facilitate, depress, or eliminate the Emerald Bay clam population. Taken together, these data will help answer the key question of how to optimize the effectiveness of bottom barriers to treat the invasive Asian clam in Emerald Bay.
Relation to Other Research Including SNPLMA Science Projects
In 2008, members of the Lake Tahoe Aquatic Invasive Species Working Group (LTAISWG) and UCD-UNR science team began to develop a strategy to control the existing Asian clam beds in Lake Tahoe. In 2009, field and laboratory research were successfully carried out with results that inform both scientists and lake managers on the extent of the Asian clam invasion as well as the demonstration of a nonchemical approach for the treatment of the clam populations. This research has continued into 2010-2011, including field testing of various control alternatives including suction removal, small-scale applications of rubber bottom barriers under cold and warm-water conditions (Marla Bay), a large-scale (one acre) deployment of bottom barriers at Marla Bay/Lakeside, and most recently, an Emerald Bay pilot study using benthic barriers. Since the Asian clam population in Emerald Bay is still currently confined to the area of the sandy sill, the potential exists to manage or extirpate this population. Dedicated funding exists for a large-scale deployment of bottom barriers (3-5 acres) in Emerald Bay. The agencies and the Asian Clam Working Group have planned for a June-July 2012 deployment. The primary goal of the Round 12 research is to monitor the large-scale benthic barrier deployment in Emerald Bay, and to provide quantitative information to improve the effectiveness of the barriers at controlling Asian clams. This study will also complement the Round 10 SNPLMA-funded projects, "Potential for pathogen growth, fecal indicator growth and phosphorus release under clam removal barriers in the Lake Tahoe Basin," and "Natural and human limitations to Asian clam distribution and recolonization—factors that impact the management and control in Lake Tahoe."
Expected date of final products:
|Last Modified: Nov 12, 2014 03:48:31 PM|