I. Title Page
Title: Emerald Bay Control and Management: Stressors and mechanisms controlling Asian clam populations in Emerald Bay
2a.
Water Quality: Understanding the impacts of aquatic invasive species Proposal subtheme
Principal
Investigator and
Receiving
Institution
Co-Principal
Investigators
Agency
Collaborators
Dr. Allison Gamble
UC Davis Tahoe Environmental Research Center
291 Country Club Drive, Incline Village, NV 89451
Phone: 775-881-7560, FAX: 775-832-1673, Email: agamble@ucdavis.edu
Dr. Sudeep Chandra
Department of Natural Resources and Environmental Science
University of Nevada Reno
1000 Valley Road/ MS 186, Reno, NV 89512
Phone: 775-784-6221, FAX: 775-784-4530, Email: sudeep@cabnr.unr.edu
Dr. John Reuter
UC Davis Tahoe Environmental Research Center, Davis, CA 95617
Phone: 530-304-1473, FAX: 530 754 9364, Email: jereuter@ucdavis.edu
Dr. Geoff Schladow
UC Davis Tahoe Environmental Research Center, Davis, CA 95617
Phone: 530-752-3942, FAX: 775-832-1673, Email: gschladow@ucdavis.edu
Patrick Stone
Tahoe Regional Planning Agency
PO Box 5310, Stateline, NV 89449
Phone: (775) 589-5213, Fax: (775) 588-4527, Email: pstone@trpa.org
Dan Sussman
Lahontan Regional Water Quality Control Board
2501 Lake Tahoe Blvd., South Lake Tahoe, CA 96150
Phone: (530) 542-5466, Fax: (530) 544-2271, Email: DSussman@waterboards.ca.gov
Ted Thayer
Tahoe Regional Planning Agency
PO Box 5310, Stateline, NV 89449
Phone: (775) 588-5301, Fax: (775) 588-4527, Email: tthayer@trpa.org
Steve Chilton
US Fish and Wildlife Service
Nevada Fish and Wildlife Office, P.O. Box 5310, Stateline, NV 89449
Phone: (775) 589-5265, Fax: (775) 588-4527, Email: steve_chilton@fws.gov
Dan Shaw
California State Parks, Sierra District
1155 North Lake Boulevard (PO Box 16)
Tahoe City, CA 96145
Phone: (530) 581-4315 , Fax: (530) 581-5849, Email: dshaw@parks.ca.gov
Grants Contact
Person
George Malyj
UC Davis John Muir Institute of the Environment (JMIE)
Watershed Sci Bldg, RM 1105G, Davis, CA 95616
Phone: 530 752 3938, FAX: 530 754 9364, Email: gjmalyj@ucdavis.edu
$301,221 Funding
Requested
Total Cost Share $64,900
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II. Proposal Narrative a. Project Abstract (1 page summary addressing the scope of the proposal)
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. In collaboration with federal and state agencies, and organizations, and funding from a variety of agency sources, researchers from UC Davis (UCD) and UN Reno (UNR) have been intensively researching the ecology and control strategies of the Asian clam. These investigations have led to two key findings relative to this proposal: (1) while the distribution of Asian clam is largely centered in the southeast portion of Lake Tahoe, limited satellite populations exist – the most important of which is located on the sandy, shallow sill between Emerald Bay and Lake Tahoe and (2) applying rubber benthic barriers over clam beds can reduce dissolved oxygen concentrations within the sediment column to levels fatal to Asian clam.
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 largescale deployment of bottom barriers in the Emerald Bay in the summer of 2012. Pilot studies there by
UCD-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 largescale 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. b. Justification Statement (explain relationship between proposal and subtheme)
The Asian clam ( Corbicula fluminea ) is an aquatic invasive species (AIS) that was first reported in
Lake Tahoe (CA-NV) in 2002. Since then, population densities have been measured up to 8000 m
-2
, primarily in the heavily infested southeast portion of Lake Tahoe (Fig. 1a). However, a recent lake-wide survey has shown that limited satellite populations exist – the most important of which is located on the sandy sill separating Emerald Bay and Lake Tahoe (Fig. 1b-c). 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 .
). In collaboration with agencies, researchers from UC Davis (UCD) and UN Reno (UNR) have been intensively studying the ecology and control of the Asian clam. The results of our science-management investigations have shown that applying benthic barriers (ethylene propylene diene monomer rubber pond liner sheets) over clam beds can reduce dissolved oxygen (DO) concentrations within the sediment column to levels that are fatal to
Asian clam (Wittmann et al. 2010).
Prior research under warm water (>15°C) conditions in Marla Bay has shown that clams underneath EPDM rubber bottom barriers experience 100% mortality after 28 days. At the coldest water temperatures (4-10°C), time to clam mortality takes between 39 and 91 days (Wittmann et al. 2011).
These findings demonstrate that it is possible to kill Asian clams in Lake Tahoe without the expense and disruption of dredging or a dependency on toxic chemicals.
The control of established populations of Asian clams is a high priority for Tahoe basin resource management and regulatory agencies, per subtheme 2a. In particular, the satellite Asian clam population
3

in Emerald Bay has the potential to be treated/controlled in its entirety. The rate of recolonization in the semi-enclosed infested area on the sill in Emerald Bay is likely to be lower than in other parts of the lake
(which are surrounded by high-density populations of Asian clams), also making the area a good candidate for treatment. 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 (refer to Fig. 1c; Gamble et al.
2011). A recent pilot study in Emerald Bay has shown that there are mechanisms that alter the time course of treatment effectiveness of the bottom barriers at that location relative to previous successful deployments in the main lake. DO levels underneath a test barrier declined to 40% saturation but did not reach zero. While clam mortality was not observed during the study period, preliminary data suggest that reproductive capacity may have been lowered by the stress resulting from a lower than optimal level of
DO (Fig. 2). Additionally, there was some qualitative evidence that stress to individual clams was increasing under the barriers towards the end of summer, when higher numbers of clams were seen at the sediment surface. This combined evidence suggests that the barriers are impacting clam reproductive potential and stress at the individual level which could result in a reduction at the population level in the future if the stressors continue to be applied.
We have hypothesized that the sill habitat is sufficiently permeable to allow for oxygenated lake water to pass through the sill. If this is the case, bottom barriers alone may not be as effective for the
Emerald Bay population as elsewhere in the lake unless allowed to remain in place for longer periods of time or otherwise amended to increase oxygen demand.
Tahoe basin agencies intend to conduct a large-scale deployment (3-5 acres) of bottom barriers in Emerald Bay in the summer of 2012. Funding exists for this treatment project. Concurrent research is needed to provide science-based monitoring of the large-scale benthic barrier installation to control Asian clams in Emerald Bay and to provide information to lake managers that will allow them to take an adaptive approach during the deployment. c. Concise Background and Problem Statement
In 2011, a pilot study examined whether bottom barriers placed on the shallow (3 m) sill in
Emerald Bay would remain in place in the presence of uneven bottom topography and turbulence from boat traffic. The pilot study was conducted in early-mid summer 2011 with a 10 x 100 foot barrier deployed. Unlike at other locations in the lake, DO levels below the barrier was not lowered sufficiently to kill clams during the pilot study period. Rather, it was observed that when there was a persistent exchange flow over the sill in excess of 2 cm/s, DO remained high. It was hypothesized that there is subsurface (hyporheic) movement of water between the lake and bay. That exchange flow is forced by a combination of wind, temperature, and pressure differences between Emerald Bay and the main lake.
When exchange flows dropped to below 2 cm/s, DO concentrations oscillated diurnally, falling precipitously for 12 hours at night and then recovering as quickly during the day (see Fig. 3). The daytime
DO recovery was strongly correlated with wave oscillations that may be due to high-speed boat passage.
The rate of oxygen decline during the night suggests that during periods of low exchange currents, if high speed boat passage is reduced, then attainment of much lower DO levels may be possible. Augmentation of oxygen demand may also be required to help drive DO towards zero.
Also in summer 2011, a SCUBA survey to quantify the extent of Asian clams ( Corbicula fluminea ) in Emerald Bay was undertaken. This was a follow-up to an earlier survey undertaken in 2009, which delineated the extent of the Asian clam infestation on the sill at the entrance to Emerald Bay. The sill is much shallower than the rest of Emerald Bay (maximum depth of 50 m). As in 2009, live clams in 2011 were again confined to the sill, and no live clams were found in other areas of the bay (Fig. 1c). The extent of live clams in 2009 was approximately 3.5 acres, whereas the extent of live clams in 2011 represented 5.5 acres. While we believe clams might be expanding on the Emerald Bay sill, the exact rate is unclear due to some sampling uncertainty in the 2009 survey data.
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. The agencies on the Asian Clam Working
Group intend to use existing funds for a large-scale deployment of bottom barriers during the early part of the summer of 2012 (see Section II b). Ongoing research from the same funding source is being conducted to establish a better relationship between the sill permeability, surface exchange currents, the
DO under the barriers, and high-speed boat passage prior to this deployment. The proposed research will help answer the key management question of how to optimize the effectiveness of bottom barriers to treat this invasive species in Emerald Bay. The Asian Clam Working Group will benefit from knowing 1) when
4

are the periods during the year where DO drops to levels that result in mortality, 2) can barriers be placed on the bottom for sufficient periods of time to cause long-term stress leading to slow mortality or a significant reduction in reproductive capacity, and 3) can organic (non-toxic) material be added under the barriers that enhance biological oxygen demand (BOD) and lower DO. d. Goals, objectives, and hypotheses to be tested
The primary goals of this research are to (1) provide science-based monitoring of the large-scale benthic barrier installation to control Asian clams in Emerald Bay, (2) determine the patterns of dissolved oxygen under the barrier as it relates to elimination or depression of clam populations, and (3) provide information relevant towards enhancing the effectiveness of the large-scale barrier deployment. We seek to achieve these goals by pursuing the following primary objectives:
Objective 1: Assess whether the large-scale (multi-acre) deployment of rubber bottom barriers over the infested areas in Emerald Bay will depress or eliminate Asian clam populations
Synoptic surveys of the distribution of the Emerald Bay clam population, both pre- and post-barrier deployment
Year-round evaluation of the influence of the bottom barrier treatment on clam mortality rate, density, reproductive condition, size structure, and other physiological indicators of stress
Use continuous monitoring to determine time needed to continue barrier deployment
Evaluate the effectiveness of the barrier treatment to both depress and eliminate clams
Objective 2: Describe the mechanisms driving the survival, depression or elimination of the Emerald Bay clam population under the barrier treatments
Track DO in the water column and sediments outside and under the barriers
Quantify the relationship between physical forcing factors such as sediment permeability, thermal stratification, wind, boating, currents, and the annual cycle of DO
Investigate the influence of food supply on the stress level, reproductive capacity and mortality of
Asian clams under the bottom barriers
Objective 3: Determine whether augmenting bottom barriers with organic carbon can further facilitate, depress, or eliminate the Emerald Bay clam population
Determine whether organic carbon additions facilitates the depletion of DO
We hypothesize that:
1) Population growth will be lower and reproductive condition will be worse in clams collected from underneath the barriers. Deployment of bottom barriers will stress clams, but mortality will require >6 months of barrier deployment time.
2) While levels of DO will go through a seasonal rise and fall within the Emerald Bay sill, levels will not be sufficiently low to result in mortality (anoxia) at the rates seen elsewhere in Lake Tahoe. The elimination of the planktonic food supply by deployment of the bottom barrier will interact with reduced DO and stress under the barrier to reduce clam reproductive capacity and increase physiological stress.
3) Augmenting the bottom barriers with organic carbon will drop DO levels sufficiently to result in more rapid mortality.
4) Bottom barriers, with some type of amendment, will be the best option for large-scale control of clam populations in Emerald Bay. e. Approach, methodology and location of the research
Objective 1: Assess whether the large-scale (multi-acre) deployment of rubber bottom barriers over the infested areas in Emerald Bay will depress or eliminate Asian clam populations
Task 1: (UNR lead) Synoptic survey pre- and post-deployment of Emerald Bay clam populations, monitoring the influence of the full bottom barrier treatment on clam mortality, density and size structure.
The spatial assessment conducted in 2011 indicated that Asian clams occupy 5.5 acres of bottom surface area, in the vicinity of the Emerald Bay sill. That study emphasized spatial mapping of clam presence/absence only. Research from other parts of the lake where clam infestations occur (e.g., Marla
5

Bay, Lakeside) suggests that clam densities and in some cases size structure are highly variable within a given area. Documenting these population parameters over the entire treatment area (both re- and postdeployment) will be needed as a basis for determining the effectiveness of the bottom barriers as a management tool in Emerald Bay. Additionally, these surveys will be needed as baseline data to assess long-term expansion of populations in the future.
Prior to barrier deployment, we will collect 550 Petite Ponar grabs over a 10-12 day period across the 5.5 acre infested. Each location will be recorded using GPS to understand the distribution of densities and size structure in the infected area to enable direct pre and post comparison of clam distribution and density. Clams (but no other invertebrates) will be identified, preserved, and measured for size. These data will be used to create an accurate map of the location, density, and size distribution of the known clam population. Post-barrier removal, we will again collect 550 Petite Ponar grabs across the 5.5 acre infested area in the sill of Emerald Bay. Each location will be recorded using GPS to understand the distribution of densities and size structure in the infected area. Only clams will be identified, preserved, and measured for size.
Task 2: (UNR lead) Describe the year-round population size structure, density, mortality rate, reproductive condition, and other physiological indicators of stress in the Emerald Bay Asian clam population inside and outside of the treatments.
To examine impacts of bottom barriers on Asian clam populations in Emerald Bay, over the duration of the barrier deployment, we will monitor clam density, reproductive potential, and size structure from 5 sites underneath the barriers and from 5 non-treatment sites as well (from outside the bottom barriers). The 10 sites will be selected based on the pre-deployment survey (Task 1). Every two months for one full year, 5 Petite Ponar grabs will be collected for analysis from each site. Ponar grabs will be pooled to determine clam density outside the barriers and underneath the barriers. DO probes will be concurrently deployed under the barriers (see Objective 3). Also using the Petite Ponar grabs, clam reproductive status (measured as eggs per clam and veligers per clam), mortality, reproductive potential, and physiological stress of clams will be quantified. Mortality is defined as the number of dead clams and the proportion of dead to live clams. We will measure heat shock proteins (HSP70) in 30 clams from under each barrier and adjacent locations. HSP70 have been used to determine the physiological stress of an organism and will aid in understanding of the mats are inducing stress to the populations (Kregel
2002). Fifty clams 10-13 mm will be measured for reproductive status from each location to understand the spatial variability in clam reproduction. Selected portions of the rubber barriers (10 x 10 foot) will be removed off the bottom by research divers. These plots will be identified and not re-sampled during the course of the experiment. We do not anticipate that the short-term disturbance associated with peeling back the barriers will have an impact to this study.
Task 3: (UCD lead) Using data collected in Tasks 1, 2, 4 and 6, we will evaluate the effectiveness of the bottom barrier treatment to (a) eliminate clams as a result of direct mortality due to insufficient dissolved oxygen, (b) reduce reproductive capacity to a low enough level to depress populations and/or (c) depress populations as a result of cumulative physiological stress. Correlative statistical techniques will be used between reproductive parameters (eggs/ clam or veligers/ clam) and environmental attributes
(temperature, dissolved oxygen, food supply). This will also include an evaluation of when the barrier removal can occur. By examining the status of the clam population under the barriers every two months, the agencies will know when to proceed with demobilization of the rubber sheets.
Objective 2: Describe the mechanisms driving the survival, depression or elimination of the
Emerald Bay clam population under the barrier treatments
Task 4: (UCD lead) Track levels of dissolved oxygen (DO) in the water column and bottom sediments outside and under the bottom barriers on the Emerald Bay sill.
We will monitor DO continuously over the course of a year to determine when it reaches levels under the bottom barriers that would result in clam mortality or otherwise control population numbers (see
Task 2). Temperature/dissolved oxygen probes will be deployed at 5 locations under the barriers
(corresponding to clam density sampling sites, see Objective 1) and a site adjacent to the barrier as a reference site. Probes will be calibrated and intercalibrated prior to deployment. The probes will be checked every 2 months. To measure sediment oxygen level, a DO probe will be placed at a depth of 10
6

cm under one of the barriers. This sub-surface DO sensor will be placed in a screened, perforated pipe to ensure it has free contact with the subsurface water and that the water is free to flow past the sensor.
Task 5: (UCD lead) Determine the relationship between physical forcing factors such as sediment permeability, thermal stratification, currents, wind, waves and the exchange of water volume between
Emerald Bay and Lake Tahoe and the annual cycle of DO in the bottom sediments outside and under the barrier treatment.
To build on the results of the pilot study and subsequent measurements, the factors driving flows over and through the sill will be monitored for a year. Acoustic Doppler Current Profilers (ADCP) will be deployed on either side of the sill, together with thermistor chains. The ADCPs will measure flows throughout the water column, and based on the vertical temperature distributions and the existing meteorological stations, the role of winds or baroclinic forces on driving the observed currents will be determined. A high resolution pressure sensor on the sill will allow further quantification of the role of high speed boat wakes on DO levels under the mats. Using sill permeability data (measured as part of present work) an estimate of hyporheic flow through the sill will be derived, and this will be used to inform the
BOD demand required from the organic material under the barriers (Objective 3).
Task 6: (UNR lead) Investigate the influence of food supply on the stress level, reproductive capacity and mortality of Asian clams under the bottom barriers.
Total organic carbon will be measured in the surficial sediments and in the overlying water column as indicators of food supply. Surficial sediment carbon will be measured via loss on ignition while seston total organic carbon will be assayed using a carbon analyzer (Shimadzu TOCV). Measurements will be made every 2 months from the 5 locations underneath the bottom barriers and 5 from the reference location adjacent to the barriers (See Task 2). In addition seston total organic carbon will be measured directly above the lake bottom from 5 locations above the barrier as well as above the reference site. These measurements will be analyzed in conjunction with the results from Objective 1
(Task 3).
Objective 3: Determine whether augmenting bottom barriers with organic carbon can further facilitate, depress, or eliminate the Emerald Bay clam population
Task 7: Determine whether augmenting bottom barriers with organic carbon facilitates the depletion of oxygen concentrations, with a concurrent effect on mortality, reproductive capacity and physiological stress.
During Asian clam working group meetings in 2009, agency and researchers suggested augmenting barriers with organic carbon (e.g. straw or plant material) to reduce the time needed to deplete dissolved oxygen (by increasing BOD - biological oxygen demand). This was not necessary for the rubber barrier applications in Marla Bay or at Lakeside since the DO reduction was very rapid.
However, we are now confronted with a different situation in Emerald Bay where, because of hyporheic flow, DO cannot be sufficiently reduced to reach anoxic conditions.
Augmenting the surface with organic carbon for treating clams on the Emerald Bay sandy sill now may be appropriate. Laboratory results from a nearly-completed SNPLMA Round 10 science project that focused on human health effects of microbial growth under barriers indicated that the time needed to reach anoxia and achieve clam mortality in the presence of algal carbon (periphyton biomass) was considerably shortened. If this technique can be demonstrated to work on the Emerald Bay sill sediments, it improve the effectiveness of bottom barriers as a viable management strategy in Emerald Bay.
As water temperature is a critical factor driving biochemical oxygen demand it is proposed that the BOD experiments be conducted in two phases, a warm-water (~20 °C) and a cooler-water (12-15°C) phase. These will compliment similar experiments that will examine the impacts of BOD-inducing material in cold water (5-6 °C) conditions (funded through separate funds; projected start date of January 2012). In our proposed study, there will be 2 experimental treatments, one in mid-summer after the large barrier deployment, and one in the fall when water temperature begins its seasonal decline. For each experiment, six 10 foot x 10 foot barrier test plots will be installed on the Emerald Bay sill. Triplicate barriers for each biomass type will have similar amounts of biomass placed underneath. We will use two types of BOD-inducing biomass that are acceptable to all regulatory agencies. We recommend 2 types: jute and straw. Our current research on the invasive plant species curlyleaf pondweed (SNPLMA Round
11 science project) has demonstrated that jute barriers alone created sufficient BOD to eventually reduce
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conditions under those barriers to anoxia. Both jute and straw are inexpensive, readily available, have appropriate C:N ratios, are not derived from any invasive aquatic plant material or any animal waste, and have previously been used in Lake Tahoe.
The experimental mats will be fitted with a Luer-lock sampling connector (standard fitting system used for making leak-free connections between a syringe and a portal that permits liquid to move in either direction) to allow us to extract water just under the mat for measurement of pH, redox potential, ammonium and dissolved oxygen. These parameters will be measured bi-weekly until DO levels under the barrier begin to decline or approach zero. After the decline occurs, the barriers will remain in place for
1-2 months. f. Relationship of the research to previous and current relevant research, monitoring, and/or environmental improvement efforts
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 our proposed 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. g. Strategy for engaging with managers and obtaining permits
We will be in close contact with the LTAISWG and the LTAISCC as the Asian clam management project continues in 2012. For some time now both UCD and UNR researchers have been engaged with the Asian Clam Working Group (ACWG) through regular weekly meetings. The ACWG is comprised of representatives from many state and federal agencies (TRPA, TRCD, USFWS, USACE, CADFG, USDA-
ARS, CA State Parks, LRWQCB, NDEP, NDOW, NDSL and TWSA) as well as UCD and UNR scientists.
Outside these weekly meetings, we will present quarterly updates as oral presentations or in written format to the LTAISWG, LTAISCC and the ACWG. When requested we will convene one technical and one public outreach meeting in collaboration with agencies and local organizations each year.
Since the treatment barriers are being deployed through the collaborative agency framework of the ACWG, permitting and environmental documentation with go through that working group. h. Description of deliverables/products and plan for how data and products will be reviewed and made available to end users
There is an urgent need to quantify factors that could help ensure the success of a large-scale deployment of benthic barriers to control Asian clam in Emerald Bay. In this proposal we are providing critical information on the management and control of Asian clam populations in Emerald Bay. Some of the findings will need to be delivered to the ACWG immediately to support an adaptive management approach to this treatment. The research group will continue to be in direct communication with lake managers and agency representatives of all levels to inform them of findings that relate directly to management of this invasive species. We will provide quarterly progress reports, a preliminary report (end of first year), and a final report (end of project). Included in the final report will be a written exploration of the feasibility of alternative strategies (e.g. diver assisted suction, freezing) for controlling clam densities in Emerald Bay, in case the bottom barriers do not appear to be effective in controlling clams. For each method of controlling clam populations, a basic analysis of costs and gaps in information or obstacles in implementation will be presented to the group.
Each of the two research partners will compile results for their specific tasks and write the results for each task as a separate report, and UC Davis will integrate the individual reports into an overall project report. Results from our project and reviews of other useful information related to Asian clam
8

ecology and management will be posted on the UCD website (terc.ucdavis.edu) and the UNR website
(environment.unr.edu). Results of the research will also be presented at the biennial Tahoe Research
Symposium. We expect to produce at least three peer-reviewed publications on the following topics; effect of the Emerald Bay treatment on mortality, reproduction and stress of Asian clam, transport of dissolved oxygen through the Emerald Bay sill, and enhancement of clam mortality under the bottom barriers through BOD amendments As part of this project we also expect to make presentations at annual scientific meetings (e.g. ASLO, ESA, regional meetings), submit manuscript(s) for publication in academic journals, and make public presentations of data as requested.
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III. Schedule of major milestones/deliverables
Milestone/Deliverables Start
Date
End
Date
Description
Submit quarterly progress reports
July
2012
May
2014
Submit brief progress report to Tahoe Science Program coordinator on quarterly basis.
Objective 1: Assess whether the large-scale (multi-acre) deployment of rubber bottom barriers over the infested areas in Emerald Bay will depress or eliminate Asian clam populations
July
2012
Aug.
2013
Synoptic survey pre- and post-deployment of Emerald
Bay clam populations.
Monitoring the influence of the bottom barrier treatment on clam mortality rate, density, reproductive condition, size structure, and stress.
Objectives 2: Describe the mechanisms driving the survival, depression or elimination of the Emerald
Bay clam population under the barrier treatments
July
2012
Aug.
2013
Track levels of dissolved oxygen (DO) in the water column and bottom sediments outside and under the bottom barriers on the Emerald Bay sill.
Determine the relationship between physical forcing factors such as sediment porosity, currents, waves and the exchange of water volume between Emerald Bay and Lake Tahoe.
Collection and analysis of food supply within sediment and water column.
Deploy and retrieve barriers augmented with organic material, monitor barriers.
Objective 3: Determine whether augmenting bottom barriers with organic carbon can further facilitate, depress, or eliminate the
Emerald Bay clam population
Data processing/analysis
July
2012
July
2012
Dec.
2013
Mar.
2014
Reporting July
2012
May
2014
Data Synthesis/Final Report Mar.
2014
June
2014
Evaluate the effectiveness of the bottom barrier treatment at eliminating clams.
Analysis of clam population structure, environmental parameters and clam dynamics.
Present brief updates to the LTAISWG, LTAISCC and
ACWG at regular meetings, calling special meetings if needed.
A final report of findings from the proposed research.
This report will be written specifically to aid managers and agency representatives in the decision making for
AIS management in Emerald Bay. Depending on the results of the large-scale, agency coordinated barrier treatment and the outcome of the BOD augmentation experiments the final report may include a review of alternate control options necessitated by environmental conditions in Emerald Bay.
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IV. Literature cited
Forrest, A.L, Wittmann, M.E., Schmidt, V., Rainault, N., Schladow, S.G., Reuter, J.E., Laval, B.E.,
Trembanis, A.C.. Benthic imagery monitoring of invasive species in lacustrine environments. Accepted,
Limnol. Oceanogr. Methods.
Gamble, A.E., Reuter, J.E., Schladow, S.G., Allen, B.C. 2011. Draft Report: 2011 Emerald Bay Clam
Survey. Submitted to Tahoe Resource Conservation District.
Kregel, K.C. 2002.
Invited Review: Heat shock proteins: modifying factors in physiological stress responses and acquired thermotolerance. J. Appl. Physiol. 92:2177-2186.
Mattice J.S., McLean R.B., Burch, M.B. 1982. Evaluation of short-term exposure to heated water and chlorine for control of the Asiatic clam ( Corbicula fluminea ). Oak Ridge National Laboratory,
Environmental Science Division, Publication No. 1748. U.S. National Technical Information Service,
Department of Commerce, Springfield, VA, 33 pp.
McMahon, R.F., Bogan, A.E. 2001. Mollusca: Bivalvia. Pages 331-429 in J. H. T. a. P. Covich, editor.
Ecology and classification of North American freshwater invertebrates. Academic Press, San Diego, CA.
McMahon, R.F., Lutey, R.W. 1988. Field and laboratory studies of the efficacy of poly[oxyethylene(dimethyliminio)ethylene(dimenthyliminio)ethylene dichloride] as a biocide against the Asian clam, Corbicula fluminea. In : Proceedings: service water reliability improvement seminar. Electric Power Research Institute, Palo Alto, CA, pp. 61-72.
Wittmann, M.W., S. Chandra, J.E. Reuter, B.C. Allen, S.G. Schladow and K. Webb. 2010. Final Report for
Asian clam Pilot Project. Technical Report – Tahoe Environmental Research Center, University of
California-Davis, One Shields Ave., Davis, CA 95616. 89 p.
Wittmann, M.E., Gamble, A.E., Allen, B.C., Webb, K., Chandra, S., Reuter, J.E., Schladow, S.G. 2011.
DRAFT Report: The Control of Asian clam ( Corbicula fluminea ) in Lake Tahoe with Benthic Barriers: The
Influence of Water Temperature on Mortality. Submitted to Tahoe Resource Conservation District.
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V. Figures
(A)
(C)
(B)
A. Gamble
(D)
Figure 1.
(A) Map of Asian clams based on a whole-lake survey and transects made by a GAVIA
Autonomous Underwater Vehicle (AUV) (from Forrest et al.
accepted). The blue sections in panel A represent areas where no clam images were found using AUV imagery, red sections represent regions with confirmed clam presence, green represents an area that false positives for C. fluminea turned out to be the natively occurring Pisidium . Panel B shows the location of the sill in relation to Emerald Bay and
Lake Tahoe. Panel C shows the 2011 survey results of clam beds around the mouth of Emerald Bay, compared to results from 2009. In this diagram, red represents the extent of live clams in 2011 (5.5 acres), orange represents where dead clams only were found in 2011 (1.5 acres), and the yellow polygon represents the extent of live clams in 2009 (3.5 acres). Yellow tacks represent the approximate locations
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of the channel markers. Panel C also provides the detailed bathymetric contours of the Emerald Bay sill
(1 m contours). Panel D shows the location and size of Emerald Bay compared to Lake Tahoe.
Figure 2.
Clam reproductive potential, measured in July and August 2011 in Emerald Bay, Lake Tahoe
(S. Chandra, Aquatic Ecosystems Analysis Laboratory, University of Nevada Reno). Number of eggs is in blue and number of veligers is in red. ―Outside‖ indicates data were collected from areas without a rubber bottom barrier; ―inside‖ indicates data were collected from underneath a 10 x 100 foot rubber bottom barrier. Data indicate that clams were negatively impacted under the barrier, with significantly lower eggs per clam and no veligers produced by clams under barriers.
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Figure 3.
Water current and DO measurements taken on the sill at Emerald Bay. Period One indicates time when relatively high exchange flow velocities (measured by Acoustic Doppler Velocimeter) were recorded. The middle panel shows the direction is approximately 90 degrees, indicating flow out of
Emerald Bay and into the lake. During this period DO under the barrier is only slightly below the DO over the barrier. Period Two indicates the time when the surface exchange velocities are low. The variability in the direction suggests that the currents are actually below the noise level of the instrument. During this period DO drops precipitously at night, but recovers each day when surface waves are present presumably due to high speed boating. The rate of DO decline each night is similar to what has been measured in other locations at Tahoe where clams have been successfully killed.
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