Title: Science to assist policy decisions regarding the prevention of invasive species: testing the survival and growth of quagga mussel in Lake Tahoe Subtheme 2a: Understanding the impacts of aquatic invasive species Principal Investigator and Dr. Sudeep Chandra Receiving Institution Department of Natural Resources and Environmental Science University of Nevada- Reno,1000 Valley Road/ MS 186 Reno, Nevada 89512 Phone: 775-784-6221;FAX: 775-784-4530, [email protected] Co-Principal Investigator
II. Proposal Narrative (up to 7 pages, single-spaced, 10 point font minimum) a. Project abstract (1 paragraph summary for public distribution) Quagga and zebra mussels are establishing in western waterways with large densities in the Colorado Aqueduct system and established populations in North Central California. This invasion is already having profound ecological and economic impacts in these ecosystems. There is a debate amongst scientists and managers on whether the current models that predict the distribution of Dreissenid mussels are accurate. Recently for example veligers have been detected in Colorado lakes some of which have low calcium levels. Furthermore, a study in Lake George (NY) suggests that adult mussels are able to grow under low calcium conditions however the veliger recruitment determined from settlement bioassays is likely limiting. Thus, what will determine a source versus sink population may not be entirely clear and deserves some attention for Western waters. A previous study using Lake Tahoe water suggests by the PI suggests that adult quagga mussel fed low calcium, low algal biomass water may survive for greater than 50 days. Reproductive analysis showed that there was some evidence of gamete development in these mussels, but findings were inconclusive as to whether mussel populations can maintain themselves in Lake Tahoe conditions. Survival from the veliger stage to adult stage is key in the establishment of dreissenid mussels in any water body—this indicates the ability for species establishment after introduction. Current knowledge suggests that Lake Tahoe can support adult mussels for s short period of time however, whether juveniles, and thus a reproducing population can sustain is currently unknown. The proposed research will directly assess the habitat suitability of Lake Tahoe and its watershed to support the establishment of quagga mussel by testing the survivability of veliger to sub-adult stage using Lake Tahoe water. This information will be important for supporting the current efforts related to inspection and washing of boats entering Lake Tahoe. b. Justification statement: explain the relationship between the proposal and the subtheme(s) Quagga and zebra mussels are establishing in western waterways (CA, NZ, AZ, UT, CO) with great densities in the Colorado Aqueduct system, and Lake Mead, NV-AZ in particular. This invasion is already having profound ecological and economic impacts--dam operators have spent millions removing mussels from penstocks (BOR 2009) and quagga mussel clearly dominates benthic invertebrate communities (Wittmann, Chandra et al. 2009). When quagga mussel establish, they can dominate and alter the ecology of lakes, impacting all trophic levels. In Lake Huron, salmon, alewife, zoo- and phytoplankton populations have declined after the establishment of quagga mussels, causing an energy shift from pelagic to benthic zones. This impact has resulted in a $19 million yr-1 decrease in revenue for sport fisheries in Lake Huron (Michigan DNR 2008). In Green Bay, Lake Michigan, dreissenids may be increasing phytoplankton biomass and cyanobacteria concentrations due to selective feeding (DeStasio et al. 2008). Dreissenid mussel invasions have the potential to cause possible biomass shifts from pelagic to benthic communities and may have impacts on lake fisheries and water quality (Umek et al. 2009). If quagga mussel were to establish in Lake Tahoe, it is likely they could have similar impacts on this ecosystem. Similar to Mead, Tahoe is an oligotrophic lake with low food availability. Unlike Lake Mead, Tahoe’s calcium levels are low and place Lake Tahoe in the low risk category for establishment based on published establishment models for dreissenids (Whittier et al. 2008, Cohen and Weinstein 2001). Recent detections of quagga veligers in low calcium reservoirs in Colorado (Table 1) challenges these previously held notions of minimum thresholds for mussel survivability and once again raise the question of whether detections in low calcium waters are source or sink populations. Previous studies in 2008-09 carried out by the University of Nevada- Reno and University of California- Davis showed that adult quagga mussel collected in Lake Mead and maintained in a laboratory setting with low calcium, low chlorophyll Lake Tahoe water can survive for greater than 50 days (Chandra et al. 2009). Reproductive analysis showed that there was some evidence of gamete development in these mussels, but findings were inconclusive as to whether mussel populations can maintain themselves in Lake Tahoe conditions. Survival from the veliger stage to adult stage is key in the establishment of dreissenid mussels in any water body—this indicates the ability for species establishment after introduction. Current knowledge suggests that Lake Tahoe can support adult mussels, whether juveniles, and thus a reproducing population can sustain is currently unknown. The proposed research will directly assess the habitat suitability of Lake Tahoe and its watershed to support the establishment of quagga mussel by testing the impacts Lake Tahoe conditions on the survivability of veligers to sub-adult stage. c. Concise background and problem statement The introduction of non-native species is a leading threat to biodiversity and function of freshwater ecosystems (Sala et al. 2000). A major introduction pathway for aquatic invasive species to North America has been ship ballast water releases into the Laurentian Great Lakes and coastal waters. Once established, species can extend their range through natural waterways via passive or active transport. The long distance spread of these species far beyond neighboring watersheds increases over time predominantly due to human recreational activity (e.g. boating, fishing) (Johnstone et al. 1985, Padilla et al. 1996, Johnson et al. 2001, Leung et al. 2006). Invasive dreissenid zebra (Dreissena polymorpha) and quagga (Dreissena rostriformis bugensis) mussels (zebra and quagga) in particular have altered the ecology of lakes and rivers by coupling pelagic and benthic trophic pathways, increasing offshore clarity, stimulating benthic production and altering biodiversity (Makarewicz et al. 1999, Bially and MacIssac 2000, Ricciardi et al. 1998). In recent years there has been a western range expansion in North America for a number of aquatic invasive species such as New Zealand mudsnail (Potamopyrgus antipodarum), dreissenid mussel species, and crayfish (Procambarus clarki). This spread has been of increasing concern to aquatic ecosystem managers in the western U.S. due to the high level of endemism in their waters (Sada and Vinyard 2002) as well as high costs often associated with the prevention, monitoring and control of introduced species. The Southern Nevada Water Authority for example has spent approximately $32 million (until 2009) to manage quagga biomass impacts on the water intake infrastructure of Lake Mead, a recently invaded reservoir in the western U.S. (Peggy Roefer, Southern Nevada Water Authority, pers. communication). While it is clear that many of these species can be viably transported to water bodies, the physiochemical characteristics of these water bodies that are necessary for successful invasive establishment are poorly understood. Dreissenid mussels have already invaded the mid-western and eastern regions of North America, with zebra mussels (Dreissena polymorpha) discovered in the Great Lakes region of North America in the mid-1980’s (Hebert et al. 1989) and quagga mussels found there in 1992 (May and Marsden 1992, Mills et al. 1993). The quagga mussel first appeared in western U.S. in Lake Mead, AZ-NV in early 2007 (Stokstad et al. 2007) and has subsequently been found in other major western impoundments including Lakes Powell and Mohave. These recent invasions have spurred efforts to determine invasion risk posed by zebra and quagga mussels in western waters. There are a large number of dreissenid mussel establishment risk assessment approaches that have been based on European and Eastern North American invasions that may or may not be appropriate for evaluations of western waterways. Risk assessment for the western U.S. may be based on these approaches, but with careful consideration of western water body characteristics such as differences in water temperature, calcium and other nutrient concentrations. Food availability is also an important variable for mollusk establishment, and is often the cause for massive dreissenid mussel population crashes after initial population explosions (Strayer et al. 1996). Water column calcium concentration is often used as an index for determining the potential for mollusk establishment, growth, and reproduction with variable requirements depending on the species (Ramcharan et al. 1992, Sousa et al. 2008, Whittier et al. 2008). Since the recent establishments in Lakes Mead, Powell and Mohave, numerous studies are underway to determine zebra and quagga mussel invasion risk to Western waterways including Lake Tahoe. Based on empirical information gathered from water quality databases and modeled systems, Whittier et al. (2008) created a watershed-scale risk model for dreissenid species. This model is based on calcium requirements, primarily derived from zebra mussel due to limited experimental data on quagga mussel survival. Managers have used this model to determine the risk-potential of quagga mussel establishment from invaded water bodies such as Lake Mead. However, because quagga mussels appear to have different environmental tolerances than zebra mussels, (Baldwin et al. 2002, Stoeckmann 2003, Roe and MacIssac 1997, Zhulidov 2004), and possibly than quagga in other parts of their range (Domm et al. 1993, Antonov and Shkorbatov 1990), the potential risk of invasion of western water bodies may be underestimated by using zebra mussel-based risk assessments. Recent findings from other western aquatic ecosystems indicate that dreissenid survival can occur under variable and lower calcium concentrations than previously reported. For example, there are currently 8 Coloradan limnetic ecosystems (some hydrologically connected) where dreissenids have been detected (Table 1). These systems exhibit varying calcium concentrations ranging from 3.5-75 mgL–1. Five of the eight locations that have been invaded by quagga mussels (Willow Creek Reservoirs, Lake Granby, Shadow Mountain Reservoir, Grand Lake and Blue Mesa Reservoir) have similar calcium concentrations and water quality characteristics to the oligotrophic water bodies in the Tahoe basin (Figure 1). It is unclear whether the newly introduced populations in the Colorado lakes and reservoir system will be able to maintain long-term growth and population expansion given variable environmental conditions (e.g. calcium and nutrient concentrations, food availability), or whether these systems will act as a sink where short-term survival occurs but growth and reproduction will be limited or nonexistent. Lake George (New York) is a second example of an ecosystem with low calcium levels (approximately 10 ppm) that has an established and managed population of zebra mussels (Frischer et al. 2005). Recently the PI’s visited the Darren Freshwater Institute (Rensselaer University) to understand this invasion and assist researchers in managing a recent invasion by Asian clam. It was clear that while the populations of dresseinids were managed they were expanding to 11 locations since the initial management was initiated less than 1 decade ago. With this information, the potential threat for quagga to establish in the low oligotrophic waters of Lake Tahoe, as well as the desire to develop boater inspections policies that would protect the lake, the Tahoe Regional Planning Agency commissioned a pilot study in 2009 to determine 1) if adult quagga mussel can survive, grow, and reproduce in Lake Tahoe and 2) their potential impacts on algae and nutrient levels. In response to this request, researchers from the Universities of Nevada- Reno and California- Davis, conducted a seminatural field experiment at the University of Nevada- Reno’s Aquatic Ecosystems Analysis Laboratory. It should be noted that the pilot investigation was not intended to evaluate the ability of quagga to complete its entire life cycle in Lake Tahoe water, which was beyond scope and funding. However results can be used to test whether or not further scientific study is warranted to support the boat inspection and washing programs. In the experiment adult mussels from Lake Mead were exposed to water from the Tahoe Keys marina of Lake Tahoe for a 51-day period. The laboratory experiment showed that quagga mussel had 87% survival with a positive growth rate over the experimental period (Figure 2). Reproductive status was variable with 43% of individuals (male and female) showing sperm and oocyte production, 14% were in a post-spawn phase, and 29% showed resorption (Table 2). One of the major conclusions of the pilot study however suggested it was very important to test the survivability of veliger, a young life history state, of quagga mussel, since their requirements for calcium are greater than for adult mussels. A secondary recommendation was to conduct a survival study of adult mussel with increased samples size to reduce the change of statistical errors since the initial study only provided pilot funding to test whether or not further study was warranted. Neither of these was conducted in the initial pilot study, due to funding constraints at the agency level. The pilot experiment also attempted to determine the potential water quality impacts that would occur if adults were established in the lake. Water quality impacts indicated that adult quagga mussels could decrease algal biomass and alter nutrient species available within the water column (Chandra et al. 2009). In particular, the findings from our short-term study showed a decrease of pelagic algal biomass with a slight increase in soluble reactive phosphorus and no change in total phosphorus. In the Tahoe experiment ammonium increased dramatically over 51 days, with a significant increase in ammonium to soluble reactive phosphorus ratio after 48 hours (Chandra et al 2009). Johengen et al. (1995) found annual mean values of dissolved inorganic nitrogen (nitrate and ammonium) were greater but also variable during post- than pre-zebra mussel periods. As mussels filter organic material from the water, they release ammonium in their pseudofeces and feces, producing some of the highest nitrogen excretion rates of any animal (Bruesewitz et al., 2006). Zebra mussels also act as a sink for phosphorus in phosphate-limiting environments (Johengen et al., 1995) and only affect water column phosphorus when the phosphorus output of mussels is greater than 20 % of the lake's phosphorus loading (Mellina et al. 1995). Lake Tahoe has already shifted from nitrogen limitation to nitrogen and phosphorus co-limitation during most of the year due to anthropogenic influences (Hackley et al. 2007). Potential greater increases in nitrogen (as ammonium) than phosphorus (as soluble reactive phosphorus) by quagga mussels, if they were to establish in Lake Tahoe, could further shift the lake toward phosphorus-limitation. A disruption in the balance of nutrients, if sustained in the environment, could affect phytoplankton composition (Conroy and Culver 2005) and nutrient limitation in Lake Tahoe. While Lake Tahoe has been categorized as “low risk” for dreissenid mussel establishment based solely on its low dissolved calcium concentrations (Cohen and Weinstein 2008), findings from the pilot study provided partial evidence that short-term adult quagga survival could be possible in Lake Tahoe. However, the pilot investigation was not intended to evaluate the ability of quagga to complete its entire life cycle in Lake Tahoe water (beyond scope and funding). This proposal is in response to the need to finalize answers to the question of whether quagga could be established in Lake Tahoe with reproductively viable populations that increase over time. This is a particularly critical question given the given the more strict control and management strategies have been adopted by the Tahoe Regional Planning Agency, particularly with respect to boat inspection and washing programs at the lake. Decisions related to future investments in costly inspection activities would clearly benefit from a better understanding as to whether quagga can survive and reproduce in Lake Tahoe. Decisions related to future investments in costly inspection activities would clearly benefit from a better understanding as to whether quagga can survive and reproduce in Lake Tahoe. d. Goals, objectives, and hypotheses to be tested The primary goal of this study is to fill in the knowledge gaps from the pilot study initiated by the Tahoe Regional Planning Agency to further develop invasive species prevention policies in the basin. To fill these knowledge gaps we will address the issues that were beyond the scope the pilot study to test the following hypotheses: 1) Veliger state of quagga mussel will NOT attach, survive and grow in the low calcium, waters of Lake Tahoe; 2) Adult quagga mussel will survive, grow, or produce viable gametes in the low calcium waters of Lake Tahoe; 3) Lake Tahoe will represent a “sink” for dreissenid populations and thus not produce viable, populations.
The specific objective for understanding the invasion potential for quagga mussel into the waters of Lake Tahoe include: 1) Determination of quagga veliger settlement, survival and growth; 2) Determination of quagga adult survival, growth, and potential for producing viable gametes; 3) Assign a probability of risk to the nearshore areas and regional water bodies based on the experiments and previously collected calcium concentrations along the nearshore of lake during the pilot study. e. Approach, methodology and location of research All proposed research will occur in controlled laboratory settings using seminatural and laboratory field based approaches. Chandra (PI) and Acharya (coPI), currently have the appropriate state permits and have extensive experience combined rearing invertebrate and algal communities in a laboratory setting. The Acharya lab at the Desert Research Institute has been maintaining adult and juvenile quagga mussels for two years and specializes in running experiments on growth, excretion and clearance rates.
Objective 1. Determination of quagga veliger attachment survival and growth The veliger stage is thought to be the vulnerable moment of mussel development and requires adequate levels of calcium for survival. In this part of the study a seminatural field and culture approach will be utilized to test whether veligers will attach and survive in Lake Tahoe’s waters under current conditions and estimate the level of calcium needed to maintain growth. We will use a veliger attachment bioassay approach adopted by Lake George researchers to accomplish this objective (Frischer et al 2005). A large number of veligers will be collected in bulk from Lake Mead using a 44 um plankton net. An equal density of veligers will be placed into triplicate, 20 gallon aquaria with 20 removable standard microscope slides lining the bottom for each treatment. Four slides will be removed every second day for a total of 8 weeks of experimental time. The number of settled larvae will be determined via cross polarizing microscopy. Treatments include:
Treatment 1 (Control)- Veligers maintained in Lake Mead water with calcium levels of 80 ppm where veliger growth is not constrained Treatment 2 (Control)- Veligers exposed to Lake Tahoe water with supplemented calcium levels above literature based thresholds for maximal growth rates (32 ppm) (Hincks and Mackie 1997) Treatment 3- Veligers exposed to Lake Tahoe water at approximately ambient calcium concentrations found in the main part of the lake (9 ppm) Treatment 4- Veligers exposed to Lake Tahoe water from the Tahoe Keys at elevated calcium concentrations (12-15 ppm) Treatment 5.- Veligers exposed to Lake Tahoe water with calcium concentrations slightly above the main part of the lake or the Tahoe Keys but similar to those found in the region (20 ppm)
Calcium chloride will be used as the calcium amendment for the respective treatments with additions. The experiments will be repeated twice, during spring run off and late summer and maintained in a constant temperature setting to replicate an ambient summer water temperatures (20-22C) following a 14: 10 day: night cycle. Thus, response variables monitored during the experiments include: survivorship, growth, developmental stage, and settling rates. ANOVA will be utilized to compare the response variables across treatments for each time period.
Since veligers transition from straight hinge and D stages through post-veliger to umbonal/settling stage, with noted mortality occurring in this settlement transition, (Wright 1996) we will monitor the development and mortality rates weekly for the first 6 weeks and every other week thereafter over 18 weeks from a subsample of veligers from each treatment similar to Stoeckel et al. (2004). The veligers settled on the slides from settlement study will be transferred for growth and mortality assessment. Growth study will be done on 5 replicates of 120 veligers per treatment. Every week (first 6 weeks) and every other week (week 7th to 18th) 10 veligers from each replicate will be removed for body size measurement. During the weekly and biweekly sampling dead veligers will be counted and removed.
Objective 2. Determination of quagga adult survival, growth, and potential for producing viable gametes. One of the major constraints with the adult quagga survival pilot study was the small sample size each treatment could accommodate in the experiment (Chandra et al. 2009). We will use adult quagga mussel growth and laboratory culture bioassay approach developed by Acharya lab to accomplish this objective (Link 2010). In this section of the study we proposed the following treatments: Treatment 1 (Control)- Isolated Lake Mead adults maintained in Lake Mead water with calcium levels of 80 ppm where survival and growth is not constrained; Treatment 2 (Control)- )- Isolated Lake Mead adults exposed to Lake Tahoe water with supplemented calcium levels above literature based thresholds for maximal growth rates (32 ppm) (Hincks and Mackie 1997); Treatment 3- Isolated Lake Mead adults exposed to Lake Tahoe water at approximately ambient calcium concentrations found in the main part of the lake (9 ppm); Treatment 4- Isolated Lake Mead adults exposed to Lake Tahoe water from the Tahoe Keys at elevated calcium concentrations (12-15 ppm); Treatment 5.- Isolated Lake Mead adults exposed to Lake Tahoe water with calcium concentrations slightly above the main part of the lake or the Tahoe Keys but similar to those found in the region (20 ppm); Treatment 6- - Isolated Lake Mead adults exposed to Lake Tahoe water with supplemented calcium levels found in Asian clam beds (25 ppm)
Modified procedures outlined in our pilot experiment will be utilized during this experiment. In order to prevent the mussels from over utilizing their food, adult quagga mussels (8-10 mm) will be placed individually in a 10 L container and provided a daily ration of 7 L of Lake Tahoe water for the duration of the experiment (120 days). To allow evacuation of stomach content material, mussels will be held for 48 h before placement in their containers. Mean initial length and blotted wet-weight and dry weight from a representative cohort in the population for each individual mussel and compared to final lengths and weights. Water quality parameters (temperature, dissolved oxygen, conductivity) using a YSI 85 multiprobe (YSI Incorporated, Yellow Springs, Ohio) and nutrients such as phosphorus (total, dissolved, reactive), nitrogen (ammonium and nitrate), and chlorophyll a (pheophytin corrected), and calcium will be measured from the field location where water is obtained every week. The mussels in their containers will be maintained in a temperature controlled chamber at 20-22 °C, on a 14: 12 hour day: night light cycle. Mussel survival will be determined daily by qualitatively noting gape size (Matthews and McMahon 1999). If gape size appeared abnormally large or mortality was suspected, the adult was gently tapped and shell closure was used as an indicatory of viability. Growth rate will be calculated plotting start- versus end weight compared to a 1:1 line, since a slope of 1 represents no growth (start = end weight) where points falling above the 1:1 line will be interpreted as weight gain and points below as weight loss over the course of the entire experiment. To determine the reproductive potential of each of the experimental mussels, gonad status will be determined for each replicate. At the end of the experiment the soft tissue of each live mussel will be removed from the shell, placed in 15 mL of 10 % neutral buffered formalin for 24 hours, and transferred to 70 % ethanol. Tissue from each replicate will be placed in a tissue cassette and processed for routine preparation of 5 µm, hematoxylin- and eosin-stained paraffin- embedded tissue sections. Due to their small size, three sections will be cut from each mussel tissue block at different levels, thus sampling most of the embedded tissue. Each mussel will be scored qualitatively for the presence of gametes with notes on the sex, gonad stage and the stage of resorption. The scoring are as follows for gonad development stage: 0, no gonad present, 1) early development, very immature sperm or egg precursors present, 2) between stages 1 and 3, 3) apparently mature sperm or oocytes present (in any volume), 4) post-spawn, empty gonad follicles present with some residual sperm or egg; and for gonad resorption stage: 0) no evidence of resorption, few or no hemocytes in gonad follicles, 1) small proportion of hemocytes present among reproductive cells, 2) between stages 1 and 3, and 3) follicles dominated by hemocytes with some residual sperm or egg.
Objective 3. Assign a probability of risk to the nearshore areas of Lake Tahoe based on the experiments and previously collected calcium concentrations along the nearshore of lake during the pilot study. The final information obtained from the experiment will be used to estimate the areas of the nearshore based on calcium levels that may or may not facilitate an invasion by quagga mussel. The information of nearshore calcium level collected at 1.5 km increments from the nearshore areas of Lake Tahoe along with regional levels collected in the pilot study will be utilized to determine potential areas for quagga survival. This information will be based on the survival determined from the veliger and adult experimental treatments. Similar to previous studies, this risk assignment will be based on based solely on calcium levels (Whittier et al. 2008). The risk evaluation will be based on the following criteria: if a water body or part of Lake Tahoe’s nearshore ambient calcium levels fall within the range of survival for both veligers and adults then this area will be identified as invadable. Noninvadable sites will be those sits that match experimental treatment outcomes where quagga veliger or adults did not survive. f. Relationship of the research to previous and current relevant research, monitoring, and/or environmental improvement efforts. The proposed research is a direct progression of from a pilot study funded by the Army Corps of Engineers and the Tahoe Regional Planning Agency in 2009 (Chandra et al. 2009) and from research that has been conducted on the lake’s newest invader, the Asian Clam (Whitmann et al. 2009). For a more complete description of the findings from previous research that support this proposal see Part IIc. Currently there are multiple projects that address invasive species concerns at Lake Tahoe. The scientific studies vary in understanding plant, invertebrate, and fish invasions in the nearshore areas of the lake. Recent study of Asian clam beds suggests elevated levels of calcium and substrate from this invader may promote quagga establishment in the lake (Whitmann et al. 2009). This proposed research expands on the latest information related to clam invasions and will also assist in determining if Asian clam patches and associated clam beds may promote the invasion of quagga mussel. g. Strategy for engaging with managers and obtaining permits Informally we will be in close contact with the Lake Tahoe Aquatic Invasive Species Working Group (LTAISWG) and Coordination Committee (LTAISCC) along with the Lake Tahoe Federal Advisory Committee as the survival and growth studies are conducted from various life stages. We will formally engage managers by presenting quarterly updates in either an oral or written format to the LTAISWG and LTAISCC. These groups were created over three years ago to address invasive species issues within the Tahoe basin and will serve as a Management Advisory Group for this project. It is comprised of agencies and researchers actively involved with controlling, managing and researching invasive species in the Tahoe basin. When requested we will convene one technical meeting with agency staff and one public outreach meeting each year. Results from our project and reviews of other useful information related to quagga mussel ecology and management will be posted on the UNR website (environment.unr.edu). Results of the research will also be presented at the biennial Tahoe Research Symposium. In the past we have obtain the appropriate permits to conduct research in the State of Nevada with quagga mussel and will seek renewal of this permit for this project at both the University of Nevada- Reno and the Desert Research Institute- Southern campus. The PI’s currently have the permits and approved protocols necessary by the Nevada Department of Wildlife to work with Dreissenid mussels. 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 develop a complete risk analysis based on early and late stage life histories of quagga and a basic predictive model for describing the locations of mussels in Lake Tahoe’s nearshore and region. Lake managers are seeking information this information to determine how strict boater inspections and policies need to be prevent invasion of quagga mussel to the basin. Thus, in this proposal we are providing critical information that will fill in critical gaps of knowledge determined in the smaller scale, pilot study. We will provide quarterly progress reports, a preliminary report (end of first year), and a final report (end of project). 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, and make public presentations of data as requested.
III. Schedule of Events/Reporting and Deliverables Milestone/Deliverables Start Date End Date Description Submit quarterly progress reports June 11 May 13 Submit brief progress report to Tahoe Science Program coordinator by the 1st of August, December, March, and June
Objectives 1 (Veliger June 11 May 12 Conduct experiments and determine veliger experiments, settlement, survival survival and growth assays)
Objective 2 (Adult quagga January 12 Dec 12 Utilize adults quagga mussel to determine survival experiments) from multiple lake locations
Objective 3: January 13 May 13 Use outcomes from the veliger study to predict Create preliminary models of potential locations for monitoring and management risk and present to the if quagga invaded the lake LTAISWG, and LTAISCC Present quarterly updates to the June 11 May 13 Present brief updates to the LTAISWG at regular LTAISWG and relevant agencies meetings, call a special meeting if needed to present (TRPA, USFS, NTCD, ACE, information that may help managers develop more BOR, etc.) precise locations or better prevention methods for quagga introduction to the lake
IV. Literature cited/References (Up to 2 pages)
Bially A and HJ MacIsaac. 2000. Fouling mussels (Dreissena spp.) colonize soft sediments in Lake Erie and facilitate benthic invertebrates. Freshwater Biology 43:1 (85-97) Bureau of Reclamation. Western Invasive Mussel Management Workshop. February 25, 2009. Las Vegas, Nevada Chandra S, M Wittmann, A Caires, A Kolosovich, L Atwell, JE Reuter, G Schladow, J Moore, and T Thayer. 2009. Risk of invasion or really no problem? An experiment test of quagga mussel survival and reproductive status using Lake Tahoe water with a prediction of invasion into Western water bodies. Submitted to the Tahoe Regional Planning Agency and the Lake Tahoe Aquatic Invasive Species Coordination Committee. Cohen, A and A Weinstein. 2001. Zebra Mussel's Calcium Threshold and Implications for its Potential Distribution in North America. DeStasio BT, MB Shrimpf, AE Barnanack, and WC Daniels. 2008. 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Journal of Environmental Management 20:263-279. Leung B., J. M. Bossenbroek, and D. M. Lodge. 2006. Boats, pathways and aquatic biological invasions: estimating dispersal potential with gravity models. Biological Invasions 8:241-254. [MDNR] Michigan Department of Natural Resources. 2008. Lake Huron's foodweb change. Southwest quagga team meeting. Henderson, NV. Link, C. 2010. Filtration and Growth Rate of Lake Mead Quagga Mussels (Dreissena Bugensis) in Laboratory Studies and Analyses of Contaminants. M.S. thesis, University of Nevada, Las Vegas. Makarewicz, JC, TW Lewis, and P Bertram. 1999. Phytoplankton composition and biomass in the offshore waters of Lake Erie: Pre- and post-Dreissena introduction (1983-1993). Journal of Great Lakes Research 25: 135- 148. May B and JE Marsden. 1992. Genetic identification and implications of another invasive species of dreissenid mussel in the Great Lakes. Can. J. Fish. Aquat. Sci. 49:1501-1506. 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V. Figures and tables (optional, up to 6 total) for project locations, schematics, sample outputs, etc. Figures do not count toward page limits unless they are embedded in the narrative.
Table 1. Ecosystems in Colorado (USA) where dreissenids have been detected, their life stage at detection, and associated environmental parameters.
Ecosystem Dressenid type Life stage Calcium Chlorophyll a Total P (mgL-1) (ugL-1) (mgL-1) Grand Lake quagga, zebra veliger 4.0-9.0 0.8-7.1 0.006-0.032
Shadow Mtn quagga veliger 3.5-9.5 0.5-25.2 0.009-0.030 Res.
Willow Creek quagga veliger 10.4-19.1 5.6-8.3 0.009-0.012 Res.
Lake Granby quagga veliger 5.5-11.0 1.0-12.8 0.006-0.038
Pueblo Res. quagga, zebra veliger 23-75 4.5-51.8 0.005-0.097
Jumbo Res. quagga veliger 26-47 0.5-102 <0.01-0.14
Tarryall Res. quagga veliger N/A N/A N/A
Blue Mesa quagga veliger 27.5-37.9 N/A 0.008-0.057 Res.
Table 2. Reproductive status of adult quagga mussel after 51 days of exposure to ambient Lake Tahoe water. See text for explanation of gonad stage and resorption indices. Replicate number Sex Gonad stage Gonad resorption Keys 1 F 3-4 2 Keys 2 M 3 0 Keys 3 M 3 0 Keys 5 F 1 3 Keys 6 F 1 3 Keys 7 M 3 2 Keys 8 F 2 2
Figure 1. Dissolved calcium concentrations from selected Western waterways of the Great Basin and Lower Colorado River ecosystems, as well as finer scale calcium concentrations from Lake Tahoe’s nearshore zone (Chandra et al. 2009). Figure 2. Start- and end (wet) weights of quagga mussels (n=7) for the overall experimental period (days 0-51). The line indicates a 1:1 relationship for reference; points falling above the line indicate positive growth, points below the line indicate negative growth.
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End weight (mg) End weight 45
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