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Lake Mead Science Symposium Concurrent Sessions
ALL POSTERS
January 13 and 14, 2009 * presented 5:00 pm – 6:00 pm * BallroomStrategic Data Mining and Database Development for Research Projects at Lake Mead, Nevada-Arizona USA
Pollard, James and Andrew, Gretchen, University of Nevada, Las Vegas“Water 2025” is a Department of Interior initiative designed to guide the management of scarce water resources in the American West. As an important Colorado River reservoir, Lake Mead is a fundamental component of Water 2025. For Water 2025 to achieve its goals, comprehensive knowledge is needed of historic and current Lake Mead water quality data. A task agreement between the National Park Service and the University of Nevada, Las Vegas, provides for a strategic data mining project to identify research and monitoring projects on Lake Mead that have been conducted in the past, prioritize relevant projects, and ensure data availability by converting the data to an electronic format.
Discussed here are the results of the comprehensive literature search and construction of the Access data base developed in phase one of the project. The literature search focused on the topics of: water quality, limnology, contaminants, fisheries, aquatic biota, and riparian/shoreline resources. The Access database was created to serve as a repository for descriptive metadata for Lake Mead research projects. Metadata is structured to allow refined searches for project results with sub-headings such as: research topics, research locations, parameters measured, and date or duration of research. A ranking system is being developed which will allow for prioritization of data mining activities and capture of electronic data during the project’s second phase. The ultimate goal of this project is to make historic data more available to the managers and researchers working towards meeting the goals of Water 2025.
Surface Water Monitoring for Fecal Indicator Bacteria in High-use Site of the Lake Mead National Recreation Area
Cruz, Patricia-1; Stevens, Vanessa L.-1; Rinella, Jessie J.-2
(1) University of Nevada, Las Vegas and (2) NPS Lake Mead National Recreation AreaThe Lake Mead National Recreation Area incorporates 1.7 million acres, including Lake Mead and Lake Mohave. The abundance of recreational activities on Lakes Mead and Mohave can impact the contaminant levels in the water, potentially affecting the health of individuals in contact with the water. The purpose of this study was to review and synthesize information obtained for projects conducted by partner agencies from the Water 2025 Conservation Initiatives, specifically bacterial concentration in high-use areas. Surface water samples were collected between May and September, at 9 high-use sites from 2003 to 2007. Culture analysis was performed to determine the concentration of fecal coliforms, Enterococcus, fecal Streptococcus, and Escherichia coli. Test results of 324 water samples analyzed for E. coli showed only one instance of a concentration higher than the acceptable limit. Enterococci concentrations above the acceptable limit were found in 13% of the samples (n= 165). In addition, 9% of 317 samples exceeded the acceptable limit for fecal Streptococcus, and fecal coliforms were present in concentrations above the acceptable limit in 3% of the 324 samples analyzed. Throughout the 4-year study, two sites, Boxcar Cove and 6-Mile Cove, were identified as those with the highest frequency of unacceptable levels of the indicator organisms monitored. The results of this study will be used to address the technical soundness of monitoring at the Lake Mead National Recreation Area, and will identify management recommendations to the National Park Service.
Monitoring Water Quality on the Overton Arm of Lake Mead and its Tributary Inflows during Flood Flows
Arufe, Jorge A., U.S. Geological SurveyThe U.S. Geological Survey (USGS), in cooperation with the National Park Service (NPS) and the Bureau of Reclamation (BOR), is determining temporal changes and spatial distributions of natural and anthropogenic compounds entering the Overton Arm of Lake Mead. These efforts and others already underway on the lake by BOR, USGS, and the Southern Nevada Water Authority (SNWA) will aid in the development of a reservoir model of the lake. The effects of flood flows on the water quality of the Overton Arm are largely unknown and necessary for model development.
Water quality physical parameters (water temperature, pH, specific conductance, dissolved oxygen, and turbidity) are continuously monitored near the mouth of the Virgin and Muddy Rivers using multi-parameter sondes. Water samples also are collected quarterly at both sites and analyzed for major ions (and bromide), trace elements, nutrients, pesticides, suspended sediment (concentration and sand/silt break), total organic carbon, and indicator bacteria.
During flows that exceed the 1.5 year flood, data collection intensifies. Water samples are collected at both river sites and analyzed for the same constituents as quarterly samples and hourly suspended sediment samples are collected with an automatic sampler over a 24 hour period. Additionally, changes in sediment load and water quality in Lake Mead are monitored during these flood events by: 1. Measuring water temperature, pH, specific conductance, dissolved oxygen, and turbidity profiles on a transect of seven sites in the Overton Arm, and 2. Collecting water samples at the epilimnion, thermocline, and hypolimnion of each of the profile sites for low-level nutrients, arsenic, bromide, total organic carbon, and total suspended sediment concentration. The same transect is sampled by BOR monthly during base flow conditions.
Keeping Fountain Grass Out of the Mojave Desert
Deuser, Curtis E. and Tietjen, Ryan, National Park Service, Lake Mead EPMTFountain grass (Pennisetum setaceum) is an escaped ornamental perennial bunchgrass from Africa that has invaded parts of Hawaii and the Sonoran Desert. It is adapted to fire and increases hazardous fuels causing wildfires in areas that may not have historically occurred. It was detected in the late 1990s within the Mojave Desert at Joshua Tree National Park and along the Colorado River corridor on the shores of Lake Mohave. The extent of these populations was limited and a rapid response was necessary to keep it from spreading out of control. If no action is taken then fountain grass would spread by windblown seed similar to the way tamarisk has invaded the region. The National Park Service began controlling these recently detected populations in 2001. Control is also occurring on adjacent U.S. Fish and Wildlife Refuges by the National Park Service Lake Mead Exotic Plant Management Team through partnership agreements. Nevada designated fountain grass on the State Noxious Weed List in 2002, and one of the largest commercial nurseries in the state voluntarily withdrew it from sales prior to listing. Populations of this weedy grass have dramatically declined due to successful control actions.
Athel (Tamarix aphylla) and Athel Hybrid (Tamarix aphylla X Tamarix ramosissima) Establishment and Control at Lake Mead National Recreation Area
Norman, Carrie M., Deuser, Curtis E., Hoines, Josh, Lake Mead National Recreation AreaAthel is a large evergreen ornamental tree that has been planted throughout the Southwest since the 1950s. Athel was considered benign because it was thought to produce non-viable seed unlike its invasive relative, tamarisk. However, athel began establishing in the wild from seed on Lake Mead in 1983. Lake Mead National Recreation Area (Lake Mead NRA) has been actively controlling athel since November 2004 along the high water mark of Lake Mead shoreline (439 miles) to prevent it from spreading throughout the Colorado River drainage. The National Park Service contracts Nevada Conservation Corps crews and the Lake Mead Exotic Plant Management Team to implement the control efforts for these species. Since 2004 Lake Mead NRA has controlled 72, 156 athel and 11, 749 hybrids. Control methods have been effective and follow-up monitoring and retreatment is planned during the 2009 field season. Based on observations at Lake Mead NRA, the invasive potential of athel is high, particularly in light of its hybridization potential with tamarisk thus creating a new noxious weed. Natural resource land managers should be vigilant in monitoring current athel populations to ensure they do not become invasive or hybridize with tamarisk.
Wastewater to Drinking Water: Are emerging contaminants making it through?
Alvarez, David A., U.S. Geological Survey; Jones-Lepp, Tammy L., US Environmental Protection AgencyLake Mead serves as the primary drinking water source for Las Vegas, Nevada and surrounding communities. Besides snow-melt from the Rockies water levels in the lake are supplemented by the inflow of treated wastewater from communities along the Colorado River, including Las Vegas. This use-reuse practice is becoming commonplace in the arid Southwest and begs the question: Are organic contaminants, originating in the wastewater, ending up in the drinking water? In 2005, a study was conducted using passive sampling devices (SPMDs and POCIS) to track the occurrence of trace amounts of pharmaceuticals and personal care products, pesticides, industrial chemicals, and chemicals characteristic of wastewater treatment plant (WWTP) effluents at two sites in Las Vegas wash (LVW), one site near Hemingway Harbor in Lake Mead, and in finished drinking (tap) water within the City of Las Vegas. As predicted, the largest abundance and highest concentrations of targeted chemicals were present at the second site in LVW downstream of the confluence of three WWTP effluents. Two antibiotics, azithromycin and clindamycin, along with two illicit drugs, methamphetamine and Ecstasy, were measured in LVW along with numerous pesticides and chemicals indicative of WWTP effluents. Several pesticides were detected above background levels in the drinking water sample at concentrations of 10 to 97 pg/L. Data from the yeast estrogen screen (YES) correlated with the chemical measurements as the highest estrogenic potential was measured in samples from the LVW. Hemingway Harbor and the drinking water samples did not have a measurable estrogenicity above background levels.
Contaminant flux in Las Vegas Bay: Are sediments a sink or source?
Alvarez, David A. and Rosen, Michael R. U.S. Geological SurveyTreated wastewater effluent from Las Vegas, Nevada and surrounding communities flows through Las Vegas Wash into Lake Mead at Las Vegas Bay (LVB). Lake sediment is a likely sink for many organic wastewater contaminants (OWCs); however, partitioning between the sediment and the overlying water could result in the sediment acting as a secondary contaminant source. Passive sampling devices (semipermeable membrane devices-SPMDs and polar organic chemical integrative samplers-POCIS) were placed in LVB between June and July of 2008 to determine the vertical gradient of OWCs in the water column and potential contribution of OWCs from the sediment. A custom deployment housing was used to bury the SPMDs and POCIS in the sediment at depths of 0-10, 10-20, and 20-30 cm. SPMDs and POCIS were also suspended in the water column at depths of 3.0, 4.9, and 6.7 (lake bottom) meters. Preliminary data indicates that the hydrophobic OWCs such as polycyclic aromatic hydrocarbons are twice as concentrated near the sediment-water interface as in the mid and upper water column. The YES assay, used to measure total estrogenicity, indicated that the chemicals sampled in the middle of the water column were twice as estrogenic as those in the upper portion and ten times as estrogenic as those near the sediment-water interface.
Endocrine Disrupting Contaminants in Common Carp from Lake Mead
Echols, Kathy R.-1; Rosen, Michael R.-1; Goodbred, Steven L.-1; Orsak, Erik-2
(1) U.S. Geological Survey, (2) U.S. Fish and Wildlife ServiceLake Mead provides drinking water and recreation for millions of people, and it provides habitat for fish and wildlife. Because of its multiple uses, water quality in the lake is vitally important. Over the past decade scientists have evaluated chemicals in the water, sediment and fish from Lake Mead, and have found synthetic organic chemicals. Recent studies evaluating biological endpoints have found evidence of endocrine disruption in male fish, specifically carp. For this study male common carp (Cyprinus carpio) were collected from four sites in and around Lake Mead - Las Vegas Wash, Las Vegas Bay, Overton Arm, and Willow Beach. Endocrine disrupting legacy chemicals were evaluated as well as emerging industrial and personal care product chemicals. The legacy chemicals determined were organochlorine pesticides and PCBs. Newer chemicals determined were polybrominated diphenyl ethers, fragrance compounds, triclosan and its derivatives, bisphenol A, and nonyl phenols. The pollutants were determined in whole fish using high resolution gas chromatography with three types of detection: high resolution mass spectrometry with selected ion monitoring (PBDEs, derivatized phenols, pesticides), quadrupole full-scan mass spectrometry (fragrances, triclosan derivatives) and electron capture detection (PCBs, pesticides).
Assessment of Endocrine and Gonadal Condition of Male Largemouth Bass from Lake Mead, Nevada
Patiño, Reynaldo-1; Goodbred, Steven L.-1; Orsak, Erik-2; Jenkins, Jill A.-1; Rosen, Michael R.-1 (1) U.S. Geological Survey and (2) U.S. Fish and Wildlife ServiceIn Lake Mead, Las Vegas Bay (LVB) receives tertiary treated wastewater effluent, urban runoff, and groundwater from the Las Vegas metropolitan area. This study examined the potential for endocrine disrupting effects of these anthropogenic inputs on male largemouth bass (Micropterus salmoides). Adult male bass were collected at two sites within Lake Mead: Overton Arm (OA, reference site), and LVB. Post-spawn fish were collected in July 2007 (n = 6-10 per site) and pre-spawn fish in March 2008 (n = 13 per site). Post-spawn fish were characterized by regressed testes whereas pre-spawn bass had ripe gonads. Mean fish lengths and weights did not vary between sites or sampling times. Significant site-associated differences in the endocrine and somatic condition of pre-spawn fish were noted. Pre-spawn LVB males had lower plasma 11-ketotestosterone, higher estradiol-17β, higher E2/KT ratio, higher hepatosomatic index (ratio of liver to body weight), higher hematocrit values, and higher condition factor compared to OA males. However, no significant differences were evident in the gonadosomatic index (ratio of testes to body weight) of either pre- or post-spawn males from the two sites. In post-spawn males, no significant site-associated differences were detected for any of the parameters measured. Overall, these results suggest the existence of site-specific environmental influences on several indices of endocrine condition and health of pre-spawn male largemouth bass from Lake Mead, and are generally consistent with outcomes from previous studies that suggested the occurrence of altered endocrine and reproductive condition in LVB males of other species, such as common carp.
Testing of Las Vegas Municipal Effluent (Clark County, Nevada) for Endocrine and Reproductive Effects to Fathead Minnow
Deng, Xin-1; Stanford, Benjamin-2; Drury, Douglas D.-3; Orsak, Erik-4; Orphan, Lynn-5; Snyder, Shane-2; Patiño, Reynaldo-6
(1) Texas Tech University, (2) Southern Nevada Water Authority, (3) Clark County Water Reclamation District, (4) U.S. Fish and Wildlife Service, (5) Clean Water Coalition, (6) U.S. Geological SurveyThis project will use fathead minnow (Pimephales promelas) to examine the potential effects of tertiary-treated wastewater effluent on indices of fish endocrine and reproductive function. The studies will be conducted at the Clark County Water Reclamation District, Nevada. The test system will consist of flow-through exposure systems using two standard formats: the 21-day and 2-generation (6-month) protocols. These protocols use experimental units (tanks) containing 4 adult females and 2 adult males, and each treatment is conducted in quadruplicate. Endpoints measured will include a number of endocrine and reproductive fitness traits, including survival, spawning success, blood vitellogenin, and secondary sex characteristics. Conventional effluent will be tested at six dilutions: 0, 6.25, 12.5, 25, 50, and 100%. In addition, the effects of enhanced treatment of wastewater (by ultrafiltration and ozonation technologies) will also be examined and compared to the effects of conventional tertiary effluent in side-by-side trials. Tests will be conducted during winter and summer to determine if seasonal differences exist in wastewater quality. The information derived from this study will assist the efforts of (1) resource managers to assess the effects that municipal effluents at the concentrations found in the lake may cause to a native fish species, the federally endangered razorback sucker (Xyrauchen texanus); and (2) wastewater treatment plant managers to evaluate the status of current conventional tertiary treatment and the effectiveness of enhanced treatments for the removal of endocrine-disrupting compounds.
Diversity of Estrogen Degrading Microorganisms in Las Vegas Wash and Lake Mead, Nevada, USA
Blunt, Susanna M.-1 and 2; Bruckner, James, C.-1; Fisher, Jen C.-1; Moser, Duane P.-1
(1) Desert Research Institute and (2) University of Nevada, Las VegasEndocrine disrupting chemicals (EDCs) are a subject of intense research as more studies reveal their persistence in the environment and detrimental effects on wildlife. Steroid hormones, including the natural and synthetic estrogens 17-beta-estradiol (E2) and 17-alpha-ethinyl estradiol (EE2), are among the most bioactive and have been detected at low concentrations in waterways downstream from wastewater treatment plants. Las Vegas Wash, a stream flowing into Lake Mead and fed primarily by treated wastewater, provides a unique experimental system in which to study the role microorganisms play in the fate and dispersal of these compounds in surface waters. The natural potential for biodegradation of the steroid hormones E2 and EE2 was examined utilizing native microorganisms from Las Vegas Wash and Lake Mead. Organisms from a variety of physiotypes, capable of mediating the degradation of E2 and EE2 while growing on their preferred substrates, were cultured and isolated from samples collected along a Las Vegas Wash–to-Lake Mead transect at base flow and identified using 16S rRNA gene sequencing. The abundance of culturable organisms capable of using these compounds as a sole carbon source was also assessed utilizing dilution cultivation and enrichment techniques. Compounds were reduced to levels below detection limits within 4 days. Terminal restriction fragment length polymorphism analysis (T-RFLP), a community DNA fingerprinting approach was used to explore the environmental abundance and diversity of microorganisms that play a role in determining the fate of these emerging contaminants.
History of Contaminant Inputs into Lake Mead Derived from Sediment Cores
Rosen, Michael R., Van Metre, Peter C., Alvarez, David, Echols, Kathy R., Goodbred, Steven L., U.S. Geological SurveyAssessing the changes in contaminant inputs (both organic and inorganic) over time is important in determining sources and sinks of these inputs. Variations in contaminant input were assessed in four sediment cores taken in 1998 from three different parts of Lake Mead (two from Las Vegas Bay and one from Overton Arm and Virgin Basin). Sediments were analyzed for major and trace elements, radionuclides, and organic compounds. Anthropogenic contaminant concentrations are greatest in Las Vegas Bay reflecting inputs from the Las Vegas urban area, although concentrations are low compared to sediment quality guidelines and to other USA lakes. One exception to this pattern was higher mercury concentrations in the Virgin Basin core. The Virgin Basin core is in the main body of the reservoir and is influenced by the hydrology of the Colorado River, which changed after completion of Glen Canyon Dam. Major- and trace-elements in the core show pronounced shifts in the early 1960s and, in many cases, gradually return to concentrations more typical of pre-1960s by the 1980s and 1990s, after the filling of Lake Powell upstream. The Overton Arm is the sub-basin least effected by anthropogenic contaminant inputs. Cores from Las Vegas Bay taken in 2007 were analyzed for emerging contaminants and although data are still preliminary, detections of musk fragrances have been found only in the upper 10 – 15 cm of the core, indicating that these compounds either degrade with time or have only been accumulating for the past 10 – 20 years.
Tracing the Sources of Uranium in the Colorado River Basin
Sanchez, Charles-1, Chesely, John-1, Asmerom, Yemane-2, Malmon, Daniel-3, (1) University of Arizona, (2) University of New Mexico, (3) U.S. Geological Survey
Renewed emphasis on alternative energy sources has revived interest in uranium (U) mining on the Colorado Plateau. The Colorado River is used both as a source of drinking water and a source of irrigation water for food crops. Therefore, the potential for mine waste and runoff into the Colorado River requires an understanding of current U concentrations, sinks, and sources as a prerequisite to limiting human exposure. In 2007 and 2008 water samples were collected in the Colorado River and tributaries, from Colorado to the last diversion near the international border with Mexico. In addition, sediment samples of various ages, through the Holocene period, were collected from the Colorado River. Water samples and various extracts from the sediment samples were analyzed for U concentrations by ICP-MS and isotopic ratios of U, lead (Pb) and strontium (Sr), were determined by MC-ICP/MS as a procedure to discern sources. The U content of the Colorado River increased from <0.05 μg/L at the headwaters near Grand Lake, Colorado, to values greater than 3 μg/L after descending onto the Colorado Plateau. Water diverted for municipal use and irrigation in the lower basin had U concentrations from 3 to 5 μg/L. The isotope data (Pb, Sr and U) are consistent with the normal weathering of U containing geomedia within the watershed and rule against major contamination from U mines. However, continued measurements should be made such that a baseline can be established before future exploration and mining activity or accidental release occurs.