"Lake Mead — Clear and Vital" is a thirteen minute documentary relating the crucial role of science in maintaining high water quality in Lake Mead. The program was produced coincident with release of the Lakes Mead and Mohave Circular a USGS publication covering past and on-going research in the lakes and tributaries of the Lake Mead National Recreation Area.
How are Endocrine-Disrupting Compounds Moving Through the Food Web in Lake Mead National Recreation Area? Completed
Water quality in the Lake Mead National Recreation Area (LAKE), particularly Las Vegas Bay, is affected by water coming from the Las Vegas Wash, an urban perennial stream whose water is comprised of treated wastewater and urban runoff coming from the Las Vegas metropolitan area. Common carp collected from Las Vegas Wash and Las Vegas Bay and largemouth bass collected from Las Vegas Bay have impaired reproductive and endocrine health that have been shown to be caused by the presence of endocrine-disrupting compounds (EDCs) in water coming from the Las Vegas Wash. Understanding the movement of EDCs through the food web is critical in determining the effects of EDCs on all organisms including endangered species such as the razorback sucker and for making informed and effective management decisions on ways to control and mitigate sources of EDCs. In addition, a new study started in 2017 looking at the effect of microplastics on the foodweb led by Austin Baldwin (ID WSC) has also been started to understand whether these plastics interrupt feeding and reproduction in the lake.
A variety of contaminants including nutrients, metals, perchlorate, and organic compounds are transported to the Las Vegas Wash from various sources. Organic compounds are some of the most commonly found contaminants in the Wash. Some of these organic compounds, such as DDT (dichlorodiphenyltrichloroethane), PCBs (polychlorinated biphenyls), PBDEs (polybrominated diphenyl ethers), PAHs (polycyclic aromatic hydrocarbons), personal care products, and human pharmaceuticals, are suspected of being Endocrine-Disrupting Compounds (EDCs). The sources of EDCs to water in the Las Vegas Wash include diffuse sources such as urban runoff as well as concentrated historical industrial sources located along the Wash, and the release of tertiary treated wastewater from 4 wastewater treatment plants that serve the Las Vegas Metropolitan area. EDCs have been found in treated and untreated wastewater in many areas of the United States and many EDCs are not completely removed by even the most advanced wastewater treatment processes.
EDCs can interfere with or disrupt endocrine and reproductive systems and can cause cancerous tumors, birth defects, and developmental disorders. In fish, EDCs are thought to be especially disruptive of the larval or developmental stages altering sexual development, behavior and fertility, and causing feminization of male fish or masculinization of female fish. Recent studies have shown that male common carp (Cyprinus carpio) collected from Las Vegas Bay and Las Vegas Wash have shown feminization with impaired endocrine and reproductive health. Largemouth bass (Micropterus salmoides) collected in Las Vegas Bay have also shown symptoms of impaired reproductive health. These adverse health effects have been shown to be caused by the presence of EDCs in water and/or sediment in these areas. Recent studies have indicated improvement in the endocrine and reproductive health of common carp collected from in Las Vegas Bay since 1995 that may have come from enhanced wastewater treatment.
In spite of these recent improvements, the evidence that EDCs may be causing adverse health effects in fish and aquatic invertebrates in LAKE has been mounting for some time. In a study completed in 1996, water, bottom-sediment, and tissue samples of carp taken from the Las Vegas Wash and Las Vegas Bay all showed the presence of EDCs. Tissue samples of carp taken from the Las Vegas Wash showed skewed sex hormone ratios with elevated concentrations of male hormones in female individuals and the presence of female hormones in male individuals. Most importantly, blood plasma samples from male carp taken from the Las Vegas Wash showed extremely high levels of vitellogenin, an egg yolk precursor protein, suggesting endocrine disruption. Samples of carp tissue collected from a reference site in Callville Bay in Boulder Basin of LAKE did not show these characteristics. The presence of EDCs in water and bottom sediment taken from the same areas of the Las Vegas Wash and Las Vegas Bay as the carp indicates that the endocrine disruption observed in carp may be due to these chemicals. However, the presence of some toxic metals may also be contributing to endocrine disruption in carp.
More recently, a study of the gonadal condition of carp from LAKE showed that male carp from Las Vegas Bay had reduced testicular development relative to male carp from a reference site in the Overton Arm. This difference in the reproductive health of male carp in LAKE was attributed to the greater number and concentration of EDCs detected in bed sediment from Las Vegas Bay relative to Overton Arm. A higher incidence of testicular macrophage aggregates, a sign of abnormal testicular development, in male carp from Las Vegas Bay relative to male carp from Overton Arm further supports the hypothesis that endocrine disruption is occurring in carp in Las Vegas Bay through exposure to environmental contaminants.
Recent studies have shown that certain microbial communities may degrade some organic chemicals, but more research is needed to determine if these breakdown products are harmful, and if there is sufficient microbial activity in Las Vegas Wash to allow sufficient breakdown of the chemicals to make them harmless.
Previous research on LAKE has identified the occurrence of EDCs in fish tissue from Lake Mead. However, no studies have attempted to determine the pathway of these contaminants to fish including determining whether they are bioconcentrated or bioaccumulated. This study will examine the extent to which EDCs in aquatic organisms in LAKE are either bioconcentrated through direct uptake from water or bioaccumulated through the food web. Understanding the pathways of EDCs to fish is critical to assessing impacts of EDCs to the entire aquatic ecosystem of LAKE. If fish are accumulating EDCs directly from water or sediment the risk of adverse health effects may be relatively minor as individual species may be affected differently. However, if fish are bioaccumulating EDCs through the food web the risk of adverse health effects is very broad as all secondary and tertiary consumers would be affected including endangered species such as the razorback sucker. Management strategies to control the sources of EDCs to LAKE and protect and restore the ecosystem may differ depending on the mode of EDC accumulation in fish.
The main scientific questions to be answered include:
- What are trophic relationships between organisms in LAKE?
- Are EDCs bioconcentrated in aquatic organisms directly from water or are they bioaccumulated through the food web?
- What is the total mass bioaccumulation of EDCs between various trophic levels in the food web and are concentrations of EDCs in organisms at the top of the food web, such as razorback suckers, high enough to cause reproductive or endocrine impairment?
- Are EDCs incorporated into quagga mussels and how do quaggas relate to other organisms in the food web?
Samples of water, sediment, plankton, invertebrate tissue, and fish tissue have been collected and analyzed for a variety of EDCs. Samples were collected at different depths in 3 sub-basins of LAKE; Las Vegas Bay, Boulder Basin, and Overton Arm. The Overton Arm site served as a reference site as samples of water, sediment, and fish tissue taken from a previous study showed minimal contamination in this area. The bioavailable fraction of EDCs in the water column was measured using Semipermeable Membrane Devices (SPMD) and Polar Organic Chemical Integrative Samplers (POCIS). Surface sediment samples were collected using a ponar sampler. Samples of plankton were collected using plankton net. Benthic invertebrates were collected using a D-net or hand picking. Invertebrate tissue was composited prior to analysis with the exception of tissue of quagga mussels which was analyzed separately from other invertebrates. Samples of invertebrate organisms were identified to the lowest taxonomic resolution possible (generally family or genus) prior to compositing for analysis. In previous studies, fish near the top of the food web such as common carp and largemouth bass were sampled and analyzed for EDCs. This study focused on fish that are intermediate in the food web such as threadfin shad and bluegill. These fish were collected in each basin using an electroshocking technique and their tissue composited for analysis.
Samples were analyzed for a variety of potential EDCs. Fish and invertebrate samples were analyzed for PCBs, DDT and other pesticides, PBDEs, and various antibacterial and fragrance compounds. Sediment and water samples were analyzed for a similar set of compounds as well as a small set of chemicals related to wastewater effluent. Prior to analysis, samples from the SPMD and POCIS were screened using the yeast estrogen screen (YES). The YES assay provides a measure of total estrogenicity of chemicals present in the sample and can be helpful in determining if chemicals in the samples are acting as estrogens or estrogen mimics and thus could be causing intersex development or other endocrine disruption effects. Tissue samples were processed to extract chemicals of interest using various specialized methods including gel permeation chromatography and adsorption chromatography. All water and sediment samples and tissue extracts were analyzed using gas chromatography-mass spectrometry to identify organic compounds.
Data from the sampling and chemical analyses will be evaluated to determine the food web structure of LAKE. Contaminants detected and their relative mass will be compared to the newly established food web structures so that contaminant pathways and mass transfer rates can be determined. From this evaluation, the potential risk of EDCs and other contaminants to razorback suckers and other fish in LAKE can be identified relative to the source of the contaminants.
Below are data or web applications associated with this project.
Sperm quality biomarkers complement reproductive and endocrine parameters in investigating environmental contaminants in common carp (Cyprinus carpio) from the Lake Mead National Recreation Area (1999-2006)
Below are multimedia items associated with this project.
"Lake Mead — Clear and Vital" is a thirteen minute documentary relating the crucial role of science in maintaining high water quality in Lake Mead. The program was produced coincident with release of the Lakes Mead and Mohave Circular a USGS publication covering past and on-going research in the lakes and tributaries of the Lake Mead National Recreation Area.
Below are publications associated with this project. You can also download a bibliography:
Report products from Lake Mead Endocrine Disruption studies
Movement of synthetic organic compounds in the food web after the introduction of invasive quagga mussels (Dreissena bugensis) in Lake Mead, Nevada and Arizona, USA
Microplastics in Lake Mead National Recreation Area, USA: Occurrence and biological uptake
Sperm quality biomarkers complement reproductive and endocrine parameters in investigating environmental contaminants in common carp (Cyprinus carpio) from the Lake Mead National Recreation Area
Association between degradation of pharmaceuticals and endocrine-disrupting compounds and microbial communities along a treated wastewater effluent gradient in Lake Mead
Reversible reduction of estrone to 17β-estradiol by Rhizobium, Sphingopyxis, and Pseudomonas isolates from the Las Vegas Wash
Novel associations between contaminant body burdens and biomarkers of reproductive condition in male Common Carp along multiple gradients of contaminant exposure in Lake Mead National Recreation Area, USA
Temporal and basin-specific population trends of quagga mussels on soft sediment of a multi-basin reservoir
Are endocrine and reproductive biomarkers altered in contaminant-exposed wild male Largemouth Bass (Micropterus salmoides) of Lake Mead, Nevada/Arizona, USA?
Bottom sediment as a source of organic contaminants in Lake Mead, Nevada, USA
Patterns of metal composition and biological condition and their association in male common carp across an environmental contaminant gradient in Lake Mead National Recreation Area, Nevada and Arizona, USA
A synthesis of aquatic science for management of Lakes Mead and Mohave
Sperm quality assessments for endangered razorback suckers Xyrauchen texanus
- Overview
Water quality in the Lake Mead National Recreation Area (LAKE), particularly Las Vegas Bay, is affected by water coming from the Las Vegas Wash, an urban perennial stream whose water is comprised of treated wastewater and urban runoff coming from the Las Vegas metropolitan area. Common carp collected from Las Vegas Wash and Las Vegas Bay and largemouth bass collected from Las Vegas Bay have impaired reproductive and endocrine health that have been shown to be caused by the presence of endocrine-disrupting compounds (EDCs) in water coming from the Las Vegas Wash. Understanding the movement of EDCs through the food web is critical in determining the effects of EDCs on all organisms including endangered species such as the razorback sucker and for making informed and effective management decisions on ways to control and mitigate sources of EDCs. In addition, a new study started in 2017 looking at the effect of microplastics on the foodweb led by Austin Baldwin (ID WSC) has also been started to understand whether these plastics interrupt feeding and reproduction in the lake.
A variety of contaminants including nutrients, metals, perchlorate, and organic compounds are transported to the Las Vegas Wash from various sources. Organic compounds are some of the most commonly found contaminants in the Wash. Some of these organic compounds, such as DDT (dichlorodiphenyltrichloroethane), PCBs (polychlorinated biphenyls), PBDEs (polybrominated diphenyl ethers), PAHs (polycyclic aromatic hydrocarbons), personal care products, and human pharmaceuticals, are suspected of being Endocrine-Disrupting Compounds (EDCs). The sources of EDCs to water in the Las Vegas Wash include diffuse sources such as urban runoff as well as concentrated historical industrial sources located along the Wash, and the release of tertiary treated wastewater from 4 wastewater treatment plants that serve the Las Vegas Metropolitan area. EDCs have been found in treated and untreated wastewater in many areas of the United States and many EDCs are not completely removed by even the most advanced wastewater treatment processes.
EDCs can interfere with or disrupt endocrine and reproductive systems and can cause cancerous tumors, birth defects, and developmental disorders. In fish, EDCs are thought to be especially disruptive of the larval or developmental stages altering sexual development, behavior and fertility, and causing feminization of male fish or masculinization of female fish. Recent studies have shown that male common carp (Cyprinus carpio) collected from Las Vegas Bay and Las Vegas Wash have shown feminization with impaired endocrine and reproductive health. Largemouth bass (Micropterus salmoides) collected in Las Vegas Bay have also shown symptoms of impaired reproductive health. These adverse health effects have been shown to be caused by the presence of EDCs in water and/or sediment in these areas. Recent studies have indicated improvement in the endocrine and reproductive health of common carp collected from in Las Vegas Bay since 1995 that may have come from enhanced wastewater treatment.
In spite of these recent improvements, the evidence that EDCs may be causing adverse health effects in fish and aquatic invertebrates in LAKE has been mounting for some time. In a study completed in 1996, water, bottom-sediment, and tissue samples of carp taken from the Las Vegas Wash and Las Vegas Bay all showed the presence of EDCs. Tissue samples of carp taken from the Las Vegas Wash showed skewed sex hormone ratios with elevated concentrations of male hormones in female individuals and the presence of female hormones in male individuals. Most importantly, blood plasma samples from male carp taken from the Las Vegas Wash showed extremely high levels of vitellogenin, an egg yolk precursor protein, suggesting endocrine disruption. Samples of carp tissue collected from a reference site in Callville Bay in Boulder Basin of LAKE did not show these characteristics. The presence of EDCs in water and bottom sediment taken from the same areas of the Las Vegas Wash and Las Vegas Bay as the carp indicates that the endocrine disruption observed in carp may be due to these chemicals. However, the presence of some toxic metals may also be contributing to endocrine disruption in carp.
More recently, a study of the gonadal condition of carp from LAKE showed that male carp from Las Vegas Bay had reduced testicular development relative to male carp from a reference site in the Overton Arm. This difference in the reproductive health of male carp in LAKE was attributed to the greater number and concentration of EDCs detected in bed sediment from Las Vegas Bay relative to Overton Arm. A higher incidence of testicular macrophage aggregates, a sign of abnormal testicular development, in male carp from Las Vegas Bay relative to male carp from Overton Arm further supports the hypothesis that endocrine disruption is occurring in carp in Las Vegas Bay through exposure to environmental contaminants.
Recent studies have shown that certain microbial communities may degrade some organic chemicals, but more research is needed to determine if these breakdown products are harmful, and if there is sufficient microbial activity in Las Vegas Wash to allow sufficient breakdown of the chemicals to make them harmless.
Previous research on LAKE has identified the occurrence of EDCs in fish tissue from Lake Mead. However, no studies have attempted to determine the pathway of these contaminants to fish including determining whether they are bioconcentrated or bioaccumulated. This study will examine the extent to which EDCs in aquatic organisms in LAKE are either bioconcentrated through direct uptake from water or bioaccumulated through the food web. Understanding the pathways of EDCs to fish is critical to assessing impacts of EDCs to the entire aquatic ecosystem of LAKE. If fish are accumulating EDCs directly from water or sediment the risk of adverse health effects may be relatively minor as individual species may be affected differently. However, if fish are bioaccumulating EDCs through the food web the risk of adverse health effects is very broad as all secondary and tertiary consumers would be affected including endangered species such as the razorback sucker. Management strategies to control the sources of EDCs to LAKE and protect and restore the ecosystem may differ depending on the mode of EDC accumulation in fish.
The main scientific questions to be answered include:
- What are trophic relationships between organisms in LAKE?
- Are EDCs bioconcentrated in aquatic organisms directly from water or are they bioaccumulated through the food web?
- What is the total mass bioaccumulation of EDCs between various trophic levels in the food web and are concentrations of EDCs in organisms at the top of the food web, such as razorback suckers, high enough to cause reproductive or endocrine impairment?
- Are EDCs incorporated into quagga mussels and how do quaggas relate to other organisms in the food web?
Samples of water, sediment, plankton, invertebrate tissue, and fish tissue have been collected and analyzed for a variety of EDCs. Samples were collected at different depths in 3 sub-basins of LAKE; Las Vegas Bay, Boulder Basin, and Overton Arm. The Overton Arm site served as a reference site as samples of water, sediment, and fish tissue taken from a previous study showed minimal contamination in this area. The bioavailable fraction of EDCs in the water column was measured using Semipermeable Membrane Devices (SPMD) and Polar Organic Chemical Integrative Samplers (POCIS). Surface sediment samples were collected using a ponar sampler. Samples of plankton were collected using plankton net. Benthic invertebrates were collected using a D-net or hand picking. Invertebrate tissue was composited prior to analysis with the exception of tissue of quagga mussels which was analyzed separately from other invertebrates. Samples of invertebrate organisms were identified to the lowest taxonomic resolution possible (generally family or genus) prior to compositing for analysis. In previous studies, fish near the top of the food web such as common carp and largemouth bass were sampled and analyzed for EDCs. This study focused on fish that are intermediate in the food web such as threadfin shad and bluegill. These fish were collected in each basin using an electroshocking technique and their tissue composited for analysis.
Samples were analyzed for a variety of potential EDCs. Fish and invertebrate samples were analyzed for PCBs, DDT and other pesticides, PBDEs, and various antibacterial and fragrance compounds. Sediment and water samples were analyzed for a similar set of compounds as well as a small set of chemicals related to wastewater effluent. Prior to analysis, samples from the SPMD and POCIS were screened using the yeast estrogen screen (YES). The YES assay provides a measure of total estrogenicity of chemicals present in the sample and can be helpful in determining if chemicals in the samples are acting as estrogens or estrogen mimics and thus could be causing intersex development or other endocrine disruption effects. Tissue samples were processed to extract chemicals of interest using various specialized methods including gel permeation chromatography and adsorption chromatography. All water and sediment samples and tissue extracts were analyzed using gas chromatography-mass spectrometry to identify organic compounds.
Data from the sampling and chemical analyses will be evaluated to determine the food web structure of LAKE. Contaminants detected and their relative mass will be compared to the newly established food web structures so that contaminant pathways and mass transfer rates can be determined. From this evaluation, the potential risk of EDCs and other contaminants to razorback suckers and other fish in LAKE can be identified relative to the source of the contaminants.
- Data
Below are data or web applications associated with this project.
Sperm quality biomarkers complement reproductive and endocrine parameters in investigating environmental contaminants in common carp (Cyprinus carpio) from the Lake Mead National Recreation Area (1999-2006)
Lake Mead National Recreational Area (LMNRA) serves as critical habitat for several federally listed species and supplies water for municipal, domestic, and agricultural use in the Southwestern U.S. Contaminant sources and concentrations vary among sub-basins within LMNRA. To investigate whether environmental contaminant exposure is associated with alterations in male common carp (Cyprinus carpio) - Multimedia
Below are multimedia items associated with this project.
Lake Mead: Clear and Vital"Lake Mead — Clear and Vital" is a thirteen minute documentary relating the crucial role of science in maintaining high water quality in Lake Mead. The program was produced coincident with release of the Lakes Mead and Mohave Circular a USGS publication covering past and on-going research in the lakes and tributaries of the Lake Mead National Recreation Area.
"Lake Mead — Clear and Vital" is a thirteen minute documentary relating the crucial role of science in maintaining high water quality in Lake Mead. The program was produced coincident with release of the Lakes Mead and Mohave Circular a USGS publication covering past and on-going research in the lakes and tributaries of the Lake Mead National Recreation Area.
- Publications
Below are publications associated with this project. You can also download a bibliography:
Report products from Lake Mead Endocrine Disruption studies
Filter Total Items: 27Movement of synthetic organic compounds in the food web after the introduction of invasive quagga mussels (Dreissena bugensis) in Lake Mead, Nevada and Arizona, USA
Introductions of dreissenid mussels in North America have been a significant concern over the last few decades. This study assessed the distribution of synthetic organic compounds (SOCs) in the food web of Lake Mead, Nevada/Arizona, USA and how this distribution was influenced by the introduction of invasive quagga mussels. A clear spatial gradient of SOC concentrations in water was observed betweAuthorsSteven L. Goodbred, Michael R. Rosen, Reynaldo Patiño, David Alvarez, Kathy R. Echols, Kerensa King, John UmekMicroplastics in Lake Mead National Recreation Area, USA: Occurrence and biological uptake
Microplastics are an environmental contaminant of growing concern, but there is a lack of information about microplastic distribution, persistence, availability, and biological uptake in freshwater systems. This is especially true for large river systems like the Colorado River that spans multiple states through mostly rural and agricultural land use. This study characterized the quantity and morpAuthorsAustin K. Baldwin, Andrew Spanjer, Michael R. Rosen, Theresa ThomSperm quality biomarkers complement reproductive and endocrine parameters in investigating environmental contaminants in common carp (Cyprinus carpio) from the Lake Mead National Recreation Area
Lake Mead National Recreational Area (LMNRA) serves as critical habitat for several federally listed species and supplies water for municipal, domestic, and agricultural use in the Southwestern U.S. Contaminant sources and concentrations vary among the sub-basins within LMNRA. To investigate whether exposure to environmental contaminants is associated with alterations in male common carp (CyprinusAuthorsJill A. Jenkins, Michael R. Rosen, Rassa O. Dale, Kathy R. Echols, Leticia Torres, Carla M. Wieser, Constance A. Kersten, S. GoodbredAssociation between degradation of pharmaceuticals and endocrine-disrupting compounds and microbial communities along a treated wastewater effluent gradient in Lake Mead
The role of microbial communities in the degradation of trace organic contaminants in the environment is little understood. In this study, the biotransformation potential of 27 pharmaceuticals and endocrine-disrupting compounds was examined in parallel with a characterization of the native microbial community in water samples from four sites variously impacted by urban run-off and wastewater dischAuthorsSusanna M. Blunt, Joshua D. Sackett, Michael R. Rosen, Mark J. Benotti, Rebecca A. Trenholm, Brett J. Vanderford, Brian P. Hedlund, Duane P. MoserReversible reduction of estrone to 17β-estradiol by Rhizobium, Sphingopyxis, and Pseudomonas isolates from the Las Vegas Wash
Environmental endocrine-disrupting compounds (EDCs) are a growing concern as studies reveal their persistence and detrimental effects on wildlife. Microorganisms are known to affect the transformation of steroid EDCs; however, the diversity of estrogen-degrading microorganisms and the range of transformations they mediate remain relatively little studied. In mesocosms, low concentrations of addedAuthorsSusanna M. Blunt, Mark J. Benotti, Michael R. Rosen, Brian Hedlund, Duane MoserNovel associations between contaminant body burdens and biomarkers of reproductive condition in male Common Carp along multiple gradients of contaminant exposure in Lake Mead National Recreation Area, USA
Adult male Common Carp were sampled in 2007/08 over a full reproductive cycle at Lake Mead National Recreation Area. Sites sampled included a stream dominated by treated wastewater effluent, a lake basin receiving the streamflow, an upstream lake basin (reference), and a site below Hoover Dam. Individual body burdens for 252 contaminants were measured, and biological variables assessed included phAuthorsReynaldo Patiño, Matthew M. VanLandeghem, Steven L. Goodbred, Erik Orsak, Jill A. Jenkins, Kathy R. Echols, Michael R. Rosen, Leticia TorresTemporal and basin-specific population trends of quagga mussels on soft sediment of a multi-basin reservoir
Invasive quagga (Dreissena bugnesis) and zebra (Dreissena ploymorpha) mussels have rapidly spread throughout North America. Understanding the relationships between environmental variables and quagga mussels during the early stages of invasion will help management strategies and allow researchers to predict patterns of future invasions. Quagga mussels were detected in Lake Mead, NV/AZ in 2007, we mAuthorsTimothy J Caldwell, Michael R. Rosen, Sudeep Chandra, Kumud Acharya, Andrea M Caires, Clinton J. Davis, Melissa Thaw, Daniel M. WebsterAre endocrine and reproductive biomarkers altered in contaminant-exposed wild male Largemouth Bass (Micropterus salmoides) of Lake Mead, Nevada/Arizona, USA?
Male Largemouth Bass were sampled from two locations in Lake Mead (USA), a site influenced by treated municipal wastewater effluent and urban runoff (Las Vegas Bay), and a reference site (Overton Arm). Samples were collected in summer (July '07) and spring (March '08) to assess general health, endocrine and reproductive biomarkers, and compare contaminant body burdens by analyzing 252 organic chemAuthorsSteven L. Goodbred, Reynaldo Patiño, Leticia Torres, Kathy R. Echols, Jill A. Jenkins, Michael R. Rosen, Erik OrsakBottom sediment as a source of organic contaminants in Lake Mead, Nevada, USA
Treated wastewater effluent from Las Vegas, Nevada and surrounding communities' flow through Las Vegas Wash (LVW) into the Lake Mead National Recreational Area at Las Vegas Bay (LVB). Lake sediment is a likely sink for many hydrophobic synthetic organic compounds (SOCs); however, partitioning between the sediment and the overlying water could result in the sediment acting as a secondary contaminanAuthorsDavid A. Alvarez, Michael R. Rosen, Stephanie D. Perkins, Walter L. Cranor, Vickie L. Schroeder, Tammy L. Jones-LeppPatterns of metal composition and biological condition and their association in male common carp across an environmental contaminant gradient in Lake Mead National Recreation Area, Nevada and Arizona, USA
There is a contaminant gradient in Lake Mead National Recreation Area (LMNRA) that is partly driven by municipal and industrial runoff and wastewater inputs via Las Vegas Wash (LVW). Adult male common carp (Cyprinus carpio; 10 fish/site) were collected from LVW, Las Vegas Bay (receiving LVW flow), Overton Arm (OA, upstream reference), and Willow Beach (WB, downstream) in March 2008. Discriminant fAuthorsReynaldo Patiño, Michael R. Rosen, E.L. Orsak, Steven L. Goodbred, Thomas W. May, David A. Alvarez, Kathy R. Echols, Carla M. Wieser, Shane Ruessler, L. TorresA synthesis of aquatic science for management of Lakes Mead and Mohave
Lakes Mead and Mohave, which are the centerpieces of Lake Mead National Recreation Area, provide many significant benefits that have made the modern development of the Southwestern United States possible. Lake Mead is the largest reservoir by volume in the nation and it supplies critical storage of water supplies for more than 25 million people in three Western States (California, Arizona, and NevAuthorsMichael R. Rosen, Kent Turner, Steven L. Goodbred, Jennell M. MillerSperm quality assessments for endangered razorback suckers Xyrauchen texanus
Flow cytometry (FCM) and computer-assisted sperm motion analysis (CASA) methods were developed and validated for use with endangered razorback suckers Xyrauchen texanus collected (n=64) during the 2006 spawning season. Sperm motility could be activated within osmolality ranges noted during milt collections (here 167–343 mOsm/kg). We hypothesized that sperm quality of milt collected into isoosmoticAuthorsJill A. Jenkins, Bruce E. Eilts, Amy M. Guitreau, Chester R. Figiel, Rassa O. Draugelis-Dale, Terrence R. Tiersch