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At least 613 records · Page 34Linked to original sources
USGS2013

Native and nonnative fish populations of the Colorado River are food limited--evidence from new food web analyses

Fish populations in the Colorado River downstream from Glen Canyon Dam appear to be limited by the availability of high-quality invertebrate prey. Midge and blackfly production is low and nonnative rainbow trout in Glen Canyon and native fishes in Grand Canyon consume virtually all of the midge and blackfly biomass that is produced annually. In Glen Canyon, the invertebrate assemblage is dominated by nonnative New Zealand mudsnails, the food web has a simple structure, and transfers of energy from the base of the web (algae) to the top of the web (rainbow trout) are inefficient. The food webs in Grand Canyon are more complex relative to Glen Canyon, because, on average, each species in the web is involved in more interactions and feeding connections. Based on theory and on studies from other ecosystems, the structure and organization of Grand Canyon food webs should make them more stable and less susceptible to large changes following perturbations of the flow regime relative to food webs in Glen Canyon. In support of this hypothesis, Grand Canyon food webs were much less affected by a 2008 controlled flood relative to the food web in Glen Canyon.

Colorado River↗
USGS2013

Real-time continuous nitrate monitoring in Illinois in 2013

Many sources contribute to the nitrogen found in surface water in Illinois. Illinois is located in the most productive agricultural area in the country, and nitrogen fertilizer is commonly used to maximize corn production in this area. Additionally, septic/wastewater systems, industrial emissions, and lawn fertilizer are common sources of nitrogen in urban areas of Illinois. In agricultural areas, the use of fertilizer has increased grain production to meet the needs of a growing population, but also has resulted in increases in nitrogen concentrations in many streams and aquifers (Dubrovsky and others, 2010). The urban sources can increase nitrogen concentrations, too. The Federal limit for nitrate nitrogen in water that is safe to drink is 10 milligrams per liter (mg/L) (http://water.epa.gov/drink/contaminants/basicinformation/nitrate.cfm, accessed on May 24, 2013). In addition to the concern with nitrate nitrogen in drinking water, nitrogen, along with phosphorus, is an aquatic concern because it feeds the intensive growth of algae that are responsible for the hypoxic zone in the Gulf of Mexico. The largest nitrogen flux to the waters feeding the Gulf of Mexico is from Illinois (Alexander and others, 2008). Most studies of nitrogen in surface water and groundwater include samples for nitrate nitrogen collected weekly or monthly, but nitrate concentrations can change rapidly and these discrete samples may not capture rapid changes in nitrate concentrations that can affect human and aquatic health. Continuous monitoring for nitrate could inform scientists and water-resource managers of these changes and provide information on the transport of nitrate in surface water and groundwater.

Illinois↗
USGS2015

Organic matters: Investigating the sources, transport, and fate of organic matter in Fanno Creek, Oregon

The term organic matter refers to the remnants of all living material. This can include fallen leaves, yard waste, animal waste, downed timber, or the remains of any other plant and animal life. Organic matter is abundant both on land and in water. Investigating organic matter is necessary for understanding the fate and transport of carbon (a major constituent of organic matter). Organic matter is necessary for maintaining a healthy ecosystem. It participates in a wide range of ecological functions, such as supplying food to the microbes that are part of the foundation of the food chain. Organic matter also plays a role in many other natural functions, including the binding and transport of some trace metals and controlling how light is absorbed in the water column. Organic matter in a stream can be found in many places, such as in the leaves that have fallen from a tree (termed "leaf litter"), in algae floating in the stream or attached to rocks, as part of the soil, or even suspended or dissolved in the water. The U.S. Geological Survey (USGS), in cooperation with Clean Water Services, recently completed an investigation into the sources, transport, and fate of organic matter in the Fanno Creek watershed. The information provided by this investigation will help resource managers to implement strategies aimed at decreasing the excess supply of organic matter that contributes to low dissolved-oxygen levels in Fanno Creek and downstream in the Tualatin River during summer. This fact sheet summarizes the findings of the investigation.

Oregon↗
USGS2016

Mercury cycling in the Hells Canyon Complex of the Snake River, Idaho and Oregon

Introduction The Hells Canyon Complex (HCC) is a hydroelectric project built and operated by the Idaho Power Company (IPC) that consists of three dams on the Snake River along the Oregon and Idaho border (fig. 1). The dams have resulted in the creation of Brownlee, Oxbow, and Hells Canyon Reservoirs, which have a combined storage capacity of more than 1.5 million acre-feet and span about 90 miles of the Snake River. The Snake River upstream of and through the HCC historically has been impaired by water-quality issues related to excessive contributions of nutrients, algae, sediment, and other pollutants. In addition, historical data collected since the 1960s from the Snake River and tributaries near the HCC have documented high concentrations of mercury in fish tissue and sediment (Harris and Beals, 2013). Data collected from more recent investigations within the HCC continue to indicate elevated concentrations of mercury and methylmercury in the water column, bottom sediments, and biota (Clark and Maret, 1998; Essig, 2010; Fosness and others, 2013). As a result, Brownlee and Hells Canyon Reservoirs are listed as impaired for mercury by the State of Idaho, and the Snake River from the Oregon and Idaho border through the HCC downstream to the Oregon and Washington border is listed as impaired for mercury by the State of Oregon.

Idaho, Oregon↗
USGS2018

The Midwest Stream Quality Assessment—Influences of human activities on streams

Healthy streams and the fish and other organisms that live in them contribute to our quality of life. Extensive modification of the landscape in the Midwestern United States, however, has profoundly affected the condition of streams. Row crops and pavement have replaced grasslands and woodlands, streams have been straightened, and wetlands and fields have been drained. Runoff from agricultural and urban land brings sediment and chemicals to streams. What is the chemical, physical, and biological condition of Midwestern streams? Which physical and chemical stressors are adversely affecting biological communities, what are their origins, and how might we lessen or avoid their adverse effects? In 2013, the U.S. Geological Survey (USGS) conducted the Midwest Stream Quality Assessment to evaluate how human activities affect the biological condition of Midwestern streams. In collaboration with the U.S. Environmental Protection Agency National Rivers and Streams Assessment, the USGS sampled 100 streams, chosen to be representative of the different types of watersheds in the region. Biological condition was evaluated based on the number and diversity of fish, algae, and invertebrates in the streams. Changes to the physical habitat and chemical characteristics of the streams—“stressors”—were assessed, and their relation to landscape factors and biological condition was explored by using mathematical models. The data and models help us to better understand how the human activities on the landscape are affecting streams in the region.

Fact Sheet↗
USGS2022

Science and innovation for battling invasive carp

The U.S. Geological Survey (USGS) is the Federal Government’s independent research agency that conducts research to inform management of invasive species. Bighead, black, grass, and silver carp, which are native to China, were originally stocked in aquaculture facilities to control algae, snails, and vegetation. These species have invaded the Mississippi River and are now established throughout the lower and middle Mississippi River Basins and some of its large tributaries where they damage ecosystems and harm economies. A reproducing population of grass carp in Lake Erie is a risk to the $7 billion Great Lakes fishery. The USGS is leading research efforts on risk assessment and on early detection of new invasions. The USGS is also developing and evaluating harvest methods, barriers and deterrents, and baits/attractants to provide Federal and State management agencies the tools needed to manage and reduce populations of these species.

Alabama, Arkansas, Illinois, Indiana, Iowa, Kansas↗
USGS2022

Utah and Landsat

Utah’s list of notable features runs long, but scenery rises to the top. The Colorado River does not simply run through southeastern Utah; it meanders through steep canyons of the eroded sedimentary rock that colors the sweeping vistas of the Colorado Plateau. Stone arches, spires, hoodoos, cliffs, and bridges in hues of red enchant residents and tourists. Mountain ranges extending through the State add dynamic views—and skiing opportunities. The Great Salt Lake in northern Utah is the largest saltwater lake in the Western Hemisphere. The western part of Utah, including the Great Salt Lake, lies in the Great Basin, a multi-State drainage area with no outlet. Because the lake has no outlet to flush out any salt, evaporation produces a higher concentration of salts in the water or soils, called salinity. The lake lacks fish but supports algae and brine shrimp, and extensive wetlands around the lake attract millions of migratory birds. Landsat imagery is useful for showing surface changes, such as the fluctuating water levels of the shallow Great Salt Lake. The lake flooded in the 1980s, but the southern part dropped to its lowest level in recorded history in 2021. Landsat data also can take a much deeper look at land and water conditions. Here are several ways Landsat benefits Utah.

Utah↗
USGS2007

The Charles River, Eastern Massachusetts: Scientific Information in Support of Environmental Restoration

Human activity has profoundly altered the Charles River and its watershed over the past 375 years. Restoration of environmental quality in the watershed has become a high priority for private- and public-sector organizations across the region. The U.S. Environmental Protection Agency and the Massachusetts Executive Office of Environmental Affairs worked together to coordinate the efforts of the various organizations. One result of this initiative has been a series of scientific studies that provide critical information concerning some of the major hydrologic and ecological concerns in the watershed. These studies have focused upon: * Streamflows - Limited aquifer storage, growing water demands, and the spread of impervious surfaces are some of the factors exacerbating low summer streamflows in headwater areas of the watershed. Coordinated management of withdrawals, wastewater returns, and stormwater runoff could substantially increase low streamflows in the summer. Innovative approaches to flood control, including preservation of upstream wetland storage capacity and construction of a specially designed dam at the river mouth, have greatly reduced flooding in the lower part of the watershed in recent decades. * Water quality - Since the mid-1990s, the bacterial quality of the Charles River has improved markedly, because discharges from combined sewer overflows and the number of illicit sewer connections to municipal storm drains have been reduced. Improved management of stormwater runoff will likely be required, however, for full attainment of State and Federal water-quality standards. Phosphorus inputs from a variety of sources remain an important water-quality problem. * Fish communities and habitat quality - The Charles River watershed supports a varied fish community of about 20 resident and migratory species. Habitat conditions for fish and other aquatic species have improved in many parts of the river system in recent years. However, serious challenges remain, including the control of nutrients, algae, and invasive plants, mitigation of dam impacts, addressing remaining sources of bacteria to the river, and remediation of contaminated bottom habitat and the nontidal salt wedge in the lower river.

General Information Product↗
USGS2003

Occurrence of the diamondback terrapin ( Malaclemys terrapin littoralis ) at South Deer Island in Galveston Bay, Texas, April 2001-May 2002

One-hundred thirty-five terrapins were captured (116 individuals, 19 recaptures) in occurrence and nesting and basking surveys at South Deer Island in Galveston Bay, Texas, during April 2001–May 2002. Along the southern shore of the island, terrapins were captured in crab traps placed in shallow water offshore; in the lagoon on the island, terrapins were captured by hand while walking along the shore. In the nesting and basking surveys, areas of the island with continuous patches of exposed shell typically were checked twice a day for nesting and basking terrapins, except during the last 2 months of the study, when more intensive monitoring was conducted. The occurrence surveys resulted in 119 terrapins captured in crab traps and nine captured by hand around the lagoon. The nesting and basking surveys yielded seven terrapins. Only one was nesting, although the nest is believed to be the first documented terrapin nest found in Texas. Three terrapins were captured swimming near shell beaches, and three more were captured basking on shell beaches. The most terrapins were captured during April–May 2001 and April–May 2002. Biometric data collected on terrapins captured showed size dimorphism on the basis of sex. The median female straight-line carapace length was 17.8 centimeters, 1.4 times larger than the median male carapace length, 13.1 centimeters. The median female mass was 1,021 grams, 2.9 times larger than the median male mass, 354 grams. Intra-specific variation occurred in the colorations and markings of terrapins captured. Anomalies - lesions, deformities, barnacles, and algae - were common among terrapins captured. Both lesions and deformities were more common among males than females. Dominant vegetation or substrate associated with terrapin habitat included saltwort, slender seapurslane, seabeach orache, shell, and woody debris.

Texas↗
USGS2003

Water-quality, streambed-sediment, and biological data from the Clark Fork-Pend Oreille and Spokane River basins, Montana, Idaho, and Washington, 1998-2001

Water-quality, streambed-sediment, and biological data were collected in the Clark Fork-Pend Oreille and Spokane River basins as part of the U.S. Geological Survey's National Water-Quality Assessment Program and are presented in this report. These river basins compose the Northern Rockies Intermontane Basins study unit which was selected to include a river system that has a mixture of forested, agricultural, urban, and developing areas. Waterquality samples were collected from 28 surface-water sites and 86 ground-water sites from June 1998 to September 2001. Data collected included measurements of physical properties and chemical analyses of concentrations of major ions, trace elements, nutrients, organic carbon, pesticides, volatile organic compounds, and radiochemical constituents. Streambed-sediment and biological tissue samples were collected from 41 sites and analyzed for trace elements and organochlorine compounds. Benthic algae were collected to determine chlorophyll concentration and areal density.

Idaho, Montana, Washington↗
USGS2001

Physical, Chemical, and Biological Methods and Data from the Urban Land-Use-Gradient Study, Des Plaines and Fox River Basins, Illinois, 1999-2001

Physical, chemical, and biological data were collected at 46 sites in the Fox and Des Plaines River Basins as part of the upper Illinois River Basin study of the U.S. Geological Survey?s National Water-Quality Assessment Program. The data, collected from 1999 to 2001, will be used to determine the effects of urbanization on streams in the Chicago, Illinois, metropolitan area. To examine the possible effects of urbanization on stream-water quality, the sampling sites were selected to represent a gradient of land use changing from agriculture into urban. Urban land use for the selected sites ranged from less than 1 percent urban to 92 percent urban. Data-collection methods are presented in the text portion of this report. Physical characteristics of the stream that were collected include descriptive and qualitative habitat and geomorphic measures. Water samples were analyzed for nutrients (nitrogen and phosphorus), 11 major ions, 46 wastewater indicators, pH, and specific conductance. Aquatic communities were sampled to identify and quantify populations of selected algae, benthic macroinvertebrates, and fish. There were 72 unique fish species collected at all of the sites. The number of benthic macroinvertebrate taxa collected at all the sites ranged from 15 to 48. The data and the associated data documentation are presented on a CD-ROM included with this report.

Open-File Report↗
USGS2004

Submarine ground-water discharge and its role in coastal processes and ecosystems

Submarine ground-water discharge (SGD) has recently been recognized as a phenomenon that can strongly influence coastal water and geochemical budgets and drive ecosystem change. For example, the discharge of nutrient-enriched ground water into coastal waters may contribute significantly to eutrophication and blooms of harmful algae. Similarly, the quantity of SGD can also directly affect the availability of fresh water to coastal communities, impact fragile coastal ecosystems such as estuaries and coral reefs, and influence geomorphology of shoreline features. Moore raised awareness of the global importance of SGD and much effort has been devoted to developing new tracer techniques and methods for the identification and quantification of SGD. Because the discharge of coastal ground water commonly occurs as diffuse seepage rather than focused discharge through identifiable springs, assessing SGD has remained difficult for both oceanographers and hydrologists. Through national and international research programs, Burnett, Moore, Charette, and others have developed a rigorous, systematic approach for quantifying SGD using a wide assortment of tracers and methods. Intercalibration experiments, such as those conducted in coastal waters off Australia, Brazil, and Long Island, NY, demonstrate that careful measurements can accurately quantify SGD, confirm some of the driving mechanisms (e.g. climatic and tidal forcing), and constrain the spatial and temporal scales at which these mechanisms operate. Now that approaches for rigorously quantifying SGD are becoming better established, scientists can now begin to investigate the wide variety of coastal processes affected by SGD.

Open-File Report↗
USGS2005

GIS compilation of data collected from the Pulley Ridge Deep Coral Reef region

Pulley Ridge is a chain of drowned barrier islands that extends almost 200 km in 60-90 m water depths (Fig. 1). This drowned ridge is located on the Florida Platform in the southeastern Gulf of Mexico about 250 km west of Cape Sable, Florida (Jarrett and others, 2005). These islands formed during the early Holocene marine transgression approximately 12,000 - 14,000 years before present, and were then submerged by sea level rise and preserved near the outer edge of the Florida Platform. The southern portion of Pulley Ridge is the focus of this study. This area hosts zooxanthellate scleractinian corals, green, red and brown macro algae, and a mix of deep and typically shallow-water tropical fishes. This largely photosynthetic community is unique in that it thrives with less than 5% of the light typically associated with shallow-water reefs with similar fauna. Several factors help to account for the existence of this unique deep-water community. First, the underlying drowned barrier islands provide both elevated topography and lithified substrate for the establishment of the hardbottom community. Second, the region is commonly bathed by the Loop Current, which brings relatively clear and warm water to this area. Third, the ridge's position on the continental shelf places it within the thermocline which provides nutrients to the reef during upwelling (Halley and others, 2003). The USGS has made two proposals to resource managers for the designation of marine protected areas based on the geophysical and photographic data in this report. The proposals describe areas that may require some regulatory protection of marine life utilizing the sea floor (Fig. 1). The first proposal is that the area of greatest hermatypic coral cover (Fig. 1) is considered for future management actions and designated a Habitat Area of Particular Concern (HAPC) by the Gulf of Mexico Fishery Management Council. HAPCs are identified on the basis of habitat level considerations: The importance of the ecological function provided by the habitat. The extent to which the habitat is sensitive to human-induced environmental degradation. Whether and to what extent development activities are or will be stressing the habitat. The rarity of the habitat type. The second proposed area is for Coral Essential Fish Habitat (CEFH, Fig. 1). CEFHs are defined as "those waters and substrate necessary to corals for spawning, breeding, feeding, or growth to maturity." The following definitions are provided for clarification: waters is defined as "aquatic areas and their associated physical, chemical, and biological properties that are used by corals" substrate means "sediment, hard bottom, structures underlying the waters, and associated biological communities" necessary means "the habitat required to support a sustainable population and the managed species' contribution to a healthy ecosystem" spawning,breeding, feeding, or growth to maturity covers the full life cycle of a species. The CEFH shown in Figure 1 is the greatest coral cover in the region as determined by the bottom photo and video transects acquired during this study. This report presents the geophysical and photographic data that were collected to describe the surficial and shallow subsurface geologic framework of the area where these deep-water corals are known to occur. The data types include multibeam bathymetry, sidescan-sonar imagery, images of high-resolution seismic-reflection profiles, and bottom photographs. In addition, the tracklines for the seismic data, locations of bottom photographs and camera drifts, and tracklines along which submersible and remotely operated vehicle (ROV) observations were made are contained in the GIS files accompanying this report. Unfortunately, video footage from the camera drifts, submersible, and ROV cruises is not available on this DVD due to the quantity of data. The bottom photograph data set has been previously published (Cross and others, 2004), however it is included in this publication in an effort to integrate the varying data sets in one location. This integration is accomplished through the GIS data included on this DVD.

Florida↗
USGS2007

Selenium concentrations in irrigation drain inflows to the Salton Sea, California, October 2006 and January 2007

This report presents raw data on selenium concentrations in samples of water, sediment, detritus, and selected food-chain matrices collected from selected agricultural drains in the southern portion of the Salton Sea during October 2006 and January 2007. Total selenium and selenium species were determined in water samples, whereas total selenium was determined in sediment, detritus, algae, plankton, midge larvae (Family Chironomidae), and two fish species (western mosquitofish, Gambusia affinis , and sailfin molly, Poecilia latipinna ).

Open-File Report↗
USGS2007

Water velocity and suspended solids measurements by in-situ instruments in Upper Klamath Lake, Oregon

The U. S. Geological Survey conducted hydrodynamic measurements in Upper Klamath Lake during four summer seasons (approximately mid-June to mid-September) during 2003 to 2006. Measurements included water current profiles made by acoustic Doppler current profilers at a number of fixed locations in the lake during all four years as well as from a moving boat during 2005 and 2006. Measurements of size distribution of suspended material were made at four locations in the lake during 2004-2006. Raw (unfiltered) data are presented as time series of measurements. In addition, water-velocity data have been filtered to remove wind-induced variations with periods less than thirty hours from the measurements. Bar graphs of horizontal and vertical water speed and acoustic backscatter have been generated to discern diurnal variations, especially as they relate to wind patterns over the lake. Mean speeds of the horizontal currents in the lake range between about 3.5 to 15 cm/s with the higher speeds at the deep locations in the trench on the west side of the lake. Current directions generally conform to the lake’s bathymetry contours and the water circulation pattern is usually in a clockwise direction around the lake as established by the prevailing north to northwesterly surface winds in the region. Diurnal patterns in horizontal currents probably relate to diurnal wind patterns with minimum wind speeds near noon and maximum wind speeds near 2100. Diurnal variations in vertical velocities do not appear to be related to wind patterns; they do appear to be related to expected patterns of vertical migration of Aphanizomenon flos aquae , (AFA) the predominant species of blue-green algae in the lake. Similarly, diurnal variations in acoustic backscatter, especially near the lake’s surface, are probably related to the vertical migration of AFA.

Oregon↗
USGS2007

Total selenium and selenium species in irrigation drain inflows to the Salton Sea, California, April and July 2007

This report presents the results for two sampling periods during a 4-year monitoring survey to provide a characterization of selenium concentrations in selected irrigation drains flowing into the Salton Sea, California. Total selenium, selenium species, and total suspended solids were determined in water samples, and total selenium was determined in sediment, detritus, and biota that included algae, plankton, midge larvae (family, Chironomidae), and two fish species-western mosquitofish (Gambusia affinis), and sailfin molly (Poecilia latipinna). In addition, sediments were analyzed for percent total organic carbon and particle size. Total selenium concentrations in water for both sampling periods ranged from 1.43 to 47.1 micrograms per liter, predominately as selenate, which is typical of waters leached out of selenium-contaminated marine shales under alkaline and oxidizing conditions. Total selenium concentrations ranged from 0.88 to 20.2 micrograms per gram in biota, and from 0.15 to 28.9 micrograms per gram in detritus and sediment.

Open-File Report↗
USGS2008

Klamath River Water Quality and Acoustic Doppler Current Profiler Data from Link River Dam to Keno Dam, 2007

In 2007, the U.S. Geological Survey, Watercourse Engineering, and the Bureau of Reclamation began a project to construct and calibrate a water quality and hydrodynamic model of the 21-mile reach of the Klamath River from Link River Dam to Keno Dam. To provide a basis for this work, data collection and experimental work were planned for 2007 and 2008. This report documents sampling and analytical methods and presents data from the first year of work. To determine water velocities and discharge, a series of cross-sectional acoustic Doppler current profiler (ADCP) measurements were made on the mainstem and four canals on May 30 and September 19, 2007. Water quality was sampled weekly at five mainstem sites and five tributaries from early April through early November, 2007. Constituents reported here include field parameters (water temperature, pH, dissolved oxygen concentration, specific conductance); total nitrogen and phosphorus; particulate carbon and nitrogen; filtered orthophosphate, nitrite, nitrite plus nitrate, ammonia, organic carbon, iron, silica, and alkalinity; specific UV absorbance at 254 nm; phytoplankton and zooplankton enumeration and species identification; and bacterial abundance and morphological subgroups. The ADCP measurements conducted in good weather conditions in May showed that four major canals accounted for most changes in discharge along the mainstem on that day. Direction of velocity at measured locations was fairly homogeneous across the channel, while velocities were generally lowest near the bottom, and highest near surface, ranging from 0.0 to 0.8 ft/s. Measurements in September, made in windy conditions, raised questions about the effect of wind on flow. Most nutrient and carbon concentrations were lowest in spring, increased and remained elevated in summer, and decreased in fall. Dissolved nitrite plus nitrate and nitrite had a different seasonal cycle and were below detection or at low concentration in summer. Many nutrient and carbon concentrations were similar at the top and bottom of the water column, though ammonia and particulate carbon showed more variability in summer. Averaged over the season, particulate carbon and particulate nitrogen decreased in the downstream direction, while ammonia and orthophosphate concentrations increased in the downstream direction. At most sites, bacteria, phytoplankton, and zooplankton populations reached their maximums in summer. Large bacterial cells made up most of the bacteria biovolume, though cocci were the most numerous bacteria type. The cocci were smaller than the filter pore sizes used to separate dissolved from particulate matter in this study. Phytoplankton biovolumes were dominated by the blue-green alga Aphanizomenon flos-aquae most of the sampling season, though a spring diatom bloom occurred. Phytoplankton biovolumes were generally highest at the upstream Link River and Railroad Bridge sites and decreased in the downstream direction. Zooplankton populations were dominated by copepods in early spring, and by cladocerans and rotifers in summer, with rotifers more common farther downstream.

Open-File Report↗
USGS2008

Year 3 summary report: Baseline selenium monitoring of agricultural drains operated by the Imperial Irrigation District in the Salton Sea Basin

This report summarizes findings from the third year of a 4-year-long field investigation to document selected baseline environmental conditions in 29 agricultural drains and ponds operated by the Imperial Irrigation District along the southern border of the Salton Sea. Routine water quality and fish species were measured at roughly quarterly intervals from April 2007 to January 2008. The water quality measurements included total suspended solids and total (particulate plus dissolved) selenium. In addition, during April and October 2007, water samples were collected from seven intensively monitored drains for measurement of particulate and dissolved selenium, including inorganic and organic fractions. In addition, sediment, aquatic food chain matrices (particulate organic detritus, filamentous algae, net plankton, and midge [chironomid] larvae), and two fish species (western mosquitofish, Gambusia affinis ; and sailfin molly, Poecilia latipinna ) were sampled from the seven drains for measurement of total selenium concentrations. The mosquitofish and mollies were intended to serve as surrogates for desert pupfish ( Cyprinodon macularius ), an endangered species that we were not permitted to take for selenium determinations. Water quality values were typical of surface waters in a hot desert climate. A few drains exhibited brackish, near anoxic conditions especially during the summer and fall when water temperatures occasionally exceeded 30°C. In general, total selenium concentrations in water varied directly with conductivity and inversely with pH. Although desert pupfish were found in several drains, sometimes in relatively high numbers, the fish faunas of most drains and ponds were dominated by nonnative species, especially red shiner ( Cyprinella lutrensis ), mosquitofish, and mollies. Dissolved selenium in water samples from the seven intensively monitored drains ranged from 0.700 to 24.1 µg/L, with selenate as the major constituent in all samples. Selenium concentrations in other matrices varied widely among drains and ponds, with at least one drain (for example, Trifolium 18) exhibiting especially high concentrations in food chain organisms (in detritus, 13.3–28.9 µg Se/g; in net plankton, 11.9–19.3 µg Se/g; in midge larvae, 12.7–15.4 µg Se/g) and fish (in mollies, 12.8-25.1 µg Se/g; in mosquitofish, 13.2-20.2 µg Se/g; all concentrations are dry weights). These elevated concentrations approached or exceeded average concentrations reported from flowing waters in seleniferous wetlands in the San Joaquin Valley.

California↗