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USGS2025

Bacterial community diversity and potential eco-physiological roles in toxigenic blooms composed of Microcystis, Aphanizomenon or Planktothrix

Cyanobacterial toxicity, cyanotoxins, and their impact on aquatic ecosystems and human health are well documented. In comparison, less is known about bloom-associated bacterial communities. Co-occurring bacteria can influence bloom development, physiology and collapse, and may also provide a niche for pathogenic bacteria. Existing research focuses on the cyanosphere of Microcystis -dominated blooms, despite the increasing prevalence of filamentous genera ( Aphanizomenon and Planktothrix ). This pilot study aimed to broaden our understanding of the bacterial consortia attached to morphologically distinct cyanobacteria (coccoid and filamentous) dominating phytoplankton communities and to explore their potential roles in amplifying the impacts of cyanobacterial blooms. We investigated four shallow freshwater bodies across three continents and two climate zones: an urban pond in the USA, a dammed reservoir and a natural lake in Poland, and an urban water body in Singapore. Amplicon sequencing (16S rRNA gene) was used to characterize bacterial communities, while shotgun metagenomics identified nitrogen- and phosphorus-cycling genes to infer potential eco-physiological functions. Cyanobacteria dominated bacterioplankton assemblages at all sites (>35.6%), with bloom composition influencing toxigenic profiles. A mixed bloom of Microcystis , Snowella , and Aphanizomenon had the broadest range of cyanotoxin synthetase genes ( mcy E, cyr J, ana F and sxt A). Microcystis blooms correlated with increased Roseomonas , while Planktothrix co-occurred with Flavobacterium – both bacteria likely contribute to nutrient-cycling within blooms and represent potential opportunistic pathogens for aquatic organisms and humans. The Microcystis cyanosphere exhibited the highest number of significant positive correlations with bacteria (19 relations), compared to Planktothrix and Aphanizomenon (11 and 2 relations, respectively). Non-diazotrophic blooms of Microcystis and Planktothrix showed greater abundances of nitrogen – ( ure B, gln A, nar B, and nar HZ) and phosphorus-cycling genes ( pho BHPR and ppk 1), indicating a strong dependence on associated bacteria for nutrient acquisition compared to diazotrophic Aphanizomenon . These findings suggest that Aphanizomenon -dominated blooms may be sustained by simpler microbiomes. Our results provide preliminary evidence of cyanosphere heterogeneity potentially shaped by the dominance or coexistence of three morphologically and eco-physiologically distinct genera of cyanobacteria. A comprehensive knowledge of the taxonomy and functional roles of bloom-associated microbiomes is therefore essential to understand bloom activity, evaluate the environmental threat, and develop effective strategies for prevention and mitigation.

Frontiers in Microbiology↗
USGS2025

Synthetic microfibers are ubiquitous in benthic algae from the Laurentian Great Lakes

Synthetic microfibers are a class of microplastics routinely released into environmental media from domestic laundry and wastewater treatment plant effluent. Areas of high human population density discharge immense amounts of synthetic microfibers that pollute and accumulate in sediments, surface waters, algae, and other parts of the ecosystem. Synthetic microfibers are abundant in the Laurentian Great Lakes of North America, but their movement and fate are not well understood. Macroalgae effectively sequester microfibers; however, it is unknown if quantities of synthetic microfibers differ in benthic algae of the Great Lakes based on human population density or algal type (such as Cladophora or charophytes). Presented here is a 4-year study that investigated benthic algae samples from four of the Laurentian Great Lakes: Lakes Michigan, Huron, Ontario, and Erie. Synthetic microfibers were isolated and quantified in the algal samples, and values were analyzed with respect to algal type, lake, and population density. The average estimated number of synthetic microfibers per kg (dry weight) of benthic algae in each lake ranged from 1.6 × 10 4 to 2.0 × 10 4 . Microscopic analysis suggested a possible interaction between epiphytic diatoms and benthic macroalgae ( Cladophora ), which may help to explain the ability of the algae to sequester microfibers regardless of algal type. The results also suggest a lack of correlation between human population density and number of synthetic microfibers in benthic algae, which could imply facile movement and distribution of microfibers in large bodies of water, that includes the aquatic food web of macroinvertebrates and fish communities.

Lake Erie, Lake Huron, Lake Michigan, lake Ontario↗
USGS2003

Athena Mars rover science investigation

Each Mars Exploration Rover carries an integrated suite of scientific instruments and tools called the Athena science payload. The primary objective of the Athena science investigation is to explore two sites on the Martian surface where water may once have been present, and to assess past environmental conditions at those sites and their suitability for life. The remote sensing portion of the payload uses a mast called the Pancam Mast Assembly (PMA) that provides pointing for two instruments: the Panoramic Camera (Pancam), and the Miniature Thermal Emission Spectrometer (Mini‐TES). Pancam provides high‐resolution, color, stereo imaging, while Mini‐TES provides spectral cubes at mid‐infrared wavelengths. For in‐situ study, a five degree‐of‐freedom arm called the Instrument Deployment Device (IDD) carries four more tools: a Microscopic Imager (MI) for close‐up imaging, an Alpha Particle X‐Ray Spectrometer (APXS) for elemental chemistry, a Mössbauer Spectrometer (MB) for the mineralogy of Fe‐bearing materials, and a Rock Abrasion Tool (RAT) for removing dusty and weathered surfaces and exposing fresh rock underneath. The payload also includes magnets that allow the instruments to study the composition of magnetic Martian materials. All of the Athena instruments have undergone extensive calibration, both individually and using a set of geologic reference materials that are being measured with all the instruments. Using a MER‐like rover and payload in a number of field settings, we have devised operations processes that will enable us to use the MER rovers to formulate and test scientific hypotheses concerning past environmental conditions and habitability at the landing sites.

Journal of Geophysical Research E: Planets↗
USGS2018

Selenium, mercury, and their molar ratios in sportfishes from drinking water reservoirs

Mercury (Hg) bioaccumulates in aquatic ecosystems and may pose a risk to humans who consume fish. Selenium (Se) has the ability to reduce Hg toxicity, but the current guidance for human consumption of fish is based on Hg concentration alone. The purpose of the present study was to examine the relationship between Se and Hg in freshwater sportfish, for which there is a paucity of existing data. We collected three species of fish from different trophic positions from two drinking water reservoirs in central North Carolina, USA, to assess Hg and Se concentrations in relation to fish total length and to compare two measures of the protective ability of Se, the Se:Hg molar ratio and Se health benefit value (HBV Se ), to current guidance for Hg. According to the Se:Hg molar ratio, all of the low trophic position fish sampled and the middle trophic position fish sampled from one of the reservoirs were safe for consumption. The same number of fish were considered safe using the HBV Se . More fish were deemed unsafe when using the Se:Hg molar ratio and HBV Se than were considered unsafe when using the U.S. Environmental Protection Agency (USEPA) Hg threshold. These findings suggest that the measures of Se protection may be unnecessarily conservative or that the USEPA Hg threshold may not be sufficiently protective of human health, especially the health of sensitive populations like pregnant or nursing mothers and young children. Future examination of the Se:Hg molar ratio and HBV Se from a variety of fish tissue samples would help refine the accuracy of these measures so that they may be appropriately utilized in ecological and human health risk assessment.

International Journal of Environmental Research an↗
USGS1986

Association between PCBs and lower embryonic weight in black-crowned night herons in San Francisco Bay

Reproductive problems, including congenital malformations, reduced hatching success, and decreased survival of hatchlings, have been observed in colonial-nesting water birds at the San Francisco Bay National Wildlife Refuge (SFBNWR). Twenty-four black-crowned night heron (Nycticorax nycticorax) eggs were collected from SFBNWR in 1983. Twelve of these were collected from separate nests when late-stage embryos were pipping, and an additional egg was randomly collected from each nest for organochlorine analysis. Overt anomalies and skeletal defects were not apparent. Embryonic weights (with partially absorbed yolk sacs removed) were 15% lower (p lt 0.05) in SFBNWR embryos compared to control embryos from the Patuxent Wildlife Research Center (PWRC). Crown-rump length and femur length were shorter for SFBNWR embryos. The geometric mean polychlorinated biphenyl (PCB) concentration in SFBNWR eggs was 4.1 ppm wet weight, with a range of 0.8-52.0 ppm. A negative correlation (r = - 0.61; p lt 0.05) existed between embryonic weight and log-transformed PCB residues in whole eggs collected from the same nest at SFBNWR, suggesting a possible impact of PCBs on embryonic growth. A correlation with embryonic weight did not occur for DDE (1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene) residues. Liver microsomal aryl hydrocarbon hydroxylase activity was neither significantly elevated nor correlated with PCB, DDE, or PCB plus DDE log-transformed residues. It is unknown whether the apparent association between PCBs and lower weight is persistent through hatching.

Journal of Toxicology and Environmental Health↗
USGS2015

Investigating the temporal effects of metal-based coagulants to remove mercury from solution in the presence of dissolved organic matter

The presence of mercury (Hg), particularly methylmercury (MeHg), is a concern for both human and ecological health as MeHg is a neurotoxin and can bioaccumulate to lethal levels in upper trophic level organisms. Recent research has demonstrated that coagulation with metal-based salts can effectively remove both inorganic mercury (IHg) and MeHg from solution through association with dissolved organic matter (DOM) and subsequent flocculation and precipitation. In this study, we sought to further examine interactions between Hg and DOM and the resulting organo-metallic precipitate (floc) to assess if (1) newly added IHg could be removed to the same extent as ambient IHg or whether the association between IHg and DOM requires time, and (2) once formed, if the floc has the capacity to remove additional Hg from solution. Agricultural drainage water samples containing ambient concentrations of both DOM and IHg were spiked with a traceable amount of isotopically enriched IHg and dosed with ferric sulfate after 0, 1, 5, and 30 days. Both ambient and newly added IHg were removed within hours, with 69–79 % removed. To a separate sample set, isotopically enriched IHg was added to solution after floc had formed. Under those conditions, 81–95 % of newly added Hg was removed even at Hg concentrations 1000-fold higher than ambient levels. Results of this study indicate coagulation with ferric sulfate effectively removes both ambient and newly added IHg entering a system and suggests rapid association between IHg and DOM. This work also provides new information regarding the ability of floc to remove additional Hg from solution even after it has formed.

Environmental Management↗
USGS2013

Maintaining and restoring sustainable ecosystems in southern Nevada

Managers in southern Nevada are challenge with determining appropriate goals and objectives and developing viable approaches for maintaining and restoring sustainable ecosystems in a time of rapid socio-ecological and environmental change. Sustainable or "healthy" ecosystems supply clean air, water and habitat for a diverse array of plants and animals. As described in Chapter 1, sustainable ecosystems retain characteristic processes like hydrological flux and storage, geomorphic processes, biogeochemical cycling and storage, biological activity and productivity, and population regeneration and reproduction over the normal cycle of disturbance events (modified from Chapin and others 1996 and Christensen and others 1996). Ecological restoration of stressed or disturbed ecosystems in an integral part of managing for sustainable ecosystems. The Society of Ecological Restoration International (SERI) defines ecological restoration as the process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed (SERI 2004). Many of the southern Nevada's ecosystems are being subjected to anthropogenic stressors that span global, regional, and local scales (Chapter 2)., and are crossing ecological thresholds to new alternative states (Chapter 4 and Chapter 5). These alternative states often represent novel communities with disturbance regimes that differ significantly from historic conditions. Past management and restoration goals often focused on returning ecosystems to pre-disturbance conditions (Harris and others 2006). This approach assumes stable or equilibrium conditions and ignores changes in ecosystems processes due to land uses, increases in CO 2 concentrations, and climate change. A more realistic approach is to base management and restoration goals on the current potential of an ecosystem to support a given set of ecological conditions, and on the likelihood of future change due to warming climate (Harris and others 2006). This approach requires understanding ecosystem resilience to anthropogenic disturbance and climate change, the alternative states that exist for ecosystems, and the factors that result in threshold crossing (Bestelmeyer and others 2009; Hobbs and Harris 2001; Stingham and others 2003; Whisemnant 1999). It also requires the ability to predict how climate is likely to influence ecosystems in the future (Harris and others 2006). This chapter addresses the restoration aspects of Sub-goal 1.3 in the SNAP Science Research Strategy which is to restore and sustain proper function of southern Nevada's watersheds and landscapes (able 1.3; Turner and others 2009). The effects of global, regional and local stresses on southern Nevada ecosystems are presented in Chapter 2. Here, we discuss appropriate objectives and develop guidelines for maintaining and restoring southern Nevada ecosystems. We then discuss the differences in ecological resilience to stress and disturbance and resistance to invasive species in southern Nevada ecosystems and describe restoration and management approaches for the different ecosystem types. We conclude with knowledge gaps and management implications.

Nevada↗
USGS2008

Infiltration from an impoundment for coal‐bed natural gas, Powder River Basin, Wyoming: Evolution of water and sediment chemistry

Development of coal‐bed natural gas (CBNG) in the Powder River Basin, Wyoming, has increased substantially in recent years. Among environmental concerns associated with this development is the fate of groundwater removed with the gas. A preferred water‐management option is storage in surface impoundments. As of January 2007, permits for more than 4000 impoundments had been issued within Wyoming. A study was conducted on changes in water and sediment chemistry as water from an impoundment infiltrated the subsurface. Sediment cores were collected prior to operation of the impoundment and after its closure and reclamation. Suction lysimeters were used to collect water samples from beneath the impoundment. Large amounts of chloride (12,300 kg) and nitrate (13,500 kg as N), most of which accumulated naturally in the sediments over thousands of years, were released into groundwater by infiltrating water. Nitrate was more readily flushed from the sediments than chloride. If sediments at other impoundment locations contain similar amounts of chloride and nitrate, impoundments already permitted could release over 48 × 10 6 kg of chloride and 52 × 10 6 kg of nitrate into groundwater in the basin. A solute plume with total dissolved solid (TDS) concentrations at times exceeding 100,000 mg/L was created in the subsurface. TDS concentrations in the plume were substantially greater than those in the CBNG water (about 2300 mg/L) and in the ambient shallow groundwater (about 8000 mg/L). Sulfate, sodium, and magnesium are the dominant ions in the plume. The elevated concentrations are attributed to cation‐exchange‐enhanced gypsum dissolution. As gypsum dissolves, calcium goes into solution and is exchanged for sodium and magnesium on clays. Removal of calcium from solution allows further gypsum dissolution.

Water Resources Research↗
USGS2021

Monthly river temperature trends across the US confound annual changes

Climate variations and human modifications of the water cycle continue to alter the Earth's surface water and energy exchanges. It is therefore critical to ascertain how these changes impact water quality and aquatic ecosystem habitat metrics such as river temperatures. Though river temperature trend analyses exist in the literature, studies on seasonal trends in river temperatures across large spatial extents, e.g. the contiguous United States (US), are limited. As we show through both annual and monthly trend analyses for 20 year ( n = 138 sites) and 40 year ( n = 40 sites) periods, annual temperature trends across the US mask extensive monthly variability. While most sites exhibited annual warming trends, these annual trends obscured sub-annual cooling trends at many sites. Monthly trend anomalies were spatially organized, with persistent regional patterns at both reference and human-impacted sites. The largest warming and cooling anomalies happened at human impacted sites and during summer months. Though our analysis points to coherence in trends as well as the overall impact of human activity in driving these patterns, we did not investigate the impact of river temperature observation accuracy on reported trends, an area needed for future work. Overall, these patterns emphasize the need to consider sub-annual behavior when managing the ecological impacts of river temperature throughout lotic networks.

Environmental Research Letters↗
USGS2002

Degradation of marine ecosystems and decline of fishery resources in marine protected areas in the US Virgin Islands

The large number of marine protected areas (MPAs) in the Caribbean (over 100) gives a misleading impression of the amount of protection the reefs and other marine resources in this region are receiving. This review synthesizes information on marine resources in two of the first MPAs established in the USA, namely Virgin Islands National Park (1962) and Buck Island Reef National Monument (1961), and provides compelling evidence that greater protection is needed, based on data from some of the longest running research projects on coral reefs, reef fish assemblages, and seagrass beds for the Caribbean. Most of the stresses affecting marine resources throughout the Caribbean (e.g. damage from boats, hurricanes and coral diseases) are also causing deterioration in these MPAs. Living coral cover has decreased and macroalgal cover has increased. Seagrass densities have decreased because of storms and anchor damage. Intensive fishing in the US Virgin Islands has caused loss of spawning aggregations and decreases in mean fish size and abundance. Groupers and snappers are far less abundant and herbivorous fishes comprise a greater proportion of samples than in the 1960s. Effects of intensive fishing are evident even within MPA boundaries. Although only traditional fishing with traps of 'conventional design' is allowed, commercial trap fishing is occurring. Visual samples of fishes inside and outside Virgin Islands National 'Park showed no significant differences in number of species, biomass, or mean size of fishes. Similarly, the number of fishes per trap was statistically similar inside and outside park waters. These MPAs have not been effective because an unprecedented combination of natural and human factors is assaulting the resources, some of the greatest damage is from stresses outside the control of park managers (e.g. hurricanes), and enforcement of the few regulations has been limited. Fully functioning MPAs which prohibit fishing and other extractive uses (e.g. no-take marine reserves) could reverse some of the degradation, allowing replenishment of the fishery resources and recovery of benthic habitats.

Environmental Conservation↗
USGS2024

Temporal analysis of water chemistry and smallmouth bass (Micropterus dolomieu) health at two sites with divergent land use in the Susquehanna River watershed, Pennsylvania, USA

Monitoring wild fish health and exposure effects in impacted rivers and streams with differing land use has become a valuable research tool. Smallmouth bass ( Micropterus dolomieu ) are a sensitive, indicator species that exhibit signs of immunosuppression and endocrine disruption in response to water quality changes and contaminant exposure. To determine the impact of agriculture and development on smallmouth bass health, two sites (a developed/agriculture site and a forested site) in the Susquehanna River watershed, Pennsylvania were selected where bass and water chemistry were sampled from 2015 to 2019. Smallmouth bass were sampled for histopathology to assess parasite and macrophage aggregate density in the liver and spleen, condition factor (Ktl), hepatic gene transcript abundance, hepatosomatic index (HSI), and a health assessment index (HAI). Land use at the developed/agriculture site included greater pesticide application rates and phytoestrogen crop cover and more detections and higher concentrations of pesticides, wastewater-associated contaminants, hormones, phytoestrogens, and mycotoxins than at the forested site. Additionally, at the developed/agriculture site, indicators of molecular changes, including oxidative stress, immune/inflammation, and lipid metabolism-related hepatic gene transcripts, were associated with more contaminants and land use variables. At both sites, there were multiple associations of contaminants with liver and/or spleen macrophage aggregate density, indicating that changes at the molecular level seemed to be a better indicator of exposures unique to each site. The findings illustrate the importance of timing for land management practices, the complex mixtures aquatic animals are exposed to, and the temporal changes in contaminant concentration. Agricultural practices that affect hepatic gene transcripts associated with immune function and disease resistance were demonstrated which could negatively affect smallmouth bass populations.

Pennsylvania↗
USGS2026

Non-physical barrier design and environmental conditions alter routing and survival of juvenile Chinook salmon (Oncorhynchus tshawytscha) in the Sacramento-San Joaquin River Delta

Pacific salmon face substantial challenges when migrating through anthropogenically modified river systems, such as the Sacramento-San Joaquin River Delta (the Delta). Non-physical behavioral barriers, such as the bioacoustic fish fence (BAFF), are one potential solution for guiding fish away from hazards without obstructing water flow. However, the effectiveness of these technologies depends on abiotic and biotic conditions. In the Delta, a BAFF was deployed at Georgiana Slough in 2011, 2012, and 2024 to deter juvenile Chinook salmon ( Oncorhynchus tshawytscha ) from migrating into the interior Delta, a region associated with lower survival than the mainstem Sacramento River. We leveraged nine years of acoustic telemetry data to evaluate BAFF performance across flow conditions and two BAFF designs (2011/2012 vs. 2024), and to assess the BAFF's contribution to improving through-Delta survival. The BAFF reduced routing into Georgiana Slough from 26.5% without a barrier to 8.9% in 2011/2012 and 15.9% in 2024. In general, routing into Georgiana Slough increased with the proportion of flow entering the channel during periods without a BAFF and during the 2024 deployment but remained constant during the 2011/2012 deployment. Additionally, BAFF effectiveness declined with increasing input flow. Ultimately, reduced routing into Georgiana Slough during the 2024 BAFF deployment resulted in an increase in estimated through-Delta survival between 0.2 and 1.6 percentage points depending on release group. Our results provide valuable insights into the role of non-physical barriers in complex river systems and inform future management strategies for protecting migrating juvenile Chinook salmon in the Sacramento-San Joaquin River Delta.

California↗
USGS2012

Factors controlling nitrate fluxes in groundwater in agricultural areas

The impact of agricultural chemicals on groundwater quality depends on the interactions of biogeochemical and hydrologic factors. To identify key processes affecting distribution of agricultural nitrate in groundwater, a parsimonious transport model was applied at 14 sites across the U.S. Simulated vertical profiles of NO 3 - , N 2 from denitrification, O 2 , Cl - , and environmental tracers of groundwater age were matched to observations by adjusting the parameters for recharge rate, unsaturated zone travel time, fractions of N and Cl - inputs leached to groundwater, O 2 reduction rate, O 2 threshold for denitrification, and denitrification rate. Model results revealed important interactions among biogeochemical and physical factors. Chloride fluxes decreased between the land surface and water table possibly because of Cl - exports in harvested crops (averaging 22% of land-surface Cl - inputs). Modeled zero-order rates of O 2 reduction and denitrification were correlated. Denitrification rates at depth commonly exceeded overlying O 2 reduction rates, likely because shallow geologic sources of reactive electron donors had been depleted. Projections indicated continued downward migration of NO 3 - fronts at sites with denitrification rates <0.25 mg-N L -1 yr -1 . The steady state depth of NO 3 - depended to a similar degree on application rate, leaching fraction, recharge, and NO 3 - and O 2 reaction rates. Steady state total mass in each aquifer depended primarily on the N application rate. In addition to managing application rates at land surface, efficient water use may reduce the depth and mass of N in groundwater because lower recharge was associated with lower N fraction leached. Management actions to reduce N leaching could be targeted over aquifers with high-recharge and low-denitrification rates.

Water Resources Research↗
USGS2022

Identifying key stressors driving biological impairment in freshwater streams in the Chesapeake Bay watershed, USA

Biological communities in freshwater streams are often impaired by multiple stressors (e.g., flow or water quality) originating from anthropogenic activities such as urbanization, agriculture, or energy extraction. Restoration efforts in the Chesapeake Bay watershed, USA seek to improve biological conditions in 10% of freshwater tributaries and to protect the biological integrity of existing healthy watersheds. To achieve these goals, resource managers need to better understand which stressors are most likely driving biological impairment. Our study addressed this knowledge gap through two approaches: 1) reviewing and synthesizing published multi-stressor studies, and 2) examining 303(d) listed impairments linked to biological impairment as identified by jurisdiction regulatory agencies (the states within the watershed and the District of Columbia). Results identified geomorphology (i.e., physical habitat), salinity, and toxic contaminants as important for explaining variability in benthic community metrics in the literature review. Geomorphology (i.e., physical habitat and sediment), salinity, and nutrients were the most reported stressors in the jurisdictional impairment analysis. Salinity is likely a major stressor in urban and mining settings, whereas geomorphology was commonly reported in agricultural settings. Toxic contaminants, such as pesticides, were rarely measured; more research is needed to quantify the extent of their effects in the region. Flow alteration was also highlighted as an important urban stressor in the literature review but was rarely measured in the literature or reported by jurisdictions as a cause of impairment. These results can be used to prioritize stressor monitoring by managers, and to improve stressor identification methods for identifying causes of biological impairment.

Chesapeake Bay Watershed↗
USGS1993

Wetland modeling and information needs at Stillwater National Wildlife Refuge

The marshes in and around Stillwater National Wildlife Refuge (the Refuge) are extremely dynamic; expanding and contracting in size both seasonally, due to runoff and subsequent evapotranspiration, and over longer periods, due to climatic variation. The dynamic nature of these marshes results in a diversity of wetland habitats, which support a variety of migratory birds. To maintain this wetland diversity and control the loss of migratory bird habitat in the Lahontan Valley, the Refuge was established and currently manages a complex of marsh units. However, changes in the hydrology, and changes that will occur as a result of the Fallon Paiute-Shoshone and Truckee-Carson-Pyramid Lake Water Rights Settlement Act (Public Law 101-618, 104 Stat. 3389), greatly affect the Refuge's wetland management capability. In light of these changes, and the legal requirements associated with environmental impact assessments, the Refuge convened a workshop to discuss several aspects of wetland management in the Lahontan Valley. The workshop, described in this report, had three primary objectives: 1. discuss the types and relative proportions of primary wetland habitats that should be provided as described in the settlement act; 2. discuss wetland management models that might be developed to help manage these marshes under hydrologic regimes likely in the future; and 3. discuss future information and monitoring needs, including proposals for valley-wide biodiversity surveys, which would be helpful when considering withdrawn Bureau of Reclamation (BR) lands for possible incorporation into the Refuge. Several presentations at the beginning of the workshop provided a common basis for discussing these objectives. Refuge staff provided background on the history and past management. The Nature Conservatory discussed their role in the settlement act, proposals for valley-wide biodiversity surveys, and results of a literature review for Stillwater Marsh and the Lahontan Valley (Nachlinger 1993). Kay Fowler provided an historical context of changes in vegetation and waterbird use of the marshes based on her ethnography of the local Paiute Indians (Fowler 1993). Finally, Bob Elston discussed a model that predicts archaeological sites based on environmental variables (Raven and Elston 1989). The workshop was organized by staff from the Refuge and facilitated by the authors of this report. Participants included Ron Anglin, Bill Henry, Anne Janik, Cliff Creger, Fred Paveglio, and Mary Jo Elpers of the U.S. Fish and Wildlife Service (the Service); Jeff Baumgartner, Jan Nachlinger, Hope Humphries, and Graham Chisholm of The Nature Conservancy; David Yardas of the Environmental Defense Fund; David Robertson of Robertson Software, Inc.; Norm Saake, Terry Retterer, and Larry Neel of the Nevada Department of Wildlife; Lew Oring and Kay Fowler of the University of Nevada; and Robert Elston of Intermountain Research.

Report↗
USGS2024

Prioritizing river basins for nutrient studies

Increases in fluxes of nitrogen (N) and phosphorus (P) in the environment have led to negative impacts affecting drinking water, eutrophication, harmful algal blooms, climate change, and biodiversity loss. Because of the importance, scale, and complexity of these issues, it may be useful to consider methods for prioritizing nutrient research in representative drainage basins within a regional or national context. Two systematic, quantitative approaches were developed to (1) identify basins that geospatial data suggest are most impacted by nutrients and (2) identify basins that have the most variability in factors affecting nutrient sources and transport in order to prioritize basins for studies that seek to understand the key drivers of nutrient impacts. The “impact” approach relied on geospatial variables representing surface-water and groundwater nutrient concentrations, sources of N and P, and potential impacts on receptors (i.e., ecosystems and human health). The “variability” approach relied on geospatial variables representing surface-water nutrient concentrations, factors affecting sources and transport of nutrients, model accuracy, and potential receptor impacts. One hundred and sixty-three drainage basins throughout the contiguous United States were ranked nationally and within 18 hydrologic regions. Nationally, the top-ranked basins from the impact approach were concentrated in the Midwest, while those from the variability approach were dispersed across the nation. Regionally, the top-ranked basin selected by the two approaches differed in 15 of the 18 regions, with top-ranked basins selected by the variability approach having lower minimum concentrations and larger ranges in concentrations than top-ranked basins selected by the impact approach. The highest ranked basins identified using the variability approach may have advantages for exploring how landscape factors affect surface-water quality and how surface-water quality may affect ecosystems. In contrast, the impact approach prioritized basins in terms of human development and nutrient concentrations in both surface water and groundwater, thereby targeting areas where actions to reduce nutrient concentrations could have the largest effect on improving water availability and reducing ecosystem impacts.

Environmental Monitoring and Assessment↗
USGS2013

Bactericidal efficacy of elevated pH on fish pathogenic and environmental bacteria

Ship ballast water is a recognized medium for transfer and introductions of nonindigenous species. There is a need for new ballast water treatment methods that effectively and safely eliminate or greatly minimize movements of these species. The present study employed laboratory methods to evaluate the bactericidal efficacy of increased pH (pH 10.0–12.0) for exposure durations of up to 72 h to kill a variety of Gram-negative and Gram-positive bacteria including fish pathogens (Aeromonas spp., Yersinia ruckeri, Edwardsiella ictaluri, Serratia liquefaciens, Carnobacterium sp.), other common aquatic-inhabitant bacteria (Serratia marcescens, Pseudomonas fluorescens, Staphylococcus sp., Bacillus sp.) and indicators listed in International Maritime Organization D2 Standards; namely, Vibrio cholera (an environmental isolate from fish), Escherichia coli and Enterococcus faecalis. Volumes of 5 N NaOH were added to tryptic soy broth to obtain desired pH adjustments. Viable cells were determined after 0, 4, 12, 24, 48, and 72 h. Initial (0 h) cell numbers ranged from 3.40 × 10 4 cfu/mL for Bacillus sp. to 2.44 × 10 7 cfu/mL for E. faecalis. The effective endpoints of pH and treatment duration necessary to realize 100% bactericidal effect varied; however, all bacteria tested were killed within 72 h at pH 12.0 or lower. The lowest parameters examined, 4 h at pH 10.0, were bactericidal to V. cholera, E. ictaluri, three of four isolates of E. coli, and (three of four) Aeromonas salmonicida subsp. salmonicida. Bactericidal effect was attained at pH 10.0 within 12 h for the other A. salmonicida subsp. salmonicida, and within 24 h for P. fluorescens, and the remaining E. coli.

Journal of Advanced Research↗
USGS2012

Arc-related porphyry molybdenum deposit model

This report provides a descriptive model for arc-related porphyry molybdenum deposits. Presented within are geological, geochemical, and mineralogical characteristics that differentiate this deposit type from porphyry copper and alkali-feldspar rhyolite-granite porphyry molybdenum deposits. The U.S. Geological Survey's effort to update existing mineral deposit models spurred this research, which is intended to supplement previously published models for this deposit type that help guide mineral-resource and mineral-environmental assessments. Arc-related porphyry molybdenum deposits are a substantial resource for molybdenum metal and may have anomalous concentrations of tungsten. The deposits contain low-grade ore (0.03-0.22 percent molybdenum) as molybdenite, but are large-tonnage, making them amenable to bulk mining open-pit techniques. The mineralizing system usually has fluorine contents of less than 0.1 percent. The cogenetic intrusion is a differentiated calc-alkaline granitoid, typically granodiorite to quartz monzonite in composition, with low rubidium and niobium, and moderate to high strontium concentrations. Metals and hydrothermal fluids are sourced from these intrusions, with an additional meteoric fluid component contributing to peripheral alteration but not adding more metal. The lithology of the surrounding country rocks is not important to the formation of these deposits, but a surrounding carbonate unit may be altered to skarn that contains economic mineralization. The creation of contact-metamorphosed hornfels adjacent to the intrusion is common. Formation of arc-related porphyry molybdenum deposits typically occurs within a continental arc environment related to arc-continent or continent-continent collision and subduction. Few deposits are found in an island arc setting. Most classified arc-related porphyry molybdenum deposits are located in the western cordillera of North America, notably in British Columbia and Alaska. Hydrothermal alteration provides a key component to the identification of a deposit. Alteration usually is zoned from a core of potassic plus/minus silicic alteration outwards through phyllic to propylitic alteration. Argillic alteration may be irregular in shape and will overprint earlier hydrothermal alteration. Exploration should be limited to magmatic arc belts that have been unroofed and eroded to levels of a few kilometers depth. Important geological vectors toward areas of higher grade mineralization include intensity of hydrothermal alteration, veining, and faulting. Anomalous levels of molybdenum, tungsten, copper, lead, or zinc in soils, tills, stream sediments, and drainage waters may indicate the presence of an arc-related porphyry molybdenum deposit. Geophysical exploration techniques have been met with minimal success because of the overall low concentration of associated sulfide and oxide minerals. Geoenvironmental concerns are generally low because of low volumes of sulfide minerals. Most deposits are marginally acid-generating to non-acid-generating with drainage waters being near-neutral pH because of the acid generating potential of pyrite being partially buffered by late-stage calcite-bearing veins. The low ore content results in a waste:ore ratio of nearly 1:1 and large tailings piles from the open-pit method of mining.

Scientific Investigations Report↗